Electro-Voice 250, 1252 User Manual

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Page 1

Nexus

1250 /1252

High Performance SCADA Monitor

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1800 Shames Drive

Westbury, New York 11590

Tel: 516-334-0870

 Fax: 516-338-4741

Sales@electroind.com

 www.electroind.com

“The Leader in Web Accessed Power Monitoring and Control”

Installation & Operation Manual

Version 1.25

November 13, 2006

Doc # E107706 V1.25

Electro Industries/GaugeTech

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Electro Industries/GaugeTech

Doc # E107706 V1.25

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Nexus 1250/1252 Installation and Operation Manual Revision 1.25

Published by: Electro Industries/GaugeTech 1800 Shames Drive Westbury, NY 11590

All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or information storage or retrieval systems or any future forms of duplication, for any purpose other than the purchaser’s use, without the expressed written permission of Electro Industries/GaugeTech.

Printed in the United States of America.

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Customer Service and Support

Customer support is available 9:00 am to 4:30 pm, eastern standard time, Monday through Friday. Please have the model, serial number and a detailed problem description available. If the problem concerns a particular reading, please have all meter readings available. When returning any merchandise to EIG, a return materials authorization number is required. For customer or technical assistance, repair or calibration, phone 516-334-0870 or fax 516-338-4741.

Product Warranty

Electro Industries/GaugeTech warrants all products to be free from defects in material and workmanship for a period of four years from the date of shipment. During the warranty period, we will, at our option, either repair or replace any product that proves to be defective.

To exercise this warranty, fax or call our customer-support department. You will receive prompt assistance and return instructions. Send the instrument, transportation prepaid, to EIG at 1800 Shames Drive, Westbury, NY 11590. Repairs will be made and the instrument will be returned.

Limitation of Warranty

This warranty does not apply to defects resulting from unauthorized modification, misuse, or use for any reason other than electrical power monitoring. Nexus 1250/1252 is not a user-serviceable product.

OUR PRODUCTS ARE NOT TO BE USED FOR PRIMARY OVER-CURRENT PROTECTION. ANY PROTECTION FEATURE IN OUR PRODUCTS IS TO BE USED FOR ALARM OR SECONDARY PROTECTION ONLY.

THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED OR IMPLIED, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. ELECTRO INDUSTRIES/GAUGETECH SHALL NOT BE LIABLE FOR ANY INDIRECT, SPECIAL OR CONSEQUENTIAL DAMAGES ARISING FROM ANYAUTHORIZED OR UNAUTHORIZED USE OF ANY ELECTRO INDUSTRIES/GAUGETECH PRODUCT. LIABILITY SHALL BE LIMITED TO THE ORIGINAL COST OF THE PRODUCT SOLD.

Statement of Calibration

Our instruments are inspected and tested in accordance with specifications published by Electro Industries/GaugeTech. The accuracy and a calibration of our instruments are traceable to the National Institute of Standards and Technology through equipment that is calibrated at planned intervals by comparison to certified standards.

Disclaimer

The information presented in this publication has been carefully checked for reliability; however, no responsibility is assumed for inaccuracies. The information contained in this document is subject to change without notice.

This symbol indicates that the operator must refer to an explanation in the operating instructions. Please see Chapter 3, Hardware Installation, for important safety information regarding installation and hookup of the Nexus 1250/1252 Meter.

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About Electro Industries/GaugeTech

Electro Industries/GaugeTech was founded in 1973 by Dr. Samuel Kagan. Dr. Kagan’s first innovation, an affordable, easy-to-use AC power meter, revolutionized the power-monitoring field. In the 1980s Dr. Kagan and his team at EIG developed a digital multifunction monitor capable of measuring every aspect of power.

EIG further transformed AC power metering and power distribution with the Futura+ device, which supplies all the functionality of a fault recorder, an event recorder and a data logger in one single meter. Today, with the Nexus 1250/1252,1262/1272 and the Shark, EIG is a leader in the development and production of power monitoring products. All EIG products are designed, manufactured, tested and calibrated at our facility in Westbury, New York.

Applications:

Multifunction power monitoring

Single and multifunction power monitoring

Power quality monitoring

On board data logging for trending power usage and quality

Disturbance analysis

Futura+ Series Products:

Power quality monitoring

High-accuracy AC metering

On board data logging

On board fault and voltage recording

DM Series Products:

Three-phase multifunction monitoring

Wattage, VAR and amperage

Modbus, Modbus Plus, DNP 3.0 and Ethernet protocols

Analog retransmit signals (0–1 and 4–20mA)

Single-Function Meters:

AC voltage and amperage

DC voltage and amperage

AC wattage

Single-phase monitoring with maximum and minimum demands

Transducer readouts

Portable Analyzers:

Power quality analysis

Energy analysis

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Chapter 1: Three-Phase Power Measurement

1.1: Three-Phase System Configurations . . . . . . . . . . . . . . . . . . . . . 1-1

1.1.1: Wye Connnection . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-1

1.1.2: Delta Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

1.1.3: Blondell’s Theorem and Three Phase Measurement . . . . . . . . . . . . . 1-4

1.2: Power, Energy and Demand . . . . . . . . . . . . . . . . . . . . . . . .1-6

1.3: Reactive Energy and Power Factor . . . . . . . . . . . . . . . . . . . . . 1-8

1.4: Harmonic Distortion . . . . . . . . . . . . . . . . . . . . . . . . . . .1-10

1.5: Power Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-13

Chapter 2: Nexus Overview

2.1: The Nexus System . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-1

2.2: DNP V3.00 Level 1 and Level 2 . . . . . . . . . . . . . . . . . . . . . . 2-2

2.3: Flicker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-2

2.4: INP2 Internal Modem with Dial-In/Dial-Out Option . . . . . . . . . . . . . . 2-3

2.4.1: Hardware Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .2-3

2.4.2: Dial-In Function . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-3

2.4.3: Dial-Out Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

2.5: Total Web Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-4

2.5.1: Hardware Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .2-4

2.5.2: Hardware Connection . . . . . . . . . . . . . . . . . . . . . . . . . .2-4

2.6: Measurements and Calculations . . . . . . . . . . . . . . . . . . . . . . . 2-6

2.7: Demand Integrators . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10

2.8: Nexus External I/O Modules (Optional) . . . . . . . . . . . . . . . . . . .2-12

2.9: Nexus 1250/1252 Meter Specifications . . . . . . . . . . . . . . . . . . . 2-13

2.10: Nexus P40N, P41N, P43N External Display Specifications . . . . . . . . . .2-14

2.11: Nexus P60N Touch Screen Display Specifications . . . . . . . . . . . . . . 2-14

Chapter 3: Hardware Installation

3.1: Mounting the Nexus 1259/1252 Meter . . . . . . . . . . . . . . . . . . . . 3-1

3.2: Mounting the Nexus P40N, P41N, P43N External Displays . . . . . . . . . . . 3-3

3.3: Mounting the Nexus P60N Touch Screen External Display . . . . . . . . . . .3-4

3.4: Mounting the Nexus External I/O Modules . . . . . . . . . . . . . . . . . . 3-6

Chapter 4: Electrical Installation

4.1: Wiring the Monitored Inputs and Voltages . . . . . . . . . . . . . . . . . . 4-1

4.2: Fusing the Voltage Connections . . . . . . . . . . . . . . . . . . . . . . .4-1

4.3: Wiring the Monitored Inputs -VRef . . . . . . . . . . . . . . . . . . . . . 4-1

4.4: Wiring the Monitored Inputs - VAux . . . . . . . . . . . . . . . . . . . . . 4-1

4.5: Wiring the Monitored Inputs - Currents . . . . . . . . . . . . . . . . . . . 4-1

4.6: Isolating a CT Connection Reversal . . . . . . . . . . . . . . . . . . . . . 4-2

4.7: Instrument Power Connections . . . . . . . . . . . . . . . . . . . . . . . 4-2

4.8: Wiring Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-3

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Chapter 5: Communication Wiring

5.1: Communication Overview . . . . . . . . . . . . . . . . . . . . . . . . .5-1

5.2: RS-232 Connection-Nexus Meter to a Computer . . . . . . . . . . . . . . .5-5

5.3: RS-485 Wiring Fundamentals (with RT Explanation) . . . . . . . . . . . . . .5-5

5.4: RS-485 Connection- Nexus Meter to a Computer or PLC . . . . . . . . . . . . 5-8

5.5: RJ-11 (Telephone Line) Connection- Nexus with Internal Modem Option to PC . . 5-8

5.6: RJ-45 Connection- Nexus with Internal Network Option to multiple PC’s . . . . . 5-8

5.7: RS-485 Connection- Nexus to an RS-485 Master (Unicom or Modem Manager) . . 5-9

5.7.1: Using the Unicom 2500 . . . . . . . . . . . . . . . . . . . . . . . . .5-9

5.8: RS-485 Connectiion- Nexus Meter to P40N, P41N, P43N External Display . . . 5-11

5.9: RS-485 Connectiion- Nexus Meter to P60N External Display . . . . . . . . . 5-12

5.10: Communication Ports on the Nexus I/O Modules . . . . . . . . . . . . . . 5-13

5.11: RS-485 Connection—Nexus Meter to Nexus I/O Modules . . . . . . . . . . 5-14

5.12: Steps to Determine Power Needed . . . . . . . . . . . . . . . . . . . . .5-15

5.13: I/O Modules’ Factory Settings and VA Ratings . . . . . . . . . . . . . . .5-15

5.14: Linking Multiple Nexus Devices in Series . . . . . . . . . . . . . . . . . 5-16

5.15: Networking Groups of Nexus Meters . . . . . . . . . . . . . . . . . . . 5-17

5.16: Remote Communication Overview . . . . . . . . . . . . . . . . . . . .5-18

5.17: Remote Communication- RS-232 . . . . . . . . . . . . . . . . . . . . . 5-21

5.18: Remote Communication- RS-485 . . . . . . . . . . . . . . . . . . . . . 5-21

5.19: Programming Modems for Remote Communication . . . . . . . . . . . . .5-22

5.20: Selected Modem Strings . . . . . . . . . . . . . . . . . . . . . . . . .5-23

5.21: High Speed Inputs Connection . . . . . . . . . . . . . . . . . . . . . . 5-23

5.22: Five Modes of Time Synchronization . . . . . . . . . . . . . . . . . . . 5-24

5.23: IRIG-B Connections . . . . . . . . . . . . . . . . . . . . . . . . . . 5-25

Chapter 6: Using the Nexus External Displays

6.1: Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

6.2: Nexus P40N, P41N, P43N LED External Display . . . . . . . . . . . . . . . 6-1

6.2.1: Connect Multiple Displays . . . . . . . . . . . . . . . . . . . . . . . . 6-2

6.2.2: Nexus P40N Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2

6.3: Dynamic Readings Mode . . . . . . . . . . . . . . . . . . . . . . . . .6-3

6.4: Navigational Map of Dynamic Readings Mode . . . . . . . . . . . . . . . . 6-5

6.5: Nexus Information Mode . . . . . . . . . . . . . . . . . . . . . . . . . .6-6

6.6: Navigational Map of Nexus Information Mode . . . . . . . . . . . . . . . .6-7

6.7: Display Features Mode . . . . . . . . . . . . . . . . . . . . . . . . . .6-8

6.8: Navigational Map of Display Features Mode . . . . . . . . . . . . . . . . .6-9

6.9: Nexus P60N Touch Screen External Display . . . . . . . . . . . . . . . . .6-10

6.10: Navigational Map for P60N Touch Screen External Display . . . . . . . . . 6-18

Chapter 7: Transformer Loss Compensation

7.1: Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

7.2: Nexus 1250/1252 Transformer Loss Compensation . . . . . . . . . . . . . . 7-3

7.2.1: Loss Compensation in Three Element Installations . . . . . . . . . . . . . . 7-4

7.2.1.1: Three Element Loss Compensation Worksheet . . . . . . . . . . . . . . .7-5

Chapter 8: Nexus Time-of-Use

8.1: Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1

8.2: The Nexus TOU Calendar . . . . . . . . . . . . . . . . . . . . . . . . . 8-1

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8.3: TOU Prior Season and Month . . . . . . . . . . . . . . . . . . . . . . . 8-2

8.4: Updating, Retrieving and Replacing TOU Calendars . . . . . . . . . . . . . . 8-2

8.5: Daylight Savings and Demand . . . . . . . . . . . . . . . . . . . . . . . 8-2

Chapter 9: Nexus External I/O Modules

9.1: Hardware Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1

9.1.1: Port Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-2

9.2: Installing Nexus External I/O Modules . . . . . . . . . . . . . . . . . . . 9-3

9.2.1: Power Source for I/O Modules . . . . . . . . . . . . . . . . . . . . . . 9-4

9.3: Using PSIO with Multiple I/O Modules . . . . . . . . . . . . . . . . . . .9-5

9.3.1: Steps for Attaching Multiple I/O Modules . . . . . . . . . . . . . . . . . 9-5

9.4: Factory Settings and Reset Button . . . . . . . . . . . . . . . . . . . . .9-6

9.5: Analog Transducer Signal Output Modules . . . . . . . . . . . . . . . . . .9-7

9.5.1: Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-7

9.5.2: Normal Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-8

9.6: Analog Input Modules . . . . . . . . . . . . . . . . . . . . . . . . . . .9-9

9.6.1: Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-9

9.6.2: Normal Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-10

9.7: Digital Dry Contact Relay Output (Form C) Module . . . . . . . . . . . . .9-11

9.7.1: Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-11

9.7.2: Communication . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-12

9.7.3: Normal Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-12

9.8: Digital Solid State Pulse Output (KYZ) Module . . . . . . . . . . . . . . . 9-13

9.8.1: Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-13

9.8.2: Communication . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-14

9.8.3: Normal Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-14

9.9: Digital Status Input Module . . . . . . . . . . . . . . . . . . . . . . . . 9-15

9.9.1: Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-15

9.9.2: Communication . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-15

9.9.3: Normal Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-16

9.10: Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-16

Chapter 10: Nexus Monitor with INP2 - Internal Modem Option

10.1: Hardware Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 10-1

10.2: Hardware Connection . . . . . . . . . . . . . . . . . . . . . . . . . . 10-2

10.3: Dial-In Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-2

10.4: Dial-Out Function . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-2

Chapter 11: Nexus Monitor with Internal Network Option

11.1: Hardware Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1

11.2: Hardware Connection . . . . . . . . . . . . . . . . . . . . . . . . . .11-3

Chapter 12: Flicker

12.1: Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-1

12.2: Theory of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 12-1

12.3: Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-3

12.4: Software - User Interface . . . . . . . . . . . . . . . . . . . . . . . .12-4

12.5: Logging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12-7

12.6: Polling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-7

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12.7: Log Viewer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-7

12.8: Performance Notes . . . . . . . . . . . . . . . . . . . . . . . . . . .12-8

Appendix A: Transformer Loss Compensation Excel Spreadsheet with Examples

A.1: Calculating Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1

A.2: Excel Spreadsheet with Example Numbers . . . . . . . . . . . . . . . . .A-1

Glossary of Terms

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Chapter 1

Three-PPhase Power Measurement

This introduction to three-phase power and power measurement is intended to provide only a brief overview of the subject. The professional meter engineer or meter technician should refer to more advanced documents such as the EEI Handbook for Electricity Metering and the application standards for more in-depth and technical coverage of the subject.

1.1: Three-PPhase System Configurations

Three-phase power is most commonly used in situations where large amounts of power will be used because it is a more effective way to transmit the power and because it provides a smoother delivery of power to the end load. There are two commonly used connections for three-phase power, a wye connection or a delta connection. Each connection has several different manifestations in actual use. When attempting to determine the type of connection in use, it is a good practice to follow the circuit back to the transformer that is serving the circuit. It is often not possible to conclusively determine the correct circuit connection simply by counting the wires in the service or checking voltages. Checking the transformer connection will provide conclusive evidence of the circuit connection and the relationships between the phase voltages and ground.

1.1.1: Wye Connection

The wye connection is so called because when you look at the phase relationships and the winding relationships between the phases it looks like a wye (Y). Figure 1.1 depicts the winding relationships for a wye-connected service. In a wye service the neutral (or center point of the wye) is typically grounded. This leads to common voltages of 208/120 and 480/277 (where the first number represents the phase-to-phase voltage and the second number represents the phase-to-ground voltage).

The three voltages are separated by 120oelectrically. Under balanced load conditions with unity power factor the currents are also separated by 120o. However, unbalanced loads and other conditions can cause the currents to depart from the ideal 120oseparation.

Phase A

Phase B

Phase C

Figure 1.1: Three-Phase Wye Winding

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Fig 1.2: Phasor Diagram Showing Three-phase Voltages and Currents

The phasor diagram shows the 120oangular separation between the phase voltages. The phase-tophase voltage in a balanced three-phase wye system is 1.732 times the phase-to-neutral voltage. The center point of the wye is tied together and is typically grounded. Table 1.1 shows the common voltages used in the United States for wye-connected systems.

Table 1.1: Common Phase Voltages on Wye Services

Usually a wye-connected service will have four wires; three wires for the phases and one for the neutral. The three-phase wires connect to the three phases (as shown in Figure 1.1). The neutral wire is typically tied to the ground or center point of the wye (refer to Figure 1.1).

In many industrial applications the facility will be fed with a four-wire wye service but only three wires will be run to individual loads. The load is then often referred to as a delta-connected load but the service to the facility is still a wye service; it contains four wires if you trace the circuit back to its source (usually a transformer). In this type of connection the phase to ground voltage will be the phase-to-ground voltage indicated in Table 1, even though a neutral or ground wire is not physically present at the load. The transformer is the best place to determine the circuit connection type because this is a location where the voltage reference to ground can be conclusively identified.

Three-phase voltages and currents are usually represented with a phasor diagram. Aphasor diagram for the typical connected voltages and currents is shown in Figure 1.2.

Phase-to-Ground Voltage Phase-to-Phase Voltage

120 volts

277 volts 2,400 volts 7,200 volts

208 volts 480 volts

4,160 volts

12,470 volts

7,620 volts 13,200 volts

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1.1.2: Delta Connection

Delta connected services may be fed with either three wires or four wires. In a three-phase delta service the load windings are connected from phase-to-phase rather than from phase-to-ground. Figure 1.3 shows the physical load connections for a delta service.

In this example of a delta service, three wires will transmit the power to the load. In a true delta service, the phase-to-ground voltage will usually not be balanced because the ground is not at the center of the delta.

Figure 1.4 shows the phasor relationships between voltage and current on a three-phase delta circuit.

In many delta services, one corner of the delta is grounded. This means the phase to ground voltage will be zero for one phase and will be full phase-to-phase voltage for the other two phases. This is done for protective purposes.

Another common delta connection is the four-wire, grounded delta used for lighting loads. In this connection the center point of one winding is grounded. On a 120/240 volt, four-wire, grounded delta service the phase-to-ground voltage would be 120 volts on two phases and 208 volts on the third phase. Figure 1.5 shows the phasor diagram for the voltages in a three-phase, four-wire delta system.

Phase A

Phase B

Phase C

Figure 1.3: Three-Phase Delta Winding Relationship

Vab

Vbc

Vca

Figure 1.4: Phasor Diagram, Three-Phase Voltages and Currents Delta Connected.

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Fig 1.5: Phasor Diagram Showing Three-phase, Four-wire Delta Connected System

1.1.3: Blondell’s Theorem and Three Phase Measurement

In 1893 an engineer and mathematician named Andre E. Blondell set forth the first scientific basis for poly phase metering. His theorem states:

If energy is supplied to any system of conductors through N wires, the total power in the system is given by the algebraic sum of the readings of N wattmeters so arranged that each of the N wires contains one current coil, the corresponding potential coil being connected between that wire and some common point. If this common point is on one of the N wires, the measurement may be made by the use of N-1 wattmeters.

The theorem may be stated more simply, in modern language:

In a system of N conductors, N-1 meter elements will measure the power or energy taken provided that all the potential coils have a common tie to the conductor in which there is no current coil.

Three-phase power measurement is accomplished by measuring the three individual phases and adding them together to obtain the total three phase value. In older analog meters, this measurement was accomplished using up to three separate elements. Each element combined the single-phase voltage and current to produce a torque on the meter disk. All three elements were arranged around the disk so that the disk was subjected to the combined torque of the three elements. As a result the disk would turn at a higher speed and register power supplied by each of the three wires.

According to Blondell's Theorem, it was possible to reduce the number of elements under certain conditions. For example, a three-phase, three-wire delta system could be correctly measured with two elements (two potential coils and two current coils) if the potential coils were connected between the three phases with one phase in common.

In a three-phase, four-wire wye system it is necessary to use three elements. Three voltage coils are

connected between the three phases and the common neutral conductor. A current coil is required in

each of the three phases.

In modern digital meters, Blondell's Theorem is still applied to obtain proper metering. The difference in modern meters is that the digital meter measures each phase voltage and current and calculates the single-phase power for each phase. The meter then sums the three phase powers to a

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single three-phase reading.

Some digital meters calculate the individual phase power values one phase at a time. This means the meter samples the voltage and current on one phase and calculates a power value. Then it samples the second phase and calculates the power for the second phase. Finally, it samples the third phase and calculates that phase power. After sampling all three phases, the meter combines the three readings to create the equivalent three-phase power value. Using mathematical averaging techniques, this method can derive a quite accurate measurement of three-phase power.

More advanced meters actually sample all three phases of voltage and current simultaneously and

calculate the individual phase and three-phase power values. The advantage of simultaneous sampling

is the reduction of error introduced due to the difference in time when the samples were taken.

Blondell's Theorem is a derivation that results from Kirchhoff's Law. Kirchhoff's Law states that the sum of the currents into a node is zero. Another way of stating the same thing is that the current into a node (connection point) must equal the current out of the node. The law can be applied to measuring three-phase loads. Figure 1.6 shows a typical connection of a three-phase load applied to a threephase, four-wire service. Krichhoff's Laws hold that the sum of currents A, B, C and N must equal zero or that the sum of currents into Node "n" must equal zero.

If we measure the currents in wires A, B and C, we then know the current in wire N by Kirchhoff's Law and it is not necessary to measure it. This fact leads us to the conclusion of Blondell's Theorem that we only need to measure the power in three of the four wires if they are connected by a common node. In the circuit of Figure 1.6 we must measure the power flow in three wires. This will require three voltage coils and three current coils (a three element meter). Similar figures and conclusions could be reached for other circuit configurations involving delta-connected loads.

Phase A

Phase B

Phase C

Figure 1.6: Three-Phase Wye Load illustrating Kirchhoff’s Law and Blondell’s Theorem

Node “n”

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1.2: Power, Energy and Demand

It is quite common to exchange power, energy and demand without differentiating between the three. Because this practice can lead to confusion, the differences between these three measurements will be discussed.

Power is an instantaneous reading. The power reading provided by a meter is the present flow of watts. Power is measured immediately just like current. In many digital meters, the power value is actually measured and calculated over a one second interval because it takes some amount of time to calculate the RMS values of voltage and current. But this time interval is kept small to preserve the instantaneous nature of power.

Energy is always based on some time increment; it is the integration of power over a defined time increment. Energy is an important value because almost all electric bills are based, in part, on the amount of energy used.

Typically, electrical energy is measured in units of kilowatt-hours (kWh). A kilowatt-hour represents a constant load of one thousand watts (one kilowatt) for one hour. Stated another way, if the power delivered (instantaneous watts) is measured as 1,000 watts and the load was served for a one hour time interval then the load would have absorbed one kilowatt-hour of energy. A different load may have a constant power requirement of 4,000 watts. If the load were served for one hour it would absorb four kWh. If the load were served for 15 minutes it would absorb ¼ of that total or one kWh.

Figure 1.7 shows a graph of power and the resulting energy that would be transmitted as a result of the illustrated power values. For this illustration, it is assumed that the power level is held constant for each minute when a measurement is taken. Each bar in the graph will represent the power load for the one-minute increment of time. In real life the power value moves almost constantly.

The data from Figure 1.7 is reproduced in Table 2 to illustrate the calculation of energy. Since the time increment of the measurement is one minute and since we specified that the load is constant over that minute, we can convert the power reading to an equivalent consumed energy reading by multiplying the power reading times 1/60 (converting the time base from minutes to hours).

Time (minutes) Æ

Kilowatts

100

Figure 1.7: Power Use Over Time

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Table 1.2: Power and Energy Relationship Over Time

As in Table 1.2, the accumulated energy for the power load profile of Figure 1.7 is 14.92 kWh.

Demand is also a time-based value. The demand is the average rate of energy use over time. The actual label for demand is kilowatt-hours/hour but this is normally reduced to kilowatts. This makes it easy to confuse demand with power. But demand is not an instantaneous value. To calculate demand it is necessary to accumulate the energy readings (as illustrated in Figure 1.7) and adjust the energy reading to an hourly value that constitutes the demand.

In the example, the accumulated energy is 14.92 kWh. But this measurement was made over a 15-minute interval. To convert the reading to a demand value, it must be normalized to a 60-minute interval. If the pattern were repeated for an additional three 15-minute intervals the total energy would be four times the measured value or 59.68 kWh. The same process is applied to calculate the 15-minute demand value. The demand value associated with the example load is 59.68 kWh/hr or

59.68 kWd. Note that the peak instantaneous value of power is 80 kW, significantly more than the demand value.

Time Interval

(Minute)

Power (kW) Energy (kWh)

Accumulated

Energy (kWh)

1 30 0.50 0.50 2 50 0.83 1.33 3 40 0.67 2.00 4 55 0.92 2.92 5 60 1.00 3.92 6 60 1.00 4.92 7 70 1.17 6.09 8 70 1.17 7.26

9 60 1.00 8.26 10 70 1.17 9.43 11 80 1.33 10.76 12 50 0.83 12.42 13 50 0.83 12.42 14 70 1.17 13.59 15 80 1.33 14.92

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Figure 1.8 shows another example of energy and demand. In this case, each bar represents the energy consumed in a 15-minute interval. The energy use in each interval typically falls between 50 and 70 kWh. However, during two intervals the energy rises sharply and peaks at 100 kWh in interval number 7. This peak of usage will result in setting a high demand reading. For each interval shown the demand value would be four times the indicated energy reading. So interval 1 would have an associated demand of 240 kWh/hr. Interval 7 will have a demand value of 400 kWh/hr. In the data shown, this is the peak demand value and would be the number that would set the demand charge on the utility bill.

As can be seen from this example, it is important to recognize the relationships between power, energy and demand in order to control loads effectively or to monitor use correctly.

1.3: Reactive Energy and Power Factor

The real power and energy measurements discussed in the previous section relate to the quantities that are most used in electrical systems. But it is often not sufficient to only measure real power and energy. Reactive power is a critical component of the total power picture because almost all real-life applications have an impact on reactive power. Reactive power and power factor concepts relate to both load and generation applications. However, this discussion will be limited to analysis of reactive power and power factor as they relate to loads. To simplify the discussion, generation will not be considered.

Real power (and energy) is the component of power that is the combination of the voltage and the value of corresponding current that is directly in phase with the voltage. However, in actual practice the total current is almost never in phase with the voltage. Since the current is not in phase with the voltage, it is necessary to consider both the inphase component and the component that is at quadrature (angularly rotated 90

or perpendicular) to the voltage. Figure 1.9 shows a single-phase

voltage and current and breaks the current into its in-phase and quadrature components.

Intervals Æ

Kilowatt-hours

100

Figure 1.8: Energy Use and Demand

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The voltage (V) and the total current (I) can be combined to calculate the apparent power or VA. The voltage and the in-phase current (IR) are combined to produce the real power or watts. The voltage and the quadrature current (IX) are combined to calculate the reactive power.

The quadrature current may be lagging the voltage (as shown in Figure 1.9) or it may lead the voltage. When the quadrature current lags the voltage the load is requiring both real power (watts) and reactive power (VARs). When the quadrature current leads the voltage the load is requiring real power (watts) but is delivering reactive power (VARs) back into the system; that is VARs are flowing in the opposite direction of the real power flow.

Reactive power (VARs) is required in all power systems. Any equipment that uses magnetization to operate requires VARs. Usually the magnitude of VARs is relatively low compared to the real power quantities. Utilities have an interest in maintaining VAR requirements at the customer to a low value in order to maximize the return on plant invested to deliver energy. When lines are carrying VARs, they cannot carry as many watts. So keeping the VAR content low allows a line to carry its full capacity of watts. In order to encourage customers to keep VAR requirements low, most utilities impose a penalty if the VAR content of the load rises above a specified value.

A common method of measuring reactive power requirements is power factor. Power factor can be defined in two different ways. The more common method of calculating power factor is the ratio of the real power to the apparent power. This relationship is expressed in the following formula:

Total PF = real power / apparent power = watts/VA

This formula calculates a power factor quantity known as Total Power Factor. It is called Total PF because it is based on the ratios of the power delivered. The delivered power quantities will include the impacts of any existing harmonic content. If the voltage or current includes high levels of harmonic distortion the power values will be affected. By calculating power factor from the power values, the power factor will include the impact of harmonic distortion. In many cases this is the preferred method of calculation because the entire impact of the actual voltage and current are included.

A second type of power factor is Displacement Power Factor. Displacement PF is based on the angular relationship between the voltage and current. Displacement power factor does not consider the magnitudes of voltage, current or power. It is solely based on the phase angle differences. As a

I I

Figure 1.9: Voltage and Complex

Angle θ

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result, it does not include the impact of harmonic distortion. Displacement power factor is calculated using the following equation:

Displacement PF = cos θ, where θ is the angle between the voltage and the current (see Fig. 1.9).

In applications where the voltage and current are not distorted, the Total Power Factor will equal the Displacement Power Factor. But if harmonic distortion is present, the two power factors will not be equal.

1.4: Harmonic Distortion

Harmonic distortion is primarily the result of high concentrations of non-linear loads. Devices such as computer power supplies, variable speed drives and fluorescent light ballasts make current demands that do not match the sinusoidal waveform of AC electricity. As a result, the current waveform feeding these loads is periodic but not sinusoidal. Figure 1.10 shows a normal, sinusoidal current waveform. This example has no distortion.

Figure 1.10: Nondistorted Current Waveform

Figure 1.11 shows a current waveform with a slight amount of harmonic distortion. The waveform is still periodic and is fluctuating at the normal 60 Hz frequency. However, the waveform is not a smooth sinusoidal form as seen in Figure 1.10.

A Phase Current

-1500

-1000

-500

500

1000

1500

13365

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Figure 1.11: Distorted Current Wave

The distortion observed in Figure 1.11 can be modeled as the sum of several sinusoidal waveforms of frequencies that are multiples of the fundamental 60 Hz frequency. This modeling is performed by mathematically disassembling the distorted waveform into a collection of higher frequency waveforms. These higher frequency waveforms are referred to as harmonics. Figure 1.12 shows the content of the harmonic frequencies that make up the distortion portion of the waveform in Figure

1.11.

Figure 1.12: Waveforms of the Harmonics

The waveforms shown in Figure 1.12 are not smoothed but do provide an indication of the impact of combining multiple harmonic frequencies together.

When harmonics are present it is important to remember that these quantities are operating at higher frequencies. Therefore, they do not always respond in the same manner as 60 Hz values.

Total A Phase Current with Harmonics

-1500

-1000

-500

500

1000

1500

13365

Expanded Harmonic Currents

-250

-200

-150

-100

-50

100

150

200

250

Amps

2 Harmonic Current

3 Harmonic Current 5 Harmonic Current

7 Harmonic Current A Cu rr ent Total Hrm

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Inductive and capacitive impedance are present in all power systems. We are accustomed to thinking about these impedances as they perform at 60 Hz. However, these impedances are subject to frequency variation.

= jωL and

= 1/jωC

At 60 Hz, ω = 377; but at 300 Hz (5

harmonic) ω = 1,885. As frequency changes impedance changes and system impedance characteristics that are normal at 60 Hz may behave entirely different in presence of higher order harmonic waveforms.

Traditionally, the most common harmonics have been the low order, odd frequencies, such as the 3

, 5th, 7th, and 9th. However newer, new-linear loads are introducing significant quantities of

higher order harmonics.

Since much voltage monitoring and almost all current monitoring is performed using instrument transformers, the higher order harmonics are often not visible. Instrument transformers are designed to pass 60 Hz quantities with high accuracy. These devices, when designed for accuracy at low frequency, do not pass high frequencies with high accuracy; at frequencies above about 1200 Hz they pass almost no information. So when instrument transformers are used, they effectively filter out higher frequency harmonic distortion making it impossible to see.

However, when monitors can be connected directly to the measured circuit (such as direct connection to 480 volt bus) the user may often see higher order harmonic distortion. An important rule in any harmonics study is to evaluate the type of equipment and connections before drawing a conclusion. Not being able to see harmonic distortion is not the same as not having harmonic distortion.

It is common in advanced meters to perform a function commonly referred to as waveform capture. Waveform capture is the ability of a meter to capture a present picture of the voltage or current waveform for viewing and harmonic analysis. Typically a waveform capture will be one or two cycles in duration and can be viewed as the actual waveform, as a spectral view of the harmonic content, or a tabular view showing the magnitude and phase shift of each harmonic value. Data collected with waveform capture is typically not saved to memory. Waveform capture is a real-time data collection event.

Waveform capture should not be confused with waveform recording that is used to record multiple cycles of all voltage and current waveforms in response to a transient condition.

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1.5: Power Quality

Power quality can mean several different things. The terms "power quality" and "power quality problem" have been applied to all types of conditions. Asimple definition of "power quality problem" is any voltage, current or frequency deviation that results in mis-operation or failure of customer equipment or systems. The causes of power quality problems vary widely and may originate in the customer equipment, in an adjacent customer facility or with the utility.

In his book Power Quality Primer, Barry Kennedy provided information on different types of power quality problems. Some of that information is summarized in Table 1.3 below.

Table 1.3: Typical Power Quality Problems and Sources

It is often assumed that power quality problems originate with the utility. While it is true that may power quality problems can originate with the utility system, many problems originate with customer equipment. Customer-caused problems may manifest themselves inside the customer location or they may be transported by the utility system to another adjacent customer. Often, equipment that is sensitive to power quality problems may in fact also be the cause of the problem.

If a power quality problem is suspected, it is generally wise to consult a power quality professional for assistance in defining the cause and possible solutions to the problem.

Cause Disturbance Type Source

Impulse Transient

Transient voltage disturbance, sub-cycle duration

Oscillatory transient with decay

Lightning Electrostatic discharge Load switching Capacitor switching

Sag / swell

Interruptions

Undervoltage / Overvoltage

Voltage flicker

Harmonic distortion

Transient voltage, sub-cycle duration

RMS voltage, multiple cycle duration

RMS voltage, multiple second or longer duration

RMS voltage, steady state, multiple second or longer duration

RMS voltage, steady state, repetitive condition

Steady state current or voltage, long term duration

Line/cable switching Capacitor switching Load switching

Remote system faults System protection

Circuit breakers Fuses Maintenance

Motor starting Load variations Load dropping

Intermittent loads Motor starting Arc furnaces

Non-linear loads System resonance

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Chapter 2

Nexus Overview

2.1: The Nexus System

Electro Industries’ Nexus 1250/1252 combines high-end revenue metering with sophisticated power quality analysis. Its advanced monitoring capabilities provide detailed and precise pictures of any metered point within a distribution network. The P60N, P40N, P41N and P43N displays are detailed in Chapter 6. Extensive I/O capability is available in conjunction with all metering functions. The optional Communicator EXT software allows a user to poll and gather data from multiple Nexus meters installed at local or remote locations (see the Communicator EXT User Manual for details). On board mass memory enables the Nexus to retrieve and store multiple logs. The Nexus Meter with Internal Modem (or Network) Option connects to a PC via standard phone line (or MODBUS/TCP) and a daisy chain of Nexus Meters via an RS-485 connection. See Chapters 10 and 11 for details.

Figure 2.1: The Nexus 1250/1252 System

Computer

or SCADA

System

Nexus

Display

Expandable I/O Modules

Nexus Meter

Modem/Ethernet

Option

Modem Gateway or

Ethernet Gateway

RS-485 Connection

Modem/Ethernet

Option

RJ-11 or RJ-45

Connection

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Nexus 1250/1252 Revenue Metering:

• Delivers laboratory-grade 0.04% Watt-hour accuracy in a field-mounted device.

• Autocalibrates when there is a temperature change of more than 10 degrees centigrade.

• Exceeds all ANSI C-12 and IEC 687 specifications.

• Adjusts for transformer and line losses, using user-defined compensation factors.

• Automatically logs time-of-use for up to eight programmable tariff registers.

• Counts pulses and aggregates different loads.

Nexus 1250/1252 Power Quality Monitoring:

• Records up to 512 samples per cycle on an event.

• Records sub-cycle transients on voltage or current readings.

• Measures and records Harmonics to the 83rd order.

• Offers inputs for neutral-to-ground voltage measurements.

• Synchronizes with IRIG-B clock signal.

Nexus 1250/1252 Memory, Communication and Control:

• Up to 4 Meg NVRAM.

• 4 High Speed Communication Ports.

• Multiple Protocols (see section below on DNP V3.00).

• Built-in RTU functionality.

• Built-in PLC functionality.

• 90msec High Speed Updates for Control.

2.2: DNP V3.00 Level 1 and Level 2

Nexus 1250 supports DNP V3.00 Level 1. Nexus 1252 supports DNP V3.00 Level 2.

DNP Level 2 Features:

• Up to 136 measurement (64 Binary Inputs, 8 Binary Counters, 64 Analog Inputs) can be mapped to DNP Static Points (over 3000) in the customizable DNP Point Map.

• Up to 16 Relays and 8 Resets can be controlled through DNP Level 2.

• Report-by-Exception Processing (DNP Events) Deadbands can be set on a per-point basis.

• Freeze Commands: Freeze, Freeze/No-Ack, Freeze with Time, Freeze with Time/No-Ack.

• Freeze with Time Commands enable the Nexus meter to have internal time-driven Frozen and

Frozen Event data. When the Nexus meter receives the Time and Interval, the data will be created.

For complete details, download the appropriate DNP User Manual from our website www.electroind.com.

2.3: Flicker

Nexus 1252 provides Flicker Evaluation in Instantaneous, Short Term and Long Term Forms. For a detailed explanation of Flicker, see Chapter 12 of this manual.

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2.4: INP2 Internal Modem with Dial-IIn/Dial-OOut Option

2.4.1: Hardware Overview

The INP2 Option for the Nexus 1250/1252 meter provides a direct connection to a standard telephone line. No additional hardware is required to establish a communication connection between the meter and a remote computer. The RJ-11 Jack is on the face of the meter. A standard telephone RJ11 plug can connect the meter to a standard PSTN (Public Switched Telephone Network).

The modem operates at up to 56k baud. The modem supports both incoming calls (from a remote computer) and automatic dial-out calls when a defined event must be automatically reported.

With the device configured with the INP2 Option, the meter has dial-in capability and provides remote access to other Modbus-based serial devices via the meter’s RS-485 Gateway over your phone line. The meter will recognize and respond to a Modbus Address of 1. With any other address, the command will pass through the gateway and become a virtual connection between the Remote Modbus Master and any Modbus Slave connected to the RS-485 Gateway.

2.4.2: Dial-IIn Function

The modem continuously monitors the telephone line to detect an incoming call. When an incoming call is detected, the modem will wait a user-set number of rings and answer the call.

The modem can be programmed to check for a password on an incoming call. If the correct password is not provided the modem will hang up on the incoming call. If several unsuccessful incoming call attempts are received in a set time period, the modem will lock out future incoming calls for a user-set number of hours.

When an incoming call is successfully connected, the control of communications is passed to the calling software program. The modem will respond to computer commands to download data or other actions authorized by the meter passwords.

Refer to the Communicator EXT Software Manual for instructions on programming the modem.

2.4.3: Dial-OOut Function

The Dial-Out Function (INP2) is intended to allow the meter to automatically report certain conditions without user intervention. The modem is normally polling the meter to determine if any abnormal or reportable conditions exist. The modem checks programmed meter conditions and programmed events (set in Nexus Communicator) to determine if a call should be placed.

If any of the monitored events exist, the modem will automatically initiate a call to a specified location to make a report or perform some other function. For log full conditions, the meter will automatically download the log(s) that are nearing the full state.

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2.5: Total Web Solutions

The 10/100BaseT Ethernet Option (INP 100) is a fully customizable web server that uses XML to provide access to real time data via Internet Explorer. EIG’s name for this dynamic system is Total Web Solutions. The system incorporates a highly programmable network card with built-in memory that is installed in the 100BaseT Option meters. Each card can be programmed to perform an extensive array of monitoring functions and the system is much faster than the 10BaseT Ethernet Option.

NOTE: Nexus meters with the INP10 Option do not support Total Web Solutions.

2.5.1: Hardware Overview

The Nexus 1250/1252 with the 10/100BaseT Ethernet Option (INP 100) has all the components of the standard Nexus 1250/1252 PLUS the capability of connection to a network through an Ethernet LAN or through the Internet via Modbus TCP, HTTP, SMTP, FTP and/or DHCP.

The Internal Network Option of the Nexus Meter is an extremely versatile communication tool.

• Adheres to IEEE 802.3 Ethernet standard using TCP/IP.

• Utilizes simple and inexpensive 100BaseT wiring and connections.

• Plugs right into your network using built-in RJ-45 jack.

• Programmable to any IP address, subnet mask and gateway requirements.

• Communicates using the industry standard Modbus/TCP protocol.

2.5.2: Hardware Connection

Use Standard RJ-45 10/100BaseT cable to connect with the Nexus. The RJ-45 line is inserted into the RJ-45 Port on the face of the Nexus with IMP100 Ethernet Option.

To make the software connection, use the following steps.

1. Using Port 1 or Port 4 (RS-485 connection), connect a PC to the meter. An RS-232/RS-485 Converter may be required (Example: Electro Industries Unicom 2500).

2. Double click on Communicator EXT Software to open.

3. Click the Quick Connect or the Connection Manager icon in the icon tool bar. Click the Serial Port button. Make sure data matches the meter then click Connect.

Set the Network Settings using the following steps: (Refer to Section 3.6 of the Communicator EXT User Manual for more details).

1. From the Device Profile screen, double-click on the Communications Ports line, then double-click on any of the ports. The Device Profile Communications Settings screen appears.

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2. If you are going to use DHCP, click the Advanced Settings Button:

Click the tab at the top of the DHCP screen. Click Enable. DHCP will automatically enter the IP Address and some or all of the Interface Settings. Click OK at the bottom of the screen to return to the Device Profile: Communication Ports screen. You may have to manually enter DNS, Email, Gateway Setting and/or a Unique Computer Name. Click OK.

3. If you are NOT using DHCP, in the Network Settings section, enter data provided by your

systems manager:

IP Address: 10.0.0.1 (Example) Subnet Mask: 255.255.255.0 (Example) Default Gateway: 0.0.0.0 (Example) Computer Name: NETWORK (Example)

Enter the Domain Name Server and Computer Name.

Customize Web Content, if desired. Default Pages with an extensive array of readings comes with the meter. The content of the pages can be customized using FTP Client.

From the Device Profile: Communications Ports screen, click Advanced Settings. Click the FTP Client tab on the top of the folder. Using FTP, you can easily replace any file by using the SAME FILE NAME as the one you want to replace.

Enter the Email Server IPAddress. The Default Settings store ONE Email Server IP Address for administrative purposes or to send an alarm, if there is a problem. An ADDITIONAL 8 can be configured with FTP Client.

Update FIRMWARE, if needed, with TFTP protocol (see Appendix C).

After the above parameters are set, Communicator EXT will connect via the network using a Device Address of “1” and the assigned IPAddress using the following steps:

1. Double click on Communicator EXT icon to open.

2. Click the Connect icon in the icon tool bar. The Connect screen will appear.

3. Click the Network button at the top of the screen. The screen will change to one requesting the following information:

Device Address: 1 Host: IP Address (per your network administrator).

Example: 10.0.0.1 Network Port: 502 Protocol: Modbus TCP

4. Click the Connect button at the bottom of the screen. Communicator EXT connects to the Nexus with the Host IPAddress via the Network.

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2.6: Measurements and Calculations

The Nexus 1250/1252 Meter measures many different power parameters. The following is a list of the formulas used to conduct calculations with samples for Wye and Delta services.

Samples for Wye: van, vbn, vcn, ia, ib, ic, i

Samples for Delta: vab, vbc, vca, ia, ib, i

Root Mean Square (RMS) of Phase to Neutral Voltages: n = number of samples

For Wye: x = an, bn, cn

Root Mean Square (RMS) of Currents: n = number of samples

For Wye: x=a, b, c, n For Delta: x = a, b, c

Root Mean Square (RMS) of Phase to Phase Voltages: n = number of samples

For Wye: x, y= an, bn or bn, cn or cn, an

For Delta: xy = ab, bc, ca

RMS

∑

==1

)(

RMS

∑

==1

)(

tytx

RMS

∑

−

)()(

)(

txy

RMS

∑

==1

)(

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Power (Watts) per phase:

For Wye: x = a, b, c

Apparent Power (VA) per phase:

For Wye: x = a, b, c

Reactive Power (VAR) per phase:

For Wye: x = a, b, c

Power (Watts) Total:

For Wye:

For Delta:

cbaT

WWWW

++=

iviv

CBCAAB

tttt

∑

•−•

)(

)()()()(

txtxn

∑

•

)()(

XXN

RMSRMSx

IVVA

•=

xxx

WattVAVAR

−=

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Reactive Power (VAR) Total:

For Wye:

For Delta:

Apparent Power (VA) Total:

For Wye:

For Delta:

Power Factor (PF):

For Wye: x = A, B, C, T For Delta: x = T

CBAT

VAVAVAVA ++=

TTT

VARWVA

Watt

CBAT

VARVARVARVAR ++=

)()(

)(

⎥

⎦

⎤

⎢

⎣

⎡

•

−•

∑

IVVAR

tAtAB

RMSRMST

AAB

)()(

)(

⎥

⎦

⎤

⎢

⎣

⎡

•

−•

∑

tCtBC

RMSRMS

CBC

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Phase Angles:

% Total Harmonic Distortion (%THD):

For Wye: x = VAN, VBN, VCN, IA, IB, I

For Delta: x = IA, IB, IC, VAB, VBC, V

K Factor: x = IA, IB, I

Watt hour (Wh):

VAR hour (VARh):

)(cos1PF

−

=∠

127

)(

RMS

THD

∑

•

127

)(

RMS

RMSh

KFactor

∑

sec/

)(

3600

∑

VAR

VARh

sec/

)(

3600

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2.7: Demand Integrators

Power utilities take into account both energy consumption and peak demand when billing customers. Peak demand, expressed in kilowatts (kW), is the highest level of demand recorded during a set period of time, called the interval. The Nexus 1250/1252 supports the following most popular conventions for averaging demand and peak demand: Thermal Demand, Block Window Demand, Rolling Window Demand and Predictive Window Demand. You may program and access all conventions concurrently with the Communicator EXT software (see the Communicator EXT User Manual).

Thermal Demand: Traditional analog watt-hour (Wh) meters use heat-sensitive elements to measure temperature rises produced by an increase in current flowing through the meter. A pointer moves in proportion to the temperature change, providing a record of demand. The pointer remains at peak level until a subsequent increase in demand moves it again, or until it is manually reset. The Nexus 1250/1252 mimics traditional meters to provide Thermal Demand readings.

Each second, as a new power level is computed, a recurrence relation formula is applied. This formula recomputes the thermal demand by averaging a small portion of the new power value with a large portion of the previous thermal demand value. The proportioning of new to previous is programmable, set by an averaging interval. The averaging interval represents a 90% change in thermal demand to a step change in power.

Block (Fixed) Window Demand: This convention records the average (arithmetic mean) demand for consecutive time intervals (usually 15 minutes).

Example: A typical setting of 15 minutes produces an average value every 15 minutes (at 12:00, 12:15. 12:30. etc.) for power reading over the previous fifteen minute interval (11:45-12:00, 12:0012:15, 12:15-12:30, etc.).

Rolling (Sliding) Window Demand: Rolling Window Demand functions like multiple overlapping Block Window Demands. The programmable settings provided are the number and length of demand subintervals. At every subinterval, an average (arithmetic mean) of power readings over the subinterval is internally calculated. This new subinterval average is then averaged (arithmetic mean), with as many previous subinterval averages as programmed, to produce the Rolling Window Demand.

Example: With settings of 3 five-minute subintervals, subinterval averages are computed every 5 minutes (12:00, 12:05, 12:15, etc.) for power readings over the previous five-minute interval (11:5512:00, 12:00-12:05, 12:05-12:10, 12:10-12:15, etc.). Further, every 5 minutes, the subinterval averages are averaged in groups of 3 (12:00. 12:05, 12:10, 12:15. etc.) to produce a fifteen (5x3) minute average every 5 minutes (rolling (sliding) every 5 minutes) (11:55-12:10, 12:00-12:15, etc.).

Predictive Window Demand: Predictive Window Demand enables the user to forecast average demand for future time intervals. The Nexus uses the delta rate of change of a Rolling Window Demand interval to predict average demand for an approaching time period. The user can set a relay or alarm to signal when the Predictive Window reaches a specific level, thereby avoiding unacceptable demand levels. The Nexus 1250/1252 calculates Predictive Window Demand using the following formula:

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Example: Using the previous settings of 3 five-minute intervals and a new setting of 120% prediction factor, the working of the Predictive Window Demand could be described as follows: At 12:10, we have the average of the subintervals from 11:55-12:00, 12:00-12:05 and 12:05-12:10. In five minutes (12:15), we will have an average of the subintervals 12:00-12:05 and 12:05-12:10 (which we know) and 12:10-12:15 (which we do not yet know). As a guess , we will use the last subinterval (12:05-12:10) as an approximation for the next subinterval (12:10-12:15). As a further refinement, we will assume that the next subinterval might have a higher average (120%) than the last subinterval. As we progress into the subinterval, (for example, up to 12:11), the Predictive Window Demand will be the average of the first two subintervals (12:00-12:05, 12:05-12:10), the actual values of the current subinterval (12:10-12:11) and the predistion for the remainder of the subinterval, 4/5 of the 120% of the 12:05-12:10 subinterval.

# of Subintervals = n Subinterval Length = Len Partial Subinterval Length = Cnt Prediction Factor = Pct

Sub

...

Sub

Partial Predict

Len Len Len Cnt Len

Len

Value

Sub

Len

∑

−

Cnt

Value

Partial

Cnt

∑

−

⎥ ⎦

⎤

⎢ ⎣

⎡

⎥ ⎦

⎤

⎢ ⎣

⎡

⎥ ⎦

⎤

⎢ ⎣

⎡

−

−×

⎥

⎦

⎤

⎢

⎣

⎡

∑

−

Pct

Len

CntLen

Value

Partial

⎥ ⎦

⎤

⎢ ⎣

⎡

⎥ ⎦

⎤

⎢ ⎣

⎡

−

⎥

⎦

⎤

⎢

⎣

⎡

−

∑

Pct

Len

CntLen

SubSub

Sub

)1(21

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2.8: Nexus External I/O Modules (Optional)

The following multiple analog or digital I/O modules mount externally to the Nexus 1250/1252 Monitor. The Nexus 1250/1252 Monitor supports up to four I/O modules using internal power. Use the additional power supply, EIG PSIO, to extend I/O capability. See section 3.4 for mounting diagrams. See Chapter 9 for details on installation and usage of the Nexus External I/O Modules.

Analog Transducer Signal Outputs (Up to two modules can be used with the Nexus 1250/1252.)

• 1mAON4: 4 Analog Outputs, self powered, scalable, bidirectional.

• 1mAON8: 8 Analog Outputs, self powered, scalable, bidirectional.

• 20mAON4: 4 Analog Outputs, self powered, scalable.

• 20mAON8: 8 Analog Outputs, self powered, scalable.

Analog Transducer Inputs (Multiple modules can be used.)

• 8AI1: 8 Analog Inputs 0–1mA, scalable and bidirectional.

• 8AI2: 8 Analog Inputs 0–20mA, scalable.

• 8AI3: 8 Analog Inputs 0–5V DC.

• 8AI4: 8 Analog Inputs 0–10V DC.

Digital Dry Contact Relay Outputs (Multiple modules can be used.)

• 4RO1: 4 Relay Outputs 10 Amps, 125VAC, 30V DC, Form C.

Digital Solid State Pulse Outputs (Multiple modules can be used.)

• 4PO1: 4 Solid State Pulse Outputs, Form A KYZ pulses.

Digital Inputs (Multiple modules can be used.)

• 8DI1: 8 Digital status inputs Wet/Dry Auto Detect, up to 300V AC/DC.

Other I/O Accessories

• PSIO: Additional power supply for up to six I/O modules. This unit is necessary if you are connecting more than four I/O modules to a Nexus 1250/1252 Monitor.

• MBIO: Bracket for surface-mounting I/O modules to any enclosure.

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2.9: Nexus 1250/1252 Meter Specifications

Specification Nexus Meter

Control Power Requirements

Option D: 24V DC (-20%) – 48V DC (+20%) Option D2: 120V AC/DC (-20%) – 230V AC (+20%)

Input Voltage Range

150 Volts Phase to Neutral (Standard; for use with PTs) 300 Volts Phase to Neutral (Option -G)

Input Current Range 10A Maximum (Programmable to any CT Ratio)

Surge Withstanding Per IEEE C37.90.1

Burden

Voltage: 0.05VA @ 120V rms Current: 0.002VA @ 5A rms

I/O Isolation 2500V DC, 60 Hz

Sensing Method RMS

Update Time 90 msec

Frequency Range

Fundamental 20–65 Hz Up to 83rd Harmonic Measuring Capability

Dimensions (HxWxL) 3.4 x 7.3 x 10.5 inches / 8.6 x 18.5 x 26.6 centimeters

Maximum Power Consumption 40 watts (with optional modules and display)

Nominal Power Consumption Approximately 12 watts (without optional modules and display)

Operating Temperature -40°C to +80°C / -40°F to +176°F

Auxiliary Output Power Voltage 15–20 V DC at 50–200mA

Maximum Auxiliary Power Current 1.6A (short protected)

Current: Continuous 200% Rated Current: Surge 10x maximum input for 3 secondsInput Withstanding Capabilities

UL Listing

1244*

*Not evaluated for accuracy, reliability or capability to perform intended function.

Flicker (1252) Evaluation per IEC 61000-4-15

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2.10: Nexus P40N, P41N, P43N LED External Display Specifications

Specification Nexus P40N, P41N, P43N LED External Display

Maximum Input Voltage 30V DC Minimum Input Voltage 7V DC

Maximum Power Consumption 8 Watts

Nominal Power Consumption Approximately 6 Watts Operating Temperature Range -40°C to + 80°C / -40°F to +176°F

Overall Dimensions (HxWxL) 2.2 x 4.4 x 4.4 in / 5.9 x 11.1 x 11.1 cm

2.11: Nexus P60N Touch Screen Display Specifications

Specification Nexus P60N Touch Screen Display

Maximum Input Voltage 30V DC

Minimum Input Voltage 10V DC

Maximum Power Consumption 5 Watts

Nominal Power Consumption Approximately 4.5 Watts

Operating Temperature Range 0°C to + 50°C / +32°F to +122°F

Overall Dimensions (HxWxL) 1.6 x 5.4 x 8.0 in / 4.0 x 13.7 x 20.3 cm

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Chapter 3

Hardware Installation

3.1: Mounting the Nexus 1250/1252 Meter

The Nexus 1250/1252 Meter is designed to mount against any firm, flat surface. Use a #10 screw in each of the four slots on the flange to ensure that the unit is installed securely. For safety reasons, mount the Meter in an enclosed and protected environment, such as in a switchgear cabinet. Install a switch or circuit breaker nearby; label it clearly as the meter’s disconnecting mechanism. NOTE: The Nexus Meter with Internal Modem Option mounts the same way.

Maintain the following conditions:

• Operating Temperature: -40°C to +70°C / -40°F to +158°F

• Storage Temperature: -45°C to +85°C / -49°F to +185°F

• Relative Humidity: 5 to 95% non-condensing

Figure 3.1: Nexus Meter Mounting Diagram, Top View

4 x 0.221” (5.61mm) Thru Slot (For #10 Screw)

2 x 3.25” (8.25cm)

2x4.0” (10.16cm)

10.5” (26.67cm)

7.25”

(18.41cm)

6.74”

(17.11cm)

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Figure 3.2

2.35” (5.96cm)

3.40” (8.63cm) (MAX)

Nexus Meter Mounting Diagram, Side View

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3.2: Mounting the Nexus LED External Displays

The Nexus 1250/1252 LED Displays, Model # P40N, P41N and P43N, mount using a standard ANSI C39.1 drill plan.

Secure the four mounting studs to the back of the panel with the supplied nuts.

Six feet of RS-485 communication/power cable harness is supplied. Allow for at least a 1.25-inch (3.17cm) diameter hole in the back for the cable harness. See Chapter 5 for communication and power supply details.

The cable harness brings power to the display from the Nexus 1250/1252 Meter, which supplies 15–20V DC. The P40N (or P41N or P43N) can draw up to 500 mA in display test mode.

Figure 3.3: Nexus P40N LED External Display Mounting Diagrams

Nexus P40N Display, Front View

Nexus P40N Display, Side View

3.38” (8.58cm) Sq.

1.687” (14.28cm)

4 X 0.198” (5.02mm)

4.00” (10.16cm)

4.38”Sq. (11.12cm)

1.438”

(3.65cm)

.75” (19.05mm)

ANSI C39.1 Drill Plan

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3.3: Mounting the Nexus P60N Touch Screen External Display

The Nexus 1250/1252 P60N Touch Screen Display mounts easily, using the diagrams above and on the next page. Abezel and a gasket are included with the P60N. Since the P60N employs an LCD display, the viewing angle must be considered when mounting. Install the P60N at a height and angle that make it easy for the operator to see and access the screen.

For optimum performance, maintain the following conditions where the Touch Screen Display is mounted:

• Operating Temperature: 0°C to

+50°C / +32°F to +122°F

• Storage Temperature: -20°C to

+70°C / -36°F to +158°F

• Relative Humidity: 25 to 65%

non-condensing

Figure 3.4: Nexus P60N Touch Screen Display Mounting Diagram

Figure 3.5: Nexus P60N Back Detail

Connect to NEXUS

Factory Test Connector

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Figure 3.6: Cutout for Nexus P60N Touch Screen Display

To bezel mount the P60N, cut an opening in the mounting panel. Follow above cutout dimensions.

Carefully “drop in” the P60N with bezel and gasket attached.

Fasten the unit securely with the four 6-32 hex nuts supplied.

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3.4: Mounting the Nexus External I/O Modules

Secure the mounting brackets to the I/O using the screws supplied (#440 pan-head screws). Next, secure the brackets to a flat surface using a #8 screw with a lock washer.

If multiple I/O modules are connected together, as shown in Figure 3.4, secure a mounting bracket to both ends of the group. One Nexus will supply power for up to four I/O modules. To connect more than four I/O modules, use an additional power supply, such as the EIG PSIO. Connect multiple I/O modules using the RS-485 side ports.

Six feet of RS-485 cable harness is supplied. The cable harness brings power to the display from the Nexus Meter, which supplies 15–20V DC at 50–200mA. See Chapter 5 for power supply and communication details.

Figure 3.7: Nexus I/O Modules Mounting Diagram, Overhead View

Mounting Bracket

Figure 3.8: Nexus I/O Module Communication Ports

Female RS-485 Side Port

I/O Port

Mounting Brackets (MBIO)

0.015” (.38mm)

1.125” (2.85cm) 2 x .625” (1.58cm)

4.215” (10.70cm)

Male RS-485 Side Port

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Figure 3.9

Mounting Bracket (MBIO)

0.605” (1.53cm)

2x1.10” (2.79cm)

1.235” (3.13cm)

1.25” (3.17cm)+Y Per Module

3.41” (8.66cm)

2.20” (5.58cm)

Nexus I/O Modules Mounting Diagram, Front View

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Chapter 4

Electrical Installation

4.1: Wiring the Monitored Inputs and Voltages

Select a wiring diagram from Section 4.8 that best suits your application. Wire the Nexus 1250/1252 exactly as shown. For proper operation, the voltage connection must be maintained and must correspond to the correct terminal. Program the CT and PT Ratios in the Device Profile section of the Communicator EXT software; see the Communicator EXT User Manual for details.

The cable required to terminate the voltage sense circuit should have an insulation rating greater than 600V AC and a current rating greater than 0.1 Amp.

Use a minimum of 14 AWG wire for all phase voltage and current connections.

4.2: Fusing the Voltage Connections

For accuracy of the readings and for protection, EIG requires using 0.25-Amp rated fuses on all voltage inputs as shown in the wiring diagrams (see section 4.8).

The Nexus Meter can handle a maximum voltage of 150V phase to neutral and 300V phase to phase. Potential Transformers (PTs) are required for higher voltages with the standard rating. With Option G, the direct voltage input is extended to 300V phase to neutral and 600V phase to phase.

4.3: Wiring the Monitored Inputs - VRef

The Voltage Reference connection references the monitor to ground or neutral.

4.4: Wiring the Monitored Inputs - VAux

The Voltage Auxiliary connection is an auxiliary voltage input that can be used for any desired purpose, such as monitoring neutral to ground voltage or monitoring two different lines on a switch.

4.5: Wiring the Monitored Inputs - Currents

Install the cables for the current at 600V AC minimum insulation. The cable connector should be rated at 10 Amps or greater and have a cross-sectional area of 14 AWG.

Mount the current transformers (CTs) as close as possible to the meter. The following table illustrates the maximum recommended distances for various CT sizes, assuming the connection is via 14 A WG cable.

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It is important to maintain the polarity of the CT circuit when connecting to the Nexus. If the polarity is reversed, the Nexus will not provide accurate readings. CT polarities are dependent upon correct connection of CT leads and the direction CTs are facing when clamped around the conductors. EIG recommends using shorting blocks to allow removal of the Nexus Meter from an

energized circuit, if necessary. Shorting blocks are not required for proper meter operation.

4.6: Isolating a CT Connection Reversal

For a WYE System, you may either:

1. Check the current phase angle reading on the Nexus External Display (see Chapter 6). If it is negative, reverse the CTs.

2. Or, go to the Phasors screen of the Communicator EXT software (see Communicator EXT User Manual). Note the Phase Relationship between the Current and Voltage; they should be in

phase.

For a DELTA System:

Go to the Phasors screen of the Communicator EXT software program. The current should be 30 degrees off the phase-to-phase voltage.

4.7: Instrument Power Connections

The Nexus requires a separate power source. To use AC power, connect the line supply wire to the L+ terminal and the neutral supply wire to the N- terminal on the Nexus. To use DC power, connect the positive supply wire to the L+ terminal and the negative (ground) supply wire to the N- terminal on the Nexus. Power supply options and corresponding suffixes are listed in the following table:

CT Size (VA) Maximum Distance from CT to Nexus (Feet)

2.5 10

5.0 15

7.5 30

10.0 40

15.0 60

30.0 120

EIG Recommendations

WWAARRNNIINNGG!!!!

DO NOT leave the secondary of the CT open when primary current is flowing. This may

cause high voltage, which will overheat the CT. If the CT is not connected, provide a

shorting block on the secondary of the CT.

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Do not ground the unit through the negative of the DC supply. Separate grounding is required.

Externally fuse the power supply with a 5 Amp fuse.

4.8: Wiring Diagrams

Choose the diagram that best suits your application. Diagrams appear on the following pages. If the connection diagram you need is not shown, contact EIG for a custom Connection diagram.

NOTE: If you purchased a “G” Option Nexus for a 300 Volt secondary, be sure to enable the option on the CT and PT screen of the Communicator EXT software’s Device Profile (see the Communicator EXT User Manual for details).

Control Power Option Suffix

18-60 Volts DC D

90-276 Volts AC/DC D2

Figure # Description

4.1 4-Wire Wye, 3-Element Direct Voltage with 4 CTs

4.2 4-Wire Wye, 3-Element with 3 PTs and 4 CTs

4.3 4-Wire Wye, 3-Element with 3 PTs and 3 CTs

4.4 3-Wire, 2-Element Open Delta with 2 PTs and 3 CTs

4.5 3-Wire, 2-Element Open Delta with 2 PTs and 2 CTs

4.6 3-Wire, 2-Element Delta Direct Voltage with 3 CTs

4.7 3-Phase, 4-Wire Wye, 2.5 Element with 2 PTs and 3 CTs

4.8 4-Wire, 3-Element Grounded Delta with 4 CTs - G Option

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Figure 4.1: 4-Wire Wye, 3-Element Direct Voltage with 4 CTs

0.25 A

INPUT

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Figure 4.2: 4-Wire Wye, 3-Element with 3 PTs and 4 CTs

INPUT

0.25A

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Figure 4.3: 4-Wire Wye, 3-Element with 3 PTs and 3 CTs

INPUT

0.25 A

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Figure 4.4: 3-Wire, 2-Element Open Delta with 2 PTs and 3 CTs.

0.25 A

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Figure 4.5: 3-Wire, 2-Element Open Delta with 2 PTs, 2 CTs.

0.25 A

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Figure 4.6: 3-Wire, 2-Element Delta Direct Voltage with 3 CTs.

0.25 A

INPUT

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Figure 4.7: 3-Phase, 4-Wire Wye, 2.5 Element with 2 PTs, 3 CTs.

0.25 A

INPUT

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Figure 4.8: 4-Wire, 3-Element Grounded Delta with 4 CTs - G Option.

0.25 A

INPUT

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Figure 5.1: Communication Overview

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Chapter 5

Communication Wiring

5.1: Communication Overview



RS-232 communication is used to connect a single Nexus 1250/1252 Meter with another device, such as a computer, RTU or PLC. The link is viable for a distance up to 50 feet (15.2 m) and is available only through the Nexus 1250/1252 Meter’s Port 1. You must set the selector switch beneath the port to RS-232 (see Figure 5.3).



RS-485 communication allows multiple Nexus Meters to communicate with another device at a local or remote site. The I/O modules and the Nexus Display use RS-485 to communicate with the Nexus Meter. All RS-485 links are viable for a distance up to 4000 feet (1220 m). Ports 1 through 4 on the Nexus 1250/1252 Meter are two-wire, RS-485 connections operating up to 115,200 baud. To use Port 1 for RS-485, set the selector switch to RS-485 (see Figure 5.3).

Nexus

1 device, 50 feet maximum, Nexus Port 1

RS-232

RS-232/485

Converter

(Unicom 2500)

Up to 31 Devices, 4000 feet maximum (without a

repeater), connected in series via RS-485 (daisy chain)

Nexus

Telephone Line,

Fiber Optic Link or

Radio Link

MODEM

RS-232/485 Converter

(Modem Manager)

RS-232

RS-485

MODEM

RS-232

Null Modem

RS-232

RS-485

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

RJ-11 Telephone Line allows a Nexus Meter with the Internal Modem Option to communicate with a PC. No other hardware is necessary for this easy-to-use connection. The Nexus 1250/1252 Meter with the Internal Modem Option can connect via RS-485 to other Nexus Meters in local or remote sites in a daisy chain configuration, as depicted below.

The Nexus Meter with the Internal Modem Option has a unique label; Port 2 is labeled Modem Gateway. If you are going to use RS-485 to connect multiple Nexus 1250/1252 meters, you MUST use the Modem Gateway. For more details, see Chapter 10 of this manual.

RJ-11

RS-485

Figure 5.2: RJ-11 Communication with Internal Modem Option

Originate Modem (or Internal to PC)

Daisy Chain

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

RJ-45 Network Connection allows a Nexus Meter with the Internal Network Option to communicate with multiple PC’s concurrently. No other hardware is necessary for this easy-to-use connection. The Nexus Meter with the Internal Network Option can connect via RS-485 to other Nexus Meters in local or remote sites in a daisy chain configuration, as depicted below.

The Nexus 1250/1252 Meter with the Internal Network Option has a unique label; Port 2 is labeled Ethernet Gateway. If you are going to use RS-485 to connect multiple Nexus meters via the network, you MUST use the Ethernet Gateway. For more details, see Chapter 11 of this manual.

Figure 5.3: RJ-45 Communication with Internal Network Option

MODBUS/TCP

over Ethernet

10/100BaseT

or 10BaseT

RJ-45

MODBUS/RTU

Daisy Chain

Network

RS-485

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––++G

A(+) B(-) S - V + A(+) B(-) S - V +

+V- SB(-)A(+)

+V- SB(-)A(+) +V- SB(-)A(+)

+V- SB(-)A(+)

87654321C -+

Port 1

RS-232 or

RS-485 (Set)

RS-232

RS-485

Port 2

Normally Slave

Modem/Ethernet Gateway

High Speed Inputs

IRIG-B

RS-485 Master

Unicom or Modem Manager

Nexus P40N External Display

Nexus I/O Module

RS-232 Extension

Cable

(1 to 1 wiring)

I/O Modules and Display require power connections to the +/- voltage terminals (dashed lines).

For all communications: S=Shield. This connection is used to reference the Nexus port to the same potential as the source. It is not an earth-ground connection. You must also connect the shield to

earth-ground at one point.

~120 Ohms

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Port 3 Port 4

Figure 5.4: Communication Wiring

NOTE: You may use ANY port to connect a Nexus Display or RS-485 Master. However, if you are using the Internal Modem (or Network) Option, Port 2 is labeled Modem (Ethernet) Gateway. Ports 1, 3 and 4 DO NOT change. The I/O Modules MUST use Port 4 (Port 3 is an alternate). Nexus P40N, P41N or P43N Display is shipped programmed to use Port 3—see section 5.7 for

details.

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+ V - S B(-) A(+)

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Figure 5.5: Nexus Port 1—RS-232/RS-485 Communication

Switch set for RS-232 communication

RS-232 RS-485

5 4 3 2 1

9 8 7 6

RS-232 Port Pin #2=Transmit Pin #3=Receive Pin #5=Ground

RS-485 Port

(see Section 5.3 for details)

Nexus Meter Port 1

5.2: RS-2232 Connection—Nexus Meter to a Computer



Use Port 1 for RS-232 communication. Set the selector switch beneath the port to RS-232.



Insert one end of an RS-232 extension cable into the Nexus Meter’s 9-pin female serial port. Insert the opposite end into a port on the computer.



The RS-232 standard limits the cable length to 50 feet (15.2m).



The RS-232 Port is configured as Data Communications Equipment (DCE).

5.3: Nexus RS-4485 Wiring Fundamentals (with RTExplanation)

Nexus RS-485 Ports (Ports 1–4)

(see Figure 5.5 above)

+V- Voltage terminals for power connections: Use with Nexus I/O Modules and the

Nexus Displays only. The Nexus 1250/1252 Meter supplies 17V DC through the +V- terminal connections. Note: Do not connect these pins to devices that receive power from another source—ie, a computer—or to devices that do not require power to operate.

S Shield: The Shield connection is used to reference the Nexus port to the same

potential as the source. It is not an earth-ground connection. You must also connect the shield to earth-ground at one point. Do not connect the shield to ground at multiple points; it will interfere with communication.

A(+)/B(-) Two-wire, RS-485 communication terminals: Connect the A(+) terminal of the Nexus

Port to the (+) terminal of the device. Connect the B(-) terminal of the Nexus Port to the (-) terminal of the device.

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For All RS-485 Connections:



Use a shielded twisted pair cable 22 AWG (0.33 mm2) or larger, grounding the shield at one end only.



Establish point-to-point configurations for each device on a RS-485 bus: Connect (+) terminals to (+) terminals; connect (-) terminals to (-) terminals.



Protect cables from sources of electrical noise.



Avoid both “star” and “tee” connections (see Figure 5.7). No more than two cables should be connected at any one point on an RS-485 network, whether the connections are for devices, converters or terminal strips.



Include all segments when calculating the total cable length of a network. If you are not using an RS-485 repeater, the maximum length for cable connecting all devices is 4000 feet (1219 meters).



RT EXPLANATION: Termination Resistors are generally used on both ends of longer length transmission lines.

The value of the Termination Resistors is determined by the electrical parameters of the cable. Use RTs only on Master and Last Slave when connecting multiple meters in a Daisy Chain.



RS-485 communication allows multiple devices to communicate on a bus. The Nexus 1250/1252 Ports 1 to 4 are RS-485 terminals, viable for a distance of up to 4000 feet (1219 m). (Nexus’ Port 1 can be switched between RS-232 and RS-485.) Below is a detail of a 2-wire RS-485 port.

2-Wire RS-485 Port

S - +

Shield

Twisted

Pair

Connect (-) to (-) of

next device

Connect (+) to (+) of

next device

Figure 5.6: 2-Wire RS-485 Port Detail

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Incorrect Connection: “T”

Figure 5.7: Incorrect “T” and “Star” Topologies

Incorrect Connection: “Star”

“Star” Connection Incorrect!

The three wires connected in a “Star” shape on both the (+) and (-) terminals will cause interference problems.

RS-485 Ports

RS-485 Port

“Tee” Connection Incorrect!

The three wires connected in a “T” shape on both the (+) and (-) terminals will cause interference problems.

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5.4: RS-4485 Connection—Nexus Meter to a Computer or PLC



Use any Port on the Nexus 1250/1252. If you use Port 1, set the selector switch beneath the port to RS-485 (see Figure 5.3).



The link using RS-485 is viable for up to 4000 feet (1219 meters).



You must use an RS-485 to RS-232 converter, such as EIG’s Unicom 2500. See sections 5.7.1.



For information on connecting the Nexus Meter to a modem, see sections 5.14–5.16.



Do not use the V(+)/V(-) pins; they supply power to the Nexus Displays and Nexus I/O Modules.

5.5: RJ-111 (Telephone Line) Connection—Nexus with Internal Modem Option to a PC



Use RJ-11 Standard Telephone Line to connect with the Nexus 1250/1252. The RJ-11 line is inserted into the RJ-11 Port on the face of the Nexus with Internal Modem Option.



The length of the connection using RJ-11 into the Nexus 1250/1252 is virtually unlimited.



To connect with other Nexus 1250/1252 Meters in either local or remote locations, you MUST use Port 2 as a Master and an RS-485 connection.



The link using RS-485 is viable for up to 4000 feet (1219 meters).



For more information on the Nexus Meter with the Internal Modem Option, see Chapter 10 of this manual.

5.6: RJ-445 Connection—Nexus with Internal Network Option to multiple PC’s



The Internal Network Option conforms to the IEEE 802.3, 10BaseT specification using unshielded twisted pair (UTP) wiring. This allows the use of inexpensive RJ-45 connectors and CAT 3 or better cabling.



Using this LAN connection allows multiple PC’s to be connected concurrently. The RJ-45 line is inserted into the RJ-45 Port on the face of the Nexus with Internal Network Option.



The connection using RJ-45 into the Nexus 1250/1252 can connect the Nexus to a network using Modbus/TCP protocol over Ethernet.



To connect with other Nexus Meters in either local or remote locations, you MUST use Port 2 (which is labeled Ethernet Gateway) as a Master and an RS-485 connection. The link using RS-485 is viable for up to 4000 feet (1219 meters).



For more information on the Nexus 1250/1252 Meter with the Internal Network Option, see Chapter 11 of this manual.

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5.7: RS-4485 Connection—Nexus to an RS-4485 Master (Unicom or Modem

Manager)



To establish communication between a Nexus Meter and any RS-485 master, such as EIG’s Unicom 2500, Modem Manager or other RS-232–485 converter, use a shielded, twisted pair cable.



Use an RS-485 port (Ports 1–4) on the Nexus Meter. If you use Port 1, set the selector switch beneath it to RS-485 (see Figure 5.3). Connect the A(+) and B(-) terminals on the Nexus to the (+) and (-) terminals on the master. Provide jumpers on the master, linking its two (-) terminals and two (+) terminals. RS-485 communication is viable for up to 4000 feet (1219 meters).



Connect the shield to the Ground (G) terminal on the Master. The (S) terminal on the Nexus is used to reference the Nexus port to the same potential as the source. It is not an earth ground connection. You must also connect the shield to earth-ground at one point.

NOTE: Refer to section 5.3 for information on using RTs.

5.7.1: Using the Unicom 2500

The Unicom 2500 provides RS-485/RS-232 conversion. In doing so it allows the Nexus to communicate with a PC or other device. See the Unicom 2500 Installation and Operation Manual for additional information.

Figures 5.8 and 5.9, on the next page, illustrate the Unicom 2500 connections for RS-485.

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The Unicom 2500 can be configured for either 4-wire or 2-wire RS-485 connections. Since the

Nexus uses a 2-wire connection, you need to add jumper wires to convert the Unicom 2500 to the 2-wire configuration.

As shown in Figure 5.9, you connect the "RX-" and "TX-" terminals with a jumper wire to make

the "-" terminal, and connect the "RX+" and "TX+" terminals with a jumper wire to make the "+" terminal

Figure 5.8: Unicom 2500 with Connections

Figure 5.9: Detail of “Jumpers”

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Nexus P40N, P41N or P43N Display, Back View

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5.8: RS-4485 Connection—Nexus Meter to the Nexus P40N External Display



Insert one end of the supplied RS-485 cable into Port 3 of the Nexus 1250/1252 Meter. Port 3 is factory-set to match the Nexus Display’s baud rate of 9600. To use a port other than Port 3, you must set the port’s baud rate to 9600 using the Communicator EXT software (see the Communicator EXT User Manual). Insert the other end of the cable into the back of the Nexus P40N, P41N or P43N Display. The connectors fit only one way into the ports.



The cable harness brings 17V DC to the displays from the Nexus 1250/1252 Meter, represented by dashed lines in the figure below. RS-485 communication is viable for up to 4000 feet (1219 meters). If your cable length exceeds 200 feet you must use a remote power supply, such as EIG’s PSIO, and:

• Connect the shield to the shield (S) terminal on the Nexus Display port. The (S) terminal on the Nexus is used to reference the Nexus port to the same potential as the source. It is not an earth-ground connection. You must also connect the shield to earth-ground at one point.

• Provide termination resistors at each end, connected to the A(+) and B(-) lines. RT is approximately 120 Ohms. NOTE: Refer to section 5.3 for RT Explanation.

+V- S B(-)A(+)

A(+) B(-) S - V +

Figure 5.10: Nexus Meter Connected to Nexus P40N, P41N or P43N External Display

Nexus P40N, P41N or P43N Display Port

Nexus Meter Port 3

V+

V-

B(-)

A(+)

Top

Bottom

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Nexus P60N Display, Back View (Detail)

Top

Bottom

5.9: RS-4485 Connection—Nexus Meter to the Nexus P60N External Display



To connect the Nexus P60N Touch Screen External Display, use the Stand Alone Interface Cable provided with the display. The cable is six (6) feet long with 20 AWG conductors (see detail below). Insert one end of the supplied cable into Port 3 of the Nexus 1250/1252 Meter. Port 3 is factory-set to match the Nexus Display’s baud rate of 9600. To use a port other than Port 3, you must set the port’s baud rate to 9600 using the Communicator EXT software (see the Communicator EXT User Manual). Insert the other end of the cable into the back of the Nexus P60N Display. The connectors fit only one way into the ports.

Stand Alone Interface Cable

Nexus P60N Display Port

Figure 5.11: Nexus Meter Connected to Nexus P60N Touch Screen Display

P60N Connection Color Key

LCD Nexus Color Pattern

5 DCIN

(12-30V DC)

4 (GND)

V+ Red

V- Black

3 (485+) A(+) White

2 (485-) B(-) Black

1 (GND) S Silver

Nexus Meter Port 3

Factory Test Connector

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5.10: Communication Ports on the Nexus I/O Modules



Female RS-485 Side Port: use to connect to another module’s female RS-485 side port.



Male RS-485 Side Port: use to connect to the Nexus Meter’s Port 4 (see section 5.8) or to connect to another module’s male RS-485 side port.



I/O Port: use for functions specific to the type of module; size and pin configuration varies depending on type of module. For more detail, refer below to section 5.11 and to Chapter 9 of this manual.

Figure 5.12: Communication Ports on the Nexus I/O Modules

I/O Port

(Size and pin

configuration vary)

Female RS-485 Side Port

Male RS-485 Side Port

Mounting Brackets

LEDs

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5.11: RS-4485 Connection—Nexus Meter to Nexus I/O Modules



Six feet of RS-485 cable harness is supplied. Insert one end of the cable into Port 4 of the Nexus 1250/1252 Meter.



Insert the other end of the cable into the I/O module’s female RS-485 side port (see Figure 5.9). The connectors fit only one way into the ports.



Use the male RS-485 side port to attach another I/O module. The Nexus 1250/1252 will power up to four connected I/O modules using 15–20V DC at 50–200mA, represented by dashed lines in the figure below. Use the steps below (section 5.12) to determine if you must use a separate power source (for example, EIG PSIO) to supply added power to the group. RS-485 communication is viable for up to 4000 feet (1219 meters). However, if your cable length exceeds 200 feet, use the remote power supply and:

• Connect the A(+) and B(-) terminals on the Nexus to the A(+) and B(-) terminals of the female RS-485 port. Connect the shield to the shield (S) terminal. The (S) terminal on the Nexus 1250/ 1252 is used to reference the Nexus port to the same potential as the source. It is not an earth ground connection. You must also connect the shield to earth-ground at one point.

• Provide termination resistors at each end, connected to the A(+) and B(-) lines. RT is approximately 120 Ohms. NOTE: Refer to section 5.3 for RT Explanation.

+V- S B(-)A(+)

A(+) B(-) S - V +

Figure 5.13: Nexus Meter Connected to Nexus I/O Module

Male Side Port on Nexus I/O Module

Nexus Meter Port 4

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5.12: Steps to Determine Power Needed

• Available power for All Ports of the Nexus 1250/1252 is 12 VA.

• Refer to the table below to determine the VA Ratings for I/O modules and displays.

• Add together the VA Ratings for I/Os and Displays in use.

• Compare Available Power to Power Needed to determine if you must use an additional

power source. EIG recommends the PSIO 12V power source. See section 9.2.1.

5.13: I/O Modules’ Factory Settings and VA Ratings



All I/Os are shipped pre-programmed with a baud rate of 57600 and addresses. The table below details the factory-set address for each module and the VA Ratings for I/O modules and Nexus displays. Refer to the previous section (section 5.12) for the steps to determine if you must use an additional power source. For programming, refer to Chapter 8 of the Communicator EXT User

Manual.

I/O MODULES’ FACTORY SETTINGS AND VA RATINGS

MODEL NUMBER

1mAON4

1mAON8 20mAON4 20mAON8

8A11 8A12 8A13 8A14

4RO1

4PO1 8D11

MODULE 0-1mA, 4 Analog Outputs 0-1mA, 8 Analog Outputs

4-20mA, 4 Analog Outputs 4-20mA, 8 Analog Outputs

0-1mA, 8 Analog Outputs

0-20mA, 8 Analog Outputs

0-5V DC, 8 Analog Outputs

0-10V DC, 8 Analog Outputs

4 Latching Relay Outputs

4 KYZ Pulse Outputs

8 Status Inputs (Wet/Dry)

NEXUS DISPLAYS’VA RATINGS

ADDRESS VA RATING

128 2.7 VA 128 3.2 VA 132 5.0 VA 132 8.5 VA 136 2.3 VA 140 2.3 VA 144 2.3 VA 148 2.3 VA 156 2.7 VA 160 2.7 VA 164 1.0 VA

P40N, P41N or P43N

P60N

Nexus LED Display

Nexus Touch Screen Display

8 VA 5 VA

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Figure 5.14: Linking Multiple Nexus Devices in Series

Nexus RS-485 Port

RS-485 to RS-232

Converter (RS-485 Master)

+ V - S B(-) A(+)

GND TX- RX- TX+ RX+

Up to 31 Nexus 1250/1252 Meters Maximum

5.14: Linking Multiple Nexus Devices in Series



You may connect a total of 31 Nexus 1250/1252 Meters in series on a single bus using RS-485. The cable length may not exceed 4000 feet (1219 meters). Before assembling the bus, each Nexus Meter must be assigned a unique address; see the Communicator EXT User Manual.



Connect the A(+) and B(-) terminals of each Nexus Meter. Use jumpers on any RS-485 Master connected at the end of the chain (see section 5.5).



Connect the shield to the (S) terminal on each Nexus and to the Ground on the RS-485 Master. This connection is used to reference the Nexus port to the same potential as the source. It is not an earth ground connection. You must also connect the shield to earth-ground at one point.



Provide resistors at each end, connected to the (+) and (-) lines. RT is approximately 120 Ohms, but this value may vary based on length of cable run, gauge or the impedance of the wire. NOTE: Refer to section 5.3 for RT Explanation.

Jumpers

+ V - S B(-) A(+)

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Nexus Nexus

Nexus

Nexus Nexus

Nexus

Nexus Nexus Nexus Nexus

Maximum 31 Nexus 1250/1252 Meters, RS-485

Maximum 31 Nexus Meters, RS-485

Maximum 31

Repeaters

Figure 5.15: Networking Groups of Nexus Meters

5.15: Networking Groups of Nexus Meters



You may connect up to 31 Nexus 1250/1252 Meters on the same RS-485 bus. Each one must be assigned a unique address; see the Communicator EXT User Manual. Use an RS-485 repeater to network several links of instruments.



A maximum number of 31 Nexus 1250/1252 Meters may be connected to one repeater. A maximum number of 31 repeaters may be included on the same network.

REPEATER

RS-485/232

Converter

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Telephone Line Remote

Modem

NULL Modem Adapter

(Required if 232/485 Converter does not support

DTE/DCE reconfigura

tion)

RS-

Originate

Modem

RS-232 to RS-485

Converter

(Modem Manager

Recommended)

Nexus 1250/1252

Meter

PC at office

Figure 5.16: Remote Connections—RS-232/RS-485

PSTN (Public

Switched

Telephone

Network)

Nexus 1250/1252

Meter

Remote

Modem

NULL Modem Adapter or Null

Cable Required

RS-232

Local

Modem

PC at office

5.16: Remote Communication Overview



Use modems (dedicated or dial-up) when devices are at great distances. EIG recommends using RS-485 wiring with a Modem Manager. See section 5.13.

Remote Connection—RS-232

Remote Connection—RS-485

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

Use RJ-11 Telephone Lines when devices are at great distances. Connections are simple, requiring no additional hardware.

RJ-11

RS-485

Figure 5.17: Remote Connections with Internal Modem Option

Originate Modem (or Internal to PC)

Daisy Chain



Standard Telephone wall to phone cabling can be used. This cabling is widely available in many lengths with RJ-11 plugs on each end.



Plug one end into the Nexus 1250/1252 and the other end into the wall jack.

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

Or, use RJ-45 Network Connection when devices are at great distances. Connections are simple, requiring no additional hardware.

MODBUS/TCP

over Ethernet

10/100BaseT

or 10BaseT

RJ-45

Network

Daisy Chain

MODBUS/RTU

RS-485

Figure 5.18: Remote Connections with Internal Network Option

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5.17: Remote Communication—RS-2232



EIG recommends using RS-485 wiring with a Modem Manager. See section 5.13.



For RS-232 communication, use Port 1. Set the selector switch under the port to RS-232 (Fig. 5.3).



Use an RS-232 serial extension cable connected to the 9-pin female serial port of the Nexus 1250/1252 Meter’s Port 1. Program this port for Modbus ASCII. See the Communicator EXT User Manual for details.



The link using RS-232 is capable for up to 50 feet (1219 meters).



You must use a Null Modem or Null Cable between the Nexus Meter and the remote modem when using RS-232. ANull Modem enables two DCE devices to communicate. The figure below details how a null modem reconfigures the RS-232 pins. Note: Connecting the Nexus Meter to a modem

via RS-485 protocol with EIG’s Modem Manager converter eliminates the need for a Null Modem; see section 5.13.



The remote modem must be programmed for auto-answer and set at a fixed baud rate of 9600 with no Flow Control. See section 5.19 and the Communicator EXT User Manual for further details.

1 6547

832

2 3 4 5 6 7 8

Pins at Null Modem Female End

Pins at Null Modem Male End

Figure 5.19: Standard Null Modem Configuration

5.18: Remote Communication—RS-4485



Use any Port on the Nexus 1250/1252. If you use Port 1, set the selector switch beneath the port to RS-485 (see Figure 5.3). The link using RS-485 is viable for up to 4000 feet (1219 meters).



Use Communicator EXT software to set the port’s baud rate to 9600 and enable Modbus ASCII protocol. See the Communicator EXT User Manual.



You must use an RS-485 to RS-232 converter and a NULL Modem. EIG recommends using its Modem Manager, a sophisticated RS-232/RS-485 converter that enables devices with different

baud rates to communicate. It also eliminates the need for a NULL modem (see section 5.12), and automatically programs the modem to the proper configuration. Also, if the telephone lines are poor, Modem Manager acts as a line buffer, making the communication more reliable.

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5.19: Programming Modems for Remote Communication

When a modem speaks to most RS-485 or RS-232-based devices, it must be programmed for the communication to work. This task is often quite complicated because modems are quirky when talking to remote devices.

If you are not using a Modem Manager device, you must set the following strings to communicate with the remote Nexus Meter(s). Consult your modem’s manual for the proper string settings or see section

5.15 for a list of selected modem strings.



Modem Connected to a Computer (the Originate Modem):

• Restore modem to factory settings. This erases all previously programmed settings.

• Set modem to display Result Codes. The computer will use the result codes.

• Set modem to Verbal Result Codes. The computer will use the verbal result codes.

• Set modem to use DTR Signal. This is necessary for the computer to ensure connection with the

originate modem.

• Set modem to enable Flow Control. This is necessary to communicate with remote modem connected to the Nexus.

• Tell modem to write the new settings to activate profile. This places these settings into nonvolatile memory; the setting will take effect after the modem powers up.



Modem Connected to the Nexus Meter (the Remote Modem):

• Restore modem to factory settings. This erases all previously programmed settings.

• Set modem to auto answer on N rings. This sets the remote modem to answer the call after N

rings.

• Set modem to ignore DTR Signal. This is necessary for the Nexus to ensure connection with originate modem.

• Set modem to disable Flow Control. Nexus RS-232 communication does not support this feature.

• Tell modem to write the new settings to activate profile. This places these settings into nonvolatile memory; the setting will take effect after the modem powers up.

• When programming the remote modem with a terminal program, make sure the baud rate of the terminal program matches the Nexus Meter’s baud rate.

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5.20: Selected Modem Strings

Modem String/Setting

Cardinal modem: AT&FE0F8&K0N0S37=9 Zoom/Faxmodem VFX V.32BIS(14.4K): AT&F0&K0S0=1&W0&Y0 Zoom/Faxmodem 56Kx Dual Mode: AT&F0&K0&C0S0=1&W0&Y0 USRobotics Sportster 33.6 Faxmodem: AT&F0&N6&W0Y0 (for 9600 baud)

DIP switch setting: Up Up Down Down Up Up Up Down

USRobotics Sportster 56K Faxmodem: AT&F0&W0Y0

DIP switch setting: Up Up Down Down Up Up Up Down

356

Optional 150V Max for wet contacts

5.21: High Speed Inputs Connection



The Nexus High Speed Inputs can be used in many ways:

Attach the KYZ HS Outputs from other meters for totalizing. Attach relaying contacts for breaker status or initiated logging.



Refer to the Communicator EXT User Manual for information on programming the functionality of these versatile inputs.



The High Speed Inputs can be used with either dry or wet field contacts. For WET contacts, the common rides on a unit-generated 15V DC. No user programming is necessary to use either wet or dry field contacts.

Figure 5.20: High Speed Inputs Connection

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5.22: Five Modes of Time Synchronization



The Nexus meter offers up to five modes of Time Synchronization, depending on options selected at the time of ordering.

1. Internal Crystal: The Default Time Constant is an Internal Crystal. The crystal is accurate to

approximately 1 minute per month.

2. Line Frequency: The meter ignores the internal crystal and counts frequency to synchronize the

clock. This feature is highly accurate in the presence of reliable system frequency. If power is lost, the unit automatically switches to the internal crystal.

3. Modbus Commands Time Synchronization: The meter uses Serial Modbus-Based Commands

to change the date and time of the clock. The meter relies upon the Internal Crystal between synchronization intervals. This mode is used in conjunction with MV90.

4. DNP Line Synchronization: The meter uses DNP Protocol Commands to change the date and

time of the clock. The meter relies upon the Internal Crystal between synchronization intervals.

5. IRIG-B: The meter uses a Signal Generating Device connected to the GPS Satellite System to

synchronize Nexus Time. This mode is accurate to within one millisecond. This mode is detailed in section 5.23.

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Nexus IRIG-B Port

5.23: IRIG-BB Connections



IRIG-B is a standard time code format that synchronizes event timestamping to within 1 millisecond. An IRIG-B signal-generating device connected to the GPS satellite system will synchronize Nexus 1250/1252 Meters located at different geographic locations. Nexus utilizes an UNMODULATED signal from a satelite-controlled clock (such as Arbiter 1093B). For details on installation, refer to the User’s Manual for the satellite-controlled clock in use. Below are installation steps and tips that will help you.



Connect the (+) terminal of the Nexus Meter to the (+) terminal of the signal generating device; connect the (-) terminal of the Nexus Meter to the (-) terminal of the signal generating device.

IRIG-B Time

Signal

Generating

Device

GPS Satellite Connection

Figure 5.21: IRIG-B Connection



Installation:

1. Set Time Settings for the meter being installed. From Communicator EXT, Device Profile,

Click Time Settings. Set the Time Zone and Daylight Savings (Select AutoDST or Enable and set dates). Click Update Device Profile to save the new settings. (See the Communicator EXT User’s Manual for details.)

2. Before connection, check that the date on the meter clock is correct (or, within 2 MONTHS of

the actual date). This provides the right year for the clock (GPS does not supply the YEAR).

3. Connect the (+) terminal of the Meter to the (+) terminal of the signal generating device; Connect the (-) terminal of the Meter to the (-) terminal of the signal generating device.



Troubleshooting Tip: The most common source of problems is a reversal of the two wires. Try reversing the wires.

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Chapter 6

Using the Nexus External Displays

6.1: Overview

Electro Industries offers four external displays for use with the Nexus 1250/1252. The P40N, P41N and P43N are LED displays that provide easy-to-use access to the information stored in the Nexus 1250/1252. The P60N is our Touch Screen Display, which provides easy access to Nexus 1250/1252 readings and information combined with a graphical touch screen presentation.

Plug one of the Nexus External Displays into Port 3 or 4 on the Nexus Meter, using the cable supplied. The Displays operate at 9600 baud; Port 3 is factory-set to 9600 baud (see Chapter 5 for communication details). To use the Displays on another port, configure that port to operate at 9600 baud, using the Communicator EXT Software; see the Communicator EXT User Manual.

6.2: Nexus P40N, P41N and P43N LED External Displays

The Nexus P40N LED External Display can be used alone or it can serve as the Master for this grouping of displays. The P40N prepares the data for the Slave displays, the P41N and the P43N. Once a second, it sends a request to the Nexus meter. All necessary data for the Slave displays is returned to the Master display upon this request and the Master sends the data to the Slaves in the proper format.

The Nexus P41N and P43N Slave displays listen to the Master and display and update values on the screen when they receive proper data. These displays have no keypads. Data can only be received; it cannot be changed. If there is no data for more than 5 seconds, “Communication Lost” will appear on the bottom of the screen. The following data is displayed when received:

• Amp Display (P41N): Amp A, Amp B, Amp C

• Power Display (P43N): Watt, VAR, PF

LED Display

Up/Down Arrows

Mode Button

Left/Right Arrows

Figure 6.1: Nexus P40N LED External Display

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6.2.1: Connect Multiple Displays

One cable (housing two-wire RS-485 and two-wire power wires plus shield) is used to connect the displays. One port of the Nexus meter supports 12 VA. Each P40N, P41N or P43N requires 3.3 VA (maximum 3.8 VA). The Master Display (P40N) is the master in communication. The Amp, Power and Nexus devices are slaves in communication. Therefore, the Master Display (P40N) should be at the end of the daisy-chained units as shown in Figure 6.2 below. The Nexus port is set at 1. Protocol is Modbus RTU and Baud Rate is 9600.

NOTE: The power lines in Figure 6.2 are shown separate for clarity. All lines are actually in one cable.

Shown here are diagrams of the P41N and P43N Displays with example readings on each screen.

6.2.2: Nexus P40N Modes

The Nexus P40N LED External Display has three modes:

• Dynamic Readings Mode (section 6.3 and 6.4)

• Nexus Information Mode (section 6.5 and 6.6)

• Display Features Mode (section 6.7 and 6.8)

Each Mode is divided into Groups. Most Groups are further broken down into Readings.

• Use the MODE button to scroll between Modes.

• Use the UP/DOWN arrows to scroll from Group to Group within each Mode.

• Use the LEFT/RIGHT arrows to scroll from Reading to Reading within each Group.

Use the Communicator EXT software to Flash Update the P40N External Display.

P40N

P41N

P43N

+V -V S B(-) A(+)

NEXUS UNIT

Figure 6.2: P40N Display Daisy Chain

Figure 6.3: P41N Display

Figure 6.4: P43N Display

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6.3: Dynamic Readings Mode

The External Display puts itself in the Dynamic Readings Mode upon power-up. Use the MODE button to access the Dynamic Readings from other Modes. Use the UP/DOWN arrows to navigate from Group to Group within this Mode. See section 6.4 for a navigational map of the Dynamic Readings Mode.

Group 1: Phase to Neutral Voltages (Use the LEFT/RIGHT arrows to access the following readings, in order.)

• Volts AN/BN/CN

• Maximum Volts AN/BN/CN

• Minimum Volts AN/BN/CN

• Volts AN/BN/CN %THD

• Volts AN/BN/CN Maximum %THD

• Volts AN/BN/CN Minimum %THD

Group 2: Phase to Phase Voltages (Use the LEFT/RIGHT arrows to access the following readings, in order.)

• Volts AB/BC/CA

• Maximum Volts AB/BC/CA

• Minimum Volts AB/BC/CA

Group 3: Current (Use the LEFT/RIGHT arrows to access the following readings, in order.)

• Current A/B/C

• Maximum Current

• Minimum Current

• Current %THD

• Current Maximum %THD

• Current Minimum %THD

• Current Calculated N/Measured N

• Maximum Current Calculated N/Measured N

Group 4: Watt/VAR (Use the LEFT/RIGHT arrows to access the following readings, in order.)

• kWatt/kVAR

• Maximum +kWatt/+kVAR/CoIn kVAR

• Maximum -kWatt/-kVAR/CoIn kVAR

• Block (Fixed) Window Average Maximum +kWatt/+kVAR/CoIn kVAR

• Predictive Rolling (Sliding) Window Maximum +kWatt/+kVAR/CoIn kVAR

Group 5:VA/PF/Frequency (Use the LEFT/RIGHT arrows to access the following readings, in order.)

• kVA/PF lag/Hz

• Maximum kVA/Hz

• Minimum kVA/Hz

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• Maximum Quadrant 1 Total PF

• Minimum Quadrant 1 Total PF

• Maximum Quadrant 2 Total PF

• Minimum Quadrant 2 Total PF

• Maximum Quadrant 3 Total PF

• Minimum Quadrant 3 Total PF

• Maximum Quadrant 4 Total PF

• Minimum Quadrant 4 Total PF

Group 6: Delivered Energy (Use the LEFT/RIGHT arrows to access the following readings, in order.)

• +kWatthr Quadrant 1+Quadrant 4 (Primary)

• +kVAhr Quadrant 1 (Primary)

• +kVARhr Quadrant 1 (Primary)

• +kVAhr Quadrant 4 (Primary)

• -kVARhr Quadrant 4 (Primary)

Group 7: Received Energy (Use the LEFT/RIGHT arrows to access the following readings, in order.)

• -kWatthr Quadrant 2+Quadrant 3 (Primary)

• +kVAhr Quadrant 2 (Primary)

• +kVARhr Quadrant 2 (Primary)

• +kVAhr Quadrant 3 (Primary)

• -kVARhr Quadrant 3 (Primary)

Group 8: Accumulations (Use the LEFT/RIGHT arrows to access the following readings, in order.)

• kI

t A

• kI

t B

• kI

t C

• kV

t A

• kV

t B

• kV

t C

Group 9: Phase Angles (Use the LEFT/RIGHT arrows to access the following readings, in order.)

• Phase Angle V an/bn/cn

• Phase Angle Ia/b/c

• Phase Angle V ab/bc/ca

• Phase Sequence

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1 Second Volts

AN,BN,CN

Maximum Volts

AN,BN,CN

Maximum Volts

AB,BC,CA

Minimum Volts

AB,BC,CA

Minimum Volts

AN,BN,CN

%THD Volts

AN,BN,CN

Max %THD

Volts

AN,BN,CN

Min %THD

Volts

AN,BN,CN

Return to

First

Reading

Return to

First

Reading

Return to

First

Reading

Return to

First

Reading

Return to

First

Reading

Return to

First

Reading

Return to

First

Reading

Return to First

Reading

Return to

First

Reading

1 Second Volts

AB,BC,CA

1 Second

kWatt, kVAR

+Max kWatt, +kVAR,CoIn

kVAR

-Max kWatt,

-kVAR,CoIn kVAR

Block WinAvg Max

+kWatt,

+kVAR,CoIn kVAR

Pred Rol Win Avg

+kWatt,

+kVAR,CoIn kVAR

1 Second

IA,IB,IC

Maximum

IA,IB,IC

Minimum

IA,IB,IC

%THD

IA,IB,IC

Max %THD

IA,IB,IC

Min %THD

IA,IB,IC

1 Second

INc,INm

1 Second

kVA, PF

lag,

Frequency

Max

kVA,

Freq

Min

kVA,

Freq

Max Q1, Total PF

Min Q1, Total PF

Max Q2, Total PF

Min Q2, Total PF

Max Q3,

Total PF

Min Q3, Total PF

Min Q4, Total PF

Positive

kWatthour

Q1+Q4

Positive

kVAhr

Positive

kVAhr

Positive

kVARhr

Positive

kVARhr

Positive

kVAhr

Positive

kVAhr

Negative

kVARhr

Negative

kVARhr

kI2t A

kI2t B

kI2t C

kV2t A

kV2t B

kV2t C

Phase Angles V

AN,BN,CN

Phase Angles I

A,B,C

Phase Angles V

AB,BC,CA

Phase

Sequence

r o u p s

6.4: Navigational Map of Dynamic Readings Mode

Use LEFT/RIGHT arrow keys to navigate Readings

Use UP/DOWN arrows to scroll between groups.

Negative

kWatthr

Q2+Q3

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6.5: Nexus Information Mode

Use the MODE button to access the Nexus Information Mode from other Modes. Use the UP/DOWN arrows to navigate from Group to Group within this Mode. See section 6.6 for a

navigational map of the Nexus Information Mode.

Group 1: Device Time

• Meter Time

Group 2: Communication Settings (Use the LEFT/RIGHT arrows to access the following readings, in order.)

• Communication Settings Port 1: Baud/Addr/Protocol

• Communication Settings Port 2: Baud/Addr/Protocol

• Communication Settings Port 3: Baud/Addr/Protocol

• Communication Settings Port 4: Baud/Addr/Protocol

Group 3: PT, CT Ratios (Use the LEFT/RIGHT arrows to access the following readings, in order.)

• PT Ratio

• CT Ratio

Group 4: External Display Units

• Primary/Secondary

• Select either Primary or Secondary units for the External Display using the Communicator EXT

software (see the Energy Manager User Manual).When Primary is selected, the Display shows all readings in Primary units based on the user programmed PT and CT Ratios. When Secondary is selected, the Display shows all readings in Secondary units.

Group 5: Firmware Versions and Serial Numbers (Use the LEFT/RIGHT arrows to access the following readings, in order.)

• Run Time External Display/Run Time DSP/RunTime Comm

• Boot External Display/Boot DSP/Boot Comm

• Serial Number External Display; Serial Number Nexus Monitor

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Meter Time

Display

Primary/Secondary

CT RatioPT Ratio

Serial #

Display, Serial

# Monitor

Boot

Display,

DSP, Comm

Run-time

Display,

DSP, Comm

r o u p s

Readings

Return

First Reading

Return

First

Reading

6.6: Navigational Map of Nexus Information Mode

Use UP/DOWN arrows to scroll between groups.

Use LEFT/RIGHT arrows to scroll between readings.

Return

First Reading

Comm

Settings

Port 4

Comm

Settings

Port 3

Comm

Settings

Port 2

Comm

Settings

Port 1

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6.7: Display Features Mode

Use the MODE button to access the Display Features Mode from other Modes. Use the UP/DOWN arrows to navigate from Group to Group within this Mode. See section 6.8 for a navigational map of the Display Features mode.

Group 1: Reset Max/Min

• Note

: If the password protection feature has been enabled with the Communicator EXT

software, you will need to enter a password to reset the max/min readings. To do this, first press the Enter button. Then enter the password, one character at a time, by pressing on the UP or DOWN arrows. Each password character begins as an “A”. Press the UP arrow to increment the character from “A–Z” and then from “0–9”. Press the DOWN arrow to decrement the character from “A” to “9–0” and then from “Z–A”. Press SET to enter each character the password. When the entire password is shown on the Display screen, press ENTER. If the password is correct you may then press Enter again to Reset the Energy readings.

• Press the Enter button to reset the Max and Min values.

Group 2: Reset Energy

• Note

: If the password protection feature has been enabled with the Communicator EXT

software, you will need to enter a password to reset the energy. To do this, first press the Enter button. Then enter the password, one character at a time, by pressing on the UP or DOWN arrows. Each password character begins as an “A”. Press the UP arrow to increment the character from “A–Z” and then from “0–9”. Press the DOWN arrow to decrement the character from “A” to “9–0” and then from “Z–A”. Press SET to enter each character the password. When the entire password is shown on the Display screen, press ENTER. If the password is correct you may then press Enter again to Reset the Energy readings.

• Press Enter button to reset the Max and Min values.

Group 3: Display Baud Rate/Address

Group 4: Display Communication Protocol

Group 5: EIG Use Only

Group 6: EIG Use Only

Group 7: Lamp Test

• Press Enter to conduct an LED test.

Group 8: Display Scroll ON/OFF

• Press Enter to turn the scroll feature on or off. When the scroll feature is on, the P40N External

Display will scroll through the first reading of each group in the Dynamic Readings Mode. If a button is pressed during the scroll, scrolling pauses for one minute.

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Reset Max/Min

Reset Energy

Communication

Protocol

Baud

Rate/Address

EIG Use Only

Display Scroll

On/Off

r o u p s

6.8: Navigational Map of Display Features Mode

Use UP/DOWN arrows to scroll between groups.

Lamp Test

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6.9: Nexus P60N Touch Screen External Display

The P60N Touch Screen External Display is ready to use upon power-up. Touching the “buttons” at the top of the screen will take you to the Groups of Readings listed below. With the “buttons” at the bottom of the screen, you can use the touch screen to review Limits and review and/or change Settings on the Display and the Nexus Meter. Also, you can Reset Max/Min and Demand, Hour, I

and V

T Counters, All Logs and TOU for Current Session and Month using the Reset Button.

All screens have a Main button that returns you to the Main screen below. All screens also have a Next button that will take you to the next group of readings. Some of the screens have additional

navigation buttons to take you to complimentary readings. See section 6.10 for a navigational map.

GENERAL PAGE: Overview of Real Time Readings

• Volts AN/BN/CN/AB/BC/CA

• Amps A/B/C

• Watts

• VARS

• VA

• FREQ

• PF

Groups of Readings

General Page

Reset Button

View Limits

View / Change Settings

Figure 6.2: Nexus P60N Touch Screen External Display (Main Screen)

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VOLTS: Voltage Readings Details

• Real Time Volts AN/BN/CN/AB/BC/CA

• Maximum Volts AN/BN/CN/AB/BC/CA

• Minimum Volts AN/BN/CN/AB/BC/CA

Touch PH-N or PH-PH to view details of Phase-to-Neutral or Phase-to-Phase Readings.

VOLTS: Voltage Readings PH-N

• Volts AN/BN/CN

Touch BACK to return to the Volts main screen.

VOLTS: Voltage Readings PH-PH

• Volts AB/BC/CA

Touch BACK to return to the Volts main screen.

AMPS: Current Readings Details

• Real Time Current A/B/C

• Maximum Current A/B/C

• Minimum Current A/B/C

• Current Calculated N/Measured N

• Maximum Current Calculated N/

Measured N

Touch A-B-C to view Currents Detail.

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AMPS: Current Readings A-B-C

• Real Time Current A/B/C

Touch BACK to view the Amps main screen.

REAL TIME POWER: Real Time Power Readings Details

• Instant Watt/VAR/VA/PF

• Average Watt/VAR/VA/PF

• Predicted Watt/VAR/VA

Touch the DEMAND button to go to the Demand Power screen (shown below)

DEMAND POWER: Demand Power Readings Details

• Thermal Window Average Maximum +kWatt/+kVAR/CoIn kVAR

• Block (Fixed) Window Average Maximum +kWatt/+kVAR/CoIn kVAR

• Predictive Rolling (Sliding) Window Maximum +kWatt/+kVAR/CoIn kVAR

Touch R/T button to view Real Time Power screen.

ENERGY: Accumulated Energy Information

• -Watthr Quadrant 2+Quadrant 3 (Primary)

• +VAhr Quadrant 2 (Primary)

• +VARhr Quadrant 2 (Primary)

• +VAhr Quadrant 3 (Primary)

• -VARhr Quadrant 3 (Primary)

• +Watthr Quadrant 1+Quadrant 4 (Primary)

• +VAhr for all Quadrants (Primary)

Touch TOU button to view TOU Register Accumulations screen.

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TOU: Accumulations

• -Watthr Quadrant 2+Quadrant 3 (Primary)

• +VAhr Quadrant 2 (Primary)

• +VARhr Quadrant 2 (Primary)

• +VAhr Quadrant 3 (Primary)

• -VARhr Quadrant 3 (Primary)

• +Watthr Quadrant 1+Quadrant 4 (Primary)

• +VAhr Quadrants 1 & 4 (Primary)

• -VARhr Quadrant 4 (Primary)

Touch DEMAND to view Register Demand screen. Touch Next Reg to scroll Registers 1 - 8 and Totals. Touch Next Group to scroll Prior Season, Prior Month, Current Season, Current Month.

TOU: Register Demand

• Block (Fixed) Window +kWatth, +kVARhr,

-kWatth, -kVARh, Coin +kVARh, Coin -kVARh

Touch ACCUM to view TOU Accumulations. Touch Next Reg to scroll Registers 1 - 8 and Totals. Touch Next Group to scroll Prior Season, Prior Month, Current Season, Current Month.

FLICKER - INSTANTANEOUS:

• Time Start/Reset, Stop, Current, Next PST, PLT

• Status (Active or Stopped)

• Frequency

• Base Voltage

• Frequency

Touch SHORT TERM or LONG TERM to view other Flicker screens. START or STOP will appear, depending on Status.

FLICKER - SHORT TERM:

• Volts A/B/C

• Max Volts A/B/C

• Min Volts A/B/C

Touch INST or LONG TERM to view screens. START or STOP will appear, depending on Status.

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FLICKER - LONG TERM:

• Volts A/B/C

• Max Volts A/B/C

• Min Volts A/B/C

Touch INST or LONG TERM to view other Flicker screens. START or STOP will appear, depending on Status.

LIMITS: Limit Status

Current Limits Settings for Nexus Meters, ID 1 - 32. For each ID number, the Type of Reading, Value, Status (In or Out of Limit) and Setting is shown. The first screen displays the settings for Meters ID 1 to 8.

Touch NEXT GROUP to scroll to the next screen, which displays the settings for Meters ID 9 to 16. Touch NEXT GROUP again to view settings for Meters ID 17 to 24 and 25 to 32.

PHASORS: Phasor Analysis

Phase Angles for Form shown at top of the screen.

• Phase

• Phase Angle V an/bn/cn

• Phase Angle Ia/b/c

• Phase Angle V ab/bc/ca

WAVEFORM: Real Time Graph.

• Channel Va/b/c

• Channel Ia/b/c

• % THD, KFactor, Frequency for

selected channel

Touch CHANNEL button to view scroll through channels.

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SPECTRUM: Harmonic Spectrum Analysis.

Select a Channel by touching the CHANNEL button. Graphs and readings appear for the selected channel.

Zoom In or Out for detail by touching IN or OUT.

REAL TIME TRENDING ANALYSIS:

Select Channel by touching the CHANNEL button. The Channel Selector screen (shown below) appears. Select a Channel and touch OK to select channel and return to this screen. Trending for the Selected Channel will begin on this screen.

To see a Detail of logs for the Selected Channel, touch the DETAIL Button. A Table of Logs for the Selected Channel appears (Volts AN shown below). Touch PREVIOUS LOGS to view other logs.

REAL TIME TRENDING CHANNEL SELECTOR:

Select Channel by touching a CHANNEL Button. The Active Channel appears at the lower right.

Data from the previously Active Channel will be lost if the Channel is changed.

The Time Interval for Trending appears at the bottom of the screen. To increase the Interval, touch the UP button. To decrease the Interval, touch DN (Down).

Touch OK to return to Trending Analysis screen.

REAL TIME TRENDING DETAIL

A Table of Logs for the Selected Channel (Volts AN shown here). Touch BACK to return to the Trending Analysis screen. Touch PREVIOUS LOGS to view other logs.

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LOG STATUS: Logging Statistics

An Overview of the Logs for the Primary Meter.

The Number of Records and Memory Used are listed for each log.

RESET: Meter Reset Commands.

WARNING! RESETS cause data to be lost.

Touch the window for the Reset you want to perform. Don’t Reset changes to Reset. Touch RESET NOW button. OK will appear. Touch OK to refresh screen (go back to original screen).

• Max/Min and Demand.

• Hour, I

T and V2T Counters.

• All Logs.

• TOU for Current Session and Month.

SETTINGS:

LCD SCREEN SETTINGS:

Contrast. Touch Up/Down buttons to increase/decrease settings. Number 37 is optimum setting. Backlight Off Delay (number of seconds after use that backlight turns off). Touch Up/Down buttons to increase/decrease settings.

NEXUS LINK SETTING:

Nexus Address (000 - 255). Touch Up/Down buttons to increase/decrease settings. Protocol (selected). Baud (selected).

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Electro-Voice 250, 1252 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

Table of Contents

1.1.1: Wye Connection

1.1.2: Delta Connection

1.2: Power, Energy and Demand

1.3: Reactive Energy and Power Factor

1.4: Harmonic Distortion

1.5: Power Quality

2.1: The Nexus System

2.2: DNP V3.00 Level 1 and Level 2

2.3: Flicker

2.4.1: Hardware Overview

2.5: Total Web Solutions

2.5.1: Hardware Overview

2.5.2: Hardware Connection

2.6: Measurements and Calculations

2.7: Demand Integrators

2.9: Nexus 1250/1252 Meter Specifications

2.10: Nexus P40N, P41N, P43N LED External Display Specifications

2.11: Nexus P60N Touch Screen Display Specifications

3.1: Mounting the Nexus 1250/1252 Meter

3.2: Mounting the Nexus LED External Displays

3.3: Mounting the Nexus P60N Touch Screen External Display

3.4: Mounting the Nexus External I/O Modules

4.1: Wiring the Monitored Inputs and Voltages

4.2: Fusing the Voltage Connections

4.3: Wiring the Monitored Inputs - VRef

4.4: Wiring the Monitored Inputs - VAux

4.5: Wiring the Monitored Inputs - Currents

4.6: Isolating a CT Connection Reversal

4.7: Instrument Power Connections

4.8: Wiring Diagrams

5.1: Communication Overview

5.7.1: Using the Unicom 2500

5.10: Communication Ports on the Nexus I/O Modules

5.12: Steps to Determine Power Needed

5.14: Linking Multiple Nexus Devices in Series

5.15: Networking Groups of Nexus Meters

5.16: Remote Communication Overview

5.19: Programming Modems for Remote Communication

5.20: Selected Modem Strings

5.21: High Speed Inputs Connection

5.22: Five Modes of Time Synchronization

6.1: Overview

6.2: Nexus P40N, P41N and P43N LED External Displays

6.2.2: Nexus P40N Modes

6.3: Dynamic Readings Mode

6.4: Navigational Map of Dynamic Readings Mode

6.5: Nexus Information Mode

6.6: Navigational Map of Nexus Information Mode

6.7: Display Features Mode

6.8: Navigational Map of Display Features Mode

6.9: Nexus P60N Touch Screen External Display