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Code No. LIT-12011874
Issued July 21, 2014
EM-3000 Series Meter Installation
and Operation Manual
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EM-3000 Series Meter Installation and Operation Manual
Published by:
Johnson Controls, Inc.
Building Efficiency
507 E. Michigan Street, Milwaukee, WI 53202
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 Johnson Controls, Inc.
Metasys® and Johnson Controls® are registered trademarks of Johnson Controls, Inc. All other marks herein are the marks of their respective owners.
© 2014 Johnson Controls, Inc.
EM-3000 Series Meter Installation and Operation Manual |
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EM-3000 Series Meter Installation and Operation Manual |
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Use Of Product for Protection
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.
Statement of Calibration
Our instruments are inspected and tested in accordance with specifications published by Johnson Controls, Inc. 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. For optimal performance, Johnson Controls, Inc. recommends that any meter be verified for accuracy on a yearly interval using NIST traceable accuracy 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.
Safety Symbols
In this manual, this symbol indicates that the operator must refer to an important WARNING or CAUTION in the operating instructions. Please see Chapter 4 for important safety information regarding installation and hookup of the meter.
Dans ce manuel, ce symbole indique que l’opérateur doit se référer à un important AVERTISSEMENT ou une MISE EN GARDE dans les instructions opérationnelles. Veuillez consulter le chapitre 4 pour des informations importantes relatives à l’installation et branchement du compteur.
The following safety symbols may be used on the meter itself:
This symbol alerts you to the presence of high voltage, which can cause dangerous electrical shock.
Ce symbole vous indique la présence d’une haute tension qui peut provoquer une décharge électrique dangereuse.
EM-3000 Series Meter Installation and Operation Manual |
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This symbol indicates the field wiring terminal that must be connected to earth ground before operating the meter, which protects against electrical shock in case of a fault condition.
Ce symbole indique que la borne de pose des canalisations in-situ qui doit être branchée dans la mise à terre avant de faire fonctionner le compteur qui est protégé contre une décharge électrique ou un état défectueux.
This symbol indicates that the user must refer to this manual for specific WARNING or CAUTION information to avoid personal injury or damage to the product.
Ce symbole indique que l'utilisateur doit se référer à ce manuel pour AVERTISSEMENT ou MISE EN GARDE l'information pour éviter toute blessure ou tout endommagement du produit.
FCC Information
Regarding the wireless module:
•This device complies with Part 15 of the FCC rules. Operation is subject to the following two conditions: 1) this device may not cause harmful interference, and
2)this device must accept any interference received, including interference that may cause undesired operation.
•The antenna provided must not be replaced with a different type. Attaching a different antenna will void the FCC approval and the FCC ID can no longer be considered.
EM-3000 Series Meter Installation and Operation Manual |
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Table of Contents
Table of Contents
Use Of Product for Protection |
iii |
Statement of Calibration |
iii |
Disclaimer |
iii |
Safety Symbols |
iii |
FCC Information |
iv |
1: Three-Phase Power Measurement |
1-1 |
1.1: Three-Phase System Configurations |
1-1 |
1.1.1: Wye Connection |
1-1 |
1.1.2: Delta Connection |
1-4 |
1.1.3: Blondel’s Theorem and Three Phase Measurement |
1-6 |
1.2: Power, Energy and Demand |
1-8 |
1.3: Reactive Energy and Power Factor |
1-12 |
1.4: Harmonic Distortion |
1-14 |
1.5: Power Quality |
1-17 |
2: EM-3000 Series Meter Overview and Specifications |
2-1 |
2.1: Hardware Overview |
2-1 |
2.1.1: Model Number plus Option Numbers |
2-3 |
2.1.2: Measured Values |
2-4 |
2.1.3: Utility Peak Demand |
2-5 |
2.2: Specifications |
2-5 |
2.3: Compliance |
2-10 |
2.4: Accuracy |
2-11 |
EM-3000 Series Meter Installation and Operation Manual |
TOC-1 |
Table of Contents
3: Mechanical Installation |
3-1 |
3.1: Overview |
3-1 |
3.2: Install the Base |
3-2 |
3.2.1:Mounting Diagrams |
3-3 |
3.3: Secure the Cover |
3-7 |
4: Electrical Installation |
4-1 |
4.1: Considerations When Installing Meters |
4-1 |
4.2: Electrical Connections |
4-5 |
4.3: Ground Connections |
4-6 |
4.4: Voltage Fuses |
4-7 |
4.5: Electrical Connection Diagrams |
4-7 |
5: Communication Installation |
5-1 |
5.1: EM-3000 Series Meter Communication |
5-1 |
5.1.1: IrDA Port (Com 1) |
5-1 |
5.1.2: KYZ Output |
5-2 |
5.1.3: Ethernet Connection |
5-4 |
6: Ethernet Configuration |
6-1 |
6.1: Introduction |
6-1 |
6.2: Factory Default Settings |
6-2 |
6.2.1: Modbus/TCP to RTU Bridge Setup |
6-3 |
6.3: Configure Network Module |
6-4 |
6.3.1: Configuration Requirements |
6-4 |
6.3.2: Configuring the Ethernet Adapter |
6-5 |
EM-3000 Series Meter Installation and Operation Manual |
TOC-2 |
Table of Contents
6.3.3: Detailed Configuration Parameters |
6-8 |
6.3.4: Setup Details |
6-9 |
6.4: Network Module Hardware Initialization |
6-14 |
6.5: Integrating the EM-3000 Series Meter into a WLAN |
6-15 |
7: Using the Submeter |
7-1 |
7.1: Introduction |
7-1 |
7.1.1: Understanding Submeter Face Elements |
7-1 |
7.1.2: Understanding Submeter Face Buttons |
7-2 |
7.2: Using the Front Panel |
7-3 |
7.2.1: Understanding Startup and Default Displays |
7-3 |
7.2.2: Using the Main Menu |
7-4 |
7.2.3: Using Reset Mode |
7-5 |
7.2.4: Entering a Password |
7-6 |
7.2.5: Using Configuration Mode |
7-7 |
7.2.5.1: Configuring the Scroll Feature |
7-9 |
7.2.5.2: Configuring CT Setting |
7-10 |
7.2.5.3: Configuring PT Setting |
7-11 |
7.2.5.4: Configuring Connection Setting |
7-13 |
7.2.5.5: Configuring Communication Port Setting |
7-13 |
7.2.6: Using Operating Mode |
7-15 |
7.3: Understanding the % of Load Bar |
7-16 |
7.4: Performing Watt-Hour Accuracy Testing (Verification) |
7-17 |
A: EM-3000 Series Meter’s Navigation Maps |
A-1 |
EM-3000 Series Meter Installation and Operation Manual |
TOC-3 |
Table of Contents
A.1: Introduction |
A-1 |
A.2: Navigation Maps (Sheets 1 to 4) |
A-1 |
B: EM-3000 Series Meter’s Modbus Map |
B-1 |
B.1: Introduction |
B-1 |
B.2: Modbus Register Map Sections |
B-1 |
B.3: Data Formats |
B-1 |
B.4: Floating Point Values |
B-2 |
B.5: Modbus Register Map |
B-3 |
EM-3000 Series Meter Installation and Operation Manual |
TOC-4 |
1: Three Phase Power Measurement
1: Three-Phase 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-Phase 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 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).
EM-3000 Series Meter Installation and Operation Manual |
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1: Three Phase Power Measurement
VC
Phase 3 |
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Phase 2 |
Phase 1 |
VB |
VA |
Figure 1.1: Three-phase Wye Winding
The three voltages are separated by 120o electrically. Under balanced load conditions the currents are also separated by 120o. However, unbalanced loads and other conditions can cause the currents to depart from the ideal 120oseparation. Threephase voltages and currents are usually represented with a phasor diagram. A phasor diagram for the typical connected voltages and currents is shown in Figure 1.2.
VC
IC
N
IA
VB IB VA
Figure 1.2: Phasor Diagram Showing Three-phase Voltages and Currents
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1: Three Phase Power Measurement
The phasor diagram shows the 120o angular separation between the phase voltages. The phase-to-phase 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 wyeconnected systems.
Phase to Ground Voltage |
Phase to Phase Voltage |
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120 volts |
208 volts |
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277 volts |
480 volts |
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2,400 volts |
4,160 volts |
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7,200 volts |
12,470 volts |
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7,620 volts |
13,200 volts |
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Table 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.
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.
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1: Three Phase Power Measurement
1.1.2: Delta Connection
Delta-connected services may be fed with either three wires or four wires. In a threephase 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.
VC
Phase 2 |
Phase 3 |
VB |
Phase 1 |
VA |
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Figure 1.3: Three-phase Delta Winding Relationship
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 threephase 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.
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1: Three Phase Power Measurement
VBC IC
IB 
VAB
Figure 1.4: Phasor Diagram, Three-Phase Voltages and Currents, Delta-Connected
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.
VC
VCA
VBC N |
VA |
VAB
VB
Figure 1.5: Phasor Diagram Showing Three-phase Four-Wire Delta-Connected System
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1: Three Phase Power Measurement
1.1.3: Blondel’s Theorem and Three Phase Measurement
In 1893 an engineer and mathematician named Andre E. Blondel set forth the first scientific basis for polyphase 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 Blondel'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, Blondel'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 single three-phase reading.
EM-3000 Series Meter Installation and Operation Manual |
1 - 6 |
1: Three Phase Power Measurement
Some digital meters measure 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 adds 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.
C
B
Phase B
Phase C
Node "n"
Phase A |
A |
N |
Figure 1.6: Three-Phase Wye Load Illustrating Kirchhoff’s Law and Blondel’s Theorem
Blondel'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 three-phase, four-wire service. Kirchhoff's Law holds 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 Blondel's Theoremthat we only need to measure the power in three of
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1: Three Phase Power Measurement
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.
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 kilowatthour 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
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1: Three Phase Power Measurement
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).
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Time (minutes)
Figure 1.7: Power Use over Time
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1 - 9 |
1: Three Phase Power Measurement
Time |
Power |
Energy |
Accumulated |
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Interval |
Energy |
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(kW) |
(kWh) |
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(minute) |
(kWh) |
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1 |
30 |
0.50 |
0.50 |
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2 |
50 |
0.83 |
1.33 |
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3 |
40 |
0.67 |
2.00 |
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55 |
0.92 |
2.92 |
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60 |
1.00 |
3.92 |
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60 |
1.00 |
4.92 |
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70 |
1.17 |
6.09 |
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70 |
1.17 |
7.26 |
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60 |
1.00 |
8.26 |
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70 |
1.17 |
9.43 |
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80 |
1.33 |
10.76 |
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0.83 |
12.42 |
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0.83 |
12.42 |
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70 |
1.17 |
13.59 |
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80 |
1.33 |
14.92 |
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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
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1: Three Phase Power Measurement
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.
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.
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Intervals (15 mins.)
Figure 1.8: Energy Use and Demand
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.
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1: Three Phase Power Measurement
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 90o 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.
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IR |
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IX |
I |
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Figure 1.9: Voltage and Complex Current
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
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1: Three Phase Power Measurement
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, some 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 result, it does not include the impact of
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1: Three Phase Power Measurement
harmonic distortion. Displacement power factor is calculated using the following equation:
Displacement PF = cos
where 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.
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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.
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1: Three Phase Power Measurement
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Figure 1.11: Distorted Current Waveform
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.
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Figure 1.12: Waveforms of the Harmonics
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1: Three Phase Power Measurement
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.
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.
XL = j L and
XC = 1/j C
At 60 Hz, = 377; but at 300 Hz (5th harmonic) = 1,885. As frequency changes impedance changes and system impedance characteristics that are normal at 60 Hz may behave entirely differently in the presence of higher order harmonic waveforms.
Traditionally, the most common harmonics have been the low order, odd frequencies, such as the 3rd, 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 a 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.
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1: Three Phase Power Measurement
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.
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. A simple 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.
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Cause |
Disturbance Type |
Source |
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Impulse transient |
Transient voltage disturbance, |
Lightning |
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sub-cycle duration |
Electrostatic discharge |
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Load switching |
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Capacitor switching |
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Oscillatory |
Transient voltage, sub-cycle |
Line/cable switching |
transient with decay |
duration |
Capacitor switching |
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Load switching |
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Sag/swell |
RMS voltage, multiple cycle |
Remote system faults |
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duration |
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Interruptions |
RMS voltage, multiple |
System protection |
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seconds or longer duration |
Circuit breakers |
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Fuses |
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Maintenance |
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Under voltage/over voltage |
RMS voltage, steady state, |
Motor starting |
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multiple seconds or longer |
Load variations |
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duration |
Load dropping |
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Voltage flicker |
RMS voltage, steady state, |
Intermittent loads |
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repetitive condition |
Motor starting |
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Arc furnaces |
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Harmonic distortion |
Steady state current or volt- |
Non-linear loads |
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age, long-term duration |
System resonance |
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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 many 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.
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2: Meter Overview and Specifications
2: EM-3000 Series Meter Overview and
Specifications
2.1: Hardware Overview
The EM-3000 Series multifunction submeter is designed to measure revenue grade electrical energy usage and communicate that information via various communication media. The unit supports RJ45 wired Ethernet or IEEE 802.11 WiFi Ethernet connections. This allows the EM-3000 Series meter to be placed anywhere within an industrial or commercial facility and still communicate quickly and easily back to central software. The unit also has a front IrDA port that can be read and configured with an IrDA-equipped device, such as a laptop PC.
The unit is designed with advanced measurement
capabilities, allowing it to achieve high performance accuracy. The EM-3000 Series meter is specified as a 0.2% class energy meter for billing applications. To verify the meter’s performance and calibration, power providers use field test standards to verify that the unit’s energy measurements are correct. The EM-3000 Series meter is a traceable revenue meter and contains a utility grade test pulse to verify rated accuracy.
EM-3000 Series meter features detailed in this manual are:
•0.2% Class Revenue Certifiable Energy and Demand Submeter
•Meets ANSI C12.20 (0.2%) and IEC 62053-22 (0.2%) Classes
•Multifunction Measurement including Voltage, Current, Power, Frequency, Energy, etc.
•Power quality measurements (% THD and alarm limits)
•Three line 0.56” bright red LED display
•Percentage of Load bar for Analog meter perception
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