Utility Relay Company AC-PRO, I-AC-PRO-QT Instruction Manual

ac-pro

®

i-ac-pro-QT ac trip unit

instruction manual

State of the art technology for low

voltage circuit breaker retrofitting

URC

Utility Relay Company

Chagrin Falls, OH 44023

Phone: [phone]

www.utilityrelay.com

AC-PRO® With QUICK-TRIP® Instruction Manual www.utilityrelay.com

Manual Rev 1.3

Section: Page

1.0 Introduction ............................................................1

2.0 UL/ULC Classification ............................................1

3.0 Trip Unit Power ......................................................1

3.1 Current Transformer (CT) Power ...................1

3.2 Battery Power ................................................1

3.3 PT Module Power ..........................................2

3.4 Auxiliary Power ..............................................2

4.0 External Connections .............................................2

4.1 Breaker Wiring Harness .................................2

4.2 Security Key ...................................................2

5.0 AC-PRO

®

Front View .............................................3

5.1 16 Character Display .....................................4

5.2 Pick-Up LED ..................................................4

5.3 Self Test LED .................................................4

5.4 Display Contrast ............................................4

5.5 UP Push Button .............................................4

5.6 DOWN Push Button .......................................4

5.7 SAVE Push Button .........................................4

5.8 REVIEW Push Button ....................................4

6.0 QUICK-TRIP

6.1 QUICK-TRIP

6.2 QUICK-TRIP

6.3 QUICK-TRIP

7.0 Commissioning the AC-PRO

®

System ...........................................5

®

Basics .....................................5

®

Installation ..............................6

®

& Pro-Display Operation .........7

®

................................7

7.1 Powering-Up the Trip Unit .............................7

7.1.1 Internal Battery ....................................7

7.1.2 External Power ....................................7

7.2 Security Key ...................................................7

7.3 CT Rating .......................................................8

7.4 Long Time (LT) Pick-Up Setting ....................8

7.5 Long Time (LT) Delay Setting ........................8

7.6 Short Time (ST) Pick-Up Setting ...................8

7.7 Short-Time (ST) Delay Setting .......................8

7.8 Short Time (ST) I

2

T ........................................8

7.9 Instantaneous (I) Pick-Up Setting ..................9

7.10 Ground Fault (GF) Pick-Up Setting ................9

7.11 Ground Fault (GF) Delay Setting ...................9

7.12 Ground Fault (GF) I

2

T ....................................9

7.13 Phase Unbalance (U/B) Pick-Up ...................9

7.14 Phase Unbalance (U/B) Delay .......................10

7.15 Address ..........................................................10

7.16 Reply Delay ...................................................10

7.17 QUICK-TRIP

7.18 QUICK-TRIP

®

Ground Fault (QT GF) ............10

®

Instantaneous (QT I) ..............10

7.19 Thermal Memory ............................................11

7.20 Exit Procedure ...............................................11

8.0 Changing Settings..................................................12

9.0 Last Trip Data Recall .............................................13

10.0 Normal Operation ...................................................14

11.0 Testing ...................................................................14

11.1 Commission the Trip Unit ..............................14

11.2 LT Trip Test ...................................................14

11.3 ST Trip Test ...................................................15

11.4 I Trip Test .......................................................15

11.5 GF Trip Test ...................................................15

11.6 QT GF Trip Test .............................................15

11.7 CT Phasing Test for GF .................................15

11.8 QT I Trip Test .................................................16

11.9 U/B Trip Test ..................................................16

11.10 Erase Last Trip Data ....................................16

12.0 Secondary Injection Testing .................................. 17

12.1 AC-PRO

®

Secondary Injection Test Set ........ 17

12.2 Standard Relay Test Set ............................... 17

12.3 LT Delay Testing Chart ................................. 18

13.0 Ratings .................................................................. 19

14.0 Warranty ................................................................ 19

15.0 Time-Current Curves ............................................. 19

15.1 LT Trip Time .................................................. 20

15.2 ST Trip Time .................................................. 20

15.3 GF Trip Time ................................................. 21

15.4 U/B Trip Time ................................................ 21

16.0 Error Message Summary ...................................... 21

16.1 Actuator Not Connected ................................ 21

16.2 Memory Error ................................................ 21

17.0 Battery Replacement ............................................. 22

Figure: Page

4.1 AC-PRO

4.2 Push Button “Key” ................................................. 2

5.1 AC-PRO

5.2 AC-PRO

6.1 QUICK-TRIP

6.2 QUICK-TRIP

®

Top View ............................................... 2

®

Horizontal Front View ........................... 3

®

Vertical Left Front View ......................... 3

®

Connections ................................... 5

®

Drilling Plan .................................... 6

6.3 Pro-Display Mounting ............................................ 6

11.1 Phase A & B, CT Phasing Test ............................. 15

11.2 Phase B & C, CT Phasing Test ............................. 15

11.3 U/B Test ................................................................ 16

12.1 AC-PRO

®

Secondary Injection Test Set ................ 17

17.1 Battery Replacement ............................................. 22

18.1 Typical Wiring Diagram ......................................... 23

18.2 Overload TCC ....................................................... 25

18.3 U/B & GF TCC ....................................................... 27

18.4 QUICK-TRIP

®

GF & I TCC .................................... 29

Firmware Revision: 5.26

AC-PRO® With QUICK-TRIP® Instruction Manual www.utilityrelay.com

1.0 Introduction

The AC-PRO is a state of the art, micro-controller based trip
unit for use on three phase, 600 Volt class, AC circuit
breakers. Models are available for use on 60 Hz, 50 Hz,
40 Hz, and 25 Hz systems.

The AC-PRO is a digital trip unit that uses a micro-controller
and a 16-character liquid crystal display (LCD).

The trip unit provides ov er-curre nt, a s well as short tim e and
instantaneous fault protection. All of the phas e protection

functions use the true RMS currents including the
instantaneous trip function.

The AC-PRO measures the true RMS current through each
of the breaker’s three poles. For ground fault current, the
trip unit also does a vector sum of the three phase currents
(and neutral current if applicable) and determines the
fundamental frequency component.

The trip unit also offe rs gr ound fault and phase u nbala nce ( U/B)
tripping functions as user selectable options. The fundamental

value of the ground fault current is used for th e ground
fault trip function to eliminate nuisance ground fau lt trips
due to multiples of the 3

The AC-PRO also has two additiona l QUICK-T RIP pr otect ive
settings that are intended t o minimize Arc Flash Hazard. The
QUICK-TRIP ground fault and instantaneous trip fu nction s are
turned ON or OFF using the QUICK-TRIP D isplay . See S ection

6.0 for complete details.
The trip unit stores the last trip data and the trip log data in a

non-volatile FRAM memory for later recall. All the settings
are stored in non-volatile EEPROM memory. Battery backup
is not required.

The trip unit does not require externa l power to op erate . Pow er
is derived from the current tran sform er s (CTs) . An inter na l
battery provides power to review a nd change pr otect ion
settings when CT power is unavailable.

All settings are made directly in amps or in seconds. A

The AC-PRO trip unit is manufactured under one or more of

US 7,646,575
US 7,889,472

Other patents may be pending.

security system reduces the risk of unauthorized tampering
with the trip unit settings.

the following patents:

2.0 UL/ULC Classification

AC-PRO is UL and ULC classified for use on the following
low voltage AC power circuit breakers:

rd

harmonic.

Westinghouse DB-50
General Electric AK-50
General Electric AK-75

ITE KB Steel Back

FPE H-3

Press the “REVIEW” push button to turn the trip unit on

When on battery power, the trip unit will automatically turn

UL and ULC classification is in accordance with UL1066,
CSA C22.2, IEEE C37.59-1991 as well as appropriate
sections of ANSI C37.17-1979 and C37.50-1989.

AC-PRO was tested by an independent laboratory and found
in compliance with the following tests:

3.0 Trip Unit Power

IEEE C37.90.2-2004, RF Susceptibility
IEEE C37.90.1-2002, Surge Withstand
15KV Electro-Static Discharge
Accuracy @ -20°C & +65°C

The AC-PRO can be powered in 4 different ways: CTs,
internal battery, PT module, or auxiliary power pack.

3.1 Current Transformer (CT) Power

The AC-PRO derives both signal and power from the
breaker phase CTs. The trip unit will power-up with less
than 10% of the rated CT tap current through a single CT
(20% for the 1/2 Amp version). This current is below the
lowest pick-up setting.

3.2 Battery Power

A 9-volt, 750 mAh, long life, lithium battery is used in the trip
unit. This battery has less than 2 grams of lithium. There are
no restrictions on transport and no special methods of
disposal required with this battery.

The battery is designed to provide two functions:

1) Allow the user to commission (program) the trip unit
without using the auxiliary power pack.

2) Allow the user to recall the last trip data even if the
breaker is open and without using the auxiliary power
pack.

under battery power.

off 30 seconds after the last button is pushed to conserve
battery energy.

The battery is NOT involved in the protective functions of
the trip unit. The trip unit will provide protection even if the
battery is removed.

The battery is NOT required for the trip unit to maintain
any of its memory including the user programmed pick-up
and delay settings and the last trip data.

See Section 17.0 for battery data and instructions on
replacing the battery.

**** NOTE ****

Page 1

Utility Relay Company

3.3 PT Module Power

The AC-PRO trip unit is available with a communication
option that has a connection for a PT module.

The PT module provides breaker 3-Phase voltage
information and also provides power for the trip unit
independently from the CTs. See the Communication
Instruction Manual for more information.

3.4 Auxiliary Power

Auxiliary power is optional. It can be used to change or
review the trip unit settings without using the internal battery.

Plug the 24-VAC auxiliary power pack into the auxiliary
power jack on the top of the trip unit.

The power pack is available from Utility Relay Company as
part number T-390.

4.0 External Connections

The external connections are made to the top of the
AC-PRO trip unit (or the left or right side for the vertical
versions).

Breaker Wiring Harness
See Section 4.1

Security Key
See Section 4.2

QT Display Jack
See Section 6.0

Battery Cover
See Section 3.2 & 17.0

4.2 Security Key

The AC-PRO trip unit contains a security feature that only
allows someone familiar with the operation of the trip unit to
commission the trip unit or make changes to the settings. A
security key is required to change any of the settings.

The "Key" is simply a short jumper wire that is connected
between the two terminals marked “KEY” on the top of the
trip unit.

Refer to Figure 4.0-1 AC-PRO top view.
To turn the security Key "ON":

Jumper the two terminals labeled “KEY” on the top of

the trip unit.

To turn the security Key "OFF":
Remove the jumper wire.

The key allows the user to commission the trip unit or to
change the settings on a trip unit by performing the steps as
outlined in Sections 7.0 and 8.0.

The “CT Rating” also has an additional security feature as
explained in Section 7.3.

+

ACTUATOR

PHASE

PHASE

A

BREAKER HARNESS

BATTERY

QT

DISPLAY

COVER

Use only 9V
Lithium Battery

24 VAC

KEY

AUXILIARY

PHASE

B

C

NEUTRAL

POWER

BATTERY

+

A

B

C

PHASE

PHASE

PHASE

ACTUATOR

BREAKER HARNESS

NEUTRAL

KEY

24 VAC

AUXILIARY

POWER

DISPLAY

COVER

QT

Use only 9V
Lithium Battery

Auxiliary Power Jack
See Section 7.1.2

Figure 4.0-1 AC-PRO® Top View

4.1 Breaker Wiring Harness

The breaker wiring harness connects the trip unit to the CTs
and actuator. The wiring harness plugs into the 10-pin
connector on the top of the trip unit and is retained with two
screws.

Pin Function Color Code
1 Actuator (+) Red
2 Actuator (-) Black
3 Phase A (Dot) Blue
4 Phase A White
5 Phase B (Dot) Yellow
6 Phase B White
7 Phase C (Dot) Brown
8 Phase C White
9 Neutral CT (Dot) Green
10 Neutral CT White

Table 4.1 Breaker Wiring Harness Pin-Out
A neutral CT wiring harness is provided as part of the neutral

CT installation kit and is only required with ground fault on a
4-wire system. The ground fault function on a 3-wire system
does not require a neutral CT.

Breaker Escutcheon

Push Button "Key"

Figure 4.0-2 Push Button “Key”

When the AC-PRO is installed on some breakers, the “Key”
terminal block on top of the trip unit is not readily accessible.

In those cases a short harness with a “Key” push button is
provided. The “Key” push button is installed in the breaker
escutcheon so it is easily accessible.

To turn the security Key "ON" with the “Key” button:
Push and hold the “Key” button.

To turn the security Key "OFF" with the “Key” button:
Release the “Key” button.

Page 2

AC-PRO® With QUICK-TRIP® Instruction Manual www.utilityrelay.com

5.0 AC-PRO® Front View

The front view of the horizontal version of the AC-PRO trip
unit is shown in Figure 5.0-1. The front view of a vertical
version of the AC-PRO is shown in Figure 5.0-2.

Wiring Harness

Battery
Cover

CE Mark

Pick-Up
LED

Self Test
LED

UL Label

AC-PRO

UTILITY RELAY COMPANY

Up

Save

Figure 5.0-1 AC-PRO

UL Label

Battery
Cover

R

PICK-UP

SELF TEST OK

SAVE

AC-PRO

Lo

9

With

V Li

n

g-Li

AC TRIP UNIT

WITH QUICK-TRIP

REVIEW

Down

®

Horizontal Front View

TM

PUSH TO
ADJUST
DISPLAY

CONTRAST

PUSH TO VIEW

LAST TRIP DATA

AND SETTINGS

th

i

fe

u

m

Battery

Review

Long-Life Battery

9

W

V

L

i

th

ith

iu

TM

AC TRIP UNIT

WITH QUICK-TRIP

m

TM

AC-PRO

60Hz

1A 0 CT

B-521H

H490F524

1A N CT

PC 01168

CE Mark

Display

Part Number
Label

Contrast

Option
Label

Serial Number
(on end)

Pick-Up
LED

Self Test
LED

Wiring Harness

Figure 5.0-2 AC-PRO

UTILITY RELAY COMPANY

1A 0 CT
1A N CT

Up

Serial Number
(on end)

PUSH TO

ADJUST
DISPLAY

PICK-UP

SELF TEST OK

SAVE

60Hz

H490F524
PC 01180

Save

CONTRAST

REVIEW

PUSH TO VIEW

LAST TRIP DATA

AND SETTINGS

AC-PRO

B-521L

Down

Option
Label

®

Vertical Left Front View

Page 3

Display

Contrast

Review

Part Number
Label

Utility Relay Company

5.1 16 Character Display

A 16-character dot matrix liquid crystal display (LCD)
provides information to the user.

The LCD is used for the following purposes:

1) Entering the CT rating and making the pick-up and time
delay settings with prompts from the display.

2) Displaying, on demand, the C T rating and the various
pick-up and delay settings.

3) Displaying, on demand, the reason for the last trip and
the currents at the time of trip.

4) Continuously displaying the actual 3-phase AC currents
on the breaker.

5.2 Pick-Up LED

The Pick-Up LED is normally off. It will turn on whenever the
breaker current is above the LT Pick-up setting.

5.3 Self Test LED

The Self Test LED is normally on. It will turn off under the
following conditions:

1) The actuator is not connected. The LCD will also
display an error message.

2) There is a checksum error in the micro-controller.

The LCD will also display an error message.

5.4 Display Contrast

The contrast level of the LCD can be adjusted by pressing
this push button.

When the contrast push button is pressed and held, the
display will begin to get either darker or lighter. To change
direction, release the push button for more than one second,
then press and the hold the push button until the desired
contrast is achieved.

5.5 UP Push Button

Use this push button to increase the setting values during
commissioning. When the “UP” push button is held longer
than one second, the settings are increased in fast mode.

When the maximum setting value is reached, the “UP” push
button will have no further effect on the setting value.

5.6 DOWN Push Button

Use this push button to decrease the setting values during
commissioning. When the “DOWN” push button is held
longer than one second, the settings are decreased in fast
mode.

When the minimum setting value is reached, the “DOWN”
push button will have no further effect on the setting value.

5.7 SAVE Push Button

Use this push button to step though the settings when in the
commissioning mode.

Holding this push button has no effect.

5.8 REVIEW Push Button

Use this push button to step though the settings in the
settings review mode. Also use this push button to turn the
trip unit on using battery power.

Hold this push button down to review trip counts during the
settings review.

Page 4

AC-PRO® With QUICK-TRIP® Instruction Manual www.utilityrelay.com

6.0 Quick-Trip® System

QT-Display
on cubicle door

2

2 Pole Plug into
back of Pro-Display

Plug into Jack
in back of
QT-DISPLAY

8/C Cable, shielded
with modular connectors
(100 foot maximum)

AC-PRO

UTILITY RELAY COMPANY

AC-PRO trip unit
on breaker

1

16 Character
display

R

AC TRIP UNIT

PICK-UP

SELF TEST OK

SAVE

WITH QUICK-TRIP

REVIEW

QT-DISPLAY

PICK-UP

SELF TEST OK

QUICK-TRIP ON

UTILITY RELAY COMPANY

Plug into

"QT Display"

jack

Long-Life

9V

With

L

i

thium

TM

Battery

B-521H

AC-PRO

PUSH TO
ADJUST
DISPLAY

H490F524

PC 01168

CONTRAST

60Hz

PUSH TO VIEW
LAST TRIP DATA
AND SETTINGS

1A 0 CT

1A N CT

R

AC-PRO

R

REMOTE DISPLAY

MICRO-CONTROLLER BASED

PUSH TO
ADJUST
DISPLAY

CONTRAST

PUSH TO VIEW

REVIEW

LAST TRIP DATA

AND SETTINGS

Red LED is "ON"
with Quick-Trip turned ON

Padlocking
Cover

To QT-Display

QUICK-TRIP
ON

OFF

Quick-Trip ON-OFF
selector switch

Quick-Trip

OFF

ON

NC
NO

Remote
Indication Contacts
for Customer Use

Quick-Trip
On-Off Contact

Selector Switch Wiring

3

Figure 6.0-1

QUICK-TRIP

6.1 Quick-Trip® Basics

The QUICK-TRIP system is a manually controlled Zone
Selective Interlock (ZSI) system. It can reduce trip times
when turned on and allows selective coordination between
circuit breakers when turned off.

If maintenance personnel must work on energized
equipment, they will first turn the QUICK-TRIP system on at
the breaker feeding the equipment. If a fault now occurs, the
upstream breaker will trip quickly based on the QUICK-TRIP
settings reducing the Arc Flash Hazard to personnel.

When the work is done, the QUICK-TRIP system is turned off
and the original selective coordination is back in effect.

The QUICK-TRIP system consists of the following
components:

1. AC-PRO trip unit with QUICK-TRIP.

2. QUICK-TRIP Display with a “QUICK-TRIP ON“ LED.

3. Padlocking selector switch mounted near the

QUICK-TRIP Display that is used to turn QUICK-TRIP

on and off.

®

Connections

When QUICK-TRIP is on, the following settings are enabled:

• GF QUICK-TRIP (G F QT)

• I QUICK- TRIP (I QT)

All other settings remain in effect.
The “QUICK-TRIP ON LED” provides positive indication that

the QUICK-TRIP settings are active if the LED is on.
The extra contact block on the QUICK-TRIP selector switch

can be used for local or remote indication of the QUICK-TRIP
selector switch setting.

A qualified engineer must determine the QUICK-TRIP
settings, calculate the incident energy levels and
determine the Hazard Risk Categories (HRC).

If an older Pro-Display without the “QUICK-TRIP ON”
LED is plugged into an AC-PRO with QUICK-TRIP, the

**** IMPORTANT ****

QUICK-TRIP settings will always be on.

Page 5

Drill 1 11/16" diameter hole
or alternately use
1 1/4" conduit knockout punch

Utility Relay Company

Outline of
QT-Display

R

1 1/4" 1 1/4"

Drill (2) 13/64"
diameter holes

Figure 6.2-1

QUICK-TRIP

6.2 Quick-Trip® Installation

The QUICK-TRIP system is easy to install on the front of the
breaker cubicle door.

To install the QUICK-TRIP Display:

1. Find a suitable location on the cubicle door and mark

the location of the three (3) holes using the
dimensions in Figure 6.2-1.

2. Drill two (2) 13/64” mounting holes.

3. For the center hole, cut a 1-11/16” diameter hole using

a hole saw or alternately, use a 1-1/4” conduit
knockout punch.

Breaker Cubicle Door

Use 22mm switch knockout punch
Locate near PRO-DISPLAY

®

Drilling Plan

4. Attach the QUICK-TRIP Display to the front of the
cubicle door using two (2) 10-32 hex nuts, flat washers
and lock washers.

5. Connect the QUICK-TRIP Display to the AC-PRO trip
unit by plugging one end of the shielded modular
cable provided into the jack on the back of the QUICK­TRIP Display. Plug the other end of the cable into the

“QT Display” jack on the top of the AC-PRO.

6. Route the cable so it does not interfere with the
opening or closing of the cubical door or with the
racking of the breaker between connect and
disconnect positions. Use cable ties and holders to
hold the cable in position.

To install the on/off selector switch:

1. Use a 22mm switch knock-out punch to make a hole
in the cubicle door for the selector switch. The selector
switch should be located near the QUICK-TRIP
Display.

2. Attach the selector switch, padlock attachment and
contact blocks to the cubicle door.

3. Plug the cable from the switch into the back of the
QUICK-TRIP Display.

(2) 10-32 hex nuts,
flat washers &
lock washers

QT-Display

R

side view

Figure 6.2-2

QUICK-TRIP Display Mounting

Page 6

AC-PRO® With QUICK-TRIP® Instruction Manual www.utilityrelay.com

®

6.3 Quick-Trip® & Pro-Display Operation

The QUICK-TRIP Display will display the same messages as
the display on the AC-PRO. It provides the capability of
viewing the breaker currents and reviewing the settings and
the last trip data without opening the breaker cubicle

door.
For security reasons, it is not possible to change any

settings from the QUICK-TRIP Display.

When the display on the QUICK-TRIP Display is off, push
the “REVIEW” button to power the QUICK-TRIP Display
from the internal battery in the AC-PRO. The following
information will be available:

• Last trip data including the type of trip and the currents

• Pushing the “REVIEW” button will display the trip log

• Continuing to push the “REVIEW” button will step

through the settings

• The “SELF TEST OK” LED will indicate proper operation

• The “QUICK-TRIP ON” LED will indicate the on/off status

of the QUICK-TRIP settings

When the display on the QUICK-TRIP Display is on, the
phase currents will be displayed (if greater than 10% of the
CT tap). The following information will also be available:

• The “PICK-UP” LED will indicate if phase currents are
above the Long Time pick-up setting

• The “SELF TEST OK” LED will indicate proper operation

• The “QUICK-TRIP ON” LED will indicate the on/off status

of the QUICK-TRIP settings

Pushing the “REVIEW” button will display:

• Last trip data including the type of trip and the currents

• Pushing the “REVIEW” button will display the trip log

• Continuing to push the “REVIEW” button will step

through the settings

7.0 Commissioning the AC-PRO

Before the AC-PRO trip unit is put into service, it must first
be commissioned so it will function. This requires the user to
enter all of the pick-up and delay settings into the unit.

The commissioning process normally takes less than a few
minutes to complete.

**** IMPORTANT ****

The trip unit will NOT FUNCTION as it is shipped from
the factory. The user must first COMMISSION the unit as
outlined in this Section to make it functional.

After the AC-PRO is installed on the breaker, it must be
commissioned as follows:

1) Connect the security key (see Section 4.2)

2) Push the "REVIEW" push button to power-up the trip

unit. The trip unit will alternately display the following:

ENTER DATA

SERIAL # XXXXXXX

Press the “SAVE” push button. The following will be
displayed:

PROD: H4.90F5.26

Press the “SAVE” push button to begin the commissioning
process.

3) Enter the appropriate CT tap, pick-up and delay
settings using the "UP", "DOWN" and "SAVE" push
buttons.

4) Remove the security key (see Section 4.2).

Sections 7.1 through 7.20 go over the commissioning
process in greater detail.

****NOTE****

An additional security feature is provided to avoid
accidentally changing the CT tap se tting. See Section 7.3.

7.1 Powering-Up the Trip Unit

In normal service, the AC-PRO trip unit is powered directly
from the breaker mounted CTs.

For commissioning, the AC-PRO trip unit can be powered-up
in either of the following two ways.

7.1.1 Internal Battery

Press the "REVIEW" button to power-up the trip unit using
the internal battery.

The trip unit is designed to shut off automatically if none of
the 4 lower push buttons on the face of the unit are pressed
for 30 seconds. It is best to have all the desired settings
readily available before commissioning the unit when using
the battery.

If the unit shuts down before the commissioning process is
completed, the process must be started again from the
beginning.

7.1.2 External Power

Apply 24 VAC to the "auxiliary power" jack located on the top
of the trip unit using the Utility Relay auxiliary power pack.
(Utility Relay Company part number T-390).

By applying external power, the unit will stay energized as
long as necessary to complete the commissioning process.

7.2 Security Key

The following will be displayed if the security key is not
already connected:

SECURITY KEY OFF

Connect the security key to continue the commissioning
process (See Section 4.2).

Page 7

Utility Relay Company

7.3 CT Rating

After the security key is connected, the following will be
displayed:

CT RATING XXXXA

Where "XXXX" represents the CT rating in amps. The CT
rating can range from 50 amps to 5,000 amps in 25 amp
steps and 5250 amps to 6000 amps in 250 amp steps.

The CT rating entered into the trip unit must correspond to
the actual rating of the phase and neutral CT tap that the trip
unit is connected to.

A security feature is provided so the CT rating will not be
accidentally changed later.

The CT security feature must be used to enter the initial CT
rating or to change the CT rating.

***To Activate the CT Security Feature***

In the commissioning mode and when the CT rating is
displayed:
Simultaneously push and release both the "SAVE"

and "REVIEW" push buttons

This allows the CT rating to be changed.

With the security feature activated, press and hold the "UP"
or "DOWN" push button as required until the correct CT
rating is displayed.

Press the "SAVE” push button to continue.

7.4 Long Time (LT) Pick-Up Setting

The following will be displayed:

LT PICK-UP XXXXA

Where "XXXX" represents the LT Pick-Up setting in amps.
The LT Pick-Up setting ranges from 20% to 100% of the CT
rating. This setting is adjustable in 5 amp steps (50 amp
steps for 5250 to 6000 amp CTs and 0.5 amp steps for 50 to
200 amp CTs).

Press and hold the "UP" or "DOWN" push button as required
until the correct LT Pick-Up setting is displayed.

Press the "SAVE" push button to continue.

7.5 Long Time (LT) Delay Setting

The following will be displayed:

LT DELAY XX.XS

Where "XX.X" represents the LT Delay band. The LT Delay
band is labeled by the number of seconds to trip at 6 times
the LT Pick-Up setting.

The LT Delay setting ranges from 2.0 to 30.0 seconds in
steps of 0.5 seconds. This provides 57 LT Delay bands.

Please note that the LT trip time is not a constant value, but
is a function of breaker current. For lower currents the trip
time is longer, and for higher currents the trip time is shorter.
The trip time is only equal to the LT Delay setting when a

current 6 times the LT Pick-Up setting is applied. See the
time-current curves in Figure 18.2.

Press and hold the "UP" or "DOWN" push button as required
until the correct LT Delay setting is displayed.

Press the "SAVE" push button to continue.

7.6 Short Time (ST) Pick-Up Setting

The following will be displayed:

ST PICK-UP OFF

If the ST function is not desired, press the "SAVE" push
button and go to Step 7.9.

If the ST function is desired, press the "UP" push button and
the following will be displayed:

ST PICK-UP XXXXA

Where "XXXX" represents the ST Pick-Up in amps.
The ST Pick-Up setting ranges from 150% to 1200% of the

LT Pick-Up setting in 100 amp steps (1000 amp steps for
5250 to 6000 amp CTs and 10 amp steps for 50 to 200 amp
CTs). Press and hold the "UP" or "DOWN" push button as
required until the correct ST Pick-Up setting is displayed.

Press the "SAVE" push button to continue.

7.7 Short Time (ST) Delay Setting

If the ST function is not off, then the following will be
displayed:

ST DELAY .XXS

Where ".XX" represents the ST Delay.
The ST Delay settings are .07, .10, .15, .20, .30 and .40

seconds.
Press and hold the "UP" or "DOWN" push button as required

until the correct ST Delay setting is displayed.
Press the "SAVE" push button to continue.

7.8 Short Time (ST) I2T

The I²T function adds a ramp to the ST delay if required for
coordination purposes as shown in the Overload TCC in
Figure 18.2.

If the ST function is not off, then the following will be
displayed:

ST I SQ T XXX

Where "XXX" represents ON or OFF.
If the ST I²T ramp is desired, press the "UP" push button. If

the ST I²T ramp is not desired, press the "DOWN" push
button.

Press the "SAVE” push button to continue.

Page 8

AC-PRO® With QUICK-TRIP® Instruction Manual www.utilityrelay.com

7.9 Instantaneous (I) Pick-Up Setting

The following will be displayed:

I PICK-UP XXXXXA

Where "XXXXX" represents the I Pick-Up in amps.
The I Pick-Up setting ranges from 150% to 1200% of the LT

Pick-Up setting in 100 amp steps (1000 amp steps for 5250
to 6000 amp CTs and 10 amp steps for 50 to 200 amp CTs).

Press and hold the "UP" or "DOWN" push button as required
until the correct I Pick-Up setting is displayed.

If the I function is not desired and the ST function is not off,
press the "DOWN" push button until the following is
displayed:

I PICK-UP OFF

**** NOTE ****

The trip unit does not allow setting both the ST and the I
functions off at the same time.

Press the "SAVE" push button to continue.

7.10 Ground Fault (GF) Pick-Up Setting

If the GF function is not desired, then press the "DOWN"
push button until the following is displayed:

GF PICK-UP OFF

If the GF function is desired, press the "UP" push button and
the following will be displayed:

GF PICK-UP XXXXA

Where "XXXX" represents the GF Pick-Up setting in amps.
The minimum GF Pick-Up setting is 20% of the CT rating

with 10 amp steps (1 amp steps for 50 to 200 amp CTs).
The maximum value is 200% of the CT rating or 1200 amps,
whatever is lower.

Press and hold the "UP" or "DOWN" push button as required
until the correct GF Pick-Up setting is displayed.

Press the "SAVE" push button to continue.

7.11 Ground Fault (GF) Delay Setting

If the GF function is not off, then the following will be
displayed:

GF DELAY .XXS

Where ".XX" represents the GF Delay.
The GF Delay settings are .10, .20, .30, .40 and .50

seconds.
Press and hold the "UP" or "DOWN" push button as required

until the correct GF Delay setting is displayed.
Press the "SAVE” push button to continue.

7.12 Ground Fault (GF) I2T

The I²T function adds a ramp to the GF delay if required for
coordination purposes as shown in the Ground Fault TCC in
Figure 18.3.

If the GF function is not off, then the following will be
displayed:

GF I SQ T XXX

Where "XXX" represents ON or OFF.
If the GF I²T ramp is desired, press the "UP" push button. If

the GF I²T ramp is not desired, press the "DOWN" push
button.

Press the "SAVE” push button to continue.

On a 4-wire system, a neutral CT must be installed to
avoid nuisance GF trips.

To implement GF protection on the main breakers and
the tie breaker of a double ended substation, contact
Utility Relay Co.

7.13 Phase Unbalance (U/B) Pick-Up

The following will be displayed:

If the U/B function is not desired, then press the "SAVE”
push button and go to Step 7.15.

If the U/B function is desired, press the "UP" push button
and the following will be displayed:

Where "XX" represents the U/B Pick-Up setting in
percentage. The minimum and maximum UB Pick-Up setting
is 20% and 50% in steps of 5 percentage points.

Press and hold the "UP" or "DOWN" push button as required
until the correct U/B Pick-Up setting is displayed.

Press the "SAVE" push button to continue.

The U/B function should not be confused with the GF
function.
The U/B function is a motor protection function and
should ONLY be used on breakers feeding a large
3-phase motor where currents are normally balanced.

**** NOTE ****

**** IMPORTANT ****

U/B PICK-UP OFF

UB PICK-UP XX%

**** NOTE ****

Page 9

7.14 Phase Unbalance (U/B) Delay

If the U/B function is not off, then the following will be
displayed:

UB DELAY XXS

Where "XX" represents the U/B Delay. The U/B Delay setting
ranges from 1 to 60 seconds in steps of 1 second.

Press and hold the "UP" or "DOWN" push button as required
until the correct U/B Delay setting is displayed.

Press the "SAVE” push button to continue.

Utility Relay Company

7.15 Address

This setting applies only to AC-PRO
communication option and will not be displayed on non­communicating trip units.

Each communicating trip unit that shares the same twisted
pair must have a unique address.

Where "XXX" represents the trip unit address and ranges
from 1 to 127 in increments of 1. Press the "UP" or "DOWN"
push button as required until the desired address setting is
displayed.

Press the "SAVE” push button to continue.
NOTE: Two trip units can have the same address as long as

they are not connected to the PC, Ethernet converter,
RS-232 converter or Local Communications Interface (LCI)
via the same twisted pair cable.

7.16 Reply Delay

This setting applies only to AC-PRO
communication option and will not be displayed on non­communicating trip units.

The reply delay setpoint is the minimum delay between the
trip unit’s receipt of a MODBUS packet and its reply.

The reply delay can be either 5 or 10 milliseconds. The
factory default is 5 milliseconds.

Where "XXMS" represents either 5 or 10 milliseconds. Press
the "UP" or "DOWN" push button as required until the
desired delay setting is displayed.

Press the "SAVE” push button to continue.

+

trip units with the

ADDRESS XXX

+

trip units with the

REPLY DELAY XXMS

7.17 Quick-Trip® Ground Fault (QT GF)

This setting applies only if the QUICK-TRIP Display and
selector switch are installed. See Section 6.0 for details.

If the QT GF function is not desired, then press the "DOWN"
push button until the following is displayed:

GF QT PICK-UP OFF

If the QT GF function is desired, press the "UP" push button
and the following will be displayed:

GF QT PICK-UP XXXXA

Where "XXXX" represents the QT GF Pick-Up setting in
amps.

The minimum QT GF Pick-Up setting is 20% of the CT rating
with 10 amp steps (1 amp steps for 50 to 200 amp CTs).
The maximum value is 200% of the CT rating or 1200 amps,
whatever is lower.

Press and hold the "UP" or "DOWN" push button as required
until the correct QT GF Pick-Up setting is displayed.

The QT GF function has a non-adjustable short delay time
as shown in Figure 18.4.

Press the "SAVE" push button to continue.

7.18 Quick-Trip® Instantaneous (QT I)

This setting applies only if the QUICK-TRIP Display and
selector switch are installed. See Section 6.0 for details.

The following will be displayed:

I QT PICK-UP XXXXXA

Where "XXXXX" represents the QT I Pick-Up in amps.
The QT I Pick-Up setting ranges from 150% to 1200% of the

LT Pick-Up setting in 100 amp steps (1000 amp steps for
5250 to 6000 amp CTs and 10 amp steps for 50 to 200 amp
CTs).

Press and hold the "UP" or "DOWN" push button as required
until the correct QT I Pick-Up setting is displayed.

The QT I function does not have an off setting. It is turned on
or off using the QUICK-TRIP ON-OFF selector switch. If the
Pro-Display with QUICK-TRIP is not installed, then this
function is always off.

Press the "SAVE" push button to continue.

Page 10

AC-PRO® With QUICK-TRIP® Instruction Manual www.utilityrelay.com

7.19 Thermal Memory

The AC-PRO trip unit has a Thermal Memory feature for the
following protective functions:
Long Time (LT)
Short Time (ST)

Ground Fault (GF)
Thermal Memory can be turned on or off for the LT and ST
protective functions only.

Thermal Memory for the GF function is always on and
cannot be turned off. The GF Thermal Memory feature

provides protection against “sputtering” ground faults.

Except for unusual conditions, it is recommended that
the Thermal Memory feature for LT and ST should be
turned on.

Cycling overloads that are not above the LT Pick-Up long
enough to cause a trip can still lead to thermal damage to
wiring and equipment. With Thermal Memory turned on a
cycling overload can still produce a LT trip to protect cables
and equipment even if any individual overload event did not
persist long enough to directly cause a LT trip.

With Thermal Memory turned off, an overload that drops
below the LT Pick-Up will reset the LT trip register. If the
current goes above the LT Pick-Up again, the LT trip register
starts from zero.

The above is also true for the ST function.
The following will be displayed:

THERMAL MEM XXX

Where "XXX" represents Thermal Memory ON or OFF for
the LT and ST functions.

If Thermal Memory for LT and ST is desired, press the "UP"
push button. If Thermal Memory for LT and ST is not
desired, press the "DOWN" push button. Thermal Memory
for LT and ST can not be individually turned on or off.

Press the "SAVE” push button to continue.

7.20 Exit Procedure

The following will be displayed:

SAVE IF DONE

REVIEW TO REVIEW

If it is desired to review the setting, push the “REVIEW” push
button. Make any changes necessary using the “UP” or
“DOWN” push buttons. As before, use the “SAVE” push
button to move to each new setting.

If the settings are as desired, push the “SAVE” push button.
The following will be displayed:

REMOVE KEY TO

COMMISSION UNIT

Remove the “key” (See section 4.2). The settings will be
saved in the non-volatile EEPROM memory.

If the commissioning process was performed using the
internal battery, the unit will turn itself off.

If external power was used to power the trip unit during the
commissioning process, the following will be displayed:

LOW CURRENT

The commissioning process is complete.

Page 11

8.0 Changing Settings

**** IMPORTANT ****

Utility Relay Company

While it is possible to make changes to the settings with
the breaker in service, it is strongly recommended that
the breaker must be removed from service while
making these changes since the breaker is energized
and the trip unit will not provide protection during a small
part of this process.

After the trip unit is commissioned, settings can easily be
changed in the following manner.

Connect the security key. See Section 4.2.
Power up the trip unit by pressing "REVIEW" or by applying

external power as described in Section 7.1.
Press the “REVIEW” push button. The following will be

displayed:

ENTER DATA

SERIAL # XXXXXXX

Press the "SAVE” push button.
Make any necessary changes using the "UP" or "DOWN"

push buttons. Use the "SAVE" push button to move to each
new setting.

**** IMPORTANT ****

The CT rating entered in the trip unit must match the
rating of the CT the trip unit is connected to.

A security feature protects against accidentally changing
the CT rating. See Section 7.3.

After going through all the settings, the following will be
displayed.

SAVE IF DONE

REVIEW TO REVIEW

If it is desired to review the setting, push the "REVIEW" push
button. Make any changes necessary using the "UP" or
"DOWN" push buttons. As before, use the "SAVE" push
button to move to each new setting.

If the settings are as desired, push the "SAVE” push button.
The following will be displayed:

REMOVE KEY TO

COMMISSION UNIT

Remove the security key (See Section 4.2). The settings will
be saved in the non-volatile EEPROM memory.

The Settings have been changed.
Remember, if the trip unit loses power during this process,

the old settings will be retained and the process must be
repeated.

Page 12

AC-PRO® With QUICK-TRIP® Instruction Manual www.utilityrelay.com

9.0 Last Trip Data Recall

The AC-PRO has an especially useful last trip data recall
and trip counter feature.

After a breaker trip, the trip unit will be able to display the
type of trip (i.e. LT, ST, I, GF, U/B, GF QT or I QT as
applicable) along with the currents at the time of trip. This
information is saved in the non-volatile FLASH memory and
is available immediately after a trip or anytime thereafter.

**** NOTE ****

Only the complete data from the last trip is saved. The
second time the breaker trips, the new trip data is written
over the first trip data. The trip counter is also updated at
this time.

Push the “Review” push button to recall the Last Trip Data
and settings. The following will be displayed if there was no
last trip:

NO LAST TRIP

If there was a last trip, the following messages will
alternately display showing the cause of the trip and the
currents at the time of trip. The messages alternate at a one
second interval rate:

LAST TRIP XXXX

PHASE A XXXXXA
PHASE B XXXXXA
PHASE C XXXXXA

GF XXXXXA

If GF current is greater than 2 times the CT Rating, the
following will be displayed for GF:

GF>2XCT RATING

Only those phase currents greater than 10% of the CT
Rating will be displayed.

U/B YY%

The U/B percentage will be displayed if on and the U/B is
greater than 4%.

The text “XXXX” is the type of tripping event (i.e. LT, ST, I,
GF, U/B, GF QT or I QT as applicable) and “XXXXX” is the
magnitude of the current at the time of trip for each phase.
The text “YY” is the percentage of unbalance at trip.

Press the “REVIEW” push button again to view the following
message:

If the “REVIEW” button is pushed again and held down for
longer than 2 seconds, each type of trip is displayed along
with the number of times that trip has occurred. If the
“REVIEW” button is pressed, but not held for 2 seconds, the
trip count is skipped and the settings are displayed.

INST TRIPS: XX

Push the “REVIEW” Button.

LT TRIPS: XX

Push the “REVIEW” Button.

ST TRIPS: XX

Push the “REVIEW” Button.

GF TRIPS: XX

Push the “REVIEW” Button.

U/B TRIPS: XX

Push the “REVIEW” Button.

GF QT TRIPS:

XX

Push the “REVIEW” Button.

I QT TRIPS: XX

The text “XX” is the number of trips since last commissioned
or reset.

By pressing the "REVIEW" push button the present settings
programmed in the trip unit can be stepped through in
sequence.

**** NOTE ****

Pushing the "SAVE", "UP" or "DOWN" push buttons
during last trip data recall has no effect because the key is
not installed.

When pushing "REVIEW” after the last setting, the trip unit
will turn it self off.

If the "REVIEW" push button is not pressed for about 30
seconds, the trip unit will also turn off.

HOLD <REVIEW> TO

VIEW TRIP COUNTS

Page 13

10.0 Normal Operations

Breaker Current Less than about 8% of CT Rating:

With all phase currents less than about 8%, the trip unit is
not receiving enough energy from the CTs to operate and
the display will be blank (except for the communication
version with a PT module).

Breaker Current Less than 12.5% of CT Rating:

When the currents are greater than about 8% but less than
about 12.5% of the CT rating, the display will show the
following:

LOW CURRENT

Utility Relay Company

Breaker Current Greater than 12.5% of CT Rating:

If the breaker current is greater than about 12.5% of the CT
rating but less than the LT pick-up value, the following will be
alternately displayed on the LCD at one second intervals:

PHASE A XXXXA
PHASE B XXXXA
PHASE C XXXXA

GF XXXXA

Where "XXXX" is the current in amps for that phase or
ground fault current.

Only those currents above 12.5% will be displayed. The GF
current will only be displayed if the GF function is on.

Breaker Current Greater than the LT pick-up:

When the trip unit detects a phase overload situation, the
“PICK-UP” LED on the front of the trip unit will go on, and the
following will alternately be displayed on the LCD at one
second intervals:

OVERLOAD
PHASE A XXXXA
PHASE B XXXXA
PHASE C XXXXA

GF XXXXA

Where "XXXX" is the current in amps for that phase or
ground fault current.

Only those currents above 12.5% will be displayed. The GF
current will only be displayed if the GF function or QT GF
function is on.

11.0 Testing

A "primary injection" test is recommended as the final test of
the AC-PRO retrofit.

It is not necessary to turn off the Unbalance (U/B) function
when doing a single-phase primary injection test.

If used, GF must be temporarily turned off when testing the
other trip functions.

11.1 Commission the Trip Unit

Before proceeding with the normal primary injection tests,
the trip unit must be commissioned to make it functional. See
Section 7.0 for the commissioning procedure.

It is best to use the final pick-up and time delay settings if
they are known. If not, use typical settings for the primary
injection test.

Make sure GF is temporarily turned off. The U/B function can
be left on if desired.

11.2 LT Trip Test

Make sure GF is temporarily turned off. The U/B function can
be left on.

To test the LT Pick-Up, increase the current until the “Pick­Up” LED illuminates.

The injected current should correspond to the programmed
LT Pick-Up setting. Verify that the correct phase is indicated
on the LCD display.

To test the LT trip time, first calculate the trip time based on
the value of the test current that will be applied. Use the
formula in Section 15.1 or the chart in Section 12.3..

A simple shortcut is to note that the trip time (center
of the curve) at 3 times the LT pick-up current is 4
times the LT Delay setting.

For example:

If LT Pick-Up is 1600A and Delay is 10.0S, then the
trip time at 4800A (3 times 1600A) is 40 sec. (4 times
10 sec).

**** NOTE ****

Page 14

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11.3 ST Trip Test

Make sure GF is temporarily turned off. The U/B function can
be left on.

To test the ST Pick-Up, temporarily set ST I
a short pulse of current that is 10% or 20% less than the ST
Pick-Up setting. Continue applying short pulses of current
while increasing the current for each pulse until a ST trip
occurs. The first current where a ST trip occurred is the ST
Pick-Up.

To test the ST Delay, turn ST I
apply a current that is at least 10% greater than the ST Pick­Up current.

The trip time should fall within the time band shown on the
Time-Current curves.

11.4 I Trip Test

2

T off and apply

2

T on again (if applicable) and

Figures 11.7-1 and 11.7-2 show a method to verify that the
breaker CT polarities match. The setup in Figure 11.7-1
verifies that the CT polarities of Phase A and Phase B
match. The setup in Figure 11.7-2 verifies that the CT
polarities of Phase B and Phase C match.

It is only necessary to inject a current slightly greater than
the GF Pick-Up setting and to verify that a GF trip does not
occur.

To Test Set

Apply current slightly greater
than GF Pick-Up to the breaker line side.

"A" "B" "C"

If Phase A & B phasing match,
a GF trip will not occur.

Make sure GF is temporarily turned off. The U/B function can
be left on.

Test the Instantaneous Pick-Up and trip time in the same
manner as ST in Section 11.3.

11.5 GF Trip Test

With GF Pick-Up and Delay set to the required values,
testing any one of the three poles will provide a GF trip.

Test the GF Pick-Up and trip time in the same manner as ST
in Section 11.3.

11.6 QT GF Trip Test

To test QT GF the QUICK-TRIP Display must be connected
to the AC-PRO trip unit and the QUICK-TRIP ON-OFF
selector switch must also be connected as shown in
Figure 6.0-1.

With QT GF Pick-Up set to the required value and the
QUICK-TRIP selector switch turned to the on position, testing
any one of the three poles will provide a QT GF trip.

Test the QT GF Pick-Up and trip time in the same manner as
the normal GF function.

11.7 CT Phasing Test for GF

The breaker CT phasing is only important for the GF function
and the QT GF function. If one of the breaker mounted CTs
has reversed polarity, a nuisance GF or QT GF trip will most
likely occur. With the breaker in service on a 3-phase

system, the last trip data with a reversed polarity CT will
show the GF current as approximately two times the
phase currents.

Since primary injection testing normally tests only one phase
at a time, a breaker CT with reversed polarity will not be
detected with the normal tests. By using the following
method, a primary injection test set can be used to test for
proper CT polarity.

CTs

Jumper load side of Phase A & B poles

Figure 11.7-1 Phase A & B, CT Phasing Test

To Test Set

"B""A"

"C"

CTs

Figure 11.7-2 Phase B & C, CT Phasing Test

If a GF trip does occur, determine which CT has the
reversed polarity. Reverse the secondary connections at the
CT to correct the reversed polarity.

The breakers shown in Figures 11.7-1 & 11.7-2 have the
CTs on the load side. Use exactly the same method if the
CTs are on the breaker line side or if they are staggered.

If a neutral CT is used, it’s polarity must match the polarity of
the breaker mounted CTs. Testing for proper neutral CT
polarity is more difficult because it is mounted remote from
the breaker.

Breaker

Apply current slightly greate r
than GF Pick-Up to breaker line side.

If Phase B & C phasing match,
a GF trip will not occur.

Breaker

Jumper load side of Phase B & C poles

Page 15

11.8 QT I Trip Test

To test QT I the QUICK-TRIP Display must be connected to
the AC-PRO trip unit and the QUICK-TRIP ON-OFF selector
switch must also be connected as shown in Figure 6.0-1.

With QT I Pick-Up set to the required value and the QUICK­TRIP selector switch turned to the on position, test all three
breaker poles in the same manner as the normal I function.

11.9 U/B Trip Test

The U/B trip function is not easy to test with a single phase,
high current test set.

Figure 11.9-1 illustrates a method to test the U/B trip
function. It requires using cable or bus to jumper the breaker
poles as shown. This generates an unbalanced current of
50% or slightly more depending on how equally the current
is split between the two poles.

It is only necessary to inject a current equal to 20% or 30%
of the CT rating for this test. It is only possible to test the U/B
trip time and not the U/B Pick-Up with this method.

Jumper 2 poles

Utility Relay Company

"A" "B" "C"

Breaker

11.10 Erase Last Trip Data

After completing the primary or secondary injection tests, it is
important to erase the last trip data from the memory of the
trip unit.

**** IMPORTANT ****

Erase the last trip data from the memory of the trip unit
after completing the primary or secondary injection tests.

To erase the memory in the trip unit after completing the
primary or secondary injection tests, use the following
method:

1) The trip unit can be either off or powered-up.

2) Push the "REVIEW" button to display the last trip data.

3) While the last trip data is flashing, push and hold both
the "UP" and "DOWN" push buttons.

4) Continue to hold the "UP" and "DOWN" buttons and
push the "SAVE" button. Release all buttons. The
following will be displayed:

NO LAST TRIP

**** IMPORTANT ****

If the last trip data is not erased after the primary or
secondary injection test, the operating personnel may later
assume that the breaker interrupted a fault at some time in
the past when they recall the last trip data. The trip counter
will also have misleading data.

Unbalance = 50%

100% Current

50% Current

50% Current

CTs

Jumper 3 poles

Figure 11.9-1 U/B Test

Page 16

AC-PRO® With QUICK-TRIP® Instruction Manual www.utilityrelay.com

12.0 Secondary Injection Testing

Although primary injection testing is the preferred method to
test an AC-PRO installation, secondary injection testing can
also be used.

12.1 AC-PRO® Secondary Injection Test

Figure 12.1-1

AC-PRO

The AC-PRO secondary injection test set
(see Figure 12.1-1) provides a quick and easy way to test
the AC-PRO trip units.

This test set can test 60Hz, 50Hz, 40Hz and 25Hz
AC-PRO trip units.

Follow the instructions provided with the test set.

®

Secondary Injection Test Set

12.2 Standard Relay Test Set

Most standard relay test sets can also be used to secondary
injection test the AC-PRO trip unit.

The following are required:

• 24Vac Power supply to power up the AC-PRO trip unit
so that it will accept current (URC Part # T-390)

• Relay test set with a 0 to 12 Amp range

• True RMS ammeter in the test set or externally

connected

• Method to stop the relay test set and test set timer when
the breaker trips

Test procedure:

1. Power up the AC-PRO trip unit with the 24Vac power
supply so it will except current

2. Temporarily turn off GF if on

3. Connect the output leads from the relay test set to the
Phase “A” CT terminals (it is not necessary to disconnect
the CT)

4. Proceed with pick-up and time testing of Phase “A”

5. When finished, similarly test Phase “B” & “C”

6. Turn GF on (if desired) and test by injecting current on
any one of the Phases

**** IMPORTANT ****

The CT circuits are internally grounded to the AC-PRO
case. If any of the CT wires are externally grounded, the
AC-PRO will not read current correctly.

Some relay test sets have a grounded current output.
To secondary injection test the AC-PRO trip unit with this
type of test set, the AC-PRO trip unit must be isolated from
the test set ground.

Page 17

Utility Relay Company

12.3 LT Delay Testing Chart

This chart provides trip times in Seconds for the LT Delay
settings at 3.0X, 4.0X and 6.0X where “X” is in multiples of
the LT Pick-Up setting.

The Maximum, Minimum and Nominal trip times are given
for each LT Delay setting and the three listed test currents.

LT Delay Trip Time Test Current LT Delay Trip Time Test Current LT Delay Trip Time Test Current

Setting Range 3.0X 4.0X 6.0X Setting Range 3.0X 4.0X 6.0X Setting Range 3.0X 4.0X 6.0X

Max

2.0 Nominal 8.00 4.50 2.00 11.5 Nominal 46.00 25.88 11.50 21.0 Nominal 84.00 47.25 21.00

2.5 Nominal 10.00 5.63 2.50 12.0 Nominal 48.00 27.00 12.00 21.5 Nominal 86.00 48.38 21.50

3.0 Nominal 12.00 6.75 3.00 12.5 Nominal 50.00 28.13 12.50 22.0 Nominal 88.00 49.50 22.00

3.5 Nominal 14.00 7.88 3.50 13.0 Nominal 52.00 29.25 13.00 22.5 Nominal 90.00 50.63 22.50

4.0 Nominal 16.00 9.00 4.00 13.5 Nominal 54.00 30.38 13.50 23.0 Nominal 92.00 51.75 23.00

4.5 Nominal 18.00 10.13 4.50 14.0 N o minal 56.00 31.50 14.00 23.5 Nominal 94.00 52.88 23.50

5.0 Nominal 20.00 11.25 5.00 14.5 N o minal 58.00 32.63 14.50 24.0 Nominal 96.00 54.00 24.00

5.5 Nominal 22.00 12.38 5.50 15.0 N o minal 60.00 33.75 15.00 24.5 Nominal 98.00 55.13 24.50

6.0 Nominal 24.00 13.50 6.00 15.5 N o minal 62.00 34.88 15.50 25.0 Nominal 100.00 56.25 25.00

6.5 Nominal 26.00 14.63 6.50 16.0 N o minal 64.00 36.00 16.00 25.5 Nominal 102.00 57.38 25.50

7.0 Nominal 28.00 15.75 7.00 16.5 N o minal 66.00 37.13 16.50 26.0 Nominal 104.00 58.50 26.00

7.5 Nominal 30.00 16.88 7.50 17.0 N o minal 68.00 38.25 17.00 26.5 Nominal 106.00 59.63 26.50

8.0 Nominal 32.00 18.00 8.00 17.5 N o minal 70.00 39.38 17.50 27.0 Nominal 108.00 60.75 27.00

8.5 Nominal 34.00 19.13 8.50 18.0 N o minal 72.00 40.50 18.00 27.5 Nominal 110.00 61.88 27.50

9.0 Nominal 36.00 20.25 9.00 18.5 N o minal 74.00 41.63 18.50 28.0 Nominal 112.00 63.00 28.00

9.5 Nominal 38.00 21.38 9.50 19.0 N o minal 76.00 42.75 19.00 28.5 Nominal 114.00 64.13 28.50

10.0 Nominal 40.00 22.50 10.00 19.5 Nominal 78.00 43.88 19.50 29.0 Nominal 116.00 65.25 29.00

10.5 Nominal 42.00 23.63 10.50 20.0 Nominal 80.00 45.00 20.00 29.5 Nominal 118.00 66.38 29.50

11.0 Nominal 44.00 24.75 11.00 20.5 Nominal 82.00 46.13 20.50 30.0 Nominal 120.00 67.50 30.00

9.88 5.56 2.47

Min 6.61 3.72 1.65 Min 38.02 21.38 9.50 Min 69.42 39.05 17.36

Max

12.35 6.94 3.09

Min 8.26 4.65 2.07 Min 39.67 22.31 9.92 Min 71.07 39.98 17.77

Max

14.81 8.33 3.70

Min 9.92 5.58 2.48 Min 41.32 23.24 10.33 Min 72.73 40.91 18.18

Max

17.28 9.72 4.32

Min 11.57 6.51 2.89 Min 42.98 24.17 10.74 Min 74.38 41.84 18.60

Max

19.75 11.11 4.94

Min 13.22 7.44 3.31 Min 44.63 25.10 11.16 Min 76.03 42.77 19.01

Max

22.22 12.50 5.56

Min 14.88 8.37 3.72 Min 46.28 26.03 11.57 Min 77.69 43.70 19.42

Max

24.69 13.89 6.17

Min 16.53 9.30 4.13 Min 47.93 26.96 11.98 Min 79.34 44.63 19.83

Max

27.16 15.28 6.79

Min 18.18 10.23 4.55 Min 49.59 27.89 12.40 Min 80.99 45.56 20.25

Max

29.63 16.67 7.41

Min 19.83 11.16 4.96 Min 51.24 28.82 12.81 Min 82.64 46.49 20.66

Max

32.10 18.06 8.02

Min 21.49 12.09 5.37 Min 52.89 29.75 13.22 Min 84.30 47.42 21.07

Max

34.57 19.44 8.64

Min 23.14 13.02 5.79 Min 54.55 30.68 13.64 Min 85.95 48.35 21.49

Max

37.04 20.83 9.26

Min 24.79 13.95 6.20 Min 56.20 31.61 14.05 Min 87.60 49.28 21.90

Max

39.51 22.22 9.88

Min 26.45 14.88 6.61 Min 57.85 32.54 14.46 Min 89.26 50.21 22.31

Max

41.98 23.61 10.49

Min 28.10 15.81 7.02 Min 59.50 33.47 14.88 Min 90.91 51.14 22.73

Max

44.44 25.00 11.11

Min 29.75 16.74 7.44 Min 61.16 34.40 15.29 Min 92.56 52.07 23.14

Max

46.91 26.39 11.73

Min 31.40 17.67 7.85 Min 62.81 35.33 15.70 Min 94.21 53.00 23.55

Max

49.38 27.78 12.35

Min 33.06 18.60 8.26 Min 64.46 36.26 16.12 Min 95.87 53.93 23.97

Max

51.85 29.17 12.96

Min 34.71 19.52 8.68 Min 66.12 37.19 16.53 Min 97.52 54.86 24.38

Max

54.32 30.56 13.58

Min 36.36 20.45 9.09 Min 67.77 38.12 16.94 Min 99.17 55.79 24.79

Max

Max

Max

Max

Max

Max

Max

Max

Max

Max

Max

Max

Max

Max

Max

Max

Max

Max

Max

The Time-Current Curves in Figure 18.2 along with the
equations in Section 15 can be used to determine the trip
times of the other trip functions.

A test chart with additional LT Delay test points is available
at www.utilityrelay.com.

56.79 31.94 14.20

59.26 33.33 14.81

61.73 34.72 15.43

64.20 36.11 16.05

66.67 37.50 16.67

69.14 38.89 17.28

71.60 40.28 17.90

74.07 41.67 18.52

76.54 43.06 19.14

79.01 44.44 19.75

81.48 45.83 20.37

83.95 47.22 20.99

86.42 48.61 21.60

88.89 50.00 22.22

91.36 51.39 22.84

93.83 52.78 23.46

96.30 54.17 24.07

98.77 55.56 24.69

101.23 56.94 25.31

Max

103.70 58.33 25.93

Max

106.17 59.72 26.54

Max

108.64 61.11 27.16

Max

111.11 62.50 27.78

Max

113.58 63.89 28.40

Max

116.05 65.28 29.01

Max

118.52 66.67 29.63

Max

120.99 68.06 30.25

Max

123.46 69.44 30.86

Max

125.93 70.83 31.48

Max

128.40 72.22 32.10

Max

130.86 73.61 32.72

Max

133.33 75.00 33.33

Max

135.80 76.39 33.95

Max

138.27 77.78 34.57

Max

140.74 79.17 35.19

Max

143.21 80.56 35.80

Max

145.68 81.94 36.42

Max

148.15 83.33 37.04

Page 18

AC-PRO® With QUICK-TRIP® Instruction Manual www.utilityrelay.com

13.0 Ratings

Ambient Temperature:
Trip Unit:

-4°F (-20°C) to 150°F (65°C)
LCD Display:
Standard Temp, Super Twist
32°F (0°C) to 122°F (50°C)

Humidity:
95% non-condensing

Conformal Coating:
Acrylic conformal coating,
HumiSeal type 1A33

Enclosure:
AC-PRO trip unit:
Extruded aluminum housing
Conductive Iridite coating
Nominal overall dimensions:

6.76 X 3.84 X 2.28 inches
172 X 100 X 58 millimeters

Pro-Display:
Conductive Plastic
Nominal overall dimensions:

4.45 X 3.66 X 0.94 inches

112.9 X 92.8 X 23.8 millimeters
Battery:

See Section 17.0

14.0 Warranty

A conditional 2-year warranty is offered with each AC-PRO
trip unit and Pro-Display.

Contact Utility Relay Company for full details.

15.0 Time-Current Curves

The Time-Current curves are shown in
Figures 18.2, 18.3 and 18.4.

For all the functions except U/B, the curves are shown on
log-log graph with seconds in the vertical direction and
current in the horizontal direction.

Overload and fault currents are shown as multiples of the LT
pick-up setting. Ground fault current is shown as a
percentage of the CT rating.

For I and QT I pick-up settings below 150% of the CT rating,
trip unit power-up time must be added to the Instantaneous
Time-Current curve (if the trip unit is not already powered
up). The allowance for 3-phase time is shown as a dotted
line on the upper right hand Time-Current curve in Figure

18.4.
For QT GF pick-up settings below 120% of the CT rating, trip

unit power-up time must be added to the QT GF Time­Current curve (if the trip unit is not already powered up). The
allowance of 1-phase time is shown as a dotted line in the
QT GF Time-Current curve in Figure 18.4.

Tolerances for the Pick-Up bands are ± 10% in the current
direction. Tolerance for LT, ST I
+ 23% and -17% in the time direction.

The curves for the following time bands:
LT
ST I²T
GF I²T
are based on the following equation:

I²T = Constant
Where: I is current in amps

T is time to trip in seconds (center of the band)
The curves for the U/B function are shown on a semi-log

graph with seconds in the vertical direction and unbalance in
percent in the horizontal direction.

Tolerance for U/B function is given in
Section 15.4.

When performing trip-timing tests using a primary injection
test set, the trip time at various test currents can be
determined by calculation as explained in Sections 15.1,

15.2 and 15.3.

2

T and GF I2 T trip times are

Page 19

Utility Relay Company

15.1 LT Trip Time

For overload currents, the "I²T = Constant" equation can be
restated as follows:

T = TBC

LT

X²

Where: T = time to trip in seconds (center of the band)
X = current in multiples of the LT pick-up setting
TBC

= the LT Time Band Constant

LT

= 36 X LT time band setting

**** NOTE ****

The LT Time Band Constant (TBCLT) is by definition 36
times the LT Time Band Setting in seconds.

EXAMPLE #1:

CT Rating 1600A
LT pick-up 1200A
LT time band 20.0S
Overload Current 3600A

TBC

= 36 X LT Time Band Setting

LT

= 36 X 20.0
= 720

and X = overload current = 3600A = 3
LT Pick-Up 1200A

therefore:
trip time = T = TBC

or 720 = 720

LT

X² 3² 9
= 80 seconds

**** IN SUMMARY ****

To calculate the LT trip time:

1) Calculate the LT Time Band Constant (TBC

2) Calculate "X" where
X = overload current
LT Pick-Up Setting

3) Solve the equation:
trip time(sec) = TBC

LT

X2

)

LT

15.2 ST Trip Time

2

T off or for currents greater than 10 X LT Pick-Up

With I
Setting, the ST trip time is a constant equal to the ST Time
Band setting.

2

T on and for currents less than 10 X LT Pick-Up

With I
Setting, the ST trip time is determined by the following
equation:

T = TBC

ST

X²
Where: T = time to trip in seconds (center of the band)

X = current in multiples of the LT pick-up
TBC

= the ST Time Band Constant

ST

**** NOTE ****

The ST Time Band Constant (TBCST) =
40 for the .40S Time Band
30 for the .30S Time Band
20 for the .20S Time Band
15 for the .15S Time Band
10 for the .10S Time Band
7 for the .07S Time Band

EXAMPLE #2:

CT Rating 1600A
LT pick-up 1200A
ST pick-up 6000A
ST time band .20S I²T ON
Overload Current 7200A

= 20

TBC

ST

and X = overload current = 7200A = 6
LT Pick-Up 1200A

therefore:
trip time = T = TBC

or 20 = 20

ST

X² 6² 36
= .556 seconds

**** IN SUMMARY ****

To calculate the ST I2T trip time:

1) Determine the ST Time Band Constant (TBC

2) Calculate "X" where
X = overload current
LT Pick-Up

3) Solve the equation:
trip time(sec) = TBC

ST

X2

)

ST

Page 20

AC-PRO® With QUICK-TRIP® Instruction Manual www.utilityrelay.com

15.3 GF Trip Time

2

T off or for ground fault currents greater than 2 times

With I
the CT rating, the GF trip time is a constant equal to the GF
Time Band setting.

2

T on and for currents less than 2 times the CT rating,

With I
the GF trip time is determined by the following equation:

T = TBC

GF

XGF²
Where: T = time to trip in seconds (center of the band)

X

= ground fault current

GF

CT rating

TBC

= the GF Time Band Constant

GF

**** NOTE ****

The GF Time Band Constant (TBCGF) =

2.0 for the .50S Time Band

1.6 for the .40S Time Band

1.2 for the .30S Time Band

0.8 for the .20S Time Band

0.4 for the .10S Time Band

EXAMPLE #3:

CT Rating 1600A
LT pick-up 1200A
GF pick-up 640A
GF time band .20S I²T ON
Ground Fault Current 800A

GF

= 0.8

TBC
and X

= ground fault current = 800A

GF

CT Rating 1600A
= 0.5

therefore:
trip time = T = TBC

or 0.8 = 0.8

GF

XGF² (0.5)² .25
= 3.20 sec

**** IN SUMMARY ****

To calculate the GF I2T trip time:

1) Determine the GF Time Band Constant (TBC

2) Calculate "X

X

GF

" where

GF

= ground fault current

CT Rating

3) Solve the equation:
trip time(sec) = TBC
X

GF

2

GF

)

GF

15.4 U/B Trip Time

U/B is calculated as follows:
U/B = (I

- INS) X 100%

NL

INL
Where:

= Largest Phase current

I

NL

= Smallest Phase current

I

NS

The U/B function is defeated if any two phase currents are
less than 10% of the CT rating.

The tolerance for the U/B Pick-Up is ± 10 percentage points.
An U/B Pick-Up of 20% would have a tolerance of 10% to
30% unbalance. An U/B Pick-Up of 50% would have a
tolerance of 40% to 60% unbalance.

The U/B trip time is a definite time as shown on the U/B TCC
in Figure 18.3

The tolerance for the U/B trip time is ± 10% of the setting.

16.0 Error Message Summary

The following is a summary of the possible error messages
and what action is necessary to correct the problem.

16.1 Actuator Not Connected

When the actuator is not connected or is open circuited, the
following message will be displayed:

NO ACTUATOR

All push buttons are disabled. To return to normal operation,
a functioning actuator must be connected.

16.2 Memory Error

The micro-controller continuously monitors its memory.
When a discrepancy occurs, the following message will be
displayed:

MEMORY ERROR

All push buttons are disabled. The micro-controller must be
replaced. Contact Utility Relay Company for more
information.

Page 21

Utility Relay Company

17.0 Battery Replacement

For best performance, replace the battery with the following
9-volt lithium battery:

Energizer LA522
A replacement battery can be purchased from:

• Utility Relay Co. Part # T-303-3

• Digi-Key Part # N538

www.digikey.com

• Newark Part # 68R2922
www.newark.com

• Allied Electronics Part # 70231992
www.alliedelec.com

• Grainger Part # 6FXX3
www.grainger.com

Lithium battery ratings:

• Rated shelf life of ten-years

• 750 mAh Capacity

(Allows the review of last trip data and settings over

1000 times on battery power only)

+

A

B

C

PHASE

PHASE

PHASE

ACTUATOR

BREAKER HARNESS

NEUTRAL

Pull tab on battery cover
to the right to remove

24 VAC

POWER

QT

DISPLAY

KEY

AUXILIARY

BATTERY

COVER

Use only 9V
Lithium Battery

Older AC-PRO trip units did not have a battery cover. To
replace the battery on these AC-PROs, the top of the trip
unit must be removed.

To replace the battery on older AC-PRO trip units without a
battery cover but in a “silver” case (clear Iridite aluminum):

• The breaker must be out of service and de-energized
for safety

• Disconnect the breaker harness from the trip unit

• Unscrew the nine (9) 4-40 X 3/8 Torx screws attaching

the trip unit top

• Lift off the trip unit top

• Remove the old battery

• Check the markings on the circuit board for the proper

batter polarity

• Slide in the new battery while maintaining proper
polarity

• Replace the cover using the previously removed Torx
screws

• Reconnect the breaker harness

By ordering the “Battery Cover Kit”, an older AC-PRO trip
unit in the “silver” case (clear Iridite aluminum) can be
upgraded with the battery cover.

AC-PRO trip units in the “black” case (black anodized
aluminum) cannot be upgraded with the battery cover.

Figure 17.1 Battery Replacement

To replace the battery:

• The breaker must be out of service and de-energized
for safety

• Pop out the plastic battery cover by pulling the tab on
the battery cover to the right

• Pull out the old battery

• Check the markings on the circuit board for the proper

batter polarity

• Slide in the new battery maintain proper polarity

• Hook the right end of the battery cover under the AC-

PRO top and snap the cover into place

**** IMPORTANT ****

For best performance, replace the battery with an
Energizer LA522 9-volt lithium battery.

An alkaline type 9-volt battery may also be used with
much shorter life.

The breaker must be removed from service before
replacing the battery.

The replacement battery must be inserted with the
proper polarity.

Page 22

AC-PRO® With QUICK-TRIP® Instruction Manual www.utilityrelay.com

Neutral CT

Only for 4-Wire system

with GF "ON"

LINE

LINE

Phase CTs

LINE

LINE

LOAD

Manual reset,
Mechanical -Auto reset or
Electric-Auto reset actuator

Red & black actuator
wires in Vinyl
sleeving

10-Pole harness plug
with hold-down screws

Phase A

L

W

Actuator

LOAD

RBL

Phase B

Y

W

W

W

Y

N

Phase C Neutral

N

W

LOAD

LOAD

Optional

To QT Display

R

(Optional)

COLOR CODE

R = Red
B = Black
W = White

W

W

G

Y = Yellow
L = Blue
N = Brown
G = Green

G

W

Top view

Figure 18.1

Typical Wiring Diagram

Page 23

Utility Relay Company

INTENTIONALLY LEFT BLANK

Page 24

AC-PRO® With QUICK-TRIP® Instruction Manual www.utilityrelay.com

AC−PRO Trip Unit

Long Time (LT) Pick−Up
5A steps
20% to 100% of CT Rating
(50A steps for CTs > 5000A)
(0.5A steps for CTs < 225A)

150% ST Pick−Up

Short Time (ST) Pick−Up
OFF & 100A steps
150% to 1200% of LT Pick−Up
(1000A steps for CTs > 5000A)
(10A steps for CTs < 250A)

1000

100

10

1X

2X

4X

6X

10X

20X

1000

LT Delay

0.5 sec. steps

2.0 to 30.0 sec.
@ 600% LT Pick−Up

3

0

s

100

600% LT Pick−Up

2

.

0

s

10

1200% ST Pick−Up

.

4

0

s

I

2

SECONDS

1

.5

T

.

3

O

0

N

s

I

2

T

.

2

O

0

s

N

I

2

T

.

1

O

5

N

s

I

2

T

.

O

1

0

N

s

I

2

T

.

0

O

7

N

s

I

2

T

O

N

.30sec

.20sec

ST Delay with
& without I

.40sec

2

T

.15sec

2

ST I

T ON

.10sec

SECONDS

1

.5

ST I

Instantaneous (I) Pick−Up
OFF & 100A steps
150% to 1200% of LT Pick−Up
(1000A steps for CTs > 5000A)
(10A steps for CTs < 250A)

I Pick−Up

2

T OFF

150%

.01

.1

.07sec

.1

1200%

I Pick−Up

1X

2X

4X

6X

10X

20X

.01

Current in Multiples of Long Time Pick−Up

Overload Time Current Curve

Figure 18.2

Overload TCC

Page 25

Utility Relay Company

INTENTIONALLY LEFT BLANK

Page 26

AC-PRO® With QUICK-TRIP® Instruction Manual www.utilityrelay.com

1000

20%

40%

60% 80%

Unballance (U/B) Pick−Up
OFF & 5% steps
from 20% to 50%

100%

1000

20%

40%

60%

100%

200%

100

20% U/B
Pick−Up

10

1

.1

50% U/B
Pick−Up

20% GF
Pick−Up

100

Ground Fault (GF) Pick−Up
OFF & 10A steps
20% to 200% of

60 Sec
U/B Delay

10

SECONDS

U/B Delay
1 Sec steps from
1 Sec to 60 Sec

CT Rating (1200A Max)
(100A steps for CTs > 5000A)
(1A steps for CTs < 250A)

.

4

0

s

.

3

0

s

.

2

0

s

.

5

0

s

SECONDS

200% GF
Pick−Up

U/B = (I − I ) X 100%

I = Largest phase current

NL

NS

I = Smallest phase current

NS

NL

NL

I

1 Sec
U/B Delay

.

1

0

2

T ON

s

I

2

T

O

.

4

0

N

s

.

3

0

s

.

2

0

s

1

GF I

GF Delay
with &
without I

.40sec

.30sec

.20sec

.50sec

2

T

U/B is defeated if any
two phase currents are
less than 10% of the CT rating

.10sec

.1

.01

20%

40%

60% 80% 100% 20%

Current Unballance in Percent

Unballance Time Current Curve

.01

Figure 18.3

U/B & GF TCC

Page 27

2

GF I

T OFF

40%

60%

100%

200%

Current in Percent of CT Rating

Ground Fault Time Current Curve

Utility Relay Company

INTENTIONALLY LEFT BLANK

Page 28

AC-PRO® With QUICK-TRIP® Instruction Manual www.utilityrelay.com

1000

100

20%

40%

20% QT GF
Pick−Up

100%

60%

Quick−Trip Ground Fault Pick−Up
(QT GF Pick−Up)
OFF & 10A steps
20% to 200% of
CT Rating (1200A Max)
(100A steps for CTs > 5000A)
(1A steps for CTs < 225A)

200%

R

.01

40%

20%

.1

SECONDS

40%

20%

Current in Percent of CT Rating

100%

60%

Minimum possible
Instantaneous (I) Pick−Up
or
Quick−Trip Instantaneous
(QT I) Pick−Up

Allowance for 3−Phase
power−up time

100%

60%

200%

R

200%

Instantaneous Allowance for 3−Phase Power−Up Time

For Very Low QT−I Settings

10

4X1X

5

SECONDS

1

Allowance for
1−Phase

power−up time

200% QT GF
Pick−Up

1

.5

2X

6X

10X

20X

Quick−Trip Instantaneous
(QT I) Pick−Up
100A steps
150% to 1200% of
LT Pick−Up
(1000A steps for CTs > 5000A)
(10A steps for CTs < 225A)

150%

QT I Pick−Up

1200%
QT I Pick−Up

R

.1

.01

Quick−Trip Ground Fault Time Current Curve

40%

20%

Current in Percent of CT Rating

60%

R

100%

200%

QUICK-TRIP

SECONDS

.1

.01

1X

2X

Current in Multiples of Long Time Pick−Up

Quick−Trip Instantaneous Time Current Curve

R

Figure 18.4

®

Ground Fault & Instantaneous TCC

Page 29

4X

6X

10X

20X

Utility Relay Company

INTENTIONALLY LEFT BLANK

Page 30