ABB REJ 527 Technical Reference Manual

ABB Substation Automation Products and Systems

1MRS750616-MUM

Issued: 07.07.99

Version: A

Checked: H.S.

Approved: L.N.

REJ 527

Directional or Non-Directional

Earth-Fault Relay

Technical Reference Manual

Data subject to change without prior notice

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Contents

1. Introduction ...........................................................................................5

1.1. About this manual .........................................................................5

1.2. The use of the relay ......................................................................5

1.3. Features ........................................................................................5

1.4. Guarantee .....................................................................................6

2. Safety information .................................................................................7

3. Instructions ...........................................................................................8

3.1. Application .....................................................................................8

3.2. Requirements ................................................................................8

3.3. Configuration .................................................................................9

4. Technical description ..........................................................................10

4.1. Functional description .................................................................10

4.1.1. Product functions ................................................................10

4.1.1.1. Schema of product functions .......................................10

4.1.1.2. Earth-fault current, zero-sequence voltage and

intermittent earth-faults ................................................10

4.1.1.3. Inputs ...........................................................................11

4.1.1.4. Outputs ........................................................................11

4.1.1.5. Circuit-breaker failure protection .................................11

4.1.1.6. Disturbance recorder ...................................................11

4.1.1.7. MMI module .................................................................11

4.1.1.8. Self-supervision ...........................................................12

4.1.2. Configuration ......................................................................12

4.1.3. Protection ............................................................................13

4.1.3.1. Block diagram ..............................................................13

4.1.3.2. Directional or non-directional earth-fault current unit ..13

4.1.3.3. Zero-sequence voltage unit .........................................17

4.1.3.4. Protection against intermittent earth-faults ..................18

4.1.3.5. Time/current characteristics ........................................19

4.1.3.6. Settings .......................................................................23

4.1.3.7. Technical data of protection functions .........................31

4.1.4. Monitoring ...........................................................................33

4.1.5. Self-supervision (IRF) .........................................................33

4.1.6. I/O test ................................................................................34

4.1.7. Disturbance recorder ..........................................................34

4.1.7.1. Function .......................................................................34

4.1.7.2. Recorder data ..............................................................34

4.1.7.3. Control and indication of recorder status .....................34

4.1.7.4. Triggering ....................................................................35

4.1.7.5. Settings and unloading ................................................35

4.1.7.6. Event code ..................................................................36

4.1.8. Recorded data ....................................................................36

4.1.9. External serial communication ............................................37

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4.1.9.1. Communication ports ..................................................37

4.1.9.2. Event codes ................................................................38

4.1.9.3. Remote transfer data ..................................................40

4.1.10.Relay parameterization ......................................................48

4.2. Design description ......................................................................48

4.2.1. Input / output connections ..................................................48

4.2.2. Serial communication connections .....................................51

4.2.3. Technical data ....................................................................52

5. Ordering information ..........................................................................58

6. References .........................................................................................59

7. Index ..................................................................................................60

8. Glossary .............................................................................................62

9. Check lists ..........................................................................................63

10.Customer feedback ............................................................................66

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1. Introduction

1.1. About this manual

This manual is intended to provide the user with thorough information on the relay

REJ 527 and its applications. The focus in the manual is on technical description of

the relay.

Instructions for using the Man-Machine Interface (MMI) are found in separate

“Operator’s Manual” and for installation in “Installation Manual”.

1.2. The use of the relay

The directional or non-directional earth-fault relay REJ 527 is intended to be used

for earth-fault protection and supervision in distribution substations. It can also be

used for protection of generators, motors and transformers. Generally the relay

measures the zero-sequence voltage, earth-fault current and phase angle of the

system.

The protection relay REJ 527 is based on a microprocessor environment. A self-

supervision system monitors continuously the operation of the relay.

The MMI includes an LCD display which makes the local use of the relay safe and

easy.

Local control of the protection relay can be carried out with a portable computer

connected to the front connector and remote control via the rear connector connected

to the distribution automation system through the serial interface and fibre-optic bus.

1.3. Features

• Directional or non-directional low-set earth-fault current stage I

0

> with definite-

time or inverse definite minimum time (IDMT) characteristic

• Directional or non-directional high-set earth-fault current stage I

0

>> with

definite-time characteristic

• Deblocking zero-sequence voltage stage U

0b

>

• The two earth-fault current stages configurable to operate alternatively as two

voltage stages: a three-stage voltage monitoring operation possible

• Intermittent earth-fault protection

• Circuit-breaker failure protection (CBFP)

• Disturbance recorder

• Two accurate measuring inputs

• Galvanically isolated binary input with a wide input voltage range

• All settings can be modified with a personal computer

• Settings are stored into non-volatile memory and remain even in case of power

supply failure

• Two normally open power output contacts

• Two change-over type signal output contacts

• Output contact functions freely configurable for desired operation

• Optical PC-connector for two-way data communication (front)

• RS-485 connector (rear) for system communication

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• Continuous self-supervision of hardware and software. At a permanent fault all

stages and outputs are blocked.

• Rated frequency user-selectable 50/60 Hz

• MMI with an alphanumeric LCD and manoeuvring buttons

• User-selectable password protection for MMI

• Display of primary current and voltage values as well as phase angle values

1.4. Guarantee

Please inquire the guarantee of your nearest ABB representative.

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2. Safety information

Dangerous voltages can occur on the connectors, even though the auxiliary voltage

is disconnected.

National and local electrical safety regulations must always be followed.

The frame of the protection relay has to be carefully earthed.

Current transformer has to be short-circuited before disconnecting the relay from it.

Only a competent electrician is allowed to carry out the electrical installation.

!

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3. Instructions

3.1. Application

The directional earth-fault relay REJ 527 is a secondary relay that is connected to

the voltage and current transformers of an object to be protected. It is designed for

earth-fault protection and supervision of distribution substations. Other application

areas are protection of generators, motors and transformers.

The relay comprises a zero-sequence voltage unit and an earth-fault current unit. The

voltage unit includes a low-set stage U

0b

> whereas the earth-fault current unit has

two stages, a low-set I

0

> and a high-set I

0

>> stage. The earth-fault current unit may

also be programmed to operate as voltage stages, a low-set U

0

> and a high-set U

0

>>

stage.

The earth-fault current and zero-sequence voltage stages of the relay continuously

measure the zero-sequence voltage, earth-fault current and phase angle of the

system. On detection of a fault the relay starts, trips the circuit breaker, provides

alarms, records fault data etc., in accordance with the application and the configured

relay functions.

The low-set earth-fault current stage can be given a definite-time or an inverse-time

characteristic whereas the high-set earth-fault current stage and the voltage stage

feature the definite-time characteristic alone. The operation of the earth-fault current

and voltage stages can be blocked by means of an external control signal.

The protection functions are independent of each other and have their own setting

groups and data recording. The voltage and current functions use conventional

transformer measurement.

Output contact matrix allows any start or trip signal from the protection stages to be

routed to the desired output contact.

3.2. Requirements

When the protection relay is operating under conditions specified below (see also

“Technical data”), the relay is practically maintenance-free. The relay includes no

parts or components subject to abnormal physical or electrical wear under normal

operating conditions.

Environmental conditions

• Specified ambient service temperature range -10...+55 °C

• Temperature influence on the operating values of the relay

within the specified ambient service temperature range 0.1% / °C

• Transport and storage temperature range -40...+70 °C

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3.3. Configuration

Setting and connection example

The appropriate configuration of the output contact matrix enables using the start

signals of the earth-fault current and voltage units as contact functions. The start

signals can be used for blocking co-operating protection relays, for signalling and

for initiating autoreclosing.

Fig. 3.3.-1 represents the relay with the default configuration: all trips are routed to

operate the circuit breaker.

Fig. 3.3.-1 Connection diagram of the directional earth-fault relay

L1

L2

L3

Optical

PC-interface

PC

Spa Bus

100V

1 A

0.2 A

PO1

IO

PO2

+ +

IRF

+

-

+

BI

REJ 527

0

I

IRF

+ -

U

aux

I/O

START

TRIP

START

TRIP

1

2

3

SGB1

INDICATORS RESET

RELAYS RESET

MEMORIZED VALUES RESET

∼

Io>>

SGR1

SGR2

SGR3

SGR4

X

3

X

3

2

X

2

X

1

X

1

X

4

X

4

X

4

X

3

2

X

1

X

SGR5

SGR6

START

TRIP

5 6

3 4

13 14 15

1 2

17 18

1 2 3 4 6

SGB1

5

6

7

Blocking of stage Io>>

Blocking of stage Io>

Blocking of stage Uob>

10 11 12

7 8 9

SO1

X2.1

SO2

X2.1

X1.1

1MKC950001-1

RER 103

Tx

Rx

Io>

Uob>

P1

P2

S2

S1

A

N

da

dn

ConD527

X=Default value

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4. Technical description

4.1. Functional description

4.1.1. Product functions

4.1.1.1. Schema of product functions

Fig. 4.1.1.1.-1 Product functions

4.1.1.2. Earth-fault current, zero-sequence voltage and intermittent

earth-faults

Refer to sections:

• 4.1.3.2. Directional or non-directional earth-fault current unit

• 4.1.3.3. Zero-sequence voltage unit

• 4.1.3.4. Protection against intermittent earth-faults

50 N

Io

PrF5_7

Uo

51 N

59 N

67 N

62 BF

EARTH-FAULT PROTECTION WITH

DEFINITE- OR INVERSE-TIME

CHARACTERISTIC, LOW-SET STAGE

EARTH-FAULT PROTECTION WITH

INSTANTANEOUS OR DEFINITE-TIME

CHARACTERISTIC, HIGH-SET STAGE

PO1

PO2

SO1

SO2

IRF

ZERO-SEQUENCE VOLTAGE

ELEMENT

CIRCUIT-BREAKER FAILURE

PROTECTION

REMOTE RESET, REMOTE SETTING CONTROL OR

BLOCKING INPUT FOR THE DIFFERENT PROTECTION

STAGES

SERIAL COMMUNICATION

DIRECTIONAL EARTH-FAULT

ELEMENT

OPTICAL

PC-INTERFACE

BINARY INPUT BI

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4.1.1.3. Inputs

The relay includes two energizing inputs and one external binary input controlled by

an external voltage. The function of the binary input is determined with selector

switches of the protection relay.

For more details of the inputs, refer to section 4.2.1. Input / output connections and

tables 9, 32 and 36.

4.1.1.4. Outputs

The relay is provided with two power outputs (PO1 and PO2) and two signal outputs

(SO1 and SO2). Switchgroups SGR1...6 are used for routing the start and trip signals

of any protection stage to the desired signal or power output.

4.1.1.5. Circuit-breaker failure protection

The relay features a circuit-breaker failure protection (CBFP) unit. The CBFP unit

generates a trip signal via output PO2 after the set operate time 0.10 s...1.00 s if the

fault has not been cleared by that time.

Normally, the CBFP unit controls the upstream circuit breaker. It can also be used

for tripping via redundant trip circuits of the same circuit breaker if the circuit

breaker is provided with two trip coils. The circuit-breaker failure protection unit is

activated with a switch of switchgroup SGF.

4.1.1.6. Disturbance recorder

The relay includes an internal disturbance recorder, which records momentary

measured values, external BI signal and states of the internal protection stages. The

disturbance recorder can be set to be triggered on operation of stages or on an

external BI signal, either on the falling or rising trigger edge.

4.1.1.7. MMI module

The MMI of the relay is equipped with six push-buttons and an alphanumeric LCD

for 2 x 16 characters. The push-buttons are used for navigating in the menu structure

and for adjusting set values.

An MMI password protects all user-changeable values from being changed by an

unauthorised person. The default value for the MMI password is “999”. With the

default value the password is not active and it is not required for altering parameter

values. For further information, refer to “Operator’s Manual”.

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4.1.1.8. Self-supervision

The self-supervision system of the relay handles run-time fault situations and

informs the user about an existing fault. When the self-supervision system detects a

permanent internal relay fault, the ready indication LED starts blinking. At the same

time the IRF relay that is normally picked up drops off and a fault code appears on

the display. During an internal fault all other output contacts are blocked.

Fig. 4.1.1.8.-1 Internal fault

The fault code is a number that identifies the fault type. (For fault codes, refer to

section “Self-supervision, IRF” in “Operator’s Manual”.)

Fault codes can indicate:

• No response on output contact test.

• Faulty program memory, work memory or parameter memory.

• Internal reference voltage error.

4.1.2. Configuration

The figure below illustrates how the start, trip and binary input signals can be

configured so that the required protection functions are obtained.

Fig. 4.1.2.-1 Signal diagram of the directional earth-fault relay

The functions of the blocking and start signals are selected with the switches of

switchgroups SGF, SGB and SGR, found in the menu group “Settings” of the

protection relay. The functions of these switches are explained in detail in the

corresponding SG_ -tables.

Faultc

C

E

INTERNAL FAULT

FAULT CODE : 56

STARTREADY TRIP

+ ++

IRF

I/O

START

TRIP

START

TRIP

1

2

3

SGB1

INDICATORS RESET

RELAYS RESET

Io>>

SGR1

SGR2

SGR3

SGR4

3

2

1

4

3

2

1

SGR5

SGR6

START

TRIP

5 6

3 4

13 14 15

17 18

SGB1

5

6

7

Blocking of stage Io>>

Blocking of stage Io>

Blocking of stage Uob>

10 11 12

7 8 9

X2.1

Io>

Uob>

MEMORIZED VALUES RESET

SGF1...SGF5

Uo

Io

BI

IRF

SO2

SO1 PO2

PO1

SDiag5_7

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4.1.3. Protection

4.1.3.1. Block diagram

Fig. 4.1.3.1.-1 Block diagram of the directional earth-fault relay REJ 527

4.1.3.2. Directional or non-directional earth-fault current unit

The directional earth-fault current unit of the relay REJ 527 comprises two earth-

fault current stages, a low-set stage I

0

> and a high-set stage I

0

>> that can be

configured as either directional or non-directional. For the directional stages there

are two alternative operation characteristics: 1) directional earth-fault with basic

angle and 2) directional earth-fault with sin(ϕ) or cos(ϕ) characteristics.

1) The operation of the directional earth-fault unit with basic angle is based on

measuring the earth-fault current I

0

and the zero-sequence voltage U

0

and further the

phase angle ϕ between the voltage and current. The earth-fault stage starts if the

following three criteria are fulfilled at the same time:

• The earth-fault current I

0

exceeds the set starting level of the earth-fault stage.

The earth-fault unit has two earth-fault current stages I

0

> and I

0

>>.

• The zero-sequence voltage U

0

exceeds the set starting level. The unit has one

starting level, U

0b

>, serving both stages in deblocking mode.

• The phase angle ϕ between the voltage and current falls within the operation

sector ϕ ±∆ϕ.

The basic angle ϕ of the network is -90° for isolated neutral networks and 0° for

resonant earthed networks, earthed over an arc suppression coil (Petersen coil) with

or without a parallel resistor. The operation sector is selectable to ∆ϕ = ±80° or ±88°,

both with the addition of a wider operation sector.

SGF1/5

1

C

to>>

1

C

START

TRIP

Uob>

Io>

Io>>

tb>

to>

SGR2/x

SGR1/x

SGR5/x

SGR6/x

SGR4/x

SGR3/x

tb>

70 ms

to>,k

70 ms

to>>

60 ms

0.12 * Io>

1.5 * Io>

1.25 * Io>

2 * Io>>

SGF2/1

Io>>

60 ms

SGB1/1

SGB1/2

SGB1/3

SGB1/5

SGB1/6

SGB1/7

SGF2/3

SGF2/7

SGF3/1

SGF3/3

SGF2/8

SGB1/4

SGB1/8

Uob

Io

BI

Uob>

Uo>

Io>

Uo>>

BlDREJ5_7

&

0.50% x Un

0.48% x In

ϕb/Ιϕ

ϕ

0.1 ... 1s

SGF1/1

C

5 s

PO1

1

SO1

SO2

4

3

2

1

C

5 s

PO2

SGF1/2

&

RESET INDICATORS AND LATCHED OUTPUT RELAYS

RESET INDICATORS, LATCHED OUTPUT RELAYS AND REGISTERS

RESET INDICATORS

SETTINGS (Group 1 / Group 2)

BASIC ANGLE CONTROL or Iϕ characteristica (sin(ϕ) or cos(ϕ))

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When an earth-fault stage starts, a starting signal is generated and simultaneously the

display on the front panel indicates starting. If the above mentioned criteria are

fulfilled long enough to exceed the set operate time, the stage that started initiates a

tripping signal. At the same time the operation indicator on the front panel is lit. The

red operation indicator remains lit although the protection stage resets. The direction

towards the fault spot is determined by means of the angle between the voltage and

current. The basic angle ϕ

b

can be set between -90° and 0°. When the basic angle ϕ

b

is 0°, the negative quadrant of the operation sector can be extended with ϕ

a

. (See Fig.

4.1.3.2.-1) The wider operation sector ϕ

a

is settable to 0...90°.

In Fig. 4.1.3.2.-1 ... Fig. 4.1.3.2.-3 examples of the operation characteristic with the

basic angle.

Fig. 4.1.3.2.-1 Operation characteristic of the directional earth-fault protection

unit when the basic angle

ϕ

b

= 0

°

, operation sector

∆ϕ

=

±

80° and

the wider operation sector

ϕ

a

=40°

Fig. 4.1.3.2.-2 Operation characteristics when the basic angle ϕ

b

= 0°, operation

sector ∆ϕ=±80° and the wider operation sector ϕ

a

=40°.

OPERATION

AREA

Io>

OPERATION

AREA

5

-80° -60° -40° -20°

0° 20° 40° 60° 80° 100°-100°

1

2

3

4

6

NON-OPERATION AREA

ϕb=0°

∆ϕ=80°

Io

In

-120°-140°

ϕa=40°

Ba_0_deg

Negative

quadrant

Positive

quadrant

OPERATION SECTOR

ϕ

b=0°

∆ϕ=80°

Uo

Io

ϕ

∆ϕ

Io>

LEAD

LAG

ϕa=40°

Ba_0_degrees

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Fig. 4.1.3.2.-3 Operation characteristics when the basic angle

ϕ

b

= -90

°

2) The operation of the directional earth-fault unit with sin(ϕ) or cos(ϕ)

characteristics is based on measuring the earth-fault current I

0

and the zero-sequence

voltage U

0

and further the phase angle ϕ between the voltage and current. The sinus

or cosinus value for the phase angle is calculated and then multiplied by the earth-

fault current. This will give the directional earth-fault current Iϕ

as a result. The

earth-fault stage starts if the following three criteria are fulfilled at the same time:

• The directional earth-fault current Iϕ exceeds the set starting level of the earth-

fault stage. The earth-fault unit has two earth-fault current stages I

0

> and I

0

>>.

• The zero-sequence voltage U

0

exceeds the set starting level. The unit has one

starting level, U

0b

>, serving both stages in deblocking mode.

• The phase angle ϕ between the voltage and current falls within the operation

sector of the angle correction factor ϕ

c

=2…7°.

When an earth-fault stage starts, a starting signal is generated and simultaneously the

display on the front panel indicates starting. If the above mentioned criteria are

fulfilled long enough to exceed the set operate time, the stage that started initiates a

tripping signal. At the same time the operation indicator on the front panel is lit. The

red operation indicator remains lit even if the protection stage resets. The direction

towards the fault spot is determined by means of the angle between the voltage and

current. The directional earth-fault characteristic sin(ϕ) corresponds to the earth-

fault protection with the basic angle -90° and cos(ϕ) to the earth-fault protection

with the basic angle 0°.

In Fig. 4.1.3.2.-4 and Fig. 4.1.3.2.-5 examples of the operation characteristics sin(ϕ)

and cos(ϕ).

Uo

Io

ϕ

∆ϕ

OPERATION SECTOR

ϕ

b=-90°

∆ϕ=80°

Io>

LEAD

LAG

Ba_-90_degrees

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Fig. 4.1.3.2.-4 Operation characteristic sin(

ϕ

)

Fig. 4.1.3.2.-5 Operation characteristic cos(ϕ)

The operation directions, forward or reverse, for the directional earth-fault stages

can be selected independently of each other. The directional stages may also be

configured separately as non-directional protection stages.

When the earth-fault current exceeds the set start current of the low-set stage I

0

>, the

earth-fault unit starts delivering a start signal after a preset ~ 70 ms start time. When

the set operate time at definite-time operation or the calculated operate time at

inverse-time operation elapses, the earth-fault unit operates. In the same way, the

high-set stage I

0

>> of the earth-fault unit starts delivering a start signal after a preset

ϕ

Io

Uo

Io>(>)

ϕc=2..7°

Sin_fi_char

ϕ

Io

Uo

Io>(>)

ϕc=2..7°ϕc=2..7°

Cos_fi_char

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~ 60 ms start time when the set start current is exceeded. When the set operate time

elapses, the earth-fault unit operates.

The low-set stage of the earth-fault unit may be given a definite-time or an inverse

definite minimum time (IDMT) characteristic. When the IDMT characteristic is

chosen, six time/current curve groups are available. Four of the groups comply with

the standards IEC 60255 and BS 142, and are called “normal inverse”, “very

inverse”, “extremely inverse” and “long time inverse”. The two additional inverse-

time curve groups are called “RI-” and “RD-curves”.

The inverse-time function of stage I

0

> can be inhibited when stage I

0

>> is started.

In this case, the operate time is determined by stage I

0

>>.

If not needed, the stage I

0

>> can be set out of operation completely. This state is

indicated by three dashes “---” on the LCD and by “999” when the set start current

value is read via serial communication.

The set start current value I

0

>>/I

n

of stage I

0

>> can be automatically doubled in a

start situation, i.e. when the object to be protected is connected to a network. Thus a

set start current value below the connection inrush current level may be selected for

the stage I

0

>>. A start situation is defined as a situation where the phase current rises

from a value below 12 % x I

0

> to a value above 150 % x I

0

> in less than 60 ms. The

start situation ends when the current falls below 125 % x I

0

>.

4.1.3.3. Zero-sequence voltage unit

The two current stages I

0

> and I

0

>> can be replaced by two additional voltage

stages, making the unit a three-stage zero-sequence voltage module. All the three

stages measure the same voltage but can have separate settings both for sensitivity

and operate time. The signalling and trip relays can also be selected separately for

all the three stages.

When the zero-sequence voltage exceeds the start voltage value set for the low-set

stage U

0

>, the voltage unit starts delivering a start signal after a preset ~ 70 ms start

time. When the set operate time at definite-time operation elapses, the voltage unit

operates. In the same way, the high-set stage U

0

>> of the voltage unit starts

delivering a start signal after a preset ~ 60 ms start time, when the set start voltage

is exceeded. When the set operate time elapses, the unit operates.

The low-set and high-set stages of the zero-sequence voltage unit operate on the

basis of the definite-time characteristic.

The high-set stage U

0

>> may be set out of operation by means of the switch SGF2/

3. When the stage is out of operation, three dashes “---” on the display and “999” in

communication via the serial bus indicate that the operation value is infinite.

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4.1.3.4. Protection against intermittent earth-faults

A typical example of an intermittent earth-fault would be one in an insulated cable

where the insulation has a crack and water leaks into the cable and causes an earth-

fault. The earth-fault dries up the crack in the cable, extinguishing the fault, but after

a short time water leaks back through the crack and the earth-fault reappears. The

process repeats giving a succession of fault current pulses.

Fig. 4.1.3.4.-1 Intermittent fault

When the reset time of the overcurrent relay is less than the interval between the

fault current pulses, the relay will be continually reset and not be able to integrate up

to the trip level. Having the reset time set to give as long a delay as possible, but less

than one that would interfere with normal operation of the protection and control

system, will help to eliminate some less common health and safety problems.

Fig. 4.1.3.4.-2 Settable resetting time

The reset delay is settable to values 80, 100, 500 and 1000 ms via the switchgroup

SGF5. If the resetting time is set to 100 ms or above, the earth-fault stage I

0

>

operates as an intermittent earth-fault stage.

Momentary peak

value of neutral

current Io

Momentary

value of

neutral

voltage Uo

Fundamental

amplitude of Io

In

t

e

r

m

2

Set value

Trip level

≥100ms

Resettime

1MRS750616-MUM 19

REJ 527Technical Reference Manual

ABB Substation Automation

Products and Systems

4.1.3.5. Time/current characteristics

The low-set earth-fault current stage I

0

> can be given a definite-time or an inverse

definite minimum time operation characteristic. The settings of switches SGF4/1...6

determine the operation mode of stage I

0

>. Refer to section “Settings” beginning

from page 23. At the IDMT characteristic, the operate time of the stage is a function

of the current: the higher the current, the shorter the operate time. Six time/current

curve groups are available. Four of these comply with the standards IEC 60255 and

BS 142 and two curve groups, RI and RD, are special type curve groups according

to ABB praxis.

Characteristics according to IEC 60255 and BS 142

The relationship between time and current is in accordance with the standards IEC

60255-3 and BS 142, and can be expressed as follows:

where t = operate time

k = time multiplier

I

0

= phase current value

I

0

> = set current value.

The standard BS 142.1966 defines the normal current range to be 2...20 times the

setting value. In addition, the relay has to start at the latest when the current exceeds

the setting value 1.3 times if the time/current characteristic is normal inverse, very

inverse or extremely inverse. For the long-time inverse characteristic the normal

current range is specified to be 2...7 times the setting, and the relay is to start when

the current exceeds the setting value 1.1 times.

Table 1: The values of constants α and β.

Time/current curve group

αβ

Normal inverse 0.02 0.14

Very inverse 1.0 13.5

Extremely inverse 2.0 80.0

Long-time inverse 1.0 120

ts[]

k β×

Io

Io>

---------





α

1–

---------------------------=

ABB Substation Automation

Products and Systems

Technical Reference ManualREJ 527

20 1MRS750616-MUM

E = accuracy in per cent; - = not specified

In the normal current range, specified above, the inverse-time stages of the

directional or non-directional earth-fault relay fulfil the tolerance requirements of

class 5 at all degrees of inversity.

The time/current characteristics according to the IEC and BS standards are

illustrated in Fig. 4.1.3.5.-1...Fig. 4.1.3.5.-2.

RI-type characteristic

The RI-type characteristic is a special characteristic that is principally used for

obtaining time grading with mechanical relays. The characteristic can be expressed

mathematically:

where t = operate time in seconds

k = time multiplier

I

0

= phase current

I

0

> = set start current.

The RI-type characteristic is illustrated in Fig. 4.1.3.5.-3.

Table 2: The operate time tolerances specified by the standard

I

0

/I

0

> Normal Very Extremely Long time

2 2,22E 2,34E 2,44E 2,34E

5 1,13E 1,26E 1,48E 1,26E

7---1,00E

10 1,01E 1,01E 1,02E -

20 1,00E 1,00E 1,00E -

ts[]

k

0.339 0.236–

Io>

Io

---------

×

-------------------------------------------------=

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ABB REJ 527 Technical Reference Manual

ABB REJ 527 Technical Reference Manual

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