ABB REX 521 Technical Reference Manual, General

Brand: ABB

Model: REX 521

Type: Technical Reference Manual, General

REX 521

Protection Relay

Technical Reference Manual, General

Protection Relay

Technical Reference Manual,

General

REX 521

1MRS 751108-MUM

Issued: 27.6.2001

Version: B/05.07.2002

Checked: ML

Approved: MK

We reserve the right to change data without prior notice.

Contents

1. Safety information .....................................................................5

2. Introduction ...............................................................................6

2.1. General .........................................................................................6

2.2. Application .....................................................................................7

2.3. Hardware versions ........................................................................7

3. Requirements ............................................................................8

4. Technical description ...............................................................9

4.1. Functional description ...................................................................9

4.1.1. Parametrization ..................................................................9

4.1.1.1. Local parametrization ...........................................9

4.1.1.2. External parametrization ......................................9

4.1.1.3. Relay Setting Tool view ......................................10

4.1.2. Non-volatile memory ........................................................10

4.1.3. Real-time clock (RTC) ......................................................11

4.1.4. Auxiliary voltage ...............................................................11

4.1.4.1. Power supply versions .......................................11

4.1.4.2. Low auxiliary voltage indication ..........................12

4.1.5. Overtemperature indication ..............................................12

4.1.6. Analogue channels ..........................................................12

4.1.6.1. Setting the rated values for the protected unit ...12

4.1.6.2. Technical data of the measuring devices ...........13

4.1.7. Digital inputs ....................................................................15

4.1.7.1. Filtering of digital inputs .....................................15

4.1.7.2. Inversion of digital inputs ....................................16

4.1.8. Outputs ............................................................................16

4.1.8.1. High-speed power output (HSPO) .....................16

4.1.8.2. Single-pole power outputs (PO) .........................17

4.1.8.3. Signalling outputs (SO) ......................................18

4.1.9. Testing inputs and outputs ...............................................18

4.1.10.Trip-circuit supervision .....................................................19

4.1.11.Self-supervision ...............................................................20

4.1.11.1.Fault indication ...................................................22

4.1.11.2.Fault indication texts ..........................................22

4.1.12.Serial communication .......................................................23

4.1.12.1.Optical communication port on the rear panel ...23

4.1.12.2.Front panel optical connection for a PC .............24

4.1.12.3.The service pin located on the rear panel ..........24

1MRS 751108-MUM

Protection Relay

Technical Reference Manual, General

REX 521

4.1.12.4.SPA bus .............................................................25

4.1.12.5.LON bus ............................................................26

4.1.12.6.IEC 60870-5-103 bus ........................................28

4.1.13.Time synchronization .......................................................29

4.1.14.Display panel (HMI) .........................................................29

4.1.15.Indication LEDs ...............................................................30

4.2. Design description ......................................................................30

4.2.1. Technical data .................................................................30

4.2.2. Terminal diagram of the REX 521: Basic .........................34

4.2.3. Terminal diagram of the REX 521: Medium .....................35

4.2.4. Terminal diagram of the REX 521: High ..........................36

4.2.5. Terminal diagram of the REX 521: Sensor ......................37

4.2.6. Terminal connections ......................................................38

5. Service ..................................................................................... 40

6. Ordering information ............................................................. 41

7. Revision history of the REX 521 ........................................... 42

7.1. Revision identification .................................................................42

7.2. Changes and additions to earlier released revision A ................42

7.3. Configuration, setting and SA system tools ................................42

8. References .............................................................................. 43

9. Index ........................................................................................ 44

10.Customer feedback ............................................................... 46

11.Appendix A: The IEC 60870-5-103 bus ................................ 48

11.1.Functions supported by the REX 521 ........................................48

11.2.The general principle of application data mapping .....................48

11.3.The principle of the protection functions mapping ......................49

11.4.Class 2 data ...............................................................................49

11.5.Default mappings .......................................................................50

12.Appendix B: Parameters visible only in the relay .............. 57

13.Appendix C: Parameters which cause reset ....................... 58

14.Appendix D: Parameters which require test mode ............ 60

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Version B/5.7.2002:

- changes in chapters “General”, “Hardware versions”, “Analogue channels”, “Setting the rated values

for the protected unit”, “Technical data of the measuring devices”, “Single-pole power outputs (PO)”,

“Trip-circuit supervision”, “Technical data”, “Ordering information”

- new terminal diagrams and terminal connections (High and Sensor)

- new chapters: “Revision history”, “Revision history of the REX 521”, “Index” and “Appendix D”

1MRS 751108-MUM

Protection Relay

Technical Reference Manual, General

REX 521

1. 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 device contains components that are sensitive to electrostatic

discharge

The frame of the device has to be carefully earthed

Only a competent electrician is allowed to carry out the electrical

installation

Non-observance can result in death, personal injury or substantial

property damage

Breaking the sealing tape on the rear panel of the device will result in

loss of warranty and a proper operation will no longer be guaranteed

1MRS 751108-MUM

Protection Relay

Technical Reference Manual, General

REX 521

2. Introduction

This document provides a general description of the protection relay REX 521

Revision B. For more information about the earlier revisions, please refer to section

“Revision history of the REX 521” on page 42.

For detailed information about the separate functions, please refer to REX 521

Technical Reference Manual, Standard Configurations (1MRS 751802-MUM).

2.1. General

The protection relay REX 521 is designed for protection, control, measuring and

supervision in medium voltage networks. Typical applications include incoming and

outgoing feeders as well as substation protection. The protection relay is provided

with energizing inputs for conventional current and voltage transformers. Also a

hardware version with inputs for current and voltage sensors is available.

The protection relay is based on a multiprocessor environment. The HMI

including

an LCD display with different views makes the local use easy and informs the user

via indication messages. Modern technology is applied both in hardware and

software solutions.

The REX 521 is part of the substation automation concept for Distribution

Automation and extends the functionality and flexibility of the concept further.

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1. HMI is referred to as MMI in the relay and in the Relay Setting Tool.

1MRS 751108-MUM

Protection Relay

Technical Reference Manual, General

REX 521

2.2. Application

The REX 521 is designed for protection of incoming and outgoing feeders in

medium voltage distribution substations. Further, the relay can, e.g., be applied to

back-up protection of power transformers and back-up for high voltage line

protection relays.

Several standard configurations are available for the protection relay. Please, refer to

REX 521 Technical Reference Manual, Standard Configurations

(1MRS 751802-MUM).

2.3. Hardware versions

Table 2.3.-1 Hardware versions of the REX 521

Relay type REX 521

Version name Basic Medium High Sensor

REX521xBxxx

REX521xMxxx

REX521xHxxx

REX521xSxxx

Transformer modules (MIM)

1111

Transformers

• Current transformers 1/5 A 4441

• Current transformers 0.2/1 A 1 1 1

• Voltage transformers 100 V 1 4 1

Sensor channels

• Current sensor inputs 3

• Voltage sensor inputs 3

Main CPU modules

1111

CPU_SP (SPA/ IEC plastic)

CPU_SG (SPA/ IEC glass)

CPU_LP (SPA/ IEC/ LON plastic)

CPU_LG (SPA/ IEC/ LON glass)

Power supply modules

1111

PS_87H (DItresh.=80 Vdc)

PS_87L (DItresh.=18 Vdc)

Display module

1111

2 x 16 character display

Digital inputs

High-speed power outputs

Power outputs (PO)

Signalling outputs (SO)

IRF outputs

Trip-circuit supervision (TCS)

1MRS 751108-MUM

Protection Relay

Technical Reference Manual, General

REX 521

3. Requirements

If the environmental conditions differ from those specified in section “Technical

data”, as to temperature and humidity, or if the environmental conditions around the

protection relay contains chemically active gases or dust, the relay should be

visually inspected in association with the secondary testing. The visual inspection

should focus on:

• Signs of mechanical damage to the relay case and terminals.

• Signs of corrosion on terminals or on the case.

• For information about the maintenance of relays, refer to section “Service” on

page 40.

Protection relays are measuring instruments and should be handled with

care and protected against moisture and mechanical stress, especially

during transport.

1MRS 751108-MUM

Protection Relay

Technical Reference Manual, General

REX 521

4. Technical description

4.1. Functional description

4.1.1. Parametrization

To ensure that a protection function block protects the feeder in the desired manner,

the default values of parameters must be checked and set before taking the function

block into use.

The parameters can be set either locally over the HMI or externally via the serial

communication using Relay Setting Tool. See “Serial communication” on page 23.

4.1.1.1. Local parametrization

The parameter to be changed is entered by navigating in the menu structure. For

detailed instructions, refer to Operator’s Manual (1MRS751107-MUM).

4.1.1.2. External parametrization

The Relay Setting Tool is used for external parametrization of the protection relay.

The parameters can be set by using a PC and downloaded to the protection relay over

a communication port. The menu structure of the setting tool, including views

relating to parametrization and settings, is the same as the menu structure of the

protection relay

. The use of the tool is instructed in ”Tools for Relays and

Terminals, User’s Guide” (refer to section “References” on page 43).

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1. A few parameters are visible only in the relay, see list on page 57.

1MRS 751108-MUM

Protection Relay

Technical Reference Manual, General

REX 521

4.1.1.3. Relay Setting Tool view

To improve usability, a REX 521 specific pull-down menu, View, with three views

has been created to the Relay Setting Tool.

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The Settings view includes the parameters for setting of all the function blocks. The

Configuration view includes signalling and hardware related settings. The

parameters in the Configuration view are advised to be set during commissioning

and service because some of the parameters cause resetting of the device. Please

refer to “Appendix C: Parameters which cause reset” on page 58 for a list of these

parameters. Measured values and registered data, e.g. current, digital input states,

can be uploaded by means of the Measurements & Registered Data view.

4.1.2. Non-volatile memory

The protection relay is equipped with a non-volatile memory for preserving

important data during auxiliary supply breaks. For example, when a setting value is

changed, the new value is stored in the memory at the moment of sending it to the

relay, without additional store commands. The memory does not need batteries, and

a lifelong service is guaranteed.

Following data is stored in the non-volatile memory:

• Setting values

• Display state

• Lockout state

• Recorded values

• Last 50 events

When the relay is restarted, the same LED indication and text as before the auxiliary

supply break are restored on the display.

1. Because the storing of the recorded values is a background task, it might be affected

by a sudden auxiliary power failure.

1MRS 751108-MUM

Protection Relay

Technical Reference Manual, General

REX 521

Recorded values are stored from start, trip and other important events. After an

auxiliary power break, time and date and fault currents for the three last events can

be viewed by navigating to the “Recorded values” section of the function block that

caused an indication.

The last 50 events that occurred before the auxiliary power supply break can be

viewed in the HMI event buffer. Time and date for the events are also restored.

4.1.3. Real-time clock (RTC)

The RTC is used for time stamping of events. It is also running during auxiliary

power breaks. When the supply is re-established, the relay sets the right time and

new events are stamped accordingly.

The protection relay is provided with a 1-week capacitor back-up protection

that

enables the internal clock to keep time in case of an auxiliary power failure.

4.1.4. Auxiliary voltage

For its operation, the protection relay requires a secured auxiliary voltage supply.

The protection relay’s internal power supply module forms the voltages required by

the protection relay electronics. The power supply module is a galvanically isolated

(flyback-type) DC/DC converter. A green LED indicator on the front panel is lit

when the power supply module is in operation.

4.1.4.1. Power supply versions

There are two basic versions of power supply modules available for the REX 521

protection relays: type PS_87H and type PS_87L.

The input voltage range of the power supply module is marked on the front panel of

the REX 521 unit. The power supply version is specified by a letter in the order

number of the protection relay (refer to section “Ordering information” on page 41).

The voltage range of the digital inputs is tied to the selected power supply. If a power

supply version with the higher rated input voltage is selected, the protection relays

will be delivered with digital inputs that also have the higher rated input voltage. The

digital input, DI9, on the CPU module has always lower rated input voltage.

The auxiliary voltages of power supply modules and the corresponding rated input

voltages of digital inputs are:

For further technical data of the power supply, refer to Table 4.2.1-2 on page 30.

1. Capacitor ageing may decrease the back-up time.

Power supply module

Rated input voltage

of power supply

Rated input voltage

of digital inputs

PS_87H 110/120/220/240 V ac

or 110/125/220 V dc

110/125/220 V dc

PS_87L 24/48/60 V dc 24/48/60/110/125/220 V dc

1MRS 751108-MUM

Protection Relay

Technical Reference Manual, General

REX 521

4.1.4.2. Low auxiliary voltage indication

The relay is provided with a low auxiliary voltage indication feature. The power

supply module issues an internal alarm signal when a drop in the power supply

voltage is detected. The alarm signal is activated if the power supply voltage falls

about 10% below the lowest rated dc input voltage of the power supply module, see

the table below:

The indication of a low auxiliary voltage (ACFail) can be seen as an event via serial

communication.

4.1.5. Overtemperature indication

The REX protection relay includes an internal temperature supervision function.

The CPU module issues an internal alarm signal when overtemperature has been

detected inside the relay enclosure. The alarm signal will be activated once the

temperature inside the relay enclosure increases approximately to +78

C. The

overtemperature indication can be seen on the HMI or as an event via serial

communication. The relay will go to the IRF state. See Table 4.1.11.2-1, “Fault

indications,” on page 22.

4.1.6. Analogue channels

The protection relay measures the analogue signals needed for protection,

measuring, etc. via galvanically separated matching transformers. In addition,

current sensors (Rogowski coil) and voltage dividers developed by ABB can be used

with the REX 521.

The different versions of the REX 521 are provided with the following matching

transformers and sensor inputs:

A letter in the order number specifies whether the protection relay is equipped with

basic, medium, high or sensor measuring input modules. (Refer to section “Ordering

information” on page 41).

4.1.6.1. Setting the rated values for the protected unit

A separate scaling factor can be set for each analogue channel. The factors enable

differences between the ratings of the protected unit and those of the measuring

device (CTs, VTs etc.) The setting value 1.00 means that the rated value of the

protected unit is exactly the same as that of the measuring device.

Rated input voltage Low indication level

PS_87H

• Rated input voltage 110/125/ 220 V dc 99 V dc

• Rated input voltage 110/120/220/ 240 V ac 88 V ac

PS_87L

• Rated input voltage 24/48/60 V dc 21.6 V dc

Version Matching transformers Sensor inputs

Basic CT1, CT2, CT3, CT4 -

Medium CT1, CT2, CT3, CT4, CT5, VT1 -

High CT1, CT2, CT3, CT4, CT5, VT1, VT2, VT3, VT4 -

Sensor CT4, CT5, VT1 RS1, RS2, RS3, VD1, VD2, VD3

1MRS 751108-MUM

Protection Relay

Technical Reference Manual, General

REX 521

When scaling factors are used, it should be noted that they affect the operation

accuracy of the relay. The accuracies stated in the description of each function block

(in the CD-ROM Technical Descriptions of Functions) only apply with the default

values of the scaling factors. For example, a high factor affects the operation of

sensitive protection functions such as the directional earth-fault protection.

The scaling factor is calculated channel by channel as follows:

Scaling factor = I

nmd

/ I

np,

where

Example:

The scaling factors for the analogue channels can be set via the HMI of the

protection relay or with the Relay Setting Tool. The HMI path for the scaling factors

is: Configuration\Protected unit\IL1: scaling, IL2:

scaling...

4.1.6.2. Technical data of the measuring devices

The technical data of the measuring devices is set using the Relay Setting Tool or

via HMI. The set values (Configuration\Meas.devices\) will affect the

measurements carried out by the REX 521.

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• rated primary current (0...6000 A) of the current transformer

• rated secondary current (5 A, 2 A, 1 A, 0.2 A) of the current transformer

• rated current (5 A, 1 A, 0.2 A) of the current measuring input (= rated current of

the matching transformer of the protection relay)

• amplitude correction factor (0.9000...1.1000) of the current transformer at rated

current

• correction parameter for the phase displacement error of the current transformer

at rated current (-5.00°...0.00°)

• amplitude correction factor of the current transformer at a signal level of 1% of

the rated current (0.9000...1.1000)

• correction parameter for the phase displacement error of the current transformer

at a signal level of 1% of the rated current (-10.00°...0.00°)

nmd

Rated primary current [A] of the measuring device

Rated primary current [A] of the protected unit connected to the

channel

Rated primary current of current trafo = 500 A: I

nmd

= 500 A

Rated current of the protected unit = 250 A: I

= 250 A

Scaling factor for current channels: 500 A / 250 A = 2.00

1MRS 751108-MUM

Protection Relay

Technical Reference Manual, General

REX 521

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• rated voltage of primary voltage transformer (0...440 kV)

• rated voltage of voltage input (same as the secondary rated voltage of the primary

voltage transformer connected to the voltage input, 100 V, 110 V, 115 V, 120 V)

• amplitude correction factor of the primary voltage transformer voltage at rated

voltage (0.9000...1.1000)

• correction parameter for the primary transformer phase displacement error at

rated voltage (-2.00°... 2.00°)

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• secondary rated voltage of the current sensor used at the preset primary rated

current (0...300 mV)

• primary rated current of the current sensor used (0...6000 A)

• amplitude correction factor of the current sensor used at rated current

(0.9000...1.1000)

• correction parameter for the phase displacement error of the current sensor

(-1.0000°...1.0000°)

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• division ratio of the voltage divider primary and secondary voltage (0...20000)

• rated value of primary phase-to-phase voltage (0...440 kV)

• amplitude correction factor of the voltage divider (0.9000...1.1000)

• correction parameter for the phase displacement error of the voltage divider

(-1.0000°...1.0000°)

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The measurement values stated by the manufacturer of the measuring device are

used for calculating the correction parameters and factors according to the following

formulas:

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Amplitude error at current I

(p = error in per cent)

Amplitude correction factor 1

= 1 / (1+ p/100)

Amplitude error at current 0.01 x I

(p = error in per cent)

Amplitude correction factor 2

= 1 / (1+ p/100)

Phase displacement error at current I

(d = error in degrees)

Phase displacement error 1 = - d

Phase displacement error at current 0.01 x I

(d = error in degrees)

Phase displacement error 2 = - d

Amplitude error at voltage U

(p = error in per cent)

Amplitude correction factor

= 1 / (1+ p/100)

1MRS 751108-MUM

Protection Relay

Technical Reference Manual, General

REX 521

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Primary values and measurement device settings

The conversion between primary and per unit values are based on the analogue

scales of the I

pu-scale), I

pu-scale), U

pu-scale)

and U

pu-scale). To ensure proper operation, it must be checked that the

analogue scales of the phase currents I

, I

and I

, and correspondingly, the

analogue scales of the phase-to-phase voltages U

, U

and U

are identical.

4.1.7. Digital inputs

The digital inputs of the protection relay are voltage-controlled and optically

isolated. For technical data of the digital inputs, refer to Table 4.2.1-3 on page 31.

4.1.7.1. Filtering of digital inputs

The filter time eliminates debounces and short disturbances on digital inputs. The

filter time may be set individually for each input.

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Phase displacement error at voltage U

(d = error in degrees)

Phase displacement error = - d

Amplitude error at the whole measuring range

(e = error in per cent)

Amplitude correction factor

= 1/(1+ e/100)

Phase displacement error at the whole

measuring range

(e = error in degrees)

Phase displacement error = - e

Amplitude error at the whole measuring range

(e = error in per cent)

Amplitude correction factor

= 1/(1+ e/100)

Phase displacement error at the whole

measuring range

(e = error in degrees)

Phase displacement error = - e

1MRS 751108-MUM

Protection Relay

Technical Reference Manual, General

REX 521

The figure above illustrates the input filtering. At the beginning, the input signal is

at high state, the first low state is filtered and no input status change is detected. The

second low state is longer than the set filter time, thus detected as a change and

attached with the time tag t

.When the input signal returns to high state, after the

filter time, the state is accepted and attached with the time tag t

Each digital input has a filter time parameter “Input # filter”

(Configuration\Digital inputs\Input filtering), where # is the

number of the input.

A risk for debounces and short disturbances on digital inputs grows if the input filter

time is changed to less than the default value.

4.1.7.2. Inversion of digital inputs

The status of digital inputs can be inverted with parameters accessible through the

HMI or the Relay Setting Tool (Configuration\Digital inputs\Input

inversion). When inverted, the status of a digital input is TRUE (1) when no

control voltage is applied to the terminals, and FALSE (0) when the control voltage

is applied.

4.1.8. Outputs

The outputs are categorized as follows:

• HSPO: High speed power output, single or double pole contact, e.g. for tripping

purposes

• PO: Power output, single pole contact

• SO: Signal output, NO/NC (Normally open/Normally closed) contact

For detailed information about terminal connections, please refer to the terminal

diagrams. Technical data of the outputs is found in the section “Technical Data” on

page 30.

4.1.8.1. High-speed power output (HSPO)

The high-speed power output HSPO1 can be connected as a double-pole output

where the object to be controlled (e.g. a circuit breaker) is electrically connected

between the two relay contacts, see the figure below. The high-speed double-pole

power output is recommended to be used for tripping purposes.

Table 4.1.7.1-1 Filter time parameter

Parameter Values Default

Input # filter 1...65535 ms 5 ms

1MRS 751108-MUM

Protection Relay

Technical Reference Manual, General

REX 521

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The high-speed power output HSPO1 can also be connected as a single-pole power

output where the object to be controlled (e.g. a circuit breaker) is electrically

connected in series with the two relay contacts, see the figure below.

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4.1.8.2. Single-pole power outputs (PO)

The single-pole power outputs PO1...3 are outputs where the object to be controlled

is connected in series with two heavy-duty output relay contacts, see the figure

below. These outputs can be used for tripping purposes and for circuit breaker and

disconnector control. Two singe-pole outputs may be used to obtain another double-

pole output.

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cbcoilrex

HSPO1

doubpolerex

HSPO1

PO1connrex

PO1...3

1MRS 751108-MUM

Protection Relay

Technical Reference Manual, General

REX 521

4.1.8.3. Signalling outputs (SO)

The signalling relay outputs (SO1 and SO2) are not heavy-duty outputs and thus

they cannot be used for controlling e.g. a circuit breaker. Available relay contacts

are Normally Open/Normally Closed type (NO/NC), see the figure below. These

outputs can be used for alarming and other signalling purposes.

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4.1.9. Testing inputs and outputs

The digital inputs and the output relays may be tested using the serial

communication or the HMI.

Generally, the relay has to be in the test mode before the inputs and outputs can be

activated. However, output relays may be activated through the serial

communication without entering the test mode. This is to enable the usage of output

relays for external purposes, not part of the protection and control in the host relay.

The test mode can be set with a parameter. The green READY LED indicator will

be blinking, to announce that the test mode has been entered. In this state, the relay

configuration is disconnected from the physical inputs so that changes on the digital

inputs will not be noticed. When the test mode is deactivated, all test parameters

requiring the test mode, will be reset.

The IRF relay may be tested by using the HMI. The IRF relay testing always requires

entering the test mode.

When testing the general output relays, the user should notice, that normal operation

of the relay cannot be disconnected. If an output relay is permanently activated by

the configuration, it cannot be deactivated for testing.

For further information, refer to Operator’s manual (see “References” on page 43).

noncrex

NO/NC

e.g.

SO1

Table 4.1.9-1 Testing of inputs and outputs

Test object Using

Requires

test mode?

Remarks

Digital inputs HMI Yes Physical inputs disconnected

Serial communication Yes

Output relays HMI Yes Normal operation still active

Serial communication No

IRF relay HMI Yes

Serial communication Yes

1MRS 751108-MUM

Protection Relay

Technical Reference Manual, General

REX 521

4.1.10. Trip-circuit supervision

The trip-circuit supervision consists of two functional units:

• a current limiter including the necessary hardware elements

• a software-based function block, named TCS

The supervision of the trip circuit is based on the constant current injection principle.

By applying an external voltage over the relay’s trip contacts, a constant current is

forced to flow through the external trip circuit. If the resistance of the trip circuit

exceeds a certain limit, for instance due to a bad contact or oxidation, the supervision

function will be activated and cause a trip-circuit supervision alarm signal after an

adjustable delay time.

Under normal operating conditions, the applied external voltage is divided between

the relay’s internal circuit and the external trip circuit so that at the minimum 20 V

(15...20 V) remains over the relay’s internal circuit. Should the external circuit’s

resistance be too high or the internal circuit’s too low, e.g. due to welded relay

contacts, the fault is detected.

Mathematically the operation condition can be expressed as:

where:

• U

= operating voltage over the supervised trip circuit

• I

= measuring current through the trip circuit, appr. 1.5 mA (0.99...1.72 mA)

• R

ext

= external shunt resistance

• R

int

= internal shunt resistance, 1kΩ

• R

= trip coil resistance

The external shunt resistance is used if the trip-circuit supervision, independent of

the circuit-breaker position, is desired. If the trip-circuit supervision is required only

in closed position, the external shunt resistance may be omitted.

Should the external shunt resistance be used, it has to be calculated not to interfere

with the functionality of the supervision or the trip coil. Too high a resistance will

cause too high a voltage drop, jeopardizing the requirement of at least 20 V over the

internal circuit, while a resistance too low may enable false operations of the trip

coil.

Following values are recommended for the external resistor R

ext

Table 4.1.10-1 Values recommended for R

ext

Operating voltage U

Shunt resistor R

ext

48 V dc

1.2 kΩ

, 5 W

60 V dc

5.6 kΩ

, 5 W

110 V dc

22 kΩ

, 5 W

220 V dc

33 kΩ

, 5 W

ext

int

++()– I

20≥× Vac dc⁄

1MRS 751108-MUM

Protection Relay

Technical Reference Manual, General

REX 521

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If there are more auxiliary contacts available, an opening contact can be series

connected with the R

ext

-resistor. The shunt-resistor circuit is opened when the CB is

closed. Therefore the supervision of the auxiliary contact is also possible.

4.1.11. Self-supervision

In order to avoid false operations due to relay faults and to maximize the overall

availability of the protection, a set of autodiagnostic circuit arrangements have been

implemented in the relay modules.

The different memory circuits, i.e. the RAM and the non-volatile memories, are

continuously tested with different methods.

TCS1

TCSSTATE ALARM

TCS

X4.2

CBPOS_open

TCS blocking

int

CBPOS_open

TCS gesperrt

TCSopen

TCS1

TCSSTATE ALARM

TCS

X4.2

TCS blocking

CBPOS_open

int

ext

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ABB REX 521 Technical Reference Manual, General

ABB REX 521 Technical Reference Manual, General

ABB REX 521 Technical Reference Manual, General

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