mri-v...characteristics in accordance with bs142 and iec 255-4. furthermore, the mri-v has an...

2/5/96 0 MRI-V 01/96H

MRI-V Digital Multifunctional Relay for Voltage

Controlled Overcurrent Protection

P&B Engineering

Belle Vue Works

Boundary Street

Manchester

M12 5NG

Tel: 0161 230 6363

Fax: 0161 230 6464

2/5/96 i MRI-V 01/96H

Contents

1. INTRODUCTION ........................................................................................................................................................ 1

2. APPLICATION ............................................................................................................................................................ 2

3. FEATURES AND CHARACTERISTICS.................................................................................................................. 2

4. DESIGN......................................................................................................................................................................... 3

4.1 CONNECTIONS ........................................................................................................................................................... 3

4.1.1 Analogue input circuits...................................................................................................................................... 3

4.1.2 Output relays ..................................................................................................................................................... 3

4.1.3 Remote data communication.............................................................................................................................. 4

4.1.4 Blocking Input ................................................................................................................................................... 4

4.2 FRONT PANEL............................................................................................................................................................. 4

4.2.1 Display............................................................................................................................................................... 4

4.2.2 LED indicators .................................................................................................................................................. 6

4.2.3 Push buttons ...................................................................................................................................................... 6

4.3 CODE JUMPERS .......................................................................................................................................................... 6

4.3.1 Password programming..................................................................................................................................... 7

4.3.2 Alarm and Trip relay function ........................................................................................................................... 7

5. WORKING PRINCIPLES........................................................................................................................................... 8

5.1 ANALOGUE CIRCUITS ................................................................................................................................................. 8

5.2 DIGITAL CIRCUITS ...................................................................................................................................................... 8

5.3 POWER SUPPLY .......................................................................................................................................................... 8

5.4 VOLTAGE DEPENDENT TRIPPING CHARACTERISTIC ................................................................................................... 9

5.5 REQUIREMENTS FOR THE MAIN CURRENT TRANSFORMERS...................................................................................... 10

5.6. RESET DELAY & DWELL TIME.................................................................................................................................. 10

6. OPERATION AND SETTING.................................................................................................................................. 10

6.1 LAYOUT OF THE CONTROL ELEMENTS ...................................................................................................................... 10

6.2 RELAY SETTING PRINCIPLES ..................................................................................................................................... 11

6.2.1 Password protected parameter adjustment ..................................................................................................... 11

6.3 SETTING PROCEDURE ............................................................................................................................................... 12

6.3.1 Starting current for phase overcurrent relay (Isn and Isl) .............................................................................. 12

6.3.2 Time current Characteristic (CHAR I>).......................................................................................................... 12

6.3.3 Tripping time delay or time multiplier for overcurrent (tI>)........................................................................... 12

6.3.4 Current setting for high set overcurrent stage (I>>)....................................................................................... 13

6.3.5 Tripping time delay for high set overcurrent stage (tI>>) .............................................................................. 13

6.3.6 Setting of the Undervoltage Switching Point ................................................................................................... 13

6.3.7. Reset & Dwell ................................................................................................................................................. 13

6.3.8 Nominal frequency........................................................................................................................................... 13

6.4 INDICATION OF MEASURED VALUES AND FAULT DATA ............................................................................................. 13

6.4.1 Indication of measured values ......................................................................................................................... 13

6.4.2 Indication of fault data .................................................................................................................................... 14

6.5 TEST TRIP ................................................................................................................................................................ 14

6.6 RESET ...................................................................................................................................................................... 14

6.6.1 Hand reset........................................................................................................................................................ 14

6.6.2 Auto-reset at Power Up ................................................................................................................................... 14

6.7 SETTING VALUE CALCULATION ................................................................................................................................ 14

2/5/96 ii MRI-V 01/96H

7. RELAY CASE............................................................................................................................................................. 15

7.1 INDIVIDUAL CASE..................................................................................................................................................... 15

7.2 RACK MOUNTING ..................................................................................................................................................... 15

7.3 TERMINAL CONNECTIONS ........................................................................................................................................ 15

8. TEST AND MAINTENANCE ................................................................................................................................... 15

9. TECHNICAL DATA.................................................................................................................................................. 16

9.1 MEASURING INPUT CIRCUITS ................................................................................................................................... 16

9.2 AUXILIARY POWER SUPPLY ...................................................................................................................................... 16

9.3 COMMON DATA........................................................................................................................................................ 16

9.4 SETTING RANGES AND STEPS.................................................................................................................................... 17

9.4.1 Definite time phase overcurrent relay ............................................................................................................. 17

9.4.2 Inverse time phase overcurrent relay .............................................................................................................. 17

9.5. INVERSE TIME CHARACTERISTICS............................................................................................................................ 18

9.6 OUTPUT CONTACT RATINGS ..................................................................................................................................... 19

9.7 SYSTEM DATA.......................................................................................................................................................... 19

9.8 HOUSING.................................................................................................................................................................. 20

9.9 TERMINAL CONNECTION DETAILS ........................................................................................................................... 21

10. ORDER FORM......................................................................................................................................................... 22

2/5/96 1 MRI-V 01/96H

1. Introduction

The application of powerful microprocessors opens a new chapter for power system

protective relaying. The digital processing of measured values and the ability to perform

complex arithmetic and logic operations, give digital protection relays significant

performance and flexibility improvements over their traditional analogue counterparts.

Additional advantages - very small power consumption, adaptability, self-supervision, fault

diagnosis through fault data recording, smaller physical construction and selectable relay

characteristics - all combine to allow the implementation of accurate and highly reliable

protection schemes at a significantly reduced financial burden.

The development of microprocessor based protective relays and their introduction into the

market has been stimulated by the recent trend to replace analogue with digital equipment.

This modern trend has prompted the development of a new P&B protective relay family - the

MR relay series. This comprehensive family of protection relays can satisfy the demands of

even the most complex protection schemes:

MRI - Overcurrent Relay (Independent time/I.D.M.T + earth + directional facilities)

MRI-V - Voltage Dependent Overcurrent Relay

MREF - Restricted Earth Fault Relay

MRAR - Auto-Reclosing Relay

MRMF - Mains Failure Relay

MRVT - Voltage Protection

MRFT - Frequency Protection

MROS - Vector Surge or Rate of Change of Frequency

MRNS - Negative Sequence Relay

MRRP - Power Relay

MRCS - Check Synchronising Relay

MRFF - Field Failure Relay

MRDG - Differential Relay

The superiority of digital protective relaying over traditional analogue devices, as embodied

by the MR relay family, is summarized by the following features:

•••• Integration of many protective functions in a single compact case

•••• High accuracy owing to digital processing

•••• Digital relay setting with very wide setting ranges and fine setting steps

•••• Comfortable setting procedure through extensive human - relay dialogue

•••• Measured values and fault data indication by means of alpha-numeric display

•••• Data exchange with DCS/SCADA by means of RS485

•••• Operational reliability through self-supervision

A similar but simplified range, with reduced functions and without display, is also available.

The MIRI - overcurrent and earth fault relays, and the MIRV - undervoltage, overvoltage

and neutral voltage displacement relays. To complement the MR series, a range of Auxiliary,

Timing and Tripping devices are also available.

2/5/96 2 MRI-V 01/96H

2. Application

The MRI-V digital voltage dependent overcurrent relay is a universal multifunctional

protection device for medium voltage networks. It offers both Definite Time and Inverse

Definite Minimum Time (IDMT) overcurrent protection in a single compact unit. IDMT

protection is also selectable between Normal Inverse, Very Inverse and Extremely Inverse

characteristics in accordance with BS142 and IEC 255-4. Furthermore, the MRI-V has an

adjustable undervoltage switching point and may be employed as protection for voltage loss

during short circuit of the generator where the decreasing current supplied may be lower than

the full load conditions prior to the fault. The protective functions of the MRI-V are

summarized as follows:

• Selectable protective functions between :

- Definite time overcurrent relay

- Inverse time overcurrent relay

• Inverse definite minimum time (IDMT) overcurrent relay with the following

selectable characteristics in accordance with BS 142 and IEC 255-4:

- Normal Inverse

- Very Inverse

- Extremely Inverse

• Two stage overcurrent relay

• High set overcurrent unit with instantaneous or definite time function

• Voltage controlled tripping characteristic

3. Features and characteristics

• Complete digital processing of the sampled measured values

• Digital filtering of measured values using discrete fourier analysis to

suppress high frequency harmonics and d.c component induced by faults or

system operations

• Extremely wide setting ranges with fine setting steps

• Unauthorized user access control through password protection

• User defined password

• Continuous self-supervision of software and hardware

• Outstanding design flexibility for easy selection of appropriate operational

scheme for numerous applications

• Numerical display of setting values, actual measured values and

memorized fault data etc.

• Serial data communication facilities via RS485

• Wide voltage range for DC or AC power supply

• Withdrawable modules with automatic short circuit of C.T. inputs

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4. Design

4.1 Connections

Application Diagram;

POWER

SUPPLY

1 2 CASE

Supply

MRI-VTypical Earthing Shown

54 5553External Reset Blocking Input

L N L

TRIP SIGNAL

ALARM

INDICATION

33

31

29

32

3034

4852

50

45

43

41

44

4246

40

38

36

37

3539

+

7 9 10

Gnd-

SELF SUPERVISION

I>>

I>

RS485

19

15

17

21

22

23

24

25

26

L1

L2

L3

I1

I2

I3

S2P2

P1

S1

AlternativeEarthing

L 1-2

L1-3

4.1.1 Analogue input circuits

The constantly detected measuring values are galvanically decoupled, filtered and finally fed

to the analogue/digital converter. The protection unit receives these analogue input signals

for the phase currents I1, I2 & I3, and phase to phase voltages V12, V23 & V31.

4.1.2 Output relays

The MRI-V has four output relays, with single or dual pole change-over contacts as detailed

in the previous diagrams and summarized below:

• Tripping relay (2)

• Self-supervision alarm relay (1)

• High set overcurrent relay (2)

• Low set overcurrent relay (2)

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4.1.3 Remote data communication

As an option, the MRI-V may have an RS485 interface for remote data communication with

a control centre. The unit provides the following information:

• Measured phase fault current values

• Status signals

• Self supervision alarm signal

• Actual measured current values

• Relay settings

• Phase fault signalling

4.1.4 Blocking Input

When required to inhibit the high set function I>>, the auxiliary supply is connected to the

blocking input terminals, 54-55.

4.2 Front panel

The front panel of the MRI-V comprises the following operation and indication elements:

• Alphanumeric display (4 Digits)

• 5 push buttons for setting and other operations

• 10 LEDs for measured value indication and setting

4.2.1 Display

The measured and set values, and recorded fault data, are shown alphanumerically on the

display. The meaning of the displayed values is easily interpreted from the LED indicators on

the front panel.

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Table: Adjustment possibilities by means of the display

Function Display Shows Pressed push button

and system reply

Illuminated LED

Measured operating

values (phase current)

Actual measured current

value, related to In

<SELECT> L1, L2, L3

Measured operating

values (line voltages)

Actual measured voltage

value, related to Vn

<SELECT> L1, L2, L3,V

Recorded fault data Tripping current in L1,

L2, L3

<SELECT> L1, L2, L3, I>,

I>>,V

Setting value current settings I>, I>>

related to In

voltage switch value

related to Vn

trip time delay in second

time multiplier

Characteristics:

- DEFT

- NINV

- VINV

- EINV

function Inhibited -

EXIT

<SELECT>

<UP>

<DOWN>

I>, CHARI>, tI>,

I>>, tI>>, V

Reset delay Os or 60s <SELECT>

<UP>

<DOWN

I> CHAR I

tI.>

Dwell time 200 or auto < SELECT>

<UP>

<DOWN.

Nominal frequency f = 50, f = 60 <SELECT>

<UP>

<DOWN>

Normal operation P&B <SELECT> long -

system reset

Inquire password PSW? <ENTER> / <TRIP>

Save parameter? SAV? <ENTER>

Save parameter SAV! <ENTER>

Manual trip TRI? <TRIP>

Relay is tripped TRIP <TRIP> / or system

reply

L1, L2, L3, I> or

I>>

Secret password XXXX Push-button

combination S,∨,∧,E

Maximum measuring

range reached

max. System reply L1, L2, L3

2/5/96 6 MRI-V 01/96H

4.2.2 LED indicators

The LEDs to the left of the display indicate measuring or tripping values. The purpose of the

corresponding LED is identified by the adjacent inscription, (e.g. L2 for current in phase 2).

The first row of three LEDs to the left of the display are bi-coloured - green indicates

measuring and red indicates fault condition.

The LED marked RS indicates active serial data communication.

Five LEDs support the setting menu selection. They are arranged at the characteristic points

on the setting curve and indicate the corresponding menu point selected.

4.2.3 Push buttons

The front panel contains five push buttons used for setting, measuring and other user

functions.

The individual setting and measuring values can be selected in turn by pressing the

<SELECT> / <RESET> push button. This button also resets the relay if pressed for

approximately 3 seconds.

The <UP> and <DOWN> push buttons are for incrementing and decrementing any selected

parameter. Continuous pressing of these push buttons will cause the parameter to change at

an increased rate.

The <ENTER> push button is used to transfer the indicated value to the internal parameter

memory. An unintended or unauthorized change of the selected parameter can be avoided

through the password protection facility.

The <TRIP> push button is used to test the output relay circuits, both for tripping and

signalling. This operation is also password protected.

4.3 Code jumpers

Behind the front panel of the MRI-V are three code jumpers used to preset the following

functions:

•••• Password programming

•••• Alarm and Trip relay functions

The following figure shows the position and designation of the code jumpers

J3 J2 J1

Code Jumper ON

Code Jumper OFF

Front Board

Code Jumper

2/5/96 7 MRI-V 01/96H

4.3.1 Password programming

The MRI-V relay is normally delivered with the preset password "∧∧∧∧". It can be

reprogrammed using the removable code jumper J1. After power on and the pressing of any

push button, the MRI-V relay enquires for a new password with the text <PSW?> appearing

on the display. A new password is then entered by pressing a combination of <SELECT>,

<UP>, <DOWN> or <ENTER>, as chosen by the user. After the new password has been

given, the relay module is extracted from its case and code jumper J1 removed.

4.3.2 Alarm and Trip relay function

The following functions of the MRI-V alarm relays may be preset using jumpers J1 & J2:

•••• Alarm relay activation upon initiation or after a trip

•••• Manual or Automatic reset of the output relays

Code jumper J2 - OFF

The alarm relays respond directly upon the initiation of the corresponding measuring

circuit. Thus, an alarm signal, e.g. for overcurrent, will be given before the relay trips.

Code jumper J2 - ON

The alarm relay responds only after the relay has tripped. Thus, the alarm relay and the

trip relay respond at the same time.

Code jumper J3 - OFF

All output relays will be reset automatically after tripping, once the fault has been

cleared.

Code jumper J3 - ON

All output relays remain activated and must be reset manually by pressing the

<RESET> push button, after the fault has been cleared.

Summarizing the coding possibilities

Code jumper Function Code jumper Position Operation Mode

J1 Password OFF

ON

Normal position

Password programming

J2 Alarm Relays OFF

ON

Alarm relays will be

activated on energizing.

Alarm relays will be

activated upon tripping.

J3 Reset OFF

ON

Output relays will be reset

automatically.

Output relays will be reset

manually.

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5. Working principles

5.1 Analogue circuits

The incoming currents from the external current transformers are converted to internal signals in

proportion to the currents, via the internal input transducers and shunt resistors. The noise signals

caused by inductive and capacitive coupling are suppressed by an analogue RC filter circuit. The

analogue signals are fed to the A/D converter of the micro-processor and transformed to digital

signals through sample-hold circuits. The analogue signals are sampled with a sampling frequency

of 800 Hz, namely a sampling rate of 1.25 mS for every measured quantity.

The incoming voltages from the external voltage transformers are fed to operational amplifiers

through the input transducers and RC filters.

5.2 Digital circuits

The essential component of the MRI-V relay is a powerful micro-controller. All of the operations,

from the analogue digital conversion to the relay trip decision, are carried out by the micro-

controller digitally. The relay program, located in EPROM, allows the CPU of the micro-

controller to calculate the three phase currents to detect a possible fault.

For the calculation of the current value, an efficient digital filter, based on the Fourier Analysis

(DFFT - Discrete Fast Fourier Transformation), is applied to suppress high frequency harmonics

and DC components caused by fault induced transients or other system disturbances. The actual

calculated current values are compared with the relay settings. When a current exceeds the starting

value the unit starts the corresponding time delay calculation. When the set time delay has elapsed,

a trip signal is given.

The relay setting values for all parameters are stored in EEPROM, so that the actual relay settings

cannot be lost, even in the event of auxiliary supply interruption. The micro-processor is

supervised through a built in "Watch-dog" timer. Should a failure occur the watch-dog timer resets

the micro-processor and gives an alarm signal via the self supervision output relay.

5.3 Power supply

Two auxiliary power supply versions are available:

Vaux = 24V in a range from 16V to 60V AC

or in a range from 16V to 80V DC



2/5/96 9 MRI-V 01/96H

5.4 Voltage Dependent Tripping Characteristic

The MRI-V is the combination of an overcurrent time relay (MRI basic unit) and an additional

undervoltage supervision unit.

The undervoltage unit has an influence on the tripping time of the overcurrent and short circuit

steps by switching in two tripping characteristics. In normal operation, at nominal voltage, the

MRI-V operates like a normal overcurrent time relay with preselected tripping characteristics

(IDMT, DMT) and an adjusted response value, Is. The following diagram shows the switching

over to another value of Is. Isn is the response value during normal operation and IsL is the value

during low voltage.

I>>L I>>NISNISL

→←

→←

Tripping characteristic as

selected in 6.3.2 & 6.3.3

Movement of trip level

upon switchover due

to undervoltage

In the case of failure, a short circuit of the alternator, the alternator voltage decreases. The MRIV

will recognize this and then switch over without delay to a lower response value of Is. The value

of IsL can be adjusted and as a result shorter tripping periods of the overcurrent and short circuit

step can be achieved. The adjusted tripping characteristics; normal inverse, very inverse,

extremely inverse or IDMT; is maintained. The undervoltage switching point can be adjusted from

10% to 100% of Vn. The reduced level of Is may be independently changed for both I> & I>>.

Other adjustable ranges are given in the technical data section.

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5.5 Requirements for the main Current Transformers

In order to ensure the correct operation of the MRI-V range of relays, protection class CT's must

be utilized. Instrument CT's are NOT a suitable alternative.

CT's should be chosen such that saturation, or loss of accuracy does not occur within the settings

and operation ranges of the relays. In the absence of known settings the following may be regarded

as an approximate guide.

For 1A secondary

CT class 5P20 or 10P20 2.5VA (Allowing for up to 1Ω of secondary lead resistance)

For 5A secondary

CT class 5P20 or 10P20 5VA (Allowing for up to 0.5Ω of secondary lead resistance)

with due regard to a suitable CT ratio and fault level capacity.

5.6. Reset delay & dwell time

In order to provide better discrimination with Electromechanical relays two additional settings are

provided. The reset delay delays the reset of the relay following a Flashing Fault which simulates

the time an electromechanical relay takes in order to “wind back” a partially rotated Disk (IDMT).

This may be selected as 0 or 60 seconds.

The dwell time, is an additional delay introduced on the output contacts used to prevent the

contacts opening during a tripping action. This may be selected as 0 or 200 mS.

6. Operation and setting

6.1 Layout of the control elements

All control elements required for the operation and adjustment of the MRI-V are located on the

front panel. They are divided according to function into the three following groups:

• Alphanumeric Display: Indication of parameter set values, actual measured values and

recorded fault data.

• LED's: Indication of selected parameters and measured quantities.

• Push Buttons: Selection of parameter to be adjusted, quantity to be measured and

adjustment of parameter values. Where;

<SELECT / RESET> Selection of the parameter to be set and the relay quantities

to be measured. Continuous pressing as the reset function.

<UP> Increment of the setting values for the parameter selected.

<DOWN> Decrement of the setting values for the parameter selected.

<ENTER> Storage of the setting values for the selected parameter.

<TRIP> Testing of the output relay circuits.

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6.2 Relay setting principles

There are eight relay parameters that can be set in the MRIV:

Isn - Value of the overcurrent step during normal operation

IsL - Value of the overcurrent step during undervoltage.

CHAR I> - Current time characteristic for the overcurrent relay.

tI> - Tripping time delay for definite time overcurrent relay or the time multiplier

for the inverse time overcurrent relay.

I>>N - Current setting for the high set stage of the phase overcurrent relay.

I>>L - Value for the fast short circuit tripping during undervoltage.

tI>> - Tripping time delay for high set stage.

V - Tripping value for undervoltage supervision.

By pressing the <SELECT/RESET> push button, the parameter to be modified is reached. The

corresponding LED illuminates on the curve and the present set value of the selected parameter is

indicated on the display. This set value may then be increased or decreased by pressing the <UP>

or <DOWN> buttons respectively. The selected set value is only stored after pressing the

<ENTER> push button and inputting the correct password. This means that adjustment of the unit

is only possible by authorized users.

6.2.1 Password protected parameter adjustment

The adjustment of all relay settings are password protected, however, to enable ease of adjustment,

for authorized users, application of the password is usually only required once for multiple

parameter adjustment. The following step by step sequence is given to illustrate the

implementation of the password protection facility, where a new relay setting is to be applied:

• After the present setting value has been selected and changed using the <UP>,

<DOWN> push buttons, the <ENTER> push button should be pressed.

• The message <SAV?> appears on the display, to confirm that the new setting value

is to be saved.

• After pressing <ENTER> again, the password will be requested. The message

<PSW?> is displayed.

• After the password has been given correctly, as indicated by the message <SAV!>,

the new setting value may be stored by pressing the <ENTER> push button for at

least 3 seconds. The new setting parameter then reappears on the display.

A password consists of four push button operations. The pressed push buttons and their sequence

define the password. If the four push buttons are defined by the following symbols:

<SELECT> = S

<DOWN> = ∨∨∨∨

<UP> = ∧∧∧∧

<ENTER> = E

Then a password "∨∨∨∨E∧∧∧∧S" is achieved by the following sequence:

<DOWN> <ENTER> <UP> <SELECT>.

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After a password is given correctly, parameter setting is permitted for five minutes. Subsequent

parameter setting made within the five minute period after the password was inputted, does not

require renewed password entry. Furthermore, the valid period for parameter setting is

automatically extended for a further 5 minutes after each push button operation.

If no push button is pressed within the 5 minute period then the validity of the password will be

suspended. To enter further parameters after this period re-application of the password is required.

During the 5 minute period when changes may be made, a new set value, acknowledged by

<SAV?> then <SAV!> , may be stored by pressing <ENTER> for approximately 3 seconds.

6.3 Setting procedure

The following sections describe in detail the setting of all relay parameters.

6.3.1 Starting current for phase overcurrent relay (Isn and Isl)

The displayed setting value for these parameters are related to the nominal rated current (IN) of

the relay. Thus;

Starting current (Isn) = Displayed Value x Rated Current (IN)

e.g. If Displayed Value = 1.25, then Isn = 1.25 x IN

The setting of the Isl value is indicated by the I> LED flashing.

6.3.2 Time current Characteristic (CHAR I>)

By setting this parameter, one of the following four options is displayed:

DEFT - Definite Time

NINV - Normal Inverse

VINV - Very Inverse

EINV - Extremely Inverse

Any one of these four characteristics can be chosen by using the <UP> <DOWN> keys and can be

stored by pressing <ENTER>.

6.3.3 Tripping time delay or time multiplier for overcurrent (tI>)

After the time/current characteristic has been selected, the time delay (or time multiplier) should

be changed accordingly. In order to avoid an unsuitable arrangement of relay modes the following

precautions are taken:

Adjustment of the time delay setting is automatically prompted for after a change in the set

time/current characteristic. LED tI> flashes yellow to remind the operator to change the time

delay setting accordingly. After pressing the <SELECT> push button, the present time delay

setting value is shown on the display. A new setting value may then be entered.

If the relay characteristic has been changed (e.g. from DEFT to NINV), but the time delay

setting has not, the relay will, after 5 minutes, automatically set itself to the most sensitive time

setting value available for that selected characteristic. The most sensitive time setting value

implies the fastest tripping for the selected relay characteristic. If the time delay or the time

multiplier is set out of range, "EXIT" appears on the display, and the low set stage of the relay

is blocked.

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6.3.4 Current setting for high set overcurrent stage (I>>)

The current setting value of this parameter is related to the nominal rated current of the relay.

Thus;

I>> = Displayed Value x Rated Current (IN)

e.g. If Displayed Value = 20, then I>> = 20 x IN

The high set stage of the overcurrent relay is blocked if the setting value is set to "EXIT".

6.3.5 Tripping time delay for high set overcurrent stage (tI>>)

Independent from the chosen tripping characteristic for I>, the high set stage I>> always has a

definite time tripping characteristic. An indication value in seconds appears on the display.

6.3.6 Setting of the Undervoltage Switching Point

The voltage setting value of this parameter is related to the nominal rated voltage of the relay, Vn.

Thus;

Undervoltage Switching Point, V = Displayed Value x Vn

e.g. If Displayed Value = 0.5, then V = 0.5 x Vn

The setting of the undervoltage switching point value is indicated by the LED flashing.

6.3.7. Reset & Dwell

If co-ordination with electromechanical relays is required tRST should be set to 60s, tTrip to Auto.

Otherwise tRST should be set to 0, tTrip to 20mS.

6.3.8 Nominal frequency

The FFT Algorithm employed requires the nominal frequency as a parameter for correct digital

filtering of the input currents.

By pressing <SELECT> the display shows "f=50" or "f=60". The desired nominal frequency may

then be selected and stored.

6.4 Indication of measured values and fault data 6.4.1 Indication of measured values

Any one of the following measured quantities may be indicated on the display during normal

service by pressing the <SELECT> button:

• Current in Phase 1 (LED L1 green)



• Phase to Phase Voltage, V12 (L1, L2 and V LED's Green)



The relevant operating values of the individual measured quantities are indicated on the display

and are referred to the rated current and voltage.

2/5/96 14 MRI-V 01/96H

6.4.2 Indication of fault data

Visual indication of faults detected by the relay is given on the front panel. The three phase LEDs

L1, L2, L3, the undervoltage LED, as well as the function LEDs I>, and I>> are used to

indicate/specify fault events.

When a fault initiates a relay function, the corresponding function LED illuminates yellow. At the

same time, the phase LED(s) flash(es) red to indicate the faulty phase or phases.

After the set time delay has elapsed, the relay trips and the LED(s) for the faulty phase(s) become

a constant red. The function LED remains illuminated. The fault currents measured at the instant

of trip are recorded in registers for fault indication.

After the occurrence of a trip, fault data for all three phase currents may be displayed in turn by

repeatedly pressing the <SELECT> key. After all phases have been indicated, the LEDs return to

red indicating the fault event. By pressing the <SELECT/RESET> button for approximately 3

seconds the relay is reset to its original status. If however, the relay was initiated by the occurrence

of a fault, which then fell below a detectable level, a slowly flashing LED corresponding to the

detected fault is displayed. This can also be reset using the <SELECT/RESET> button.

6.5 Test Trip

The whole tripping circuit of the protection system may be tested by simulating a fault with the

<TRIP> push button. This button is also used to interrogate the relay for its software version

number. A single press reveals the first half of the software version number and a second press

reveals the second half. A third press will be responded to by <PSW?>. Entering the correct

password will be responded to by <TRI?> . Pressing <TRIP> again energizes all output relays in

turn with a delay time of 1 second. All relays will stay energized until manually reset.

6.6 Reset

There are two ways in which to reset the MRI-V relay:

6.6.1 Hand reset

By pressing the <SELECT/RESET> for approximately 3 seconds the relay is reset.

6.6.2 Auto-reset at Power Up

After loss of supply voltage and upon its reconnection the unit resets itself and displays P&B.

This resetting of the unit does not effect the set parameters which are stored in an EEPROM.

6.7 Setting value calculation

In order to ensure that protection relays form an integral part of any system, a full protection co-

ordination study should normally be undertaken which considers both upstream and downstream

equipment. Further details may be obtained by contacting P&B Engineering.

2/5/96 15 MRI-V 01/96H

7. Relay case

The MRI-V is delivered in an individual case for flush mounting.

7.1 Individual case

The MRI-V is supplied in a UK manufactured industry standard drawout case suitable for flush

mounting. For case dimension and cut-out, refer to Technical Data.

7.2 Rack mounting

MRI-V relays may be supplied mounted in 19" racks if specified by the user.

7.3 Terminal connections

The MRI-V plug in module is supplied in a case which has a very compact plug and socket

connector. The current terminals are equipped with self closing short circuit contacts. Thus the

MRI-V module can be unplugged even with current flowing without endangering personnel.

8. Test and maintenance

Currents may be supplied to the input transformers to test the behaviour of the relay. By switching

on test currents and measuring the tripping time, the whole system can be accurately tested. A

portable overcurrent test case can be supplied which is suitable for testing the MRI-V.

All measuring input circuits of the MRI-V are of static design and the relay functions are fully

digitized. Thus, the MRI-V has no particular demand on maintenance.

2/5/96 16 MRI-V 01/96H

9. Technical Data

9.1 Measuring Input Circuits

Rated Data

Rated current, IN 1A or 5A

Rated voltage, VN 110V, 230V or 400V

Rated frequency, fN 50Hz, 60Hz

Power consumption

@ IN = 1A 0.2 VA

@ IN = 5A 0.1 VA

In voltage circuit < 1 VA

Thermal withstand

Half wave 250 x IN

for 1 second 100 x IN

for 10 seconds 30 x IN

Continuously 4 x IN

In voltage circuit 1.2 x VN

9.2 Auxiliary power supply

Supply Voltage





Power Consumption

Quiescent Approx. 3W

Operating Approx. 6W

9.3 Common data

Drop Off/Pick Up ratio >97%

Drop Off time 30mS

Time Lag error ± 10mS

Minimum operating time 30mS

Transient over-reach £ 5%

Factors effecting current measurement:

Auxiliary voltage No changes measured

Frequency harmonics in the range 0.9 < f/fN < 1.1 = < 0.02% /Hz

Up to 20% of the third harmonic = < 0.08% /Hz

Up to 20% of the fifth harmonic = < 0.07% /Hz

Factors effecting delay times:- No influences could be measured.

2/5/96 17 MRI-V 01/96H

9.4 Setting ranges and steps

9.4.1 Definite time phase overcurrent relay

Setting range / step Tolerance

I> Isn; IsL

tI>

0.5...2 x In / 0.05; 0.1 x In

0.03...165s / 0.01; 0.02; 0.05; 0.1;

0.2; 0.5; 1.0; 2.0; 5.0 seconds

± 5% from set value

± 3% or ± 10mS

I>> I>>N; I>>L

tI>>

2...40 x In / 0.1; 0.2; 0.5; 1.0 x In

0.03...2s / 0.01; 0.02; 0.05s


± 3% or ± 10mS

V V 10...100% Vn / 5% x Vn ± 5% from set value

9.4.2 Inverse time phase overcurrent relay

Characteristics according to IEC 255-4 or BS 142

Normal Inverse t = 0.14 tI> [s]

(I/IS)0.02 - 1

Very Inverse t = 13.5 tI> [s]

(I/Is) - 1

Extremely Inverse t = 80 tI> [s]

(I/Is)2 - 1

Where: t = Tripping Time

tI> = Time Multiplier

I = Fault Current

Is = Starting Current

Inverse time phase overcurrent relay setting ranges and steps

Setting range / step Tolerance

I> Isn; IsL

tI>

0.5...2 x In / 0.05; 0.1 x In

0.05...1.6 / 0.01; 0.02;


± 3% or ± 10mS

I>> I>>N; I>>L

tI>>

2...40 x In / 0.1; 0.2; 0.5; 1.0 x In

0.03...2s / 0.01; 0.02; 0.05s


± 3% or ± 10mS

V V 10...100% Vn / 5% x Vn ± 5% from set value

2/5/96 18 MRI-V 01/96H

9.5. Inverse time characteristics

Normal Inverse

Extremely Inverse

Very Inverse

Definite Time

I/I s

2/5/96 19 MRI-V 01/96H

9.6 Output contact ratings

Number of relays = 4

Contacts = 2 change over contacts for trip signal, I> alarm, & I>> alarm.

1 change over contact for self supervision.

Maximum breaking capacity

250V AC / 1500VA / continuous current 6A

for DC voltage:

ohmic L/R = 4ms L/R = 7ms

300 V DC 0.3 A / 90 W 0.2 A / 63 W 0.18 A / 54 W

250 V DC 0.4 A / 100 W 0.3 A / 70 W 0.15 A / 40 W

110 V DC 0.5 A / 55 W 0.4 A / 40 W 0.2 A / 22 W

60 V DC 0.7 A / 42 W 0.5 A / 30 W 0.3 A / 17 W

24 V DC 6 A / 144 W 4.2 A / 100 W 2.5 A / 60 W

Max. rated making current: 64A(IEC65)

mechanical life span: 3 × 106 operating cycles

electrical life span: 2 × 105 operating cycles at 220 V AC / 6A

Contact material Silver Cadmium Oxide (AgCdO)

9.7 System data

Design standard = IEC 255-4, BS 142

Operating temperature range = -20°C to 70°C

Storage temperature range = -40°C to 85°C

Relative humidity = 93% @ 40°C for 56 days

Test Voltages to EN50081-1, EN50082-2

Isolation Test = 2.5kV / 50Hz / 1 min.

Impulse Test = 5kV, 1.2 / 50mS, 0.5J

High frequency interference Test = 2.5kV / 1MHz

Burst transient Test = 4kV / 2.5KHz, 15mS

ESD Test = 8kV

RFI Suppression Test = 10V/m, 27 - 500MHz, 1 Octave/ 3 min.

EMI Suppression Test = 10V/m

Mechanical Tests:

Shock = IEC 41B (CO) 38, Class 1

Vibration = IEC 41B (CO) 35, Class 1

Degree of Protection = Front - IP52

Rear - IP00

Weight = Approx. 2kg.

2/5/96 20 MRI-V 01/96H

9.8 Housing

Throughout the MR series range a modular housing system has been employed, utilizing the latest

high quality UK manufactured industry standard case components. This approach affords

maximum flexibility for both the relay scheme designer and the maintenance engineer. The relay

modules are fully withdrawable for ease of maintenance and where applicable incorporate

automatic short-circuiting CT connections to avoid dangerous open circuit CT overvoltages. A

clear plastic front cover is provided for inspection purposes.

MRI-V units are supplied in standard height (179mm≅7in.) cases, complying with IEC 297 size 4U.

The rigid case wall is manufactured from a single sheet of hot dipped galvanized steel coated

externally with Plastisol PVC and internally with a low gloss alkyd paint finish. This construction

technique provides improved thermal transfer characteristics over plastic walled cases and

combines exceptional corrosion and flame resilience with good electromagnetic and electrostatic

screening properties allowing many relays to be freely situated in close proximity and hazardous

environments. When the relay is inserted a leaf spring along the top edge of the module makes

contact with a solidly bonded nickel plated steel strip on the interior of the case, providing

excellent earth continuity. This strip is brought out at the rear of the case, above the terminal

block, where it forms a separate earthing terminal. A rigid front mounting flange is provided

allowing the entire range of standard cases to be flush mounted without alteration. These flanges

are also used to mount the relay inspection cover which is secured by thumbscrews. Securely

bonded channels can be provided on the top and bottom surfaces toward the rear of the case

allowing large rigid assemblies to be created by the use of joining strips located in these channels.

This uniform but highly flexible housing system integrates excellent mechanical strength with

good electrical practice in industry standard sizes.

PANEL CUT OUT FLUSH

MOUNTING FIXING DETAILS

4 HOLES 4.4mm DIAMETER

99

168 159

52 23.5

10

97

45

PUSH BUTTON

PROJECTION 10mm

NOT SHOWN TO SCALE

103

177

212

Clearance

25 min

157

32

OPTIONAL

OPTIONAL

OPTIONAL

Min28

NOTE Minimum gap between vertical

spacing is required in order to

withdraw relay from the case above.

178

Required to open case SIZE 100 CASE

2/5/96 21 MRI-V 01/96H

9.9 Terminal Connection Details

The rear terminal block accepts both pre-insulated screw and push-on blade type connectors which

may be used singly or in combination. Each terminal has 1 screw type and 2 blade type

connectors.

Screw: Each connection uses a 4mm (M4) screw outlet and accepts standard

L-shaped ring type connectors designed for 4mm screws.

Blade: Each connection facilitates 2 pre-insulated push-on blades 4.8mm

wide 0.8mm thick complying with BS5057.

Combinations: Each terminal will accept either;

2 ring type connectors

or 2 push-on blade type connectors

or 1 ring type connector & 1 push-on blade type connector

1

3

5

7

9

11

13

15

17

19

21

23

25

27

2

4

6

8

10

12

14

16

18

20

22

24

26

28

Earth

Rear terminal block connections.

Each terminal

1 screw &

2 spade29

31

33

35

37

39

41

43

45

47

49

51

53

55

30

32

34

36

38

40

42

44

46

48

50

52

54

56

All information subject to change without notice

Publication number MRIV-02/96H

2/5/96 22 MRI-V 01/96H

10. Order Form

Digital Multifunctional Relay for Voltage Controlled Overcurrent Protection MRI-V

MRI-V

Rated Current, 1A 1

5A 5

Rated Voltage, 100 V (110V) 1

230 V (240V) 2

400 V (415V) 4

Power Supply, 24V (16-60Vac, 16-80Vdc) L

110V (50-270Vac, 70-360Vdc) H

Data Communications, RS485 R

Housing, 19" Rack A

Flush Mounting D

PBSI Ltd Trading as

P&B ENGINEERING

Bell Vue Works,

Boundary Street,

Manchester.

M12 5NG.

Tel: 0161-230-6363

Fax: 0161-230-6464

mri-v...characteristics in accordance with bs142 and iec 255-4. furthermore, the mri-v has an...

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