MRRP Digital Reverse Power Relay

P&B Engineering

Belle Vue Works

Boundary Street

Manchester

M12 5NG

Tel: 0161 230 6363

Fax: 0161 230 6464

Contents

CONTENTS ........................................................................................................................................................... I

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

2. APPLICATIONS ................................................................................................................................................ 2

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

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

4.1. Application Diagrams ............................................................................................................................ 3

4.1.1 Analogue input circuits......................................................................................................................... 4

4.1.2 Output relays ........................................................................................................................................ 4

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

4.2 Front panel .............................................................................................................................................. 4

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

4.2.2 LED indicators ..................................................................................................................................... 5

4.2.3 Push buttons ......................................................................................................................................... 5

4.3 Code jumpers........................................................................................................................................... 6

4.3.1 Password programming ....................................................................................................................... 6

4.3.2 Alarm and Trip relay function .............................................................................................................. 6

5. WORKING PRINCIPLES .................................................................................................................................... 7

5.1 Analogue Circuits .................................................................................................................................... 7

5.2 Digital Circuits ........................................................................................................................................ 7

5.3 Power supply ........................................................................................................................................... 8

5.4 Measuring Principles .............................................................................................................................. 8

5.5 Requirements for the main Current Transformers................................................................................... 9

6. OPERATION AND SETTING............................................................................................................................... 9

6.1 Layout of the control elements................................................................................................................. 9

6.2 Relay setting principles ........................................................................................................................... 9

6.2.1 Password protected parameter adjustment ........................................................................................ 10

6.2 Setting Procedure .................................................................................................................................. 10

6.2.1 Settings for Overpower (P>), Underpower (P<) and Reverse Power (Pr) ........................................ 10

6.2.2 Tripping Times for Overpower (P>), Underpower (P<) and Reverse Power.................................... 11

6.2.3 Y/∆ - Change Over of the Input Transformers.................................................................................... 11

6.4 Indication of measured values and fault data ....................................................................................... 12

6.4.1 Indication of measured values............................................................................................................ 12

6.4.2 Indication of fault data ....................................................................................................................... 12

6.5 Test Trip................................................................................................................................................. 13

6.6 Reset ...................................................................................................................................................... 13

6.6.1 Hand reset .......................................................................................................................................... 13

6.6.2 Auto-reset at Power Up ...................................................................................................................... 13

6.7 Setting value calculation ....................................................................................................................... 13

6.8 Setting Values ........................................................................................................................................ 13

6.8.1 Nominal Power................................................................................................................................... 13

6.8.2 Conversion to Setting ......................................................................................................................... 13

6.8.3 Star-Delta Connection........................................................................................................................ 14

6.8.4 Setting Calculation Example .............................................................................................................. 14

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

7.1 Individual case ...................................................................................................................................... 15

7.2 Rack mounting....................................................................................................................................... 15

7.3 Terminal connections ............................................................................................................................ 15

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

08/10/98 ii Issue J

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

9.1 Measuring Input Circuits....................................................................................................................... 16

9.2 Common Data........................................................................................................................................ 16

9.3 Setting Ranges and Steps....................................................................................................................... 17

9.4 Output contact ratings........................................................................................................................... 17

9.5 System data............................................................................................................................................ 17

9.5 Housing ................................................................................................................................................. 18

9.6 Connection Details ................................................................................................................................ 19

10. ORDER FORM ............................................................................................................................................. 20

08/10/98 1 Issue J

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 summarised 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.

08/10/98 2 Issue J

2. Applications

The MRRP relay is used for single and three phase power measurement in low and medium

voltage networks. It serves:

• For supervision of load flow between two systems.

If the power generation of one system fails, then non critical users have to be disconnected

by the MRRP Relay. Thereby the mains is stabilised and the supply to critical users is

maintained. For generators operating in parallel the users can be disconnected if the load

remains below the set minimum value or, in peak operating mode, be connected if the set

value for the mains power is exceeded.

• As a reverse power relay, to protect turbines and diesel generators from reverse power if the

prime mover fails.

For generators operating in parallel with mains supply or another generator, it is

imperative to supervise the power direction. If, for example, the prime mover fails, the

alternator operates as a motor and drives the generator (diesel or turbine). The MRRP

recognises the reverse power direction and switches off the alternator. This way power

losses and danger to the prime mover are avoided.

3. Features and characteristics

• Complete digital processing of the sampled measured values

• Extremely wide setting ranges with fine setting steps

• Unauthorised 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 memorised

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

08/10/98 3 Issue J

4. Design 4.1. Application Diagrams

MRRP-1

POWER

SUPPLY

1 2 CASE

Supply

MRRP-1Typical 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

P<

P>

RS485

15

V1

21

22

L1L2

L3

I1

AlternativeEarthing

4751

49REVERSE POWER

16

MRRP-3

POWER

SUPPLY

1 2 CASE

Supply

20

MRRP-3Typical 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

P<

P>

RS485

19

15

17

V1

V2

V3

21

22

23

24

25

26

L1

L2

L3

I1

I2

I3

S2P2

P1

S1

AlternativeEarthing

4751

49REVERSE POWER

18

16

08/10/98 4 Issue J

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 voltages V1, V2 & V3 via separate input transformers.

4.1.2 Output relays

The MRRP has five output relays, with single or dual pole change-over contacts as detailed in the

previous diagrams and summarised below:

• Tripping relay (2)

• Self-supervision alarm relay (1)

• Overpower alarm relay (2)

• Underpower decrease alarm relay (2)

• Reverse power relay (1)

4.1.3 Remote data communication

As an option, the MRRP may have an RS485 interface for remote data communication with a

control centre. The unit provides the following information:

• Actual measured current, voltage and power values

• Recorded measured current, voltage and power values

• Status signals

• Self supervision alarm signal

• Relay settings

• Alarm and trip signalling

4.1.4 Blocking Input

When required to inhibit all the functions of the relay, the auxiliary supply is connected to the

blocking input terminals, 54-55.

4.2 Front panel

The front panel of the MRRP comprises the following operation and indication elements:

• Alphanumeric display (4 Digits)

• 5 push buttons for setting and other operations

• 11 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.

08/10/98 5 Issue J

Table: Adjustment possibilities by means of the front panel.

Function Display Shows Push-button Pressed LED Illuminated

Normal Operation P&B <SELECT> for 3 s

Inquire Password PSW? <ENTER>/<TRIP>

Save Parameter SAV? <ENTER>

Saved Parameter SAV! <ENTER>

Manual Trip TRI? <TRIP>

Relay Tripped TRIP <TRIP> L1,L2,L3,®,¬

Enter Password XXXX Combination of

<SELECT>,<∨>,<∧>

or <ENTER>

Measured Values Currents as related to

In, Power as related

to Pn & Actual

Voltages

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

Fault Data Tripping values

P>,P<,Pr

<SELECT> L1,L2,L3,P>,P<,Pr

Adjustable Values Star/Delta setting

"DELT"/"Y".

Overpower P>.

Tripping time, tP>.

Underpower P<.

Tripping time, tP<.

Reverse Power Pr.

Tripping time, tPr.

<SELECT>

<∧>

<∨>

L1,L2,L3

P>

tP>

P<

tP<

Pr

tPr

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 four LEDs below the display are bi-coloured; green for P>, P<, Pr and D/Y. Red for tP>, tP<

and tPr. The MRRP also has an LED to indicate direction (green and red arrows). Green indicates

generator power, red indicates reverse power.

The LED marked RS indicates active serial data communication.

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.

08/10/98 6 Issue J

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

memory. An unintended or unauthorised 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 MRRP are three code jumpers used to precept 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

4.3.1 Password programming

The MRRP relay is normally delivered with the precept password "∧∧∧∧". It can be

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

button, the MRRP 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 MRRP alarm relays may be precept 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 reverse power, will be given before the relay trips.

08/10/98 7 Issue J

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.

Summarising 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 energising.

Alarm relays will be

activated upon tripping.

J3 Reset OFF

ON

Output relays will be reset

automatically.

Output relays will be reset

manually.

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. There is no digital filtering and hence detection of the

measured values takes place at a sampling frequency of 900 Hz, namely a sampling rate of 1.11

mS.

5.2 Digital Circuits

The essential component of the MRRP 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 processes current and voltage information and calculate the existing power.

The actual measured power is compared with the relay threshold settings. When the power

changes beyond the set starting values the unit initiates 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.

08/10/98 8 Issue J

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

Vaux = 110V in a range from 50V to 270V AC

or in a range from 70V to 360V DC

5.4 Measuring Principles

Through multiplication of the actual current and voltage values, P(t) = V(t) x I(t), the

microprocessor calculates the phase power. 18 values are measured and recorded per voltage cycle

from which the mean value of the power during one cycle is calculated:

P = 1 x ò P(t) x dt

T

Consequently, the total three phase current is calculated using;

P tot = P1 + P2 + P3

0

Time →

V [t]

↑

0Time →

i [t]

↑

Time →

P [t]

↑

0

0

Time →

P(t) = V(t) i(t)××××

P = P(t) d(t)×××× ∫∫∫∫ ××××1T

08/10/98 9 Issue J

5.5 Requirements for the main Current Transformers

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

be utilised. 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.

6. Operation and Setting

6.1 Layout of the control elements

All control elements required for the operation and adjustment of the MRRP 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.

6.2 Relay setting principles

There are seven relay parameters which may be set for the MRRP:

P> Overpower Setting

P< Underpower Setting

Pr Reverse Power Setting

tP> Overpower Tripping Time

tP< Underpower Tripping Time

tPr Reverse Power Tripping Time

D/Y Delta/Star Setting

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

08/10/98 10 Issue J

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 authorised users.

6.2.1 Password protected parameter adjustment

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

for authorised 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>.

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.

6.2 Setting Procedure

6.2.1 Settings for Overpower (P>), Underpower (P<) and Reverse Power (Pr)

After setting the value for Overpower (P>), Underpower (P<) and Reverse Power (Pr); the display

indicates a value related to the three phase Nominal Power, Pn. This means:

Set Value = Indicated Value x Nominal Power

08/10/98 11 Issue J

The <∧> and <∨> push buttons can be used to change the indicated value, once selected the

<ENTER> push button is used to store. Both P> and Pr can be blocked by incrementing using the

<∧> button until the display shows "EXIT". P< can be blocked by decrementing until "0" appears

and then storing using the <ENTER> key.

6.2.2 Tripping Times for Overpower (P>), Underpower (P<) and Reverse Power

After the setting of the tripping times, a value in seconds is shown on the display. The required

time delay can by entered by using the <∧> and <∨> keys and stored using the <ENTER> key.

6.2.3 Y/∆∆∆∆ - Change Over of the Input Transformers

The voltage sensing circuits of the MRRP may be connected in either star or delta configuration.

The relay rated voltage, Vn, refers to the Line-Line voltage in the star connection. The maximum

line-to-line voltage must not exceed the thermal withstand, please refer to the Technical Data

Section.

Input Transformers in Star Configuration

V2

V3

V1

15

17

19

16

18

20

Alternative EarthingTypical earthing shown

L1L2L3 N

Input Transformers in Delta Configuration

V2

V3

V1

15

17

19

16

18

20

L1L2L3

08/10/98 12 Issue J

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:

•••• Total Three-Phase Power (LED's L1, L2, L3 - Green)

•••• Power in Phase L1 (LED L1 - Green)

•••• Power in Phase L2 (LED L2 - Green)

•••• Power in Phase L3 (LED L3 - Green)

In Star Connection only:

•••• Voltage in Phase L1 (LED's U and L1 - Green)

•••• Voltage in Phase L2 (LED's U and L2 - Green)

•••• Voltage in Phase L3 (LED's U and L3 - Green)

In Delta Connection only:

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

• Phase to Phase Voltage V23 (LED's U, L2 and L3 - Green)

• Phase to Phase Voltage V31 (LED's U, L3 and L1 - Green)

Note: It is only possible to indicate individual phase power when the voltage input transformers

are connected in Star configuration.

• Current in Phase L1 (LED's I and L1 - Green)

• Current in Phase L2 (LED's I and L2 - Green)

• Current in Phase L3 (LED's I and L3 - Green)

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

and are referred to the rated current and power.

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, as well as the function LEDs P>, P< and Pr 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.

08/10/98 13 Issue J

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 energises all output relays in

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

6.6 Reset

There are two ways in which to reset the MRRP 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.

6.8 Setting Values

The nominal full load current is not generally the same as the CT ratio. Thus, a significant

difference between an apparent setting and the required setting often occurs.

6.8.1 Nominal Power

In order to determine the nominal power, Pn, of the relay, it is necessary to take into account the

CT & VT ratios and connection arrangement.

Pn In Vn Nv Nc= 3

Where;

In = Nominal Relay Current rating;

Vn = Nominal Relay Voltage rating (measurement);

Nv = V.T. Ratio

Nc = C.T. Ratio

6.8.2 Conversion to Setting

If the required operate power is Pop, then the required setting is

SetP

P100%

op

n

= ×

08/10/98 14 Issue J

6.8.3 Star-Delta Connection

If the relay operates on a three wire system, the relay must be set and wired for the Delta

connection. If the relay operates on a four wire system, the relay must be set and wired for the Star

connection.

6.8.4 Setting Calculation Example

A 2.5 MVA 11kV generator of full load current 131A at 0.8 power factor, must be set for trip at an

actual reverse power of 5%.

The CT ratio is 150/5A, class 10P20.

The VT ratio is 11000/110

The relay has a rating of 5A, 100V (In, Vn)

Trip Value

Pop = × × =5

1002 5 0 8 100. . kW

Nominal Power

Pn 5 10011000

110= × × × =3

150

52 598. MW

Relay Setting

= × =100

2598100 3 85. %

In this case, the relay setting of 3.85% corresponds to an actual trip value of 5% of the generator

active rated power.

08/10/98 15 Issue J

7. Relay case

The MRRP is delivered in an individual case for flush mounting.

7.1 Individual case

The MRRP 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

MRRP relays may be supplied mounted in 19" racks if specified by the user.

7.3 Terminal connections

The MRRP 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

MRRP module can be unplugged even with current flowing without endangering personnel.

8. Test and maintenance

Currents and voltages may be supplied to the input transformers to test the behaviour of the relay.

By changing the phase angle between them and measuring the tripping time, the whole system can

be accurately tested.

All measuring input circuits of the MRRP are of static design and the relay functions are fully

digitised. Thus, the MRRP has no particular demand on maintenance.

08/10/98 16 Issue J

9. Technical Data

9.1 Measuring Input Circuits

Rated Data

Rated Current, In 1 A or 5 A

Rated Voltage, Vn 100/110 V, 230/240 V, 400/415 V **

Rated Frequency, Fn 50 Hz to 60 Hz

Power Consumption

Current Circuits @ In = 1 A - 0.2 VA

@ In = 5 A - 0.1 VA

Voltage Circuits < 1 VA per phase @ Vn

Thermal Withstand

Current Circuits Half Wave - 250 x In

For 1 s - 100 x In

For 10 s - 30 x In

Continuously - 4 x In

Voltage Withstand Continuously - 1.5 x Vn

9.2 Common Data

Drop Off / Pick Up Ratio P> = 50 - 97% (Adjustable)

Pr = 50 - 97% (Adjustable)

P< = <102%

Return Time 30 mS

Time Lag Error ± 10 mS

Minimum Operating Time 30 mS

Transient Overreach ≤ 5%

Sensitivity @ Vn and Cos ϕ = 0.01 x In

@ Vn and In to Cos ϕ = 0.0087 ⇒ 89.5°

Influences on Measurement

Auxiliary Voltage In the range of 0.8 < Vh / Vhn < 1.2 - No influences

Frequency No Influence

Delay Times No influences

** For setting value calculations, the individual nameplate rating shown on the relay should be

used. In the absence of these the underlined figures can be used

08/10/98 17 Issue J

9.3 Setting Ranges and Steps

Function Parameter Setting Range Step Tolerances

P> / < P> / <

tP> / <

0.01 - 2.0 x Pn

0.5 - 100 s

0.01, 0.02, 0.05,

0.1 x Pn

0.1, 0.2, 0.5,

1.0, 1.0, 5.0 s

± 0.5% Pn

±3% or ±10mS

Pr Pr

tPr

0.01 - 2.0 x Pn

0.5 - 100 s

0.01, 0.02, 0.05,

0.1 x Pn

0.1, 0.2, 0.5,

1.0, 1.0, 5.0 s

± 0.5% Pn

±3% or ±10mS

9.4 Output contact ratings

Number of relays = 5

Contacts = contacts for trip relays as detailed in application diagrams

1 change over contact for self supervision relays

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)

9.5 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.

08/10/98 18 Issue J

9.5 Housing

Throughout the MR series range a modular housing system has been employed, utilising 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.

MRRP 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 galvanised 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

08/10/98 19 Issue J

9.6 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 MRRP-Issue J

08/10/98 20 Issue J

10. Order Form

Digital Multifunctional Relay MRRP

MRRP

No Of Phase Elements 1

3

Reduced Setting Range 3R

Rated Current, 1A 1

5A 5

Rated Measurement 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