MRD1-T - Transformer Differential Protection System

2 TB MRD1-T 10.01 E

Contents

1 Preface and Application

2 Features and Benefits

3 Design3.1 Relay front3.1.1 Display3.1.2 LEDs3.1.3 Push-buttons3.1.4 Parameter interface RS2323.2 Master module3.2.1 Interface RS4853.2.2 CAN-Bus (optionally)3.2.3 Function inputs and signal inputs

(optionally)3.3 Basic module and additional module3.3.1 Basic module NT 6I (MRD1-G,

MRD1-T2 and MRD1-T3)3.3.2 Additional module 3I (MRD1 T3)

4 Working principle4.1 Protective functions4.1.1 Transformer differential protection4.2 Analogue measured value detection4.2.1 Current measuring4.3 Digital signal processor4.4 Digital main processor4.5 Block diagram4.6 General functions4.6.1 Event-Recorder4.6.2 Fault-Recorder4.6.3 Self-test relay4.6.4 Self-test4.6.5 Output relay settings4.6.6 Parametrizing blocking

5 Operation5.1 General5.1.1 Data organization5.1.2 Parameter sets5.1.3 Key function5.1.4 LEDs5.1.5 VIEW mode / EDIT mode5.1.6 OFFLINE-TEST mode5.1.7 Reset (DEVICE RESET)5.1.8 Enter password5.1.9 Password forgotten

5.2 SYSTEM settings5.2.1 Selection5.2.2 Overview5.2.3 Time / Date5.2.4 Password change5.3 PARAMETER-pages5.3.1 Selection5.3.2 Overview5.3.3 Transformer ratings5.3.4 Protection parameters5.3.5 Relay-settings5.3.6 Setting of logic functions5.3.7 Blocking Setting5.3.8 Validity check5.4 DATA pages5.4.1 Selection5.4.2 Overview5.4.3 Measured and calculated data5.4.4 FAULT Recorder5.4.5 EVENT-Recorder5.4.6 Statistic data5.5 TEST-routines page (Self-test)5.5.1 Page selection5.5.2 Overview5.6 Parameter programming help

6 Relay Tests

7 Commissioning7.1 Check list7.2 C.T. connection

8 Technical Data8.1 MRD - Transformer Differential

Protection Relay

9 Tables / Connection diagrams9.1 Possible event messages9.2 View

10 Type code

This technical manual is valid for software versionV01-1.03.

TB MRD1-T 10.01 E 3

1 Preface and Application

MRD1 is a modular system to protect electrical appa-ratus and it is used for complex applications in theenergy distribution, primarily designed for transformer,generator, motor or line protection; additionally it canbe integrated into automation systems. Due to itsmodular design, the MRD1 can be adapted to indi-vidual applications without problem, with all imple-mented functions remaining combined in one singledevice. All vacant rack places in the basic unit can op-tionally be used for modules according to require-ments. The modules provide the necessary measuringinputs e.g. for two-winding or three-winding transform-ers as well as increase the number of output relays ordigital inputs according to requirements.

The high-performance digital technique of data calcu-lation makes complex mathematical algorithm formeasured value processing possible for the MRD1 aswell as utilization of the trip decision resulting from theindividual protection functions. The MRD1 software isalso of modular structure. Each protection function is al-located to a special program segment and so it ispossible to subsequently add further functions.

All essential parameters, measuring data or valuescalculated from these can be called off and are shownlocally on the display. The MRD1 is equipped with anEvent Recorder which stores all system signals, protec-tion activations or trip events. When trips occur a FaultRecorder records all fault data mesaured at the instantof the trip. Data of both recorders is provided with atime stamp and can be called off either at the displayor interface.

At present the following versions of MRD1 are avail-able :

• MRD1-T2 Transformer differential protection fortwo-winding transformers

• MRD1-T3 Transformer differential protection forthree-winding transformers

• MRD1-G Differential protection for generators andmotors

4 TB MRD1-T 10.01 E

2 Features and Benefits

Basic Unit

Standard equipment• Modular design

with automatic short circuiting C.T.-inputs• Signal and data processing in a separate digital

signal processor (32 samples per cycle)• Digital filtering of measured quantities• Three possibilities of parameter setting and data

calling:1) keyboard and display2) RS232 interface at the front (lap top)3) RS485 interface for integration into control systems at the rear

• Safety interlocking preventing parameter setting viadifferent ways at the same time

• extensive internal plausibility check of modified pa-rameters

• Event Recorder for recording system messages• Fault Recorder for recording measured fault data• Four programmable independent parameter sets• Non-volatile memory for parameter sets, events and

fault data• Indication of measured operational values and re-

sulting quantities• Wide-ranging automatic self-tests• Small relay size• Indication of relay functions optically or via sepa-

rate self supervision relay• Three possibilities for relay resetting• All data interfaces galvanical isolated• Rated frequency selectable: 50 Hz/60 Hz• Parameter setting protected by password

Functions which can be programmed by the user :• Protection and system parameters• Latched position or minimal signal duration for

each of the output relays

Optional equipment• CAN Bus• FO connection (fibre optic) for RS485 interface• Addition of further protection functions after installa-

tion of additional software modules

Transformer differential protection• Stabilization against transformer inrush and CT

saturation• Adaption to vector groups and transformation ratio

by means of software without additional interpos-ing CTs

• Compensation of tap changer position• Waveform recognition technique with a special

Fourier algorithm (inrush element)• No complete blocking of differential element but

only reduced sensivity• Independent High Set differential element for heavy

faults

TB MRD1-T 10.01 E 5

3 Design

This chapter informs briefly about operation elementsand indication elements of the MRD1. Name and po-sition of the individual modules are also described. Inchapter 5 operating of the relay and type specificfunctions are explained in more detail.

!NoteNoteNoteNoteFront view and rear view illustrations of the MRD1 aswell as connection diagrams can be found at the endof the manual.

3.1 Relay front

Display in Home Position

3.1.1 Display

The MRD1 is provided with a 16-digit, double-lineliquid crystal display (LCD), which is of alphanumericaldesign for an easy dialog. The figure above shows thebasic status of the display. Dependent on the mode se-lected, the following data can be shown on the dis-play:

• Date / Time / Relay type (Home Position)• Measured operational data• Measured fault data• System parameters and protection parameters• System signals and fault signals

3.1.2 LEDs

Additionally to the display there are max. 30 LEDs atthe front, indicating each of the operational status inthe MRD1. All LEDs are two-coloured (red/green) andarranged in two groups:

a) System and relay status indicationsThe 15 system indications are arranged underneaththe alphanumerical display. They are allocated to acertain function and show:

• Operational voltage available• Trip• OFFLINE TEST mode active• Edit mode active• Displayed parameter is modified but has not been

stored yet• Switch status of the 5 (optionally 10) output relays• Display of the relay function (self-test)

b) Status display of the 15 digital inputs (if provided)These 15 indications are shown at the left of the dis-play informing about the status of the digital inputs.

3.1.3 Push-buttons

All necessary MRD1 adjustments and inquiries can becarried out from the front of the relay by pressing therespective push-button (9 in total). Individual function ofthese push-buttons is explained in chapter Operating.

3.1.4 Parameter interface RS232

At the left of the relay front there is a 9-pole, D-SUBplug-and-socket connector for temporary lap-top con-nection. At this connection a serial interface RS-232 isprovided. A standard IBMTM compatible PC or port-able notebook can be connected to this PC interface.To connected MRD1 and PC a 1:1 modem-cable with9-pole plug-and-socket is used. By using SEG softwareHTLSOFT 3, which is WindowsTM compatible, MRD1parameters can comfortably be set. Additionally allmeasured operational and fault data can be read outof the relay integrated non-volatile memories.

6 TB MRD1-T 10.01 E

3.2 Master module

The master module is fitted right in the middle and con-tains componentries for data processing, the mainprocessor and the following connections:

3.2.1 Interface RS485

Interface RS485 at the rear of the relay is a permanentconnection between the MRD1 and the host computer.This interface operates at a constant transmission ratioof 9600 Baud if |SEG interface recorder "RS485pro"is used. Via RS485 interface all measured operationaland fault data as well as operational status indicationscan be read out - identical to RS232 interface. Remotesetting of parameters is also possible from the controlstation. The 8-pole plug-and-socket connector containsall necessary connections for this interface.

3.2.2 CAN-Bus (optionally)

This data interface is used for integrating the MRD1into special automation systems and for specific func-tion additions (e.g. temperature measuring module,graphic-display module). For the CAN Bus interfacestwo 9-pole D-SUB plug-and-socket connectors areused.

3.2.3 Function inputs and signal inputs(optionally)

These 15 digital inputs (contacts 1-15) are combinedon the 16-pole plug-and-socket connector. The six-teenth contact is the common return wire. Any incom-ing information

a) can direct be assigned to selectable output relays.This application method enables recording of the con-tact status (open or closed) of external protection de-vices (e.g. Buchholz relay at transformers)

b) can logically be interlinked with MRD1 internal pro-tection functions. The logical interlinking result can thanbe assigned to output relays.

An input can be considered active when a voltagequantity within the permissible high range (see Tecni-cal Data) is connected to the input contact and thecommon return wire. If the voltage is lower, the input isclassed as being inactive. Specific function of the indi-vidual inputs can be defined during programming (seechapter 6). Digital inputs are galvanical isolated fromthe relay electronics.

TB MRD1-T 10.01 E 7

3.3 Basic module and additional module

Plug-in units 1 and 3 are intended for individual appli-cations and at our works they are equipped with mod-ules for measuring value detection in compliance withthe relay function. (see folding page)

!Important Note

The MRD1 must only be dismantled or opened by authorized staff .Removal of live modules entail severe danger for the person(s) involved because there can no sufficient protectionagainst accidental contact be guaranteed as soon as the relay has been opened. Furthermore there is the risk ofthe modules being damaged by electrostatic discharge (ESD/EGB) when handled improperly.

Identical modules must not be exchanged between different MRD1 basic versions....

Calibration of every MRD1 is done at work with regard to the specific features of that relay. A random changeof modules would lead to unreliable operation of the relay because the compatibility of the relay componentsamong each other would be in disorder and could not be guaranteed any longer.Any modification jobs on the MRD1, for instance, exchange of modules or software additions, are only allowedto be done at our works or by authorized agents.

3.3.1 Basic module NT 6I (MRD1-G,MRD1-T2 and MRD1-T3)

For generator, motor and transformer differential pro-tection, module NT-61 is plugged into the first space.

Measuring inputsThe module consists of six current measuring channelswhich are used for measuring the three conductor cur-rents of each winding. The CT start point must beformed outside the relay since all 12 CT connectionsare wired separately on terminals. In addition to othermeasuring or protection devices the MRD1 can belooped in to existing CT lines, assumed the CT beingable to carry the total burden.

Apart from further connections for voltage supply of therelay, the module is also provided with a digital inputfor remote resetting as well as connection facilities forthe five output relays. Four of these are free to be usedacc. to requirement, the fifth is assigned for Selftest Re-lay.

Input RESETIf a voltage is applied to terminals of the RESET input(C8-D8), the MRD1 is reset to its basic status. By thisprocedure possible alarms and trip signals are can-celled.The voltage applied for resetting must be within thepermissible high-range (see technical data), although itmust not necessarily be identical with the latter.

The input is galvanical isolated from the relay electron-ics. Contact D8 is also the neutral or minus for theblocking input.

Blocking InputIf a voltage is applied to the terminals of the blockinginput (D8-E8), all protection functions assigned to theoutput relays are blocked. Terminal D8 is also the neu-tral or minus for the reset input.

Alarm relaysPotential free outputs of the five alarm relays providedare at terminals C, D and E, series 1 to 7. Exact allo-cation can be taken from the connection diagram. Re-lay 5 is permanently assigned to Selftest Relay. Func-tion allocation of the remaining relays is free and canbe defined when programming (see chapter 5). Twoof these four relays are provided with two changeovercontacts each and the other two with one changeovercontact each.

3.3.2 Additional module 3I (MRD1 T3)

Module 3I is used for three-winding transformers andapplied to rack place 3. By this module the number ofmeasuring channels is increased by three currents forthe tertiary winding of the transformer and it providesalso five additional output relays.

8 TB MRD1-T 10.01 E

4 Working principle

In this chapter the individual functions and workingprinciple of the MRD1 are described.

4.1 Protective functions

4.1.1 Transformer differential protection

Term Explanation

ID Bias current This is the current flowing from the input side into the object to be protected, hav-ing a respective output current available at the output side. This current is repre-senting the normal load and the load at external faults.

Id Differential current The current resulting from the difference of incoming and outgoing conductor cur-rents when these were converted at one transformer side.In other words: The differential current is the component at the transformer inputcurrent which has no related output current.

Ia Pickup current If the differential current exceeds the pickup current, the relay trips.

Fault current due tooperational condi-tions

This kind of fault current is the component of the measured differential currentwhich, however, is not caused by a fault of the object to be protected but is ofsystematic nature

Stabilization Under this heading all measures are compiled which stabilize the differential relayagainst nuisance tripping. Stabilizing always means the pickup current is raisedand by this the differential relay becomes more intensitive, but is never completelyblocked.

IS Stabilizing current This current develops from the bias current and represents the extent of stabilizingmeasures necessary as result of the fundamental analysis. Parameters of the stabi-lizing characteristic can be set.

m Harmonic stabilizingfactor

This factor, derived from the analysis of the harmonic frequency, is apart from ISthe second stabilizing factor and in case of rush and saturation by following aspecial characteristic makes the differential relay stable against tripping errors.

d[Id] Characteristic Offset The characteristic curve is raised up by the value d[Id] immediately after a har-monic stabilization factor “m” is measured to be greater than zero. This is to givea basic stabilization after detection of inrush or ct-saturation during external faultby means of harmonic measurement.

Pickup characteristic In this characteristic both stabilizing quantities (stabilizing current and stabilizingfactor) are brought together and from this the pickup current is defined necessaryfor the operational condition of the object to be protected at that instant.

Table 1: Term definitions

TB MRD1-T 10.01 E 9

General idealized view

Differential protection is a strict selective object protec-tion and is based on the current measuring principle atthe input and output side of the object being pro-tected. Dependent on the earthing method used, theneutral can also be included in measuring and bal-ance.The area between input and output CTs of the objectis classed as protection zone supervised by theMRD1. Included in the protection zone are also CTsand CT connection wire to the relay.

protected area

transformer

MRD

I 1 I 2GRID GRID

Fig. 1: Definition of protection zone

The relay checks constantly if the incoming currents ofthe input side are met by respective outgoing currentsat the output side. If the balance of the conductor cur-rents shows a difference, this may suggest a faultwithin the protection zone. Especially where trans-formers are concerned it is necessary that all conductorcurrents are converted to one reference transformerside according to their transformation voltage ratioand to their vector group so that quantities and phasescan be compared.

To distinguish between faults occuring within (inter-nally) or outside (externally) of the protection zone isthe main purpose of the differential protection becauseat internal faults the differential protection relay musttrip, but not so at external faults.

Examples:

External fault

During a short circuit occuring at the right grid, thecomplete short circuit current flows through the trans-former. The difference between incoming and outgo-ing currents of all transformer terminals is small (in idealcases = zero) I1-I2 = 0. The differential protection relaydoes not trip. (Switching off in such cases probably tobe realized by an overcurrent relay).

protected area

transformer

MRD

I 1 I 2

short circuit current

GRID GRID

Fig. 2: External fault

Internal fault

When an internal fault occurs the current balance isdifferent. Dependent on the kind of fault a deficit in thetotal of incoming currents can be observed. A windingshort circuit, for instance, can be fed from both sides,even if with different intensity. But this short circuit doesnot go through the transformer, it is fed from both gridsinto the transformer. So therefore the current balanceshows a difference.

protected area

transformer

MRD

I 1 I 2

short circuit current

GRID GRID

Fig. 3: Internal fault (example of a short circuit fed fromtwo sides)

Due to the chosen direction of the reference arrow,current I2 flows here in negative direction.

The differential relays detects a current difference of I1-I2 = Id and trips when Id has exceeded the set thresh-old.

10 TB MRD1-T 10.01 E

Stabilizing

At first approximation this idealized view applies tostationary states only. In reality other effects, especiallydynamic processes, may cause the established currentdifference to rise, even if there is no internal fault. Insuch cases a simple static differential relay would mis-takenly trip and to prevent this stabilizing measureshave to be taken. Possible sources of measuring errorsare systematic and can be duly taken into account.Especial measures for detecting switching actions (in-rush), CT saturation or to counteract errors caused bytransformer tap changer position switches are here ref-ered to.

Stabilizing the MRD1 means always an action tomake the relay more insensitive. By the MRD1 two in-dependent stabilizing quantities are calculated fromthe fundamental oscillation and harmonic analysis (seefollowing paragraphs).

Fundamental analysis

Distortion factors for differential current measuring are:• Measuring errors of angle and value of the CTs

used• Poor adjustment of rated CT data to rated trans-

former data• Effects caused by no-load currents• Adverse effects caused by tap changer position

By these factors a fault current is caused which mainlydepends on the biasing current. This fault current is be-ing measured as a differential current, although atransformer fault must not necessarily have occured.When the pickup current is set at a very sensitivevalue, each of these static factors can cause unin-tended trippings. With increasing bias current thepickup current has to be corrected upwardly.The following pickup characteristic (exact characteris-tic) gives an detailed study of the individual fault fac-tors and the resulting fault current. In fig. 4 the ex-pected fault current versus tripping characteristic isshown.

If a real fault occurs, the measured differential currentexceeds the biasing current caused by operationalconditions. Therefore the pickup characteristic must ex-ceed the biasing current characteristic by the requiredsensitivity value. The exact course can be approxi-mated by a simplified characteristic consisting of twolinear sections (I and II). The higher the characteristicbegins, the higher the permissible differential current. Ifthe characteristic begins at a very low point this meansmaximum sensitivity. If the pickup characteristic is be-low the biasing characteristic, systematic effects cancause unintended trips.

Stabilisierungsstromstabilizing current Is / In

Differenzstromdifferential currentId / In

I

II

AUSLÖSUNGTRIP

KEINE AUSLÖSUNGNO TRIP

tatsächlicher Fehlerstromlinieexact fault characteristic

Angenäherte Kennlinieapproximated characteristic

Fig. 4: Typical pickup characteristic (without considering transient processes)

Calculation of the differential current and stabilizing current resulting from the fundamental oscillation of the inputand output currents (current of the negative and positive phase sequence system) produces a point on the charac-teristic. If this point is within the tripping range, the output relay picks up.

TB MRD1-T 10.01 E 11

Harmonic analysis

The analysis of harmonics allows detection of specialprocesses in the grid, which also distort ascertainteddifferential current values.

These factors are:• Inrushes• Overexcitation of the transformer by overvoltage or

underfrequency• CT saturation at very high current load caused by:

- severe faults (external short circuit at high load)- start-up phases of big motor-operated drives- magnetizing currents of unloaded transformers- faults within the zone to be protected (short circuits)

We will explain the harmonic oscillation analysis moredetailed by taking the example "CT saturation" :In unstabilized transformer differential protection sys-tems instabilities can arise which may have grave con-sequences because the CT core is saturated due totransient processes. In this state the CTs, arranged ateither side of the zone to be protected, do not portraythe "right" secondary current (when compared to theprimary side). Through this constallation the differentialprotection relay detects at the secondary side of theCTs a differential current Id' which does, however, notexist at the primary side and this may cause unin-tended tripping.

In fig. 5 core saturation due to short circuit current is il-lustrated.Short circuit currents often contain a DC component.The high primary current arising during this kind of faultgenerates a magnetic B induction, causing saturationof the iron core.

The iron core keeps this high induction until the primarycurrent has reached zero. During the time the core issaturated, the secondary current is not in compliancewith the primary current, but becomes zero. During thetime the core is not saturated, the CT induces a currentwhich does not represent the real current for the entirecycle duration, its effective value is far too low.

Fig. 5 Core saturation of a CTa) primary current with DC componentb) induction in the corec) secondary current

Different saturation of CTs belonging to one protectionzone generate differential current Id' causing some un-stabilized relay to trip.For the harmonic analysis the MRD1 exploits thesecond, fourth and fith harmonic.

Important Note.For perfect functioning of the rush stabilization system itis essential that the MRD-T is connected in the correctphase sequence, i.e. that there is a positive rotatingfield. Refer also to page 11.

12 TB MRD1-T 10.01 E

Trip characteristic

The MRD1 identifies such factors by using the har-monic analysis and calculates a second dynamic stabi-lizing quantity, i.e. stabilzing factor m. Harmonicanalysis makes also detection of an inrush and trans-former saturation caused by overvoltage possible andare added to the calculation of the stabilizing factor.The MRD1 ascertains stabilizing factor m for thepresent situation with the effect of further lifting thecomplete characteristic. Calculation of m is definedand cannot be adjusted.m and IS each stabilize the relay entirely separate fromeach other, but never have a complete blocking effect.Both stabilizing quantities together define the pickupvalue in the trip characteristic.

A basic stabilization is performed by the parameterd[Id]. For all cases m>0 (rush current, single sided ct-saturation and external faults) the characteristic curve israised up for the minimum amount of d(Id). Anotheradditional raising is performed for raising m (moreservere rush, more severe ct-saturation).

The additionally adjustable parameter Idiff high set(Idiff >>) is a high current differential element. This set-ting value is not subjected to stabilization and specifiesthe highest permissible differential current. This pa-rameter defines characteristic sector III.

Tripping procedure

The protection program permanently checks the meas-urements that the DSP (digital signal processor) deliv-ers. When the DSP gives a new differential current theprotection task checks whether it lies within the trippinglimits. If this is the case the MRD1 is internally ener-gized. Tripping occurs when the calculated differencecurrent is consecutively three times within the trippinglimits. To prevent the energized state from being resettoo quickly, a hysteresis of 75 % is programmed. Thismeans that a newly calculated difference current mustbe smaller than 75 % of the present characteristic tripvalue in order for the energized condition to be reset.The total tripping time of the Relay is below 35 ms.

0Stabilisierungstromstabilizing current Is / In

Differenzstromdifferential currentId / In

I

II

III

AUSLÖSUNGTRIP

KEINE AUSLÖSUNGNO TRIP

m

Idiff >>(Für interne Fehler)(for internal faults)

d[Id]

Fig. 6: Dynamic stabilized trip characteristic (pick-up value).

TB MRD1-T 10.01 E 13

4.2 Analogue measured value detection

4.2.1 Current measuring

For measuring the relevant currents there is a separatetransducer for each of the existing measured quantities.This transducer provides galvanical isolation to the re-lay electronics. Adjustment to transformer vector groupand to the main CT rated currents is realized via thesoftware. The input signal is transmitted by internal CTsup to 64 times rated current linear. To achieve an ut-most accuracy there are two current measuring ranges,changeover of which is automatically.Each channel has its own sample-and-hold circuit. Allchannels are scanned simultaneously.

4.3 Digital signal processor

The digital signal processor (DSP) in the MRD1 ismainly used for processing measured values by con-trolling and monitoring data entry from the differentmeasuring channels. In addition all input signals aredigitally Fourier filtered. Among other values this proc-essor calculates RMS values and analyzes harmonicsby processing sampled data and stores digitalizedsignal sequences to the memory. Apart from datamanagement and processing the DSP keeps perform-ing wide-ranging self-tests.

4.4 Digital main processor

The main processors is the highest control elementwithin the MRD1 and processes the actual protectionprogram which interprets data obtained by the DSPand so refers to the operational status of the object tobe protected and to the own device. Special protec-tion mechanism enable the MRD1 to detect problemsin the own hardware. All communication betweenMRD1 and the outside world is also controlled by themain processor. This does not only mean control of in-dications or handling of key inputs but also harmoniz-ing the different data interfaces as well as control ofoutput relays.

14 TB MRD1-T 10.01 E

4.5 Block diagram

∩∩∩∩

∩∩∩∩

RS485

serialports

display and keyboard

CTs

real timeclock

CANBus1

CANBus2

LWL

CAN-con-tro-ller

faultmemory

programmemory

3

3

3

∩∩∩∩

anal

ogue

mea

sure

men

ts

PCMmemory card

serial PC-interfaceRS232

signal-processor

mainprocessor

central module

extension module

base module

mai

n pr

oces

sor b

us

optional

communi-cation

parameter-memory

blockinginput

supply

5outputrelays

SOFTWARERelaymatrix

∩∩∩ ∩

### #

RESETinput

dual portedmemory

5outputrelays

TB MRD1-T 10.01 E 15

4.6 General functions

4.6.1 Event-Recorder

The MRD1 is provided with an event recorder for re-cording events in a chronological order and thenstores them on a non-volatile memory. Any data entryhas a time stamp so that time of the event can al-ways be traced back. Data can be called off eithervia keys and display or data interfaces.Important events, such as trippings, are not only re-corded in the memory but also shown on the display.Pure informative events are stored in the recorderonly and are not displayed.

More details on calling off events and further infor-mation on the event recorder can be found in chap-ter 5.

The system messages are listed in chapter 9.1.

4.6.2 Fault-Recorder

At each tripping of the relays, the fault recorder rec-ords all measured data and resulting quantities. Anytripping event is automatically numbered consecu-tively in the recorder. Additionally to the measureddata the following details are also stored: the causefor tripping, serial number of the incident as well asdate and time at the instant of tripping.

The MRD1 is able to record several incidents in aFIFO memory. The longest stored data is overwrittenwhen a new incident occurs. Complete data of alto-gether 10 incidents can always be called off.More information on storage capacity and calling offrecorder data via keyboard can be found in chapter 5.

4.6.3 Self-test relay

The self-test relay (relay 5) is energized during nor-mal operation of the MRD1 and deenergized in thefollowing events:

• failure of aux. voltage• failure of internal partial power supply• processor failure detected by the internal watch-

dog• detection of an internal fault by software routines• when protection function of the output relays is

decoupled in OFFLINE TEST mode• when the default parameterset was loaded and

the device automatically switched in OFFLINETEST mode

• During power on initialisation• self-test of the output relays is performed

16 TB MRD1-T 10.01 E

4.6.4 Self-test

By pressing the TEST key several menu guided spe-cial test routines can be started in the MRD1 for in-ternal test purposes. Some tests disable the trans-former protection. These tests are locked by pass-word.

The following tests and information can be per-formed/is available :

Test / Inquiry Description Passwordre-quested

Protectionfunction

Software version number Number of version and date of software are in-quired no remains active

LED-Test • all LEDs light-up red f. 2s• all LEDs light up green f.2s no remains active

Test of output relays Sequence in one-second interval:• self-test relay de-energizes• all other relays de-energize• all relays energize one after the other (with LED)• relays return to actual position• self-test relay energizes

yes inactive during thetest

Memory test Test of software and memory by checking the pro-gram check sum no remains active

TB MRD1-T 10.01 E 17

4.6.5 Output relay settings

Reset time of the output relays:

With the exception of the self-supvervision relay, allexisting output relays are assigned to the differentialcurrent element. It is possible to define a proper resettime for each individual relay. For this period - fromthe moment of tripping - the relay remains in tripcondition even if the cause for the tripping does nomore exist.

!Note:If the time for which the relay has been energizedexceeds the adjusted reset time, the relay will releaseinstantaneously after trip condition is canceld. This isparticularly important for relay tests (test of the resettime) where the test current is not switched off imme-diately with tripping.

TRIP conditionAuslösebedingung

Relay energizedRelais angezogen

RESET TIMEMindestkommandozeit

t

RESET TIMEMindestkommandozeit

1

0

1

0

Fig.: Reset time

If a relay is to remain self-holding after tripping, thereset time has to be set to „exit“. Setting as per cus-tomer’s requirements can be noted down in the „se-lection“ line.

RelayBasic equipment Option

1 2 3 4 5 6 7 8 9 10Function Idiff

Idiff >>Idiff

Idiff >>Idiff

Idiff >>Idiff

Idiff >> STIdiff

Idiff >>Idiff

Idiff >>Idiff

Idiff >>Idiff

Idiff >>Idiff

Idiff >>

Pre-adjustment(in s) 0,20 0,20 0,20 0,20 • 0,20 0,20 0,20 0,20 0,20

Custom•

Setting range: 0 -...1,00 s or exit (=latching- contact un-til a DEVICE RESET is performed)ST=Self-Test relay• = no selection

18 TB MRD1-T 10.01 E

4.6.6 Parametrizing blocking

Blocking of protective function

The MRD1 offers a configurable blocking function.When applying a voltage to terminals D8-E8 all protec-tive functions are blocked that are configured for block-ing. In case of active blocking the output relays don’tact, but the device shows the fictive trip by means ofTrip-LED.

A minimum hold time can be set for the blocking. Duringthis time, starting from the begin of external blocking, allprotective functions are blocked, also in case the exter-nal blocking may was released. In case of longer con-tinuous external blocking the blocking can be stoppedafter a maximum hold time tmax for enabling the relay totrip in case of ongoing faults.

wirksame Blockierzeiteffective block. time

ext. Block. Eingangext. blockage input

tmin

t

tmax

!Note:Repeated impulse at the blocking time within tmin restartthe hold times.

Assignment of functions to output relays

The MRD1 offers 5 output relays. Relay number 5 ispreassigned to the selftest function of the relay and isworking with zero-signal current principle. Output relays1 – 4, and 6 – 10 are open-circuit relays and can beassigned to internal logic functions.

TB MRD1-T 10.01 E 19

5 Operation

5.1 General

5.1.1 Data organization

Data and settings in the MRD1 are subdivided into 4groups and each of those are allocated to one menukey or key combination. Related parameters or measur-ing data of one group are combined on individualpages. General settings can be made on the SYSTEMparameter page. Test routines are also on separatepages.

EVENTRecorder

PARAMETER measurementsdata recorder

PARAMETERpage 3

parameter 3.1parameter 3.2parameter 3.3.........

...

PARAMETERpage 2

parameter 2.1parameter 2.2parameter 2.3.........

...

PARAMETERpage 1

parameter 1.1parameter 1.2parameter 1.3...

TEST-routines

TESTroutines

software versionrelays testLED testmemory test

4 parameter sets

SYSTEM-parameter

SYSTEMPARAMETER

clock settingserial port optionswork set selectionOFFLINE TEST m.change passwordrestore default rated frequency

FAULTRecorder

...

...

...

+

DATApage 1

measurement1.1measurement 2.2measurement 3.3...

Statistic Data

Fig. 5.1: Data organization

20 TB MRD1-T 10.01 E

5.1.2 Parameter sets

MRD1 has access to four independent parametersets. Each of these data sets comprises a completeparameter set which makes individual setting of theMRD1 possible. If required by the operational pro-cedure several different settings can be stored andthen called off when needed.Data of SYSTEM parameters (e.g. rated frequency,slave address, date, time etc.) are not filled in thefour parameter sets, they do always apply.

EDIT-memory

display / keyboardserial interface

parameter set1

parameter set2

parameter set3

parameter set4

protection-program

output relay

messagedisplay / LED

measurement switch open in Offline Test Mode

SYSTEM-parameter

transformer

Fig. 5.1.2: Parameter sets, principle

For processing the selected set is loaded into theEDIT memory (switch: Set to Edit). After parametershave been changed, the EDIT memory is completelyrestored in the parameter set memory. All changesare then jointly read-in.Another switch (Work Set) defines on which of thedata sets the protection program is based. Allswitches are adjusted via software.

OFFLINE TEST mode is specified in chapter 5.1.6.

TB MRD1-T 10.01 E 21

5.1.3 Key function

KeyFunction short actuated long actuated (2s)

a) from HOME POSITION: View active parameter set (VIEW mode)

b) leaf to next PARA page

from HOME POSITION:" select one of the four parameter sets to edit (EDIT-mode)

++++

#

from HOME POSITION:" select SYSTEM-parameter page •

a) from HOME POSITION: View DATA pagesb) leaf to next DATA page

•

select the selftest routines page•

scrolling up / downsingle step

scrolling up / downfast

a) " change value. single stepb) move cursor

" change value, fast

a) confirm selection (YES)b) toggle setting in EDIT mode (yes/no ; on/off)

finish working in EDIT mode, perform parameter plausi-bility check and save (if check passed) all modifications

a) reject selection (NO)b) cancel modificationc) clear message

a) From HOME POSITION DEVICE RESETb) From Sub-Menu back to home position

• - no operation" - password protected# - press and hold down PARA, press UP in addition to PARA, release both

!NoteNoteNoteNoteIn the following paragraphs key symbols are mainlyused when explaining an operational procedure.Keys with the term "long" on them have to be pressedfor about 2s for actuating the function. If there isnothing stated, the respective key has only to bepressed briefly.

Fig.: Display in HOME POSITION

22 TB MRD1-T 10.01 E

5.1.4 LEDs

LEDs arranged at the relay front can light up in dif-ferent colours and can also either show permanentlight or flash in different frequencies.

LED lights up ON / OFF-ratio

green / redein / on

aus / off

green / red flashing a

green / red flashing b

t

Meaning of the LED-signals

LED name LED lights up Meaning

POWER green • Device OK

red flashing a • FAULT of an internal supply

off • Device OFF

TRIP off • Normal

red • Tripred flashing a • Energized

TEST off • Normal

red flashing a • OFFLINE-TEST-mode active

EDIT off • Normal, VIEW mode

red • EDIT mode after password access

MODIFIED off • Normal

red • EDIT mode: parameter modified

Relay off • Relays off

red

green

• Relays energized

• Relay-test

red flashing b • Relay off after energizing (until DEVICE RESET)

red flashing a • Relay blocked

SELFTEST green • Protection o.k. (selftest relay on)

red • System initialization (after power on)

red flashing a • OFFLINE TEST mode / Relay-TEST. no protec-tion, only messages

off • Internal fault. no protection

TB MRD1-T 10.01 E 23

5.1.5 VIEW mode / EDIT mode

There are two modes for selecting PARAMETERpages:A short press on the PARA-key activates the VIEW-mode. The EDIT-mode can be selected by pressingthe PARA-key for approx. 2 s (long press).• VIEW mode (viewing)

On pressing the key this mode only allows viewingthe active parameters

• EDIT mode (processing)Unlike in mode VIEW, in EDIT mode one of thefour parameter sets can be selected. That parame-ter set is then copied automatically into the EDITmemory and can be viewed there. At the first at-tempt of changing a parameter, the password isrequested. After entering the password (LED EDITlights up if the password was correct), the parame-ter can be changed. For any further change of pa-rameter(s) the password is not requested again. Incase the user does not know the password, thepassword entering mode can be cancelled andstill parameter sets be viewed but as explainedabove, they cannot be changed.

It is not necessary to acknowledge any changeseparately by pressing the ENTER key since at firsteverything is processed in the EDIT memory only.Each of the changes can be cancelled again. LEDMODIFIED indicates that the parameter displayedwas changed. If it should be set back to the initialvalue, only brief actuation of key RESET (cancelfunction) is needed. If the process is closed (with:ENTER, long), all the changes can be rejectedagain or be accepted. (Checkback: ARE YOUSURE?). Before the parameter set ist finally storedan internal plausibility check is performed to ensurethat all settings are conclusive. If the check routinedetects a irresolute combination of settings, theuser will be informed and the settings are notstored. e.g. an unsuitable combination of trans-former rated current (which is calculated from ratedvoltage and power capacity setting) an the settedCT primary rated current.

The protection program executed in the MRD1 at thetime is not effected by this procedure. Values of theactive parameter sets filed in the PARAMETER mem-ory are still being used until the complete EDIT mem-ory is recopied into the respective PARAMETERmemory. Only then all changes made taking effecttogether in the protection program.

!NoteNoteNoteNote

If during processing the aux. voltage fails, the com-plete EDIT memory is erased. After aux. voltage hasreturned, the protection program starts with those set-tings which were stored in the PARAMETER memorybefore the last processing operations. By this it is en-sured that the protection program does not work withincompletely changed data or meaningless data.

If due to the continously running check-sum test dataerror or loss of parameter memory is noted duringstart-up of the relay or during operation, a defaultparameter is loaded automatically. In such case therelay changes to the Offline mode (see next chapter)and the self-supervision relay de-energizes.

The EDIT-mode is left automatically if there is no inputlonger than 10 minutes (time out). Changed parame-ters wil not be stored.

24 TB MRD1-T 10.01 E

5.1.6 OFFLINE-TEST mode

For testing a parameter set the OFFLINE TEST modecan be activated. In this mode all output relays arebeing switched off. Now it can be changed over toanother parameter set for testing without risking nui-sance tripping. If the parameter set causes tripping,alarms are only shown on the MRD1 display or indi-cated via LEDs. The OFFLINE TEST mode is enabledor disabled on the SYSTEM SETTING page.

The OFFLINE TEST mode is indicated by:• Self-supervision relay de-energizes

(to inform the control system about the missingprotection function)

• Self-supervision LED flashes red (= no protection)• LED TEST flashes red (= TEST mode active)

!Important NotesImportant NotesImportant NotesImportant Notes

To prevent an unintended trip the OFFLINE TESTmode is activated as default setting on first commis-sioning. When the MRD1 recognizes a damagedparameter memory the default settings are loadedautomatically and the Offline mode is activated (withselftest relay unenergized).

During OFFLINE TEST mode the transformer is notprotected by the MRD1. Although a failure could bedetected during this mode, the MRD1 would not ini-tiate a trip of the transformer.

In order to prevent dangerous conditions, the trans-former must either have a sufficient backup protectionor has to be switched off.

After an intended OFFLINE TEST this mode must bedisabled so that protection is ensured again.

5.1.7 Reset (DEVICE RESET)

System messages in the display can be cancelledwith a short press on the RESET key. The message isnot removed at all but stored in the EVENT-memory.A trip will also cause a message which is also to becancelled with a short RESET press. After this allmeasured and calculated values can be recalledfrom the fault recorder. All output relays and LEDs (ifset to self-holding contact) will remain in energizedposition until a DEVICE RESET is initiated to theMRD1 by a long RESET press from home position.The DEVICE RESET can also be initiated by the ex-ternal reset input or via serial interface.

Info-messages do not need to be reset manually.They extinguish automatically after 5 s.

TB MRD1-T 10.01 E 25

5.1.8 Enter password

The MRD1 calls for a password if parameters are in-tended to be changed in the memory or other impor-tant functions to be activated. Nearly all data can becalled off by the user without entering a password,but for changing any data, the password is required.Some test functions can only be started after thepassword has been entered (see chapter 5.5).If a password is required this is indicated on the dis-play. The password consists of four digits and keycombination , has to be actuated.

Display Process Key

request to enter password

entering password

with every keypress a further willappear in the display

"

password correct.LED EDIT on

"

password incorrectLED EDIT remains off

Table: Procedure for entering a password

" Message appears for app. 2 s

!NoteAny process started can be stopped at any time bypressing key RESET:

The password entered at our works consists of key

sequence It is adviseable to change this password immediatelyto an individual one.

LED EDIT indicates if the password entered is cor-rect. In this state changes on MRD1 settings can bemade. When changing over to another function insome cases the password has to be entered again.Also after storing or cancelling, editing authority be-comes invalid. Hence it is very important that the re-lay is only left after LED EDIT has extinguished to pre-vent unauthorized change of settings.

5.1.9 Password forgotten

! ImportantIn case the password has been forgotten our workshave to be contacted to inquire about the measuresfor regaining access.

26 TB MRD1-T 10.01 E

TB MRD1-T 10.01 E 27

5.2 SYSTEM settings

5.2.1 Selection

On this page the general functions are shown whichare not stored in the four parameter sets. They arestored separately and always apply, irrespectively ofthe parameter set selected. The SYSTEM SETTINGScan only be selected from Home Display.

page select Display

+ "

" Starting at Home Display: press UP and hold, press PARA inaddition to, release both

SYSTEMparameterpage

line 1line 2line 3line 4...

select line

change value

password access

line 2[___________]

line 2[acual setting]

to change a value or start an operation :ENTER

to confirm or saveENTER

Fig.: System settings, principle

Note:

To change any setting or start an operation:• Select parameter or option with UP / DOWN• Press ENTER• Enter password if requested• If necessary: select setting with the +/- keys.

On setting date/time the arrow keys (up/down) are used to scroll to the next value.• Press ENTER to get new value valid.

28 TB MRD1-T 10.01 E

5.2.2 Overview

Key Existing lines Settings Range Default Actualsetting

scroll

Headline

change time and date see5.2.3

rated frequency in Hz 50 Hz60 Hz

50 Hz

select serial port disableRS232RS485CAN

RS485

Slave-address of RS485-interface 1-32 1

A...F Goup selectiont Time-/Date setting via

master

"

programming via interface enabledisable

disable

parameter set switch over via interface enabledisable

disable

activate Offline-TEST-Mode enabledisable

enable

select active parameter set 1 ... 4 1

change password see5.2.4

clear all parameter sets and set to defaultThe device switches to OFFLINE TESTmode automatically!

clear event recorder

clear fault recorder

Table: SYSTEM settings page, overview

" Select with cursor and

To change any setting or start an operation press

while shown in display.

TB MRD1-T 10.01 E 29

5.2.3 Time / Date

Key Display Remark Change value Setting range

Headline • Password input

scroll

change year 1980-2099

change month 1-12

change day 1-31(depends on year/month)

change hours 0-23

change minutes 0-59

change seconds 0-59

accept settings andstart new time / date

• •

cancel settings and restore oldtime / date

• •

• No selection possible

Table: Date /time-setting

!NoteNoteNoteNoteBoth arrow keys have the same function for this set-ting procedure. Both move the cursor always to thenext digit group. After reaching the SECOND col-umn, it is switched back to YEAR again. Digits for theyear and month have to be entered before digit(s) forthe day to enable the MRD1 to carry out correct cal-culation of intercalary days as well as the max. daysin a month. The internal clock does not stop duringthe setting procedure so that when cancelled byRESET key the actual time is not changed. Afterpressing ENTER the modified time becomes valid.

Date/time setting may be synchronized via serial in-terface (see setting "GROUP ADDRESS").

30 TB MRD1-T 10.01 E

5.2.4 Password change

The password in the MRD1 can be changed at anytime. For changing a password it is necessary toknow the present one. To rule out any typing errors,the password has to be entered twice. If the entriesare not identical, the password is not changed andthe previous one still applies. (Please see table be-low).

Display Step Key

Password change with ENTER

Request to enter old password

enter new password

enter new password again

" changing done

" The new password wouldn’t betyped 2 times identically

Try again " message appears for app. 2 s

Table: Password change, procedure

TB MRD1-T 10.01 E 31

5.3 PARAMETER-pages

5.3.1 Selection

This table gives an overview about all pages of aparameter set and the parameters belonging to.

Select PARAMETER-pages in VIEW- or EDIT mode

Key Display Remark

short

VIEW active parameter set continued at 5.3.2.

long

EDIT modeselect one of the four parameter setsto view or editconfirm with ENTER

e.g. set 2 was loaded and is nowready for editing

continued at 5.3.2.

PARApages

page 1page 2page 3page 4...

page 2

param 2.1param 2.2param 2.3param 2.4...

PARAMETER 2.3[ value ]

leaf to nextpage

select line

change value

password access

Fig: Parameter pages, organization

Possibilities after modifying a parameter:

• Keep modifications and scroll to next line (up/down)• Keep modifications and leaf to next page (PARA short)• Cancel modification of the displayed value (RESET short)• Finish working, accept all modifications and store (ENTER long)• Finish working and refuse all modifications, no store (RESET long)

32 TB MRD1-T 10.01 E

5.3.2 Overview

Key PagesHeadline

Parameter see

leaf to nextpage

or

Parameter pages active parameter ready for viewing(e.g. set 1)

selected set ready for viewing and editing(e.g. set 2)

Data of pro-tected device forall windingsW 1W 2W 3

Rated powerRated voltageCT primary currentConnection groupPhase shifttap ratioCT connection

5.3.3

parameter ofdifferential-protection

Difference current at Is=0 × InDifference current at Is=2 × InDifference current at Is=10 × Inmax. Difference current Idiff>>d[Id] Offset in case of harmonics

5.3.4

Parameter of lo-gic functions

Assignment of protective and logic functions(AND-logic)

Parameter ofoutput relays

Reset time or self-holding of the output relay 5.3.5

Parameter of ex-ternal blocking

Table: Parameter pages, overview

On the first attempt to change a setting with the+/- keys in a edit session the password is asked. Toview only parameter settings the PARA key is used toleaf to the next page and the UP/DOWN keys areused to select the parameter.

TB M

RD1-

T 1

0.01

E33

5.3

.3

Transf

orm

er r

atings

Key

Dis

play

Para

met

erA

vaila

ble

in M

RD1-

T2

T

3

Sele

ctSe

tting

rang

e

(• n

o se

lect

ion)

Def

ault

actu

al

Set 1

Set 2

Set 3

Set 4

Hea

dlin

e×

×no

ne•

••

••

•

rate

d ap

pare

nt p

ower

of

win

ding

1(H

igh-

volta

ge-si

de)

××

10 k

VA -

800

MVA

17.3

MVA

corre

spon

ding

to w

indi

ng 2

×10

kVA

- 80

0 M

VA17

.3 M

VA

corre

spon

ding

to w

indi

ng 3

×10

kVA

- 80

0 M

VA17

.3 M

VA

rate

d vo

ltage

of w

indi

ng 1

(pha

se to

pha

se v

olta

ge o

n hi

gh-

volta

ge-si

de)

××

100

V....

800

kV20

kVA

corre

spon

ding

to w

indi

ng 2

××

100

V....

800

kV6.

6 kV

corre

spon

ding

to w

indi

ng 3

×10

0 V.

...80

0 kV

6.6

kV

rate

d pr

imar

y cu

rrent

of p

hase

CT

win

ding

1×

×1.

....5

0.00

0 A

500

A

corre

spon

ding

to w

indi

ng 2

××

1....

.50.

000

A15

00 A

corre

spon

ding

to w

indi

ng 3

×1.

....5

0.00

0 A

1500

A

34TB

MRD

1-T

10.

01 E

Key

Dis

play

Para

met

erA

vaila

ble

in M

RD1-

T2

T

3

Sele

ctSe

tting

rang

e

(• n

o se

lect

ion)

Def

ault

actu

al

Set 1

Set 2

Set 3

Set 4

conn

ectio

n sy

stem

of w

indi

ng 1

××

wye

, del

ta, z

igza

g,w

ye+n

, zig

zag+

nw

ye +

n

corre

spon

ding

to w

indi

ng 2

××

wye

, del

ta, z

igza

g,w

ye+n

, zig

zag+

nw

ye +

n

phas

e sh

ift in

win

ding

2 i

n ×

30°

in re

latio

n to

win

ding

1×

×0-

110

conn

ectio

n sy

stem

in w

indi

ng 3

×w

ye, d

elta

, zig

zag,

wye

+n, z

igza

g+n

wye

+ n

phas

e sh

ift in

win

ding

3 i

n ×

30°

in re

latio

n to

win

ding

1×

0-11

0

volta

ge d

ispla

cem

ent b

y tra

nsfo

rmer

tap

chan

ger i

n w

indi

ng 1

××

- 20

%...

+ 20

%0,

0

Win

ding

1 C

T co

nnec

tion

in n

or-

mal

pol

arity

(lik

e co

nnec

tion

dia-

gram

) or i

nver

ted

(reve

rse

pola

rity)

"

××

norm

al,

inve

rted

norm

al

corre

spon

ding

to w

indi

ng 2

"×

×no

rmal

,in

verte

dno

rmal

corre

spon

ding

to w

indi

ng 3

"×

norm

al,

inve

rted

norm

al

" N

OTE

: The

Par

amet

er m

ust b

e se

t to

inve

rted

pola

rity,

if th

e di

rect

ion

of c

urre

nt fl

ow in

the

seco

ndar

y ci

rcui

t is

reve

rse

to th

e in

put t

erm

inal

s of

MRD

1 ac

cord

ing

to th

eco

nnec

tion

diag

ram

(Cha

pter

10)

.

TB MRD1-T 10.01 E 35

5.3.4 Protection parameters

Differential protection

The tripping characteristic of the MRD1 can be set with four parameters:

Idiff0: Error caused by no load current and error of the CTsIdiff2: Additional error by tap and linear error of the CTs (linear range of the CTs)Idiff10: Additional error by saturation of the CTsIdiff>>: maximum permitted difference currentd[Id]: raise up of characteristic curve by offset in case of characteristic harmonics

In: Transformer nominal current

0Stabilisierungsstromstabilizing currentIs / In

Differenzstromdifferential currentId / In

5

Idiff (Is/In=10)

10

Idiff >>

1

2

8

Einstellbereich der Kennliniesetting range of characteristic

2

8

I

II

III

Idiff (Is/In=2)Idiff (Is/In=0)

1

0,20,10,5

d[Id]

Fig: Possible setting range of the characteristic

36TB

MRD

1-T

10.

01 E

Key

Dis

play

Para

met

ers

of th

e ch

arac

teris

ticSe

lect

Setti

ng ra

nge

(• n

o se

lect

ion)

Pre-

adju

st-m

ent

actu

al

Set 1

Set 2

Set 3

Set 4

Hea

dlin

eno

ne•

••

••

•

diffe

rent

ial c

urre

nt Id

iff a

t sta

biliz

ing

curre

ntIs/

In=0

(s

ee p

ictu

re) #

0.1.

..0.5

× In

"0.

5

corre

spon

ding

to Is

/In

=2 #

0.2.

..1 ×

In"

1.0

corre

spon

ding

to Is

/In

=10 #

2.0.

..8.0

× In

8.0

max

imum

per

mitt

ed d

iffer

entia

l cur

rent

2.0.

..20.

0 ×

In20

.0

Offs

et o

f cha

ract

erist

ic c

urve

from

sta

tic b

asic

char

acte

ristic

cur

ve0.

0...8

.02.

0

Tabl

e: A

djus

tabl

e pr

otec

tion

para

met

er

" T

o ge

t no

nega

tive

slope

in th

e ch

arac

teris

tic p

art I

the

setti

ng Id

iff (I

s=2)

mus

t not

be

less

then

the

setti

ng Id

iff (I

s=0)

. The

MRD

1 w

ill ch

eck

the

inpu

ts on

this

mus

t.

# In

= T

rans

form

er n

omin

al c

urre

nt

TB M

RD1-

T 1

0.01

E37

5.3

.5

Rel

ay-s

ettings

Key

Dis

play

Setti

ngSe

lect

Setti

ng ra

nge

(• n

o se

lect

ion)

defa

ult

actu

al

Set 1

Set 2

Set 3

Set 4

head

line

none

••

••

•

Ass

ignm

ent o

f rel

ay 1

to lo

gic

func

tions

A...

P,O

R-lo

gic

[ ↵]

ABC

....P

AB.

...

corre

spon

ding

to re

lay

2

[ ↵]

ABC

....P

AB.

...

corre

spon

ding

to re

lay

3

[ ↵]

ABC

....P

AB.

...

corre

spon

ding

to re

lay

4

[ ↵]

ABC

....P

AB.

...

corre

spon

ding

to re

lay

6

[ ↵]

ABC

....P

AB.

...

corre

spon

ding

to re

lay

7

[ ↵]

ABC

....P

AB.

...

corre

spon

ding

to re

lay

8

[ ↵]

ABC

....P

AB.

...

corre

spon

ding

to re

lay

9

[ ↵]

ABC

....P

AB.

...

optio

-na

l

corre

spon

ding

to re

lay

10

[ ↵]

ABC

....P

AB.

...

38TB

MRD

1-T

10.

01 E

Key

Dis

play

Setti

ngSe

lect

Setti

ng ra

nge

(• n

o se

lect

ion)

defa

ult

actu

al

Set 1

Set 2

Set 3

Set 4

min

imun

Res

et ti

me

/la

tchi

ng ti

me

for r

elay

10.

00 ..

.. 1

.00s

/ex

it

"

0.2

s

corre

spon

ding

to re

lay

20.

00 ..

.. 1

.00s

/ex

it

"

0.2

s

corre

spon

ding

to re

lay

30.

00 ..

.. 1

.00s

/ex

it

"

0.2

s

corre

spon

ding

to re

lay

40.

00 ..

.. 1

.00s

/ex

it

"

0.2

s

ifeq

uippe

d

corre

spon

ding

to re

lay

6 (If

equ

ippe

d)0.

00 ..

.. 1

.00s

/ex

it

"

0.2

s

corre

spon

ding

to re

lay

7 (If

equ

ippe

d)0.

00 ..

.. 1

.00s

/ex

it

"

0.2

s

corre

spon

ding

to re

lay

8 (If

equ

ippe

d)0.

00 ..

.. 1

.00s

/ex

it

"

0.2

s

corre

spon

ding

to re

lay

9 (If

equ

ippe

d)0.

00 ..

.. 1

.00s

/ex

it

"

0.2

s

corre

spon

ding

to re

lay

10 (I

f equ

ippe

d)0.

00 ..

.. 1

.00s

/ex

it

"

0.2

s

Tabl

e: R

eset

tim

e of

the

outp

ut re

lays

" T

he re

set t

ime

ist th

e m

inim

um ti

me

the

rela

y ke

eps

ener

gize

d af

ter a

trip

. If t

he ti

me

is se

t to

exit

the

outp

ut re

lay

is co

nfig

urat

ed a

s a

latc

hing

con

tact

.

The

rela

y ke

eps

ener

gize

d af

ter a

trip

unt

il th

e M

RD1

is RE

SETe

d. (D

EVIC

E RE

SET)

39TB

MRD

1-T

10.

01 E

5.3

.6

Sett

ing o

f lo

gic

funct

ions

Taste

Dis

play

Setti

ngSe

lect

Setti

ng ra

nge

(• n

o se

lect

ion)

Def

ault

Act

ual

Set 1

Set 2

Set 3

Set4

Hea

der l

ine

Ass

ignm

ent o

f log

ic fu

nctio

ns A

to p

rote

ctiv

e fu

ncti-

ons

(her

e: p

rote

ctiv

e fu

nctio

n A

= Id

>)

Ass

ignm

ent o

f log

ic fu

nctio

ns B

to p

rote

ctiv

e fu

ncti-

ons

(her

e: p

rote

ctiv

e fu

nctio

n B=

Id>>

)

Ass

ignm

ent o

f log

ic fu

nctio

ns C

to p

rote

ctiv

e fu

nc-

tions

(her

e: p

rote

ctiv

e fu

nctio

n A

and

B)

Ass

ignm

ent o

f log

ic fu

nctio

ns P

to p

rote

ctiv

e fu

nc-

tions

(her

e: n

o pr

otec

tive

func

tion)

!N

ota

Not

aN

ota

Not

aFo

r MRD

1 th

ere

is th

e fo

llow

ing

defin

ition

:Pt

otec

tive

func

tion

A: D

iffer

entia

l pro

tect

ion

Id>

(Low

Set

)Pr

otec

tive

func

tion

B: Id

> (H

igh

Set)

40 TB MRD1-T 10.01 E

Scheme:

41TB

MRD

1-T

10.

01 E

5.3

.7

Blo

ckin

g S

etting

Key

Dis

play

Setti

ngSe

lect

Setti

ng ra

nge

(• n

o se

lect

ion)

Vor-

eins

tel-

lung

Sele

ct

Set 1

Set 2

Set 3

Set 4

Hea

der L

ine

Bloc

king

of p

rote

ctiv

e fu

nctio

ns(h

ere:

pro

tect

ive

func

tion

A a

nd B

)--,

AB

AB

Min

hol

d tim

e of

blo

ckin

g«e

xit»:

no m

in. h

old

time

0.0

... 6

0.0

exit

0.1s

Max

. blo

ccki

ng ti

me

whe

n co

ntin

uoui

ng b

lock

ing

si-gn

al «

exit»

: lat

ched

as

long

as

signa

l hol

ds0.

1 ...

60.

0ex

it2.

0s

42 TB MRD1-T 10.01 E

5.3.8 Validity check

The MRD1 is provided with a special parameterchecking facility as protection against wrong set-tings. However, to prevent that the actual settingrange is too much restricted , this facility can onlyprotect against gross setting errors. Before they arestored, changed settings are checked for their mu-tual validity. The procedure is such that firstly theparameters are compared to the calculated ratedcurrents IN (per winding) of the component, whichresult from the rated apparent power and ratedvoltage. Thereafter interrelation of the parameters ischecked.If there is a discrepancy when setting parametersvia the keyboard, either the MRD1 does not allowthe respective value to be further changed or refersto the inconsistent value

by issuing a clear text message when trying tostore the parameter. In this case the EDIT mode isnot left and the value can be corrected.When setting parameters via an interface, validityerrors are indicated by a spezial telegramm mes-sage.

A setting is not regarded to be valid if one of thefollowing conditions are not met :

• CT mismatch for each winding1/8 × IN < IWPN < 2 × IN

• CT transformation ratio at MRD1 rated currentIWPN ≥ 5 A

• Relation of voltage levelsFor three-winding transformers (MRD1-T3)UN Winding 1 ≥ UN Winding 2 ≥ UN Winding 3

For two-winding transformers (MRD1-T2)UN Winding 1 ≥ UN Winding 2

• Tripping characteristicId(IS=0) ≤ Id(IS=2)i.e.gradient Sector I ≥ 0andgradient Sector I ≤ gradient Sector II

• Ext. Blockagetmin > tmax

minimum hold time is greater than maximum holdtime

Abbreviations :Abbreviations :Abbreviations :Abbreviations :

SN set rated vector powerUN set rated component voltage (phase-to-phase voltage)IN rated component current (IN = SN / √3 x UN)) calculated from UN and SN

IWPN set rated C.T. primary currentGradient characteristic gradient in the respective linear sector (see chapter 5.3.4)

TB MRD1-T 10.01 E 43

5.4 DATA pages

5.4.1 Selection

All measured, calculated and stored data canbe recalled on the data pages

Key Display

DATApage

page 1

Fault RecEvent Rec

page 1

meas. 1.1meas. 1.2meas. 1.3...

measurement 1 .3[ value ]

leaf to nextpage

select line

Data recorder (last but one)

time

FAULT EVENTI DIFF> TRIP

select a stored value

date event value 1 value 2 ...

DATA recorder

1 2 3 4 ....

Fig.: Data pages, organization

44 TB MRD1-T 10.01 E

5.4.2 Overview

Key PageHeadline

Data

leaf to nextpage

Data pages selected

Actual measurementsand calculated datas

Phase current (L1 L2 L3)Differential currentStabilizing current Is (fundamental oszillation analysis)Stabilizing factor m (harmonic analysis)

Recall stored trip datas Trip message, date / time ,measurementscalculated measurements

Recall event messages Message textdate / time

Recall statistic Data Operating hoursTrip counterAlarm counter

Table: Data pages, overview

TB MRD1-T 10.01 E 45

5.4.3 Measured and calculated data

Key Display Data

scroll

Headline

Actual measuring value of the phase current L1of winding 1 in A

corresponding to L2

corresponding to L3

...etc. Phase current in A (all phases, all windings)

calculated difference current (Idiff) "calculated stabilizing current (Irestr) "calculated stab. factor (harm restr.)

Table: Operational measured data

" related to the transformer nominal current

46 TB MRD1-T 10.01 E

5.4.4 FAULT Recorder

Key Display Value

scroll

Headline

see be-

low

Record 0 (last trip)Trip number date/timetrip reason,all stored data

Record 1 (last trip but one)Trip number date/timetrip reason,all stored data

for all existing registers Record n in chronological or-der

Trip number date/timetrip reason,all stored data

The display shows „“ at the end of the list or if no trips are stored.

Table: Fault-Recorder

Key Display Value

next value

Headline of the last trip (e.g.)

Trip number

Reason of the trip

Date of trip

Time of trip

Current L1 of winding 1 in A

etc. corresponding for all storeddatas

Table: Data of a fault recorder

TB MRD1-T 10.01 E 47

5.4.5 EVENT-Recorder

Key Display Value

scroll

headline

see below

Event 0event messagedate/timeof the last event

Event 1event messagedate/timeof the last trip but one(previous)

corresponding to all storedevents

Event nevent messagedate/timein chronological order

The display shows „“ at the end of the list.

Table: Event-Recorder

Key Display Value

next value

Event number and event mes-sage

e.g. last event

Date of event

Time of event

Table: Message and time / date

48 TB MRD1-T 10.01 E

5.4.6 Statistic data

Key Display Value

next value

Headline

MRD1 Operating hours

Trip counter

Alarm counter

Table: Statistic data

!NoteNoteNoteNoteThis statistic counters can not be resetted.

TB MRD1-T 10.01 E 49

5.5 TEST-routines page (Self-test)

5.5.1 Page selectionPage select Display

TEST-routines

test 1test 2test 3...

test 2

select testpassword access

start test

test is running

50 TB MRD1-T 10.01 E

5.5.2 Overview

Key Test Description execute

scroll

Headline

Display of version and date of the software onlydisplay

Test Test of the LEDs:

all LEDs will be illuminated green and red for twoseconds (no password needed)

Test Test of the output relays:

IMPORTANT: all relays will be energised in a 1 sinterval. The Selftest Relay keeps off for the durationof the test. After the test all relays will be set to thestate before.

"

Test Memory / program test:

This routine will test the memory and the programby calculating a checksum.

" NOTE: Password is needed, because the protection function is disabled during the test!

Table: Implemented test routines

TB MRD1-T 10.01 E 51

5.6 Parameter programming help

This chapter is a step by step help how to enter the first specific settings into the MRD1 by keyboard. Formore information about the parameter and its setting ranges see chapters: PARAMETER-pages andSYSTEM settings.

Step Key

1 select PARAMETER-page in EDIT-mode

long

2 if necessary: select the set No. to edit

3 confirm selection(set will be loaded in EDIT memory)

4 leaf to first parameter page

5 scroll to the first line of this page(first parameter)

6 if necessary:change displayed value

on first modification: enter password

For bit-wise parameter like system-parameter “Group Ad-dress” press [↵ ] shortly

7 scroll to next line(second parameter)

there is no need to confirm the modification of step 6with a separately ENTER press.

8 if necessary:change displayed value

repeat step 6 and 7 as long as needed

9 leaf to next page

continue at step 5

52 TB MRD1-T 10.01 E

Other operations Keyfinish working and store all modifications(EDIT-memory will be copied back to parameter memory)

long

abandon working and refuse all modifications(no storing)

long

cancel modification on the displayed parameter and reset to oldvalue.(if LED MODIFIED illuminated) short

edit another parameter set finish with ENTER long or RESET long andcontinue on step 1

!NoteNoteNoteNoteThere is no need to confirm any modification by pressing ENTER. All modifications are temporarily storedin the edit memory when scrolling with up/down keys. When pressing ENTER long all modifications in theedit memory will be stored in the parameter set memory after an ensurance request.

TB MRD1-T 10.01 E 53

6 Relay Tests

For testing the MRD1 the following has to be takeninto account:The test current source must supply a current free ofharmonics. Should this not be the case, measuringerrors may result from this if the reference ammeterused is an RMS instrument (which is common prac-tice).

Test circuits for differential current Idiff and stabilizingcurrent Is:

The rated value indication for differential currentand stabilizing current can be gathered from thefollowing table. Test current I should be in compli-ance with the transformer nominal current.

A B C DIdiff 2/3 × I 0 1× In 0Is 0 2/3 × I 0 1 × In

Value indications dependent on the test circuit used

I

MRD1

B3

B4

B5

B6

B7

B8

I

MRD1

A3

A4

A5

A6

A7

A8

W1

W2

W1

W2

B3

B4

B5

B6

B7

B8

A3

A4

A5

A6

A7

A8

A A

A) B)

MRD1

W1

W2

I

B3

B4

B5

B6

B7

B8

A3

A4

A5

A6

A7

A8

I

I L1

L2

L3

L1

L2L3

LFG1

A

A

A

D)

Symmetrisches Dreiphasensystemsymmetrical three phasesystem

MRD1

W1

W2

I

B3

B4

B5

B6

B7

B8

A3

A4

A5

A6

A7

A8

I

IL1

L2

L3

L1

L2L3

LFG1

A

A

A

C)

Symmetrisches Dreiphasensystemsymmetrical three phasesystem

NOTE for relay tests:• Stated accuracies apply to rated values• Currents must be free of harmonics• When a three-phase connection is used for the test, the current must form a symmetric system• Parameters W1 CT connection and W2 CT connection must be in normal position• Rated data parameters must be adjusted for a transformer of vector group Yy0• The settings of the primary nominal current of the CTs and the nominal voltages for all windings must be

the equal (transmission ratio 1:1).• LFG = |SEG-Power Function Generator

54 TB MRD1-T 10.01 E

7 Commissioning

7.1 Check list

Check Remark ok.Safety Measures Observe relevant safety regulationsAux. voltage range Prior to connection it has to be checked whether existing aux. voltage is

within the permissible range for MRD1Rated system data Secondary currents of CTs provided in the system have to be in compli-

ance with rated currents of the MRD1 (1 A or 5A) in the respective wind-ing

Connection Check MRD1 for correct connection in the switchboardEntry of rated systemdata

Has all rated system data correctly been programmed ?Are the indices of the vector group setted.Are the CTs connected normal or revers

Setting of parame-ters for protection

Have all parameters for protection correctly been programmed ?

Reset time Are the reset times set to all output relays?Selection of workparameter set

Has the right parameter set been selected as working set?

Protection function Does LED SELF-TEST light up green and is Selftest relay energized ?Device tests Selftest routines

- Lamptest- Test of the output relays- Checksum test- Test of the working parameter set in OFFLINE TEST mode

TB MRD1-T 10.01 E 55

7.2 C.T. connection

The right polarity of the C.T. is very important andso when the MRD1 is initially connected this has tobe checked carefully. Reverse polarity at even oneC.T. only is likely to cause trip errors. Whetherconnection of the MRD1 is correct can roughly beseen from the differential current indication, pro-vided the object to be protected operates trouble-free. To check the correct C.T. connection, firstlythe MRD1 should be operated at the object to beprotected in OFFLINE TEST mode.

! Important Note:In this operational mode, the object to be protectedmust have a sufficient back-up protection. Further-more it is assumed that the supervised componentis not faulty and all parameters are correct. Whenin OFFLINE TEST mode it is ensured that a CT withperhaps reverse polarity does not cause an unin-tended trip.

Now the supervised component can be switchedon while observing and interpreting the differentialcurrent indication. Interpretation of the indicatedvalue is always subject to local conditions (opera-tion related fault current) and can here only be de-scribed generally. The test circuits described inchapter 6 can be of help for fault identification.

The following table can be considered as refer-ence when checking the connection. The statedvalues are based on symmetrical load I=IL1=IL2=IL3.Where loads are involved which are not 100 %symmetrical, the observed values may deviate fromthe table. All figures are to be understood as ap-proximate values and are a multiple of the loadcurrent.

Case Differential currentIdiff / In

Through currentIs / In

1 All CTs are correctly connected 0 12 One CT connect. with rev.polarity 1,33 0,663 Two CTs connect. with rev.polarity 2,0 04 Three CTs connect. with rev.polarity 2,0 0

Table: Recommended values for differential current and stabilizing current indication at the MRD1 with assumed faultlesscomponents and different numbers of CTs connected

1) Correct connection :All C.T.s are correctly connected. This case is iden-tical to that where all C.T.s are wrongly connectedor the direction of energy flow is reverse. Butchanges at the C.T. connection are not necessary.

2) One C.T. wrongly connectedIn this case the current balance is out of place.There is about 1/3 x I through current missing andthe MRD1 recognizes 2/3 x I differential currentinstead. Input and output currents in the phase withwrong polarity are interpreted by the MRD1 thatway as if 1/3 x I each flow into the faulty phase.Thus the resulting differential current is 2/3 x I.

3 / 4) Two or three C.T.s wrongly connectedIn these two cases the indication does not distin-guish between two or three C.T.s wrongly con-nected because of the internal calculation. If threeCTs are wrongly connected, the respective faultcan be eliminated by changing parameter "C.T.Connection" without having to change the wiring .

For locating all other faults either the complete C.T.wiring has to be checked after disconnection of thecomponent or the reversed connections to betraced by means of a suitable test current source.

56 TB MRD1-T 10.01 E

8 Technical Data

8.1 MRD - Transformer Differential Protection Relay

Common data

Rated frequency: 50 Hz, 60 HzDisplay: LED and LCD-Display (2 × 16 digits)

Voltage supply

Aux. voltage ranges Range Rated voltage RangeDC L 24 V 19-40 V

M 48/60 V 38-72 VH 110/125/220 V 88-264 V

AC on request

Power consumption stand-by 13 VAmaximum 16 VA

Permissible interruption of the max. 50 ms (at rated voltage)auxiliary voltage supply

Input CTa) Phase current CT

Rated current IN 1 A or 5 APower consumption in current path: at IN: < 0.1 VA

Thermal withstand capabilityin current circuit: 250 × IN (VDE 435, T303),

dynamical current withstand (half-wave)100 × IN for 1 s30 × IN for 10 s4 × IN continuously (VDE 435, T303)

linear range Low-Range 0.05...2 × INHigh-Range 2...64 × IN

Range setting automatical

Resolution 12 Bit per range

Failure < 0.1 % at IN< 0.1 % at 64 × IN

Accuracy 0.05×IN <2%(related to the measured value) 1×IN <1%

15×IN <2%

Operating time 25-30 msC.T. requirements: recommended min. requirements to expoit device accuracy 5P20

TB MRD1-T 10.01 E 57

Function- and signal inputs

Digital inputs

Thermal withstand capability max. 310 V DC, 265 V ACCoupling galvanically isolated with common return wireHigh-level U > 18 V DC/ACLow-level U < 12 V DC/AC

Reset and blocking input

Thermal withstand capability max. 310 V DC, 265 V ACCoupling galvanically isolated with common return wire (D8)High-level U > 18 V DC/AC function activatedLow-level U < 12 V DC/AC Function not activated

Communication serial interface RS232C

Data transmission rate 9600 BaudConnection 9-pin D-sub plugInsulation voltages DIN 19244 part 3 (IEC 870-3):

RS485

Data transmission rate 9600 BaudConnection plugged terminals

(RXT/TXD-P, RXT/TXD-N, Signal Ground, PE)Insulation voltages DIN 19244 part 3 (IEC 870-3):

Output relay

Contact class IIB DIN VDE 435 part 120max. breaking voltage: 250 VAC / 300 VDCmax. closing power: 1500 VA (250 V)max. breaking power: 11 VA (220 VDC) at L/R = 40 msmax. rating making current: 6 AShort circuit current: 20A / 16 msRated inrush current load: 64AReturning time: 20 ms (without minimum operating time!)Contact material: AgCdOContact life span: electrical: 2x105 switching points at 220V AC / 6A

mechanical: 30x106 switching points

Rated insulation voltage: 600 VAC (450V DC / 380 VAC) (VDE 435, T303)Air- and creeping distance VDE 0160

Insulation coordination: pollution degree 3 for terminals, pollution degree 2 for the electronic

58 TB MRD1-T 10.01 E

Temperature range forOperation: -5°C to +55°C (within class 3K3)Transport: -25°C to +70°C (class 1K4)Storage: -25°C to +70°C (class 2K3)

Insulation test voltage, inputs and outputs between themselves andto the relay frame as per IEC 255-5: 2.0 kV (RMS.) / 50 Hz.; 1 min.

Impulse test voltage, inputs andoutputs between themselves andto the relay frame as per IEC 255-5: 5 kV; 1.2 / 50 µs, 0.5 J

High frequency interference testvoltage, inputs and outputs betweenthemselves and to the relay frame asper IEC 255-22-1: 2.5 kV / 1 MHz

Electrical discharge (ESD)test as per VDE 0843, part 2IEC 77B(CO)21; IEC 255-22-2: 8 kV

Electrical fast transient (Burst)test as per DIN VDE 0843, part 4IEC 77B(CO)22; IEC 255-22-4: 4 kV / 2.5 kHz, 15 ms

Radio interference suppressiontest as per EN 55011: limit value class B

Radiated electromagnetic fieldtest as per ENV 50140: electric field strength: 10 V / m

Power frequency magnetic fieldimmunity test 100 A/m continuousIEC 1000-4-8 (EN 61000-4-8): 1000 A/m 3 s

Surge immunity test(asymmetrical / symmetrical)IEC 1000-4-5 (EN 6100-4-5): 4 kV

Mechanical test:

Shock: Class 1 as per DIN IEC 255 T 21-2Vibration: Class 1 as per DIN IEC 255 T 21-1Degree of protection: Front IP40Overvoltage class: III

Setting ranges: s. tables chapter 5 and 10

GL-Approbation: 99 360-97 HH

TB MRD1-T 10.01 E 59

9 Tables / Connection diagrams

9.1 Possible event messages

Display Event

Parameterset x is selected to active working set

Parameter setting via interface is active

Parameter setting via interface is not permitted

Default parameter settings reloaded

Manual DEVICE RESET is performed

External DEVICE RESET is performed

Software DEVICE RESET is performed

Blocking feature activated by external input

End of blocking

Difference current trip

Difference current trip released

Difference current high-set trip

Difference current high-set trip released

Change output relay state (except Selftest relay)

Selftest relay is energized

Selftest supervision relay is de-energized

Lamp test is finished

Test of the output is finished

Self-test is finished

Offline-Test-Mode is active

Offline-Test-Mode is not active

Fault recorder is cleared

Event recorder is cleared

System start / device initialization

Time/date setting was changed (old time)

Time/date setting was changed (new time)

60 TB MRD1-T 10.01 E

9.2 View

Frontpanel:

Rear panel

Module 3Extension module

Module 2Central module

Module 1Base module

digital inputs

CAN-Bus

RS-485-port

reset- and blocking input

auxiliary voltageandearth connection

measuring inputsB column: W3 (low voltage side)

output Relays

measuring inputsA column: W2 (low / medium voltage side)B column: W1 (high voltage side)

output Relays

2

3

4

5

6

7

8

9

C D E

A B

12

34

5

6

78

F

1

2

3

4

5

6

7

8

9

C D E

A B

12

34

5

6

78

F

1

CAN1

CAN2

12345678910111213141516

SEG MRD1 RWI D

RS485

GND

PEPE

P

N

GNDP

N

TB MRD1-T 10.01 E 61

Fig.: Connection diagram MRD1-T2 (2-winding transformer)

The System W1 is assigned to the high voltage side.

Important Note.For perfect functioning of the rush stabilization system it is essential that the MRD-T is connected in the cor-rect phase sequence, i.e. that there is a positive rotating field. Refer also to page 11.

62 TB MRD1-T 10.01 E

Fig.: Connection diagram MRD1-T3 (3-winding transformer)

The System W1 is assigned to the high voltage side.If the voltages in the systems W2 and W3 are differ-ent, the system W3 must be assigned to the lower voltage level.

Technical data subject to change without notice!

Important Note.For perfect functioning of the rush stabiliza-tion system it is essential that the MRD-T isconnected in the correct phase sequence,i.e. that there is a positive rotating field.Refer also to page 11.

TB MRD1-T 10.01 E 63

10 Type code

Transformer - Differential protection

MRD1- T A2-winding3-winding

23

Rated current primary 1 A5 A

15

secondary 1 A5 A

15

tertiary(for 3-winding)

1 A5 A

15

DC-Auxiliary voltage24 V (19 to 40 V DC).........................................................48V / 60V (38 to 72 V DC)................................................110V / 125V / 220V (88 to 264 V DC)...............................

LMH

Housing (42TE) additional MRD1-T2-HTL-3F42 for T2+G resp. MRD1-T3-HTL-3F42 forT3 available "

" necessary rack for the single components

!NoteNoteNoteNoteNormally the MRD1 is provided with one type of current transformer only (1A or 5A). Equipment with twoCTs of different current ratings in one relay only on request.

64 TB MRD1-T 10.01 E