mrm3-2 proddocspdf_2_273.pdf

8/17/2019 MRM3-2 proddocspdf_2_273.pdf

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MRM3-2 – Motor Protection Relay


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Contents

1 Introduction and Application

2 Characteristics and Features

3 Design 3.1 Connections

3.1.1 Analog Inputs 3.1.2 Output Relays

3.1.3 Digital Inputs 3.1.4 Low/High Range of the Digital Inputs 3.2 Front plate 3.2.1 Indicating LEDs 3.2.2 Adjusting LEDs 3.3 Analog part 3.4 Digital part

4 Working Principle 4.1 Start Recognition

4.1.1 Criteria for Blocking the Start 4.2 Starting time

4.3 Thermal Image 4.4 Requirement on the Main Current

Transformers

5 Operation and Adjustments 5.1 Displayed text for parameter settings 5.2 Setting Procedure 5.3 System parameters 5.3.1 Presentation of Measuring Values as

Primary Quantities on the Display

(Iprim Phase)

5.3.2 Rated-Frequency 5.3.3 Operating Hour Meter (h) 5.3.4 Number of Motor Starts (No.) 5.3.5 Indication of pickup 5.3.6 Parameter Set Changeover Switch (P2) 5.4 Protection Parameters 5.4.1 Thermal Overload Protection (k x IB) 5.4.2 Warning/Tripping with thermal

Overload 5.4.3 Tripping Delay for Thermal Overload 5.4.4 Heating Period Constant τW and

Cooling-Down Time Factor τC 5.4.5 t2x and t6x Minimal Trip Time During

the Starting Process. 5.4.6 Phase Undercurrent Element (I) 5.4.8 Trip Characteristics for the Phase

Overcurrent Element (I>+CHAR) 5.4.9 Tripping Time or Time Factor for the

Phase Overcurrent Element (I>+t>) 5.4.10 Reset Mode for the Trip Characteristics in

the Phase Current Path (I>+CHAR+t>) 5.4.11 Phase Short-Circuit Trip (I>>) and

(I>>+Start)

5.4.12 Negative Phase Sequence 5.4.13 Earth Fault Element (IE>)

5.4.14 Switching Over Warning/Tripping 5.4.15 Trip Characteristics for the Earth-Fault

Element (IE>+CHAR)

5.4.16 Tripping Time or Time Factor for theEarth Fault Element (IE>+t>)

5.4.17 Reset Time for the Earth Fault Element(IE>+CHAR+t>)

5.4.18 Tripping Time for the CB Failure-Protection (CB+t>)

5.4.19 External Trip (delayed) (Trip+t>) 5.4.20 Trip Blocking in case of Excessive Phase

Current (Trip+Block) 5.5 Start Supervision

5.5.1 Duration of a Start Cycle (No.+Start)

5.5.2 Number of Starts per Cycle (No.+Start) 5.5.3 Start Blocking Time (Start+Block+t>) 5.5.4 Characteristic for the Starting Time 5.5.5 Rated starting current I_Start 5.5.6 Maximal Start Time (Start+t>) 5.5.7 Start-up recognition time or Motor

running time 5.5.8 Stopping time 5.6 Interface Parameters 5.6.1 Adjustment of the Slave-Address (RS) 5.6.2 Adjustment of the Baud-Rate

(only for Modbus Protocol) 5.6.3 Adjustment of the Parity

(only for Modbus-Protocol) 5.7 Recorder (FR) 5.7.1 Fault Recorder or Disturbance Recorder 5.7.2 Number of Fault Recordings 5.7.3 Adjustment of the Trigger Event 5.7.4 Pre-Trigger Time (Tvor) 5.8 Setting of the Clock 5.9 Additional Functions 5.9.1 Blocking of the Protective Functions 5.9.2 Allocation of the Reset Functions

5.9.3 Allocation of the Output Relays

5.10 Measuring Value and Fault Indications 5.10.1 Measuring Value Indications 5.10.2 Units of the Displayed Measuring Values- 5.10.3 Indication of the Fault Data 5.10.4 Fault Memory 5.11 Reset 5.11.1 Erasure of the Fault Memory 5.11.2 Reset of the Thermal Memory 5.12 Digital Inputs 5.12.1 Parameter Set Changeover Switch

5.12.2 External Trigger of the Fault Recorder

5.12.3 Recognition of “Motor Running” Condition 5.12.4 Undelayed External Trip 5.12.5 Delayed External Trip


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6 Notes on Relay Tests andCommissioning 6.1 Connection of the auxiliary voltage 6.2 Testing of Output Relays and LEDs 6.3 Test circuit for MRM3-2

6.3.1 Checking of Input Circuits and of theMeasuring Values

6.3.2 Testing the START-STOP-RUNNINGRecognition

6.3.3 Testing the Pick-Up and DisengagingValues

6.3.4 Testing the maximum starting time 6.3.5 Testing the thermal image 6.3.6 Testing the Control Inputs 6.3.7 Testing the CB Failure Protection 6.4 Primary Test 6.5 Maintenance

7 Technical Data 7.1 Measuring input 7.2 Common data 7.3 Setting ranges and steps 7.3.1 System parameter 7.3.2 Time overcurrent protection 7.3.3 Load Unbalance Protection 7.3.4 Earth fault protection 7.3.5 Circuit breaker failure protection 7.3.6 External trip delay 7.3.7 Trip blocking beginning with the

adjusted rated current 7.3.8 Start parameter

7.3.9 Interface parameter 7.3.10 Fault recorder parameter 7.4 Tripping characteristics 7.4.1 Tripping characteristic for max. starting

time 7.4.2 Thermal image 7.4.3 Initial load factor 7.4.4 Tripping of t2x and t6x - times 7.4.5 Inverse time overcurrent protection 7.4.6 Trip characterisitcs 7.4.7 Inverse Time Characteristic for Load

Unbalance7.5 Output relays

8 Order form


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1 Introduction and Application

The motor protection relay MRM3-2 offers reliable pro-tection for LV and MV motors which are either oper-ated via power contactors or power circuit breakers.The following functions are integrated into this relay:

• Overload protection acc. to IEC 255-8 in consid-eration of the initial load factor (thermal image)

• Definite undercurrent protection• Definite time overcurrent protection (DMT)• Inverse time overcurrent protection (IMT) with select-

able trip characteristics• Short-circuit protection• Load unbalance supervision with definite or inverse

trip characteristics• Earth-fault detection with suppression of harmonics

The MRM3-2 recognises the “Start-Up“ and “MotorRunning“ phase.

Motors with a limited number of starts can be con-trolled by the start limiting function of the relay.

The earth-fault supervision is either realised in Holm-green connection or by means of a core-type currenttransformer.

The motor can be stopped in delayed or undelayedmode via digital inputs.

The MRM3-2 is available with rated currents of 1A or5A.

Important:For additional common data of all MR -relays pleaserefer to manual "MR - Digital Multifunctional relays".On page 45 of this manual you can find the validsoftware versions.

2 Characteristics and Features

• Microprocessor technology with self-supervision,• Measuring of phase currents as RMS value,• Digital filtering of the earth current with discrete Fou-

rier analysis, by which the influence of interference

signals, such as harmonics and transient DC com-ponents during an earth-fault are suppressed.• Two sets of parameters,• Operating hour meter,• Complies with the requirements of IEC 255-8,

VDE435, part 301-1 for overload relays,• Definite time undercurrent protection,• Selectable protective functions : Definite time over-

current protection (DMT) and inverse time overcurrentprotection (IMT)

• Selectable IMT trip characteristics of IEC 255-4:Normal inverse (Type A)

Very inverse (Type B)Extremely inverse (Type C)Special-purpose characteristics

• Reset mode for DMT/IMT trip characteristics is se-lectable,

• Definite element for short-circuit high-speed trip• Single-step earth fault supervision,• Load unbalance protection with inverse or definite

trip characteristics (NPS),• CB failure protection,• Display of the measuring values as primary quanti-

ties,• Measuring of the phase currents during short-circuitfree operation,

• Blocking of the individual protective elements or thetrip elements can be set freely,

• The protective functions can be freely allocated tothe output relays. (Relay Matrix),

• Suppression of an LED indication after activation(LED flash),

• „Manual/Automatic“ reset function of the trip ele-ments adjustable via the configuration matrix,

• Saving of trip values and the switch-off times (tCBFP) of

25 fault events (voltage fail-safe)• Recording of up to 8 fault events with time stamp,• Display of date and time,• Trip via digital inputs,• Rack mounting, with self-acting short-circuit mecha-

nism for CT circuits,• Possibility of serial data exchange via the RS485 in-

terface, optionally with SEG RS485 Pro-Open-DataProtocol or Modbus Protocol.


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3 Design

3.1 Connections

Figure 3.1: Connection Diagram MRM3-2

P1

P2

S1

S2

P1

P2

S1

S2

P1

P2

S1

S2

I1

I2

I3

IE

L1.1B3

B4 L1.2

L2.1B5

L2.2B6

L3.1B7

L3.2B8 B1

B2

L1

L2L3

Figure 3.2: Measuring of phase currents and earth current detectionin Holmgreen connection (IE)

This kind of connection can be used where threephase CTs are available and a combination of phaseand earth current measuring is required.

Figure 3.3: Measuring of earth current with core-type CT (IE)

With the combination of phase and earth currentmeasuring, CTs to be connected according to Figure

3.2. and Figure 3.3.


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3.1.1 Analog Inputs

The analog input signals of the phase currents IL1 (B3 -B4), IL2 (B5 - B6), IL3 (B7 - B8) and the earth current IE (B1 - B2) are fed to the protection device via separateinput CTs.The current measuring quantities are galvanical de-

coupled, analogously filtered, and then fed to the ana-log/digital converter.

3.1.2 Output Relays

The MRM3-2 has 5 output relays. Two of these relayswith two change-over contacts and three relays withone change-over contact each are used for signalling.The protective functions can be freely allocated exceptof those for the self-supervision relay.

• Relay 1: C1, D1, E1 and C2, D2, E2• Relay 2: C3, D3, E3 and C4, D4, E4• Relay 3: C5, D5, E5• Relay 4: C6, D6, E6• Relay 5: Self-supervision C7, D7, E7

All relays are operating according to the n. o. princi-ple with the exception of the self-supervision relay,which operates acc. to the n. c. principle.

3.1.3 Digital Inputs

The MRM3-2 has 7 digital inputs with fixed functions.All inputs have a common reference point : TerminalD8. (See Chapter 3.1)

No Terminal Function CodingPlug

1 C8 External reset 22 E8 External blocking 13 A2 Parameter set change-

over switch

3

4 A5 External trigger for thefault recorder

4

5 A6 Identification „MotorRunning“

7

6 A7 Ext. trigger, undelayed 67 A8 Ext. trigger, delayed 5

3.1.4 Low/High Range of the DigitalInputs

The MRM3-2 is equipped with a wide-range powersupply unit and hence the supply voltage is freely se-lectable. The switching threshold of the digital inputs,however, has to be fixed in compliance with the sup-

ply voltage. Two different switching thresholds can beadjusted:

Range Plug U not active U active Low Plugged in = 10VHigh Open = 80V

Figure 3.4: Coding Plug


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3.2 Front plate

Figure 3.5 : Front plate MRM3-2-IE

Figure 3.6: Front plate MRM3-2-I

The LEDs ϑ, h, RS and FR on the MRM3-2 emit a yel-low light, all other LEDs are bi-coloured. The LEDs atthe left next to the alphanumerical display give agreen light during measuring and a red one when afault signal occurs.

The LEDs underneath the - push but-ton emit a green light during adjustment and inquiry ofthe setting quantities left to the LEDs. They show a redlight if the printed setting quantities right to the LEDsare activated.

3.2.1 Indicating LEDs

L1, L2, L3 Indication of the phase currents

E Indication of the earth currentI2 Indication of the unbalanced loadcurrent (NPS)

ϑ Indication of the temperature equivalenth Operating hour meter

! Date and time

3.2.2 Adjusting LEDs

IB> Rated motor currentK Constant quantity (k*IB = 100%

thermal load)τW Heating period constantτC Cooling down factort> Tripping times, generallyϑ> Switching threshold of the thermal

overload alarmNo. Number of motor startsCHAR Characteristics settingI< Undercurrent settingI> Overcurrent settingI2> Load unbalance setting (NPS)

I>> Short-circuit settingIE> Earth current settingCB CB failure protectionBlock Start blocking/Protective blocking0 Current>0/


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3.3 Analog part

The alternating currents injected by the CTs are con-verted into galvanical isolated voltages via inputtransmitters and burden in the analog part.The effect of inductive and capacitive coupled interfer-ences are suppressed by RC analog filters. The meas-

uring voltages are fed to the analog inputs (A/D trans-former) of the micro-processor and then converted intodigital signals by means of sample and hold circuits.These digitised values are then used for further proc-essing. The measuring values are acquired at fn = 50Hz (fn = 60 Hz) with a sampling frequency of 800 Hz(960 Hz), and thus the instantaneous values of themeasured quantities are acquired every 1.25 ms(1.04 ms).

3.4 Digital part

The protection relay is equipped with a powerful mi-cro-controller, being the core element of the protectionunit. With this micro-controller all tasks are completelydigitally processed, from discretisation of the measur-ing quantities to protective tripping.

With the protection program, stored in the programstorage (EPROM), the micro-processor processes thevoltages applied to the analog inputs and from thiscalculates the fundamental harmonics of the current.Digital filtering (DFFT-Discrete Fast-Fourier-Transforma-

tion) for suppression of harmonics as well as suppres-sion of DC components during the short-circuit is usedin the process.The micro-processor compares the existing current withthe threshold value (setting value) stored in the parame-ter storage (EEPROM) and up-dates the thermal image.If a current exceeds the threshold value for longer thanthe trip delay or if the thermal image exceeds its ratedvalue, a fault signal occurs. Dependent on their set-tings, the output relays pick up as well. When settingthe parameters, all setting values are read-in by the

micro-processor and saved in the parameter storage.

The program flow is continuously monitored by the in-corporated "Hardware-Watchdog". Processor failure issignalled by the “Selfsupervision” output relay.

Figure 3.7: Block Diagram of Protective Functions


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4 Working Principle

4.1 Start Recognition

The MRM3-2 monitors the flow of the current fromwhich the following operational conditions of the mo-

tor are gathered.• STOP• START• RUNNING

Figure 4.1: Different Start-Up Behaviour of Motors

STOP - Condition:If no current can be measured (I < Stop threshold),

STOP conditions are recognised after expiration of thestop time.

Start/Stop ThresholdThis threshold is fixed at 2% of IN

Stop time:The Stop time is adjustable in order to toleratea brief off-time of the current flow (e.g. change-over Star/Delta) from the START or RUNNINGconditions. STOP is only indicated if the currentwas under 2% IN for longer than the stop time.

Based on this time the running down periodcan be considered in a certain way for the LEDindication.

START -Condition:START is only recognised if the previous condition was

STOP and the motor current has exceeded the startthreshold. If the STOP or RUNNING conditions arerecognised, the START condition is terminated.

Overload Threshold:This corresponds to the permissible thermal con-tinuous current k x IB and is adjusted by the pa-rameter of the thermal image.

Starter Recognition Time:This adjustable time has only to be extended for

special start procedures in order to prevent thatthe RUNNING conditions are indicated tooearly in advance.


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• No exceeding of the start threshold during pony mo-tor start-up or when soft starters are used.

• Multistage resistance start where the start threshold iseither exceeded several times or not at all.

The time is running from the instance the start thresholdis exceeded. RUNNING is only accepted by the su-pervision after the time has elapsed or the overloadthreshold is undershot. If the overload threshold is not aclear criterion, the time has to be set at least for solong that the longest regular start procedure is cov-ered.

RUNNING can be recognised in different ways:• If the START has been successfully completed. This

is the case when the motor current has droppedbelow k x IB and the start recognition time haselapsed. (direct start)

or

• if the motor is connected across several resistancesteps, it is possible that the start threshold ispassed through repeatedly. RUNNING conditionsare recognised when the start recognition time hasrun out after the last step and a current has settledbetween 2% IN and k x IB t.

(Resistance start).• if after STOP a motor current has settled between

2% IN and k x IB and the start recognition timehas elapsed. The overload threshold has not nec-essarily to be exceeded.(soft start)

• If the «Motor Running» input was activated but theoverload threshold is not (or not any longer) ex-ceeded. (See Chapter 5.12.3 )

With the recognition of STOP, the RUNNING condi-tions have ceased to exist.

Figure 4.2: Flow Diagram of the Start Conditions

4.1.1 Criteria for Blocking the Start

Number of monitored starts :

The MRM3-2 is equipped with a flexible supervisionelement which can limit the sequence of possiblestarts.

A start should be prevented if it is obvious that it islikely to be interrupted due to overload so that in totalthe down-time can be curtailed. If a start is not rec-ommendable at a certain time (with the motorswitched off), the MRM3-2 activates an allocated out-put relay until the waiting time has elapsed. Irrespec-tively of the adjustment of this element, the thermal im-age is always activated and shuts the motor down assoon as the thermal overload threshold is reached (dueto a start or overload).

The protective element can either be tied to the thermal

image or be manually defined by the number of startsand cycle duration.


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Number of Starts/Cycle DurationThese two are defined as parameters.

Example:The motor should be allowed to be started three timesan hour:This means that in theory the motor can be started

every 20 minutes (= 60 min/3).From this it can be concluded that the load generatedby the start procedure has decayed after these 20minutes. If the motor would be successfully startedthree time in quick succession, an immediate fourthstart would overload the motor. The start blocking re-lay would be activated and the next start would onlybe advisable after about 20 minutes. The protectiveelement ensures that the start sequence is kept withinsafe intervals but that at least three starts are allowedduring the given time frame. If the intervals between

each start are long enough then even more than threestarts an hour might be possible because the motorwas able to cool down in the mean time. The delaycan be firmly defined (through start blocking time) orbe automatically ascertained (VARI ) until the 20 min-utes given in the example are over. The state of thethermal image has no influence on the delay.

Figure 4.3: Relation Start Period/Start Blocking Time

Figure 4.4: Relation Start Period/Start Blocking Time withfirm Start Blocking Time

Thermal ImageA start is always possible as long as there is enoughthermal reserve for a start. This start limitation is a dy-namic one and is orientated on the data the thermalimage is parameterised with. For this the MRM3-2 de-tects the average thermal load of the latest starts. Withthe motor shut down, the start blocking relay is acti-vated for the time when there is not enough thermal re-serve in the storage through cooling down to enable a

new start.

Figure 4.5: Start Blocking through Thermal Image


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4.2 Starting time

With certain applications it is possible that the startingphase of the engines is extended. One reason for thisinsufficient terminal voltage which may be caused bythe high starting current or by a high grid load in gen-eral. When starting under load, the starting phases

must not be too long because this could overheat themotor.For these applications the MRM3-2 offers a variablemaximum starting time. It refers to the rated startingcurrent of the motor I_Start. If the actual starting current(e.g. at 80% UN) is lower than the rated starting cur-rent, the starting time is extended automatically.

Q = I² x ts

The supplied heat energy is equal to the square value

of the current times the starting time. If the starting cur-rent decreases, the starting time can be extended. Thistime can be extended by a maximum of twice the setvalue. If the actual starting current is higher than itsrated value, the max. starting time decreases (refer toFig. 7).

4.3 Thermal Image

The fed thermal energy Q and the temperature ϑ ofthe motor when in steady state condition is propor-

tional to the square of the phase current (e.g. ohmiclosses and iron losses):

Q ∼ I² oder ϑ ∼ I²

In the thermal image this temperature is described bythe temperature equivalent ϑ (in %). For loading withthe maximal permissible operational current k x IB , themotor reaches the maximal permissible temperature ϑB.if it has been in steady state condition for a certaintime. For this load the thermal equivalent is defined to100% = trip threshold:

Stationary final value:

%100*)I(k

=(%)2

B

2I⋅

ϑ

Note:When testing the thermal image it has to be taken intoconsideration that in case k x IB is slightly exceeded(= long tripping time), a small current change withinthe permissible measuring tolerances can cause a highdispersion of the tripping time (clearly by more than1%). This is related to the slope of the trip characteris-

tic. Furthermore it is important to start from the same ini-tial level of the image when testing. Otherwise thetripping times may be shorter than expected.

Automatic Reset During the starting process the MRM3-2 observes therise of the thermal image. From the average of the lasttwo successful starts the unit detects the start load. Afteroverload conditions, the thermal image is only re-leased when the motor has cooled down far enoughto deal with the demand of a new start.

4.4 Requirement on the Main CurrentTransformers

The CTs chosen have a considerable influence on theaccuracy of the protective system. In order to select theright type of transformer, the requirements and condi-tions on site have to be considered carefully.

Type of TransformerCurrent transformers have to be designed as protection

transformers (P).

Overcurrent Factor:To ensure precise operation of the protection unit evenunder full short-circuit current, the chosen transformersmust not saturate in this current range. This means thatthe overload factor must be sufficiently large.

ClassFor the nominal range or the lower load range it hasto be taken into account that not only the basic accu-racy of the MRM3-2 has to be considered but also thetransformer accuracy. This applies especially for caseswhere the Holmgreen circuit is used and for low earthfault currents in isolated networks.

Power RatingThe transformer must be rated sufficiently to cover allmeasuring instruments and protective devices con-nected as well as the losses on the transformer measur-ing line without becoming overloaded.


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5 Operation and Adjustments

5.1 Displayed text for parametersettings

Function Displayed Text Related LED References

Normal operationSEGExceeding the measuring range max. ϑ

Sec. transf. currents indication SEK L1, L2, L3,E

Chap. 5.3.1

Rated frequency f = 50 / f = 60 Chap. 5.3.2LED flashing after activation FLSH/NOFL Chap. 5.3.5Parameter set change-over switch SET1, SET2, P2 Chap. 5.3.6Blocking of a function EXIT LED of the blocked

parameterCharacteristics phase current DEFT,NINV, VINV, EINV,

LINV, RINV,CHAR + I> Chap. 5.4.8

Characteristics earth current DEFT, NINV, VINV, EINV,LINV, RINV, RXIDG

CHAR + IE>> Chap. 5.4.15

Characteristics DEFT, INVS CHAR + I2> Chap. 5.4.12Reset mode 0s / 60s CHAR + I> + t>

CHAR + I2> + t>CHAR + IE> + t>

Chap. 5.4.10

Chap. 5.4.17Start blocking by thermal supervision AUTO Start + No Chap. 5.5.1Auto. definition of the remainingblocking time

VARI Start + block + t> Chap. 5.5.3

CB failure protection CBFP CB + t> Chap. 5.4.18Inquiry of the fault memory FLT1, FLT2..... Trip = type dependent Chap. 5.10.3Erase fault memory wait Chap. 5.10.4Relay tripped TRIP Trip = type dependentReset the system SEG

Password inquiry PSW? LED of the set parameterHidden password „XXXX“ Chap. 5.2Parameter to be saved? SAV?Save parameter ! SAV!Manual trip TRI?Blocking of the protec. function BLOC, NO_B, PR_B, TR_B LED of the set parameterRelay assignment z. B. _ 2 _ _ LED of the set parameterTrip signal for the fault recorder P_UP; A_PI; TRIP; TEST FR Chap. 5.7.3Number of fault events S = 2, S = 4, S = 8 FR Chap. 5.7.2Indication of date and time Y = 01, M = 01, D = 04,

h = 12, m = 2, s = 12! Chap. 5.8

Slave address of the serial interface 1-32 RS Chap. 5.6.1

Baud-Rate

1)

1200-9600 RS Chap. 5.6.2Parity-Check 1) even odd no RS Chap. 5.6.3

Table 5.1: Indication Possibilities via the Display

1) Modbus only


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5.2 Setting Procedure

short advancing the indicationlong reset

Saving of an entry

Before parameters can be set a password is inquired(see chapter 4.4 of descrip. ”MR – Digital Multifunc-tion Relay”).

5.3 System parameters

5.3.1 Presentation of Measuring Values asPrimary Quantities on the Display

(Iprim Phase)

This parameter makes it possible to present the indica-tions of phase current and earth-fault current sepa-rately, i.e as primary or secondary measuring value.Currents in the kiloampere range are indicated withthe symbol of unit of measurement k (kilo) as three-digitpoint.

Example:A 1500/5 A CT is used with a primary current of1380 A. The parameter for the CT primary current is

given in kiloampere.

• The parameter is set to ”1.50“ (kA). Then ”1K38“is displayed as I-measurement.

• If the setting is set to ”sec.“, ”0.92“ x IN. is dis-played as I-measurement.

Note:The settings for the pick-up value are adjusted to a mul-tiple of the secondary rated CT current.The settings for phase and earth current transformerscan be done separately.

5.3.2 Rated -Frequency

The FFT-Algorithm used for the data acquisition needsthe set point of the rated frequency, i.e. 50 Hz or60 Hz, for correct digital filtering of the earth current.

5.3.3 Operating Hour Meter (h)

As soon as the conditions START or RUNNING havebeen recognised, the operating hour meter starts. Themeter can also be preset. Years and hours are shownin two windows. After every 8760 h the value is car-ried over to the window ”Year”.

In the display the years are marked with the letter “Y”(engl.: year)

5.3.4 Number of Motor Starts (No.)

Every start is counted, even unsuccessful ones. Thenumber of motor starts can be preset.

5.3.5 Indication of pickup

If the momentary current drops below the pickupthreshold, e.g. I>, after the relay was activated andthere was no tripping, then the activation is signalledby short flashing of LED I>. The LED keeps flashing untilthe push-button is pressed. By setting the pa-rameter to FLSH/NOFL, flashing can be suppressed.

5.3.6 Parameter Set Changeover Switch (P2)

By means of this switch two different parameter sets

can be activated. The changeover procedure can berealised either by the software or via the digital input(A2). If the parameter set changeover switch is ad-justed to ”SET2“, the active parameter set can bechanged to ”SET1“ via the external input. If thechangeover switch is set to ”SET1“, then it can bechanged to ”SET2“ via the digital input.The LED P2 on the front cover always indicates whichof the parameter sets is active. Furthermore it is possi-ble to indicate via an assigned output relay that pa-rameter set 2 is active.

During the setting procedure the LED P2 gives off a yel-low light.


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5.4 Protection Parameters

5.4.1 Thermal Overload Protection (k x IB)

With the product of setting values k x IB the continu-ously permissible maximal current of the motor is ad-justed. At this current the thermal image reaches

100 % after a long period – i.e. the trip threshold.With IB normally the rated current of the motor is ad-justed and with k an overload factor (e.g. 1.05)It is also possible to adjust the maximal continuous cur-rent directly, if k = 1 was selected.

5.4.2 Warning/Tripping with thermalOverload

Sometimes it is necessary that the thermal protectionbeyond the 100 % limit does not lead to shut-down(e.g. fire extinguisher pump). For this reason it is pos-sible to differentiate between tripping and warning. Incase of the warning function the display does notshow "TRIP". The relay assigned to this step respondsand should therefore be configured onto a different re-lay than the one leading to tripping.

5.4.3 Tripping Delay for ThermalOverload

The starting current of motors is normally many timeshigher than the rated current. In that case the thresholdfor recording the thermal overload k*IB> is exceeded.The warning relay responds and the LEDs signal exci-tation. Excitation signalling remains active beyond thestarting phase as well. Since starting of the motor is anormal process and not a malfunction, it is possible atthis point to delay detection of the excitation for ther-mal overload. If the motor is overloaded often and thisis permissible for a short period (e.g. breakers) it mayalso make sense to operate this overload with delayaction. This delay is also effective in motor

OPERATING mode and has no effect on the trippingbehaviour of the MRM3-2 .

Note:In this case, the signalling of the LED fulfills a specialfunction: The excitation is always indicated without de-lay. If the excitation limit value is under-run within thedelay time, there will be no “flash” function (seechapter 5.3.5).

5.4.4 Heating Period Constant !!!! W andCooling-Down Time Factor !!!!C

With this time constant the thermal image is adaptedto the heating behaviour of the motor. It is the timeconstant of an e-function.

Normally the motor is cooling down with a slowertime constant. Parameter !C is to be understood as afactor. The cooling-down behaviour in the thermalmodel proceeds with the time constant !C x !W. If!C = 1 is selected, then heating and cooling-downproceed at an identical speed in the thermal image.

5.4.5 t2x and t6x Minimal Trip TimeDuring the Starting Process.

With this parameter the fastest trip time during the start-up phase is limited for the thermal image. If the se-lected pick-up value k x IB is exceeded by two timesor six times, the characteristic breaks to definite time.This prevents that a higher start current causes thethermal image to overflow at the first instant. Normallysix times the value is selected. If not desired, the char-acteristic can be operated without breaking by settingEXIT.

5.4.6 Phase Undercurrent Element (I


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5.4.7 Phase Overcurrent Element (I>)

When adjusting the pick-up value for the phase over-current element I>, an indicating value, referring to thesecondary rated current IN , is displayed. This elementis only active during mode RUNNING.

5.4.8 Trip Characteristics for the PhaseOvercurrent Element (I>+CHAR)

There are the following standard trip time characteris-tics available (see 7.4.6:

DEFT - Definite Time (definite timeovercurrent protection)

NINV - Normal inverseVINV - Very inverseEINV - Extremely inverse

RINV - RI-InverseLINV - Long term Inverse

5.4.9 Tripping Time or Time Factor for thePhase Overcurrent Element (I>+t>)

Normally, after change of the trip characteristics, thetripping time or the time factor also has to be changedaccordingly. In order to avoid an unsuitable combina-tion between trip characteristics and tripping time or

time factor, the following measures are initiated by theMRM3-2 ::::The LED for adjustment of the tripping time or time fac-tor (I> + t>) starts to flash after the trip characteristicshave changed. By this warning signal the operator isreminded to adjust the tripping time or time factor tothe changed operational mode or trip time characteris-tics. This warning signal keeps flashing until the trip-ping time or time factor are re-adjusted. If re-adjust-ment has not been done within 5 minutes (the time toenable parameter setting), then the processor sets thetripping time or time factor to the highest sensible

value (smallest possible tripping time ).

When adjusting to the “Definite Time” trip characteris-tic, the definite tripping time displayed is shown asseconds (e.g. 0.35 = 0.35s). By pressing push-buttons this time can be changed step by stepin the range 0.04s – 260s

When adjusting to the “Inverse Time” trip characteris-tics, the time factor (tI>) is displayed. This factor canbe changed also by push buttons step by stepin the range 0.05 – 20.0.

If the tripping time or time factor are set to infinite long(on the display “EXIT” is shown) then trip of the relayovercurrent element is blocked. TheWARNING/ALARM function is still active. During thistime LEDs I> and t> are red.

5.4.10 Reset Mode for the Trip Characteris-tics in the Phase Current Path(I>+CHAR+t>)

In order to ensure that the trip function is reliable evenwith repeated error pulses, each of them shorter thanthe set tripping time, the RESET mode for the trip char-acteristics can be changed over. With a setting of“60s“ the elapsed tripping time is frozen and is only

reset after 60s faultless operation. Should another faultoccur within these 60s, the tripping time counter re-mains in operation. With the setting “_ 0s“ the counteris immediately reset when the fault current is inter-rupted and it is restarted when the fault current has re-turned again.

5.4.11 Phase Short-Circuit Trip (I>>) and(I>>+Start)

The short-circuit element has two threshold values and

two time delays. The first threshold value applies forthe mode RUNNING and the second one for modeSTART.Possible variations are:• During the start procedure the existing inrush cur-

rent can be higher than the desired short-circuitthreshold during operation. e.g. direct start)

• It is also possible that the slip rings are put at riskespecially during the start procedure so that forSTART a more sensitive adjustment is required thanfor RUNNING.

• Both elements can be set to the same value sothere is no differentiation.

If it is set to EXIT then the respective element isswitched off.

Irrespectively of the selected trip characteristics for I>,the short-circuit high-speed trip element I>> has a trip-ping time which does not depend on the current. Thistime applies for both elements I>>START and I>>RUNNING.


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5.4.12 Negative Phase Sequence

Load unbalance can, for example, be caused by aphase failure or fault in a one motor winding.

Load unbalances give rise to negative phase sequencecurrents in the stator, causing odd harmonics in the sta-

tor winding and even harmonics in the rotor winding.

Especially the rotor is endangered by this becauseasymmetric conditions mean additional thermal stressfor the rotor winding and eddy currents are induced inthe solid iron of the rotor which can cause destructionof the metal structure or even melting of the metal.

Within certain limits and by observing the ultimatethermal strength of the motor, load unbalance is per-missible, though. The details given by the motor manu-

facturer mostly refer to the negative phase sequencesystem and thus can be programmed directly.

According to the method of “Symmetric Components“,a rotating three-phase system can be sectionalised intoa positive phase sequence system, negative phase se-quence system and a zero phase sequence system.The current in the negative phase sequence system isthe measure for the load unbalance quantity. The ef-fective value of the current of the negative phase se-quence system I2 is calculated by the MRM3-2 .

When setting the threshold value for the load unbal-ance current I2> , the indicated value referring to therated current (IN). is displayed.

When adjusting the trip characteristics either « DEFT »for “definite” trip characteristics is shown on the dis-play or « INVS » for “inverse” trip characteristics. (seechapter 7.4.7)

5.4.13 Earth Fault Element (IE>)

The setting procedure outlined in chapter 5.4.5 ap-plies here as well. The required value in the 0.01 x IN – 2.00 x IN range can be set with push-buttons and .

5.4.14 Switching Over Warning/Tripping

An earth fault can be parameterised as follows. Afterthe delay time has expireda) the warning relay responds (warning)

b) the tripping relay responds (tripping)The tripping values are stored in the fault recorder.

5.4.15 Trip Characteristics for the Earth-Fault Element (IE>+CHAR)

When adjusting the trip characteristics one of the fol-lowing 7 abbreviations is displayed:DEFT - Definite Time (definite time over-

current protection)NINV - Normal inverse (Type A)VINV - Very inverse (Type B)EINV - Extremely inverse (Type C)RINV - RI-InverseLINV - Long-term inverseRXID - Special purpose characteristics

The displayed text can be changed by push-buttons . By pressing the required tripcharacteristics is selected. The allocated LED IE> is red,the LED CHAR green.

5.4.16 Tripping Time or Time Factor forthe Earth Fault Element (IE>+t>)

The setting procedure outlined in chapter 5.4.9 ap-plies here as well.

5.4.17 Reset Time for the Earth FaultElement (IE>+CHAR+t>)

The setting procedure outlined in chapter 5.4.10 ap-plies here as well.

5.4.18 Tripping Time for the CB Failure-Protection (CB+t>)

This protection is activated after a protective trip and itmonitors if all phase currents have dropped within theset time tCBFP to )

Via the digital input A8/D8 an external trip with timedelay can be activated. Trip is initiated if the


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5.4.20 Trip Blocking in case of ExcessivePhase Current (Trip+Block)

This function is important where power contactors areused and they are not designed to disconnect highshort-circuit currents. In such a case no function of theMRM3-2 must initiate tripping. The trip function is thenallocated to a preceding protective element (e.g.fuse).Trip blocking is activated as soon as the set current isexceeded. When this threshold is undershot, all func-tion are released again.

If the circuit breakers used are able to disconnect theshort-circuit current to be expected, the function is setto EXIT.

5.5 Start Supervision

The MRM3-2 can offer two start supervision methods:• Automatically by means of the thermal load• By a limited number of starts per time interval

5.5.1 Duration of a Start Cycle (No.+Start)

AUTOIf this mode is selected, a start is always possible if suf-ficient start reserves are available according to the

thermal image. This function operates dynamically onthe data of the previous starts (see chapter 4.1.1).

Time AdjustmentBy this the interval of the permissible number of starts istimed.The number is defined in the next parameter.

EXITThe element is de-energised.

5.5.2 Number of Starts per Cycle(No.+Start)

This parameter is only visible if a time was selectedwith the preceding parameter which defines the num-ber of permissible starts during the respective interval.

5.5.3 Start Blocking Time (Start+Block+t>)

This parameter is only visible if a time was selected(chapter 5.5.1). It defines the time for a new start

when the number of starts per interval was exceeded.The following is possible:

VARIA new start is possible after the remaining time of theinterval has run down.

Time Adjustment (s):Restarts are blocked for the adjusted time.

5.5.4 Characteristic for the Starting Time

In some motor applications it may happen that thesupply voltage is lower than the rated value. Lowerrated values have lower starting currents and conse-quently longer starting times. The starting time can beextended by selecting a characteristic. The setting"DEFT" means that a maximum starting time is fixed.The subsequent parameter "Rated starting current" isnot active. The setting "INVS" means that the maximumstarting time is variable. It is determined by the ratedstarting current and the permissible starting time atrated voltage (refer to Chapter 7.4.1).

5.5.5 Rated starting current I_Start

The basis for calculating the maximum starting time isthe rated starting current I_Start of the motor at ratedvoltage.

5.5.6 Maximal Start Time (Start+t>)

Exceedingly long acceleration can only be recognisedif the threshold k*IB is once overshot after the STOPthreshold was exceeded.

With the setting "DEFT" The time meter for the max. start time is activated uponexceeding of the threshold k*IB>. If the set time haselapsed and the current lies (still or again) above theSTART threshold, the start procedure is stopped. Whenmode RUNNING is recognised, this element is de-activated until the next start attempt.

With the setting "INVS"If the characteristic is selected for the maximum startingtime, this parameter is valued as rated startingtime/time multiplier ts and multiplied by the calculatedtripping time.Example: If the starting current is lower than the ratedstarting current by the factor 0.707, the maximumstarting time is doubled (refer to Chapter 7.4.1).


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5.5.7 Start-up recognition time or MotorRunning time

The start-up recognition time is a criterion for switchingover to OPERATION. The MRM3-e recognises the op-erating mode if the threshold IB*K> is fallen short ofand the start-up recognition time has expired. (refer toChap. 4.1)

5.5.8 Stopping time

A motor is considered to be stopped if the measuredcurrent has fallen short of the value


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trigger occurence

recording duration

Tpre

[s]

Figure 5.2: General Set-Up of the Fault Recorder

Each of the storage segments have a fixed storagetime where the time before the trigger event can bedefined.

Via the RS485 interface the data can be read out bymeans of a PC provided with HTL/PL-Soft4. The datais graphically edited and represented. Binary tracksare recorded additionally, e.g. activation and trip.

5.7.2 Number of Fault Recordings

The max. recording time is 16 s at 50 Hz or 13.33 sat 60 Hz.The max. number of recordings to be stored has to bedefined beforehand. There is the choice between (1)*2, (3)* 4 and (7)* 8 recordings. Hence the existingmemory space can be used as follows:

(1)* 2 recordings for 8 s at 50 Hz and 6.66 s at60 Hz.(3)* 4 recordings for 4 s at 50 Hz and 3.33 s at60 Hz.(7)* 8 recordings for 2 s at 50 Hz and 1.66 s at60 Hz.* will be overwritten when a new trigger signal oc-curs.

5.7.3 Adjustment of the Trigger Event

There is the choice between four different triggerevents:

P_UP (PickUP) Data saving begins when a generalactivation is recognised.

TRIP Data saving begins when a generaltrip is recognised.

A_PI (After Pickup) Data saving begins when the last acti-vation threshold is undershot (recog-nises, for instance, CB failure protec-tion)

TEST Data saving is activated when push-buttons and are pressedsimultaneously (immediately uponpressing the buttons). For recordingtime, the mode TEST is displayed.

5.7.4 Pre-Trigger Time (T vor)

The time Tpre defines the period to be saved prior to thetrip event. This time can be set between 0.05 s andthe max. recording time (2, 4 or 8 s). With push-buttons and the values can be changed andwith they can be saved.

5.8 Setting of the Clock

When date and time are set, the LED „!“ is on. Thefollowing method is used:

Date: year Y=00month M=00day D=00

time: hour h=00minute m=00second s=00

Immediately when the supply voltage is applied theclock starts with the respective date and time. The timeis buffered against short-term voltage failures (min. 6minutes).

Note:The window for setting the clock is behind the measur-ing value reading. Access to the window via push-button .


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5.9 Additional Functions

5.9.1 Blocking of the Protective Functions

Blocking of the protective functions

After voltage has been applied to blocking input

D8/E8, the intended reaction for each of the protec-tive functions can be defined individually. (Observevoltage adjustment !) See chapter 3.1.4

Setting Effect when voltage has been appliedto the blocking input

PR_B Complete blocking of the protective ele-ment. Activation and trip are suppressed.

TR_B Blocking of trip elements.The individual protective elements areactivated and this is signalled accord-ingly, but there is no tripping.

BLOC Complete blocking of the protective ele-ment. Activation and tripping are sup-pressed. This is displayed if it is not dif-ferentiated between PR_B and TR_B in aparameter.

NO_B No blocking.This element operates normal, it is notblocked

Table 5.3: Adjustment Possibilities

Setting of parameters should be done as follows:

• To come to the blocking menu push-buttons and are to be pressed at thesame time. The function being set is indicated byLEDs.

• If necessary the blocking function can be changedwith or and saved with Perhaps a password has to be entered.

• Proceed to the next function with

• After selection of the last blocking function settingsfor the 2nd parameter set can follow.

• For allocating the RESET function press push-button

again. (See next chapter).

Symbol Protective Function DefaultSetting

Possible Settings LED/Colour

ϑ> Overload warning element NO_B NO_B ; BLOC ϑ> redIB> x k Overload element NO_B NO_B ; PR_B ; TR_B IB> green/τW green I< Undercurrent element NO_B NO_B ; PR_B ; TR_B I< redI> Overcurrent element NO_B NO_B ; PR_B ; TR_B I> redI>> Start Short-circuit element at start-up BLOC NO_B ; PR_B I>> red/Start greenI>> Short-circuit element during operation PR_B NO_B ; PR_B ; TR_B I>> redI2> Load unbalance element NO_B NO_B ; PR_B ; TR_B I2> redIE> Earth current element NO_B NO_B ; PR_B ; TR_B IE> red

tCBFP CB failure protection NO_B NO_B ; BLOC CB greenTrip External trip NO_B NO_B ; BLOC Trip red

Table 5.4: Default Setting of the Blocking Functions


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5.9.2 Allocation of the Reset Functions

When setting of the parameters for the blocking func-tion is completed you are in the allocation mode forthe reset functions. Whether the assigned relay shouldbe reset manually or automatically after activation ortrip can be allocated to each of the activation or trip

elements. Which of the reset function

• If necessary the reset function can be changedwith or and saved with Perhaps a password has to be entered.

• Proceed to the next function with

• After selection of the last reset function settings forthe 2nd parameter set can follow.

• For allocation of the output relays press push-button again. (See next chap-

ter).

Symbol Protective Functions DefaultSetting

Possible Settings LED/Colour

ϑ> Overload warning AUTO HAND ; AUTO ϑ> redIB> x k Overload alarm AUTO HAND ; AUTO IB> greenIB> x k Overload trip AUTO HAND ; AUTO IB> green/τW greenI< Undercurrent alarm AUTO HAND ; AUTO I< redtI< Undercurrent trip AUTO HAND ; AUTO I< red/t> redI> Overcurrent alarm AUTO HAND ; AUTO I> redtI> Overcurrent trip AUTO HAND ; AUTO I> red/t> red

I>> Start Short-circuit tripping whenstarting* AUTO HAND ; AUTO I>> rot/t> rot/Start greenI>> Start Short-circuit tripping during oper. AUTO HAND ; AUTO I>>redtI>> Start/op. Short-circuit tripping during oper. AUTO HAND ; AUTO I>> red/t> redI2> Load unbalance alarm AUTO HAND ; AUTO I2> redtI2> Load unbalance trip AUTO HAND ; AUTO I2> red/t> redIE> Earth current alarm AUTO HAND ; AUTO IE> redtIE> Earth current trip AUTO HAND ; AUTO IE> red/t> redtCBFP CB failure protection AUTO HAND ; AUTO CB greenTrip External trip AUTO HAND ; AUTO Trip red

Table 5.5: Default setting of the Reset Functions* Short-circuit excitation during starting always has automatic reset


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5.9.3 Allocation of the Output Relays

The MRM3-2 has five output relays. The fifth output re-lay is an alarm relay for the self-supervision and its al-location is fixed; it is operated acc. to the closed cir-cuit principle.Output relays 1 - 4 can be freely allocated to the cur-rent functions either as alarm or trip relay; they are op-erated acc. to the open circuit principle. Allocation ofthe output relays is similar to the parameter settingmethod in the BLOCKING mode or RESET mode. T

The allocation mode is activated with the last actuationof the push-button in the RESETmode (as explained above).

Each of the protective functions has two states:

AlarmThis state is active, as soon as the setting value of theelement is exceeded.

TripThis state is active after the time of the trip delay haselapsed.

The adjustment procedure is as follows:Allocation of one or more of the 4 output relaysto “Alarm” or “Trip” of each of the protective functions.Which of the function is just being processed is sig-

nalled by the LEDs.

In addition to the protective functions special-purposesignals can be given by the relays:• Startblock (Start is not recommended)• START (Motor is starting)• LAUF (Motor in operation)

Indication LED Allocated relay(s)_ _ _ _ None1 _ _ _ 1

_ 2 _ _ 2... ..._ 2 3 4 2, 3 and 41 2 3 4 all

By pressing push-buttons and all possiblecombinations can be realised. The selected allocationcan be saved by and subsequent entry ofthe password.

Any allocation mode can be stopped by pressing the button for a certain time (about 3s).

Note:• Coding plugs J2 and J3, described in the general

description „MR- Digital Multifunctional Relay“have no function in the MRM3-2.

• At the end of this description an Adjustment Listcan be found in which the customer-specific ad-justments can be filled-in.


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Relay functions Output relays Displayedfigures

CorrespondingLED

Symbol Function 1 2 3 4

ϑ> Alarm X _ 2 _ _ ϑ> redIB> x k Alarm X _ 2 _ _ IB> green

IB> x k Tripping X 1 _ _ _ IB> green/τ

W greenI< Alarm X _ 2 _ _ I< redtI< Tripping X 1 _ _ _ I< red/t> redI> Alarm X _ 2 _ _ I> redtI> Tripping X 1 _ _ _ I> red/t> redI>> Alarm X _ 2 _ _ I>>red/Start greenI>> Start Tripping X 1 _ _ _ I>> red/t> red/

Start greenI>> Alarm X _ 2 _ _ I>>redtI>> Tripping X 1 _ _ _ I>> red/t> redI2> Alarm X _ 2 _ _ I2> redtI2> Tripping X 1 _ _ _ I2> red/t> red

IE> Alarm X _ 2 _ _ IE> red tIE> Tripping X 1 _ _ _ IE> red/t> red tCBFP Tripping _ _ _ _ CB greenExt. TripUndelayed

Tripping X 1 _ _ _ Trip red

Ext. TripDelayed

Tripping X 1 _ _ _ Trip red / t> red

Start/Block Start blocking X _._.3._ Start green/Block green

Start Motor starting _ _ _ _ Start greenOperation Motor running X _ _ _ 4 S/R green

Start time Excessive start-ing time X 1 _ _ _ Start green/t> red

ParaSet 2 Parameter set2 is active

_._._._ P2 yellow

Table 5.6: Example of an Allocation Matrix of the Output Relays (Default Setting))

5.10 Measuring Value and FaultIndications

5.10.1 Measuring Value Indications

The following measuring values can be displayed duringnormal operation:• Current in phase 1 (LED L1 green),• Current in phase 2 (LED L2 green),• Current in phase 3 (LED L3 green),• Earth current (LED E green),• Load unbalance current (LED I2 green),• Temperature equivalent ϑ> in % (LED ϑ> red),• Operating hours (LED h yellow)• Number of motor starts (LED No. green)• Time until tripping in min. (LED Trip/t> red)

• Remaining time of start blocking in min. (LEDStart/Block green and t> red)

• Date and time (LED! green)


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5.10.2 Units of the Displayed Measuring Values-

Indication of the measuring value can be represented inthe display optionally as multiple of the secondary ratedcurrent (x In) or as primary current (A).Consequently the units displayed are changing, i.e. for:

Phase Current

Indicated as Range UnitSecondary current .000 – 40.0 x InPrimary current .000 – 999.

k000 – k9991k00 – 9k9910k0 – 99k0100k – 999k1M00 – 2M00

AkA*kAkAkAMA

* for rated transformer current starting at 2kA

Earth Current

Indicated as Range UnitSecondary current .000 – 15.0 x InPrimary earth cur-rent

.000 – 999.k000 – k9991k00 – 9k9910k0 – 99k0100k – 999k1M00 – 2M00

AkA*kAkAkAMA

* for rated transformer current starting at 2kA

5.10.3 Indication of the Fault Data

All fault events acquired by the relay are optically indi-cated on the front cover. For the MRM3-2 the four LEDs(L1, L2, L3, I2; E) and the functional LEDs (ϑ>; IB>; I, I>>, I2> and IE>) are provided. Not only fault sig-nals are put out but also the activated protective functionis indicated. If, for instance, overcurrent occurs, the LEDsassigned to the respective phases are flashing. LED I>

comes on also at the same time. After elapse of the trip-ping time the flashing LEDs change to permanent light.

5.10.4 Fault Memory

In case of actuation or tripping of the relay, the faultvalues and times are stored in a voltage fail-safe way.The MRM3-2 has a fault value memory covering up to25 fault events. If this number is exceeded, the eldestdata set is then overwritten.

Besides the tripping values, the LED states are alsosaved for fault indication.

Inquiry of the fault memoryWhen the push-button is pressed during normalmeasuring value indication, the fault data is displayed.

FLT1 last faultFLT2 fault before lastetc.By pressing the respective fault can be selected.

During fault value indication FLT

• it can be changed over to another fault data set bypressing or • it is displayed, which of the parameter sets was ac-

tive during the event• the LEDs are flashing according to the stored pick-up

values/trip information, i.e. LEDs showing a perma-nent light when the trip occured, start to flash in or-der to indicate that is was a past fault condition.Those LEDs, which were flashing when the trip oc-cured, (element was actuated) are flashing briefly

• the individual fault measuring values for the respec-tive fault can be inquired by pressing

If the relay has not been reset after tripping (TRIP is dis-played), measuring values cannot be indicated.

The fault memory can be cleared by pressing the buttoncombination and for about 3s. Inthe display „wait“ is shown.

Trigger signal for the fault memoryThere are three trigger signals for the fault recorder1. End of a starting phase,2. A tripping signal,3. End of a protection excitation in OPERATING mode

depending on which event has occurred, the followingvalues are recorded.


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1. Values recorded at the end of a starting phase• max. staring current in Phase 1,• max. staring current in Phase 2,• max. staring current in Phase 3,• Earth current E,

• Load-unbalance current I2,• Temperature equivalent ϑ in % at this time,• Change in the temperature equivalent ϑ in % during

the starting phase• Duration of start in s,• Date and time.

2. Values recorded after an excitation• Peak current during this excitation in Phase 1,• Peak current during this excitation in Phase 2,• Peak current during this excitation in Phase 3,

• Peak current during this excitation in the earth currentpath• Peak current during this excitation for load unbalance• Temperature equivalent ϑ in % at this time,• Date and time.

3. Values recorded after a tripping action• Tripping current in Phase 1,• Tripping current in Phase 2,• Tripping current in Phase 3,• Tripping value for earth current E,• Tripping value for load-unbalance current I2,• Tripping value for the temperature equivalent ϑ in %,• Switch failure time,• Date and time.

5.11Reset

The MRM3-2 offers the following three ways to reset thedisplayed indications as well as the output relay.

• Manual reset

By pressing the push-button forsome time (about 3 seconds

• External resetBy applying aux. voltage to C8/D8

• Reset via interfaceBy transmitting the RESET command from the MasterPC.

An indication can only be reset if there is no protectivefunction activated. (Otherwise "TRIP" remains in the dis-play).The set parameters are not changed by the reset proce-dure.

5.11.1 Erasure of the Fault Memory

For erasure of the fault memory the push-button combina-tion and has to be pressed forabout 3 s. During the erasure procedure „wait“ is dis-played.

5.11.2 Reset of the Thermal Memory

It is possible to erase the thermal memory ϑ to 0%. Bypressing the push-button combination and for some time (about 3 s) the thermal memoryis reset to 0%.

IMPORTANT:This function has to be used with extreme care. Duringsecondary tests it can be very useful to have always

constant start conditions. If, however, after overloadtripping the thermal image is reset in order to restart themotor as quickly as possible, then there is the risk ofoverloading the motor because it is still hot but the pro-tective unit proceeds on the assumption that the motor iscold.

5.12 Digital Inputs

5.12.1 Parameter Set Changeover Switch

When voltage is applied to this input it is changed overto the other parameter set.

5.12.2 External Trigger of the FaultRecorder

Via this input fault recording can be triggered withoutthe MRM3-2 necessarily recognising a trip.


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5.12.3 Recognition of “Motor Running”Condition

This input can be used if the motor runs without loadand does not need much current (I < 2% x IN). In such acase the motor current may lie below the STOP thresholdand so recognition of the RUNNING conditions is notsecure. In order to maintain the RUNNING conditions,voltage can be applied to this input by means of anaux. contact of the CB. This is necessary so that all func-tions which depend on the RUNNING conditions canoperate faultless (e.g. I>> LAUF, I>, start counter etc.)and the LEDs are signalling the correct motor status. Insuch a case the underload element must not be used. (I<must be set to EXIT)

5.12.4 Undelayed External Trip

A trip is immediately triggered if voltage is detected bythis input. The fault recorder is activated and the as-signed output relay picks up.

5.12.5 Delayed External Trip

In principle this input has the same effect as the input forundelayed trip, but a trip is only triggered if the inputsignal was available during the entire adjusted delaytime.


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6 Notes on Relay Tests andCommissioning

6.1 Connection of the auxiliary voltage

To prevent destruction of the relay during tests the follow-

ing has to be observed:• The aux. voltage supply of the relay must be within thepermissible ranges.

• The test current must not exceed the thermal rating ofthe measuring circuits.

• The CTs must be connected properly.• All control and measuring circuits as well as the output

relays must be connected properly.• The voltage ranges of the digital inputs must be ad-

justed correctly.

For further information please see Technical Data

6.2 Testing of Output Relays and LEDs

Checking of the output relays and of all LEDs can betriggered by the -push-button.

Test procedure

Entry Display Note DO1 Display of the relay software

version (part 1)* 1.00 Display of the relay softwareversion (part 2)*

PSW ? Call for enter the passwordPSW? ****

TRI ?Password entryReady for tests

TRIP Start the testRelease of self-test relayPick-up of all output relaysTest of all LEDs

|SEG Finish the test,Output relays return to their cur-

rent operational state* If possible please state when writing to us.

Careful when the relay is installed:

The relay test is not a pure internal test. All the output re-lays will be energised! After starting test the self-supervision relay releases first. Hereby a relay faultcould be adopted by a connected control gear.Thereafter all other existing output relays will pick upone after another. The reaction in the relevantswitchboard could be accordingly (e.g. trip of a priorityCB).


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6.3 Test circuit for MRM3-2

For testing the MRM3-2 relays only one power source isnecessary. Figure 6.1 shows a simple example of asingle-phase testing circuitry with controllable powersource for testing the unit.

Figure 6.1: Test circuit

6.3.1 Checking of Input Circuits and of theMeasuring Values

Single-phase conductor current testThe test can be carried out with a single phase. For thisprocedure all three phase current measuring inputs haveto be connected in series. Restriction : For single-phase

testing the load unbalance element has to be deacti-vated because it cannot be tested with three equal-phase currents.

Three-phase conductor current testFor this test a relevant three-phase test source (120°phase shift !) must be available. Each channel of thesource is connected with one conductor current input.This test circuitry is recommended because with this mostof the tests can be carried out. For testing the earth faultchannel a single-phase test should then follow.

For tests in Holmgreen connection, simulation of anearth fault current has to be considered. Conductor cur-rents have to be fed by the source the geometrical totalof which has to be in accordance with the required

earth fault current. But such asymmetry of the conductorcurrents can cause the load unbalance element to trip(dependent on its setting).


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6.3.2 Testing the START-STOP-RUNNINGRecognition

In a secondary test this elementary function can only bereliably tested if the test source can generate the exactchronological course of a starting current. If ever possi-ble this should be carried out as primary test. Under allnormal start conditions, the status indications should besignalled correctly. Please bear in mind: the STOP con-dition is only signalled after the STOP time has elapsedand RUNNING is only indicated after elapse of thestart recognition time the earliest. Dependent on the ac-tual kind of start or on the spectrum of possible varyingstarting conditions, modification of both parametersmight be necessary.

6.3.3 Testing the Pick-Up and Disengaging

Values

For optimal protection many functions in this motor pro-tection relay are interlinked and hence it is not possibleto have all protective elements tested independently fromeach other.For all functions linked with theSTART/STOP/RUNNING recognition, a start simulationhas to be performed so that the function can be testedunder real conditions. Some of the tests could be simpli-fied if special parameters would be set, but in most ofthe cases this is not wanted.

Hence for testing the short-circuit element I>>RUNNING, forinstance, the MRM3-2 has to recognise the simulatedrunning condition firstly. The test source must be able tocopy the course of the motor current exactly as it is inreality. The required test short-circuit current can only beinjected after the MRM3-2 has recognised the runningcondition. The test conditions of the other elements, i.e.:

I>I<I>> StartI>> RUNNING

have to be adjusted according to the application of theselected parameters.

6.3.4 Testing the maximum starting time

The timer for maximum starting time starts running if theimpressed current exceeds the overload threshold ofk*IB> immediately after exceeding the starting thresholdaand within the start recognition time. There will be trip-ping if the threshold k*IB> is not underscored again after

the set time has expired. There are two possibilities ofadjustment. If the tripping characteristic for the max.starting time is set to "DEFT" (Definite Time), trippingtakes place after the set time has expired. If the parame-ter is set to "INVS" (Inverse Time Characteristic), the trip-ping time is dependent on the set rated starting currentand a time multiplier. The multiplier is set with the sameparameter as in case of the maximum starting time withdefined tripping time. The maximum tripping time is lim-ited to 2 x standard time. The minimum tripping time islimited to the shortest possible tripping time of theMRM3-2

.

6.3.5 Testing the thermal image

For the thermal image there is no start simulation re-quired. But for true propositions it is important that eachstart proceeds from distinct start conditions. The thermalbehaviour of the motor is taken into account in the ther-mal image. This means that the time for simulated cool-ing down and for the store to be back to zero after atest can be accordingly. (The store can also be reset

manually). As general rule applies that at constant cur-rent 99 % of the thermal processes have reached theirfinal value after 5 times the time constant (warming upor cooling down).

6.3.6 Testing the Control Inputs

Prior to the test it should be ensured that the voltageranges of the inputs (jumper) are correctly adjusted (seechapter 3.1.4).

6.3.7 Testing the CB Failure Protection

For this test the test source must be able to simulate acircuit breaker and switch-off the current after a select-able time when the MRM3-2 was triggered (see chapter5.4.18). To meet these requirements, the test sourcemust have a respective signal input and a timer forswitching-off the current.


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6.4 Primary Test

As a rule, tests with currents at the CT primary side (realtest) can be performed in the same way as tests withsecondary currents. It is recommended to carry out pri-mary tests only as an exception and only if it is abso-lutely necessary (for very essential protective facilities)

because in some cases the costs involved and the strainon the system can be rather high. Many functions of theMRM3-2 can be checked during normal operation ofthe system due to the efficient fault and measuring valueindications. So it is possible, for example, to comparethe currents shown on the display with the values shownon the ammeters in the switchboard.

6.5 Maintenance

Normally the relays are checked at regular maintenanceintervals at site. From user to user these intervals mayvary because among other things they depend on thetype of relay, the kind of application, significance of theobject to be protected, previous experience of the useretc.

For electro-mechanical or static relays normally an an-nual check is required. For the MRM3-2 the mainte-nance intervals can be much longer because:

• the MRM3-2 relays are provided with wide-ranging

self-test functions and consequently relay faults are de-tected and indicated. It is, of course, imperative thatthe internal self-supervision relay is connected to acentral display board.

• The combined measuring functions of the MRM3-2 make monitoring during operation possible.

• The trip test function (TRIP-Test) allows testing of theoutput relays.

Therefore a maintenance interval of two years is suffi-cient. When servicing all relay functions incl. setting val-ues, trip characteristics and tripping times ought to bethoroughly checked.


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7 Technical Data

7.1 Measuring input

Rated data: Rated current IN 1A or 5ARated frequency fN 50/60 Hz adjustable

Power consumption in current path: at IN = 1 A 0.2 VAat IN = 5 A 0.1 VA

Thermal withstand capabilityOf the current paths: Current surge

(on half-wave) 250 x IN for 1 s 100 x IN for 10 s 30 x IN continuously 4 x IN

Fault recorderRecorded tracks: iL1, iL2, iL3, iE

Sampling rate: 1.25 ms at 50 Hz1.041 ms at 60 Hz

Storage capacity: 16 s (at 50 Hz) resp.13.33 s (at 60 Hz)

Number of events: 1-8

7.2 Common data

Dropout to pickup ratio: >97%Returning time: 40 msTime lag error class index E: ±20 ms

Minimum operating time: 40 msT5ransient overreach atinstantaneous operation: ≤5%Permissible interruption of thesupply voltage without affectingthe relay function: 50 ms

Influences on the current measurements

Auxiliary voltage: in the range of 0.8 < UH / UHN < 1,2

No additional influences can be measured

Frequency: in the range of 0.9 < f / fN < 1.1;


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7.3 Setting ranges and steps

7.3.1 System parameter

*) One parameter can be marked by several LEDs

Parameter LED * Setting range Range Step ToleranceTransformer ratio phasecurrentIprim

L1 L2 L3 SEK0.002... 50.0 kA

Displayed in x IN Displayed in kA

0.002 - 0.2000.200 - 0.5000.500 - 1.001.00 - 2.002.00 - 5.005.00 - 10.010.0 - 20.020.0 - 50.0

0.001;0.002;0.005;0.01;0.02;0.05;0.1;0.2

Transformer ratio earthcurrentIprim E

E SEK0.002... 50.0 kA

Displayed in x IN Displayed in kA

0.002 - 0.2000.200 - 0.5000.500 - 1.001.00 - 2.002.00 - 5.005.00 - 10.0

10.0 - 20.020.0 - 50.0

0.001;0.002;0.005;0.01;0.02;0.05;

0.1;0.2

Operating hour meter h Y=00...28 years 1 year

h 0000... 8759 hours 1 hour

Motor starts No 0000... 9999 Number of starts 1

Rated frequency - f=50f=60

Hz

LED flashing after activa-tion

- NOFLFLSH

no yes

Date and time ! Y=00... 99M=01...12D=01... 31*h=00... 23

m=00...59s=00... 59

YearMonthDay (* depends on month)Hour

MinuteSecond

1 year1 month1 day1 hour

1 minute1 second

Parameter set change-over switch

P2 SET1SET2

active parameter set


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7.3.2 Time overcurrent protection

Parameter LED Setting range Notes Range Step ToleranceTherm. Permissible con-tin. current k x I B

IB 0.20...4.00EXIT

x INStep switched off

0.01;0.02;0.05; 0.1x IN

±3% of settingvalueor ±10mA

Overload factor k 0.80...1.20 0.01

As warning ortripping step

IB>+τW warntrip

Step signals warningStep signals tripping

Excitation delay forIB>*k

IB>+t> 0,1...260 0.04 - 1.001.00 - 2.002.00 - 5.005.00 - 8.008.00 - 10.010.0 - 20.020.0 - 50.050.0 - 100100 - 200200 - 260

0.020.050.10.20.51.02.05.010.020.0

±3% of settingvalue or ±20ms

Heating time constant τW 0.5...180 min 0.5 - 2.0

2.0 - 5.05.0 - 1010 - 2020 - 5050 - 100100 - 180

0.1

0.20.51.02.05.010.

±3% referring to

current measur-ing valueor ±20ms(See EN60255-3)

Time limit τWStart

t2xt6xEXIT

ab 2 x k*IB ab 6 x k*IB no limitation

Cooling down factor τC 1.00...8.00 x τW 1.00 - 2.002.00 - 5.005.00 - 8.00

0.050.10.2

±3% referring tomeasuring valueor ±20ms(See EN60255-3)

Warn step ther. image ϑ> 20...99

EXIT

Warning at % ϑ>Step switched off

20 - 99 1 ±1% of the set-ting value

Undercurrent I< 0.10...1.00EXIT

Trip delay x IN Step switched off

0.100 - 0.2000.200 - 0.5000.500 - 1.00

0.0050.010.02

±3% of the set-ting value or±10mA

I 0,1...260EXIT

Trip delay in sWarning only

0.04 - 1.001.00 - 2.002.00 - 5.005.00 - 8.008.00 - 10,010.0 - 20,020.0 - 50,050.0 - 100100 - 200200 - 260

0.020.050.10.20.51.02.05.010.020.0

±3% of the set-ting value or±20ms

Overcurrent I> 0.2...4.0EXIT

Pick-up value x IN Step switched off

0.20 - 0.500.50 - 1.001.00 - 2.002.00 - 4.00

0.010.020.050.1


Characteristics I>+CHAR DEFTNINVVINVEINVRINVLINV

definitenormal inversevery inverseextremely inverseRI-inverseLong-term inverse


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Parameter LED Setting range Notes Range Step ToleranceTime delay I>+t> at DEFT:

0.04 ...260 Time delay in s0.04 - 1.001.00 - 2.002.00 - 5.005.00 - 8.008.00 - 10.010.0 - 20.0

20.0 - 50.050.0 - 100100 - 200200 - 260

0.020.050.10.20.51.0

2.05.010.020.0


at _INV:0.05 - 20

EXIT

Characteristic parameter

Warning only

0,05 - 0,500,50 - 1,001,00 - 2,002,00 - 5,005,00 - 10,010,0 - 20,0

0,010,020,050,10,20,5

±3% related tothe measuredcurrent valueor ±20ms(See EN60255-3)

Short-circuit stepat start

I>>Start

0.5...40

EXIT

Pick-up value x IN during StartStep switched off

0.50 - 1.001.00 - 2.002.00 - 4.004.00 - 10.0

10.0 - 20.020.0 - 40.0

0.020.050.10.2

0.51.0


Time delay I>>Start+t>

0.04...10EXIT

Tripping delay in swarning only

0.04 - 1.001.00 - 2.002.00 - 5.005.00 - 10.0

0.020.050.10.2


Running I>> 0.5...40

EXIT

Pick-up value x IN During runningStep switched off

0.50 - 1.001.00 - 2.002.00 - 4.004.00 - 10.010.0 - 20.020.0 - 40.0

0.020.050.10.20.51.0


Trip delay I>>+t> 0.04...10EXIT

Trip delay in sWarning only

0.04 - 1.001.00 - 2.002.00 - 5.005.00 - 10.0

0.020.050.10.2



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7.3.3 Load Unbalance Protection

Parameter LED Setting range Notes Range Step ToleranceLoad unbalance I2>

0,02...1,00EXIT

Pick-up value negativephase sequence system- displayed in x IN - Step switched off

0.020 0.0500.050 - 0.1000.100 - 0.2000.200 - 0.5000.500 - 1.00

0.0010.0020.0050.010.02

±3% of settingvalueor ±10mA

Characteristics I2>+CHAR DEFTINVS

definite DMTinverse IDMT

±3% in relationto the measuredcurrent value or±20ms (see EN60255-3)

Time delay/characteristic parameter

I2+t> At DEFT:1.00 ...600 Trip delay in s

1.0 - 5.05.0 - 10.010.0 - 20.020.0, - 50.050.0 - 100100 - 200200 - 600

0.10.20.51.02.05.010.0


at INVS:10.0 - 5000

EXIT


Warning only

10.0 - 20.020.0 - 50.0

50.0 - 100100 - 200200 - 500500 - 10001000 - 20002000 - 5000

0.51.0

2.05.0102050100

±3% referring tocurrent measur-

ing value or±20ms(See EN60255-3)

7.3.4 Earth fault protection

Parameter LED Setting range Notes Range Step ToleranceEarth fault protection IE> 0,01...2,0

EXITpickup value x IN element blocked

0.010 - 0.0500.050 - 0.100

0.100 - 0.2000.200 - 0.5000.500 - 1.001.00 - 2.00

0.0010.002

0.0050.010.020.05

±3% of the set-ting value or

±0.5% of therated value

As warning or trippingstep

IB>+τW warntrip

Step signals warningStep signals tripping

Characteristics IE+CHAR DEFTNINVVINVEINVRINVLINVRXIDG

definitenormal inversevery inverseextremely inverseRI-inverseLong-term inverseSpecial characteristic

Time delay IE>+t> at DEFT:

0.04 ...260 Trip delay in s

0.04 - 1.00

1.00 - 2.002.00 - 5.005.00 - 8.008.00 - 10.010.0 - 20.020.0 - 50.050.0 - 100100 - 200200 - 260

0.02

0.050.10.20.51.02.05.010.020.0

±3% of the set-

ting value or±20ms

Characteristics parame-ter

at _INV:0.05 - 20

EXIT


Warning only

0.05 - 0.500.50 - 1.001.00 - 2.002.00 - 5.005.00 - 10.010.0 - 20.0

0.010.020.050.10.20.5

±3% referring tocurrent measur-ing value or±20ms(See EN60255-3)

Table 7.1: Setting ranges and steps


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7.3.5 Circuit breaker failure protection

Parameter LED Setting range Notes Range Step ToleranceCB+t> 0.1...2.00

EXITCB timeStep switched off

0.10 - 1.001.00 - 2.00

0.020.05

7.3.6 External trip delay

Parameter LED Setting range Notes Range Step ToleranceTrip+t> 0,1...260

EXITSwitching delay in sNo trip

0.04 - 1.001.00 - 2.002.00 - 5.005.00 - 8.008.00 - 10.010.0 - 20.020.0 - 50.050.0 - 100100 - 200200 - 260

0.020.050.10.20.51.02.05.010.020.0


7.3.7 Trip blocking beginning with the adjusted rated current

Parameter LED Setting range Notes Range Step ToleranceTrip+Block 0.5...40

EXIT

Trip blocking from thresh-old value (x IN)Function is switched off

0.50 - 1.001.00 - 2.002.00 - 4.004.00 - 10.010.0 - 20.020.0 - 40.0

0.020.050.10.20.51.0



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7.3.8 Start parameter

Parameter LED * Setting range Notes Range Step ToleranceStart blocking Start+No AUTO*

1.0... 60.0

EXIT

Supervision by thermalreserve

Supervision by intervaltime:Duration of the start period(min)

No supervision

1 - 60 1,0

±2s for onestart cycle

*faded out in AUTO No. 1...20 Permitted starts per period 1

*faded out in AUTO Start+Block +t>

VARI

1.0...60

Remaining interval time

Fixed start blocking timemin.

1 - 60 1,0 ±3% of the set-tingvalue or ±20ms

Starting time Start +CHAR

DEFTINVS

Independent time ±3% in relationto the measuredcurrent value or±20ms (see EN60255-3)

Rated starting current IB> +Start 0.5...40

EXIT

Start current at ratedvoltage (x IN)Function switched off

0.50 - 1.001.00 - 2.002.00 - 4.004.00 - 10.010.0 - 20.020.0 - 40.0

0.020.050.10.20.51.0


Max./Rated startingtime of the engine

Start+t> 0.02...500EXIT

Tripping delay sStep switched off

0.20 - 1.001.00 - 2.002.00 - 5.005.00 - 10.010.0 - 20.020.0 - 50.050.0 - 100

100 - 200200 - 500

0.020.050.10.20.51.02.0

5.010.0


max starting time(Protective functionagainst prolonged startprocedure)

I>+0+t> 0.02...500EXIT

Trip delay sStep switched off

0.20 - 1.001.00 - 2.002.00 - 5.005.00 - 10.010.0 - 20.020.0 - 50.050.0 - 100100 - 200200 - 500

0.020.050.10.20.51.02.05.010.0


Stopping timeSTOP recognition

I 0.05...10.0 Time until STOPis recognised s

0.50 - 1.001.00 - 2.002.00 - 5.00

5.00 - 10.0

0.020.050.1

0.2



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7.3.9 Interface parameter

Parameter LED * Setting range Notes Step ToleranceRS 1 - 32 Slave-Address

RS24004800

9600

Baud-Rate**

*/**RS

evenoddno

Parityeven*/**odd*none*

* selectable when Modbus Protocol is used** fixed setting for RS485

7.3.10 Fault recorder parameter

Parameter LED Setting range Notes Range Step Tolerance

Number of recordings* FR

137

248

Existing recordings to beoverwritten*1 x 8 s (6.66s)3 x 4 s (3.33s)7 x 2 s (1.66s)

Existing recordings not to beoverwritten*2 x 8 s (6.66s)4 x 4 s (3.33s)8 x 2 s (1.66s)

Trigger event FR P_UPTRIPA_PITEST

At actuationAt tripAfter actuationTest recording with button and

Pre-trigger time FR 0,05...8,00 Duration of the previousevent S

0.05 - 8.00 0.05

* All given times refer to 50 Hz (60 Hz in brackets)


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7.4 Tripping characteristics

7.4.1 Tripping characteristic for max. starting time

The formula for calculating the tripping characteristic is:

Inverse Time Characteristic s2aus t

start_I

I

1t ⋅

! "

#$%

& = this applies if I/I_Start > = 0,707

taus = 2 x ts this applies if I/I_Start< 0,707

With: taus = tripping timets = starting time at rated starting current (rated voltage) or rated starting timeI = effective currentI_start = setting value of rated starting current

0,01

0,10

1,00

10,00

100,00

1000,00

0,01 0,10 1,00 10,00

[s]

500400

ts =

200

10080

40

20

10

1

[I_Start]

Figure 7.1: Tripping characteristic for max. starting time

'(

)*+

,

start_I

I


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7.4.2 Thermal image

The formula for calculating the trip characteristics is as follows:

( ) 1p k I

I

pfür1

)k I(

I

p)k I(

I

lnt2

2B

22

2B

2

22

B

2

aus ≤∩×<

''''

''

(

)

****

**

+

,

!!

"

#

$$

%

& −

×

!!

"

#

$$

%

& −

×

⋅τ=

with τ = thermal time constant of the object to be protectedI = Relay current (highest measuring value)IB = Basic currentIP = Initial load currentp = Initial load factor (p = 0 means cold operating component)k = Constant

7.4.3 Initial load factor

Presentation of the trip with variable initial load factor:

'''''

(

)

*****

+

,

!!

"

#

$$

%

& −

!!

"

#

$$

%

& −

⋅τ=

1)k *I(

I

p)k *I(

I

lnt

2B

2

22

B

2

aus

1 1.25 1.5 1.75 2 2.25 2.5

I/IB

0.01

0.02

0.04

0.06

0.08

0.1

0.2

0.4

0.6

0.8

1

2

t a u s

/ τ

p=0.2p=0.3p=0.4p=0.5

p=0.6p=0.7

p=0.8

p=0.9

p=0

Figure 7.2: Trip Characteristics for Various Initial Load Factors p


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7.4.4 Tripping of t2x and t6x - times

0,1

1,0

10,0

100,0

1000,0

1 10

τ = 0.5 min

I / IB*k

[min]

τ = 1 min

τ = 10 min

τ = 100 min

τ = 180 min

Figure 7.3: Limitation of tripping time 2 x I N

0,0

0,1

1,0

10,0

100,0

1000,0

1 10

τ = 0.5 min

τ = 1 min

τ = 10 min

I / IB*k

[min]

τ = 100 minτ = 180 min

Figure 7.4: Limitation of tripping time 6 x I N


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7.4.5 Inverse time overcurrent protection

Trip characteristics acc. to IEC 255-4 or BS 142

Normal inverse (Type A) [ ]sIt

102.0

Is

I

14.0t >

−! "

#$

%

&

=

Very inverse (Type B) [ ]sIt

1Is

I

5.13t >

−! "

#$%

& =

Extremely inverse (Type C) [ ]tIIs

tI

s=&

% $ #

"! −

>802

1

Long time inverse [ ]st1

Is

I120t I >! "

#$%

& =-

RI-inverse [ ]st

I

I

236.0339.0

1t I

S

>

!! "

#$$%

& −

=

RXIDG – characteristics [ ]stIs

I n3.18.5t I>⋅!!

"

#$$%

& ! "

#$%

& ⋅−= !

Where: t = Tripping timetI> = Time multiplierI = Fault currentIs = Setting value of the currentn! = natural logarithm


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7.4.6 Trip characteristics

1 2 3 4 5 6 7 8 910 20

I/IS

0.1

1

mrm3-2 proddocspdf_2_273.pdf

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