Seg MRM3 User manual

MRM3 –Motor Protection Relay

2TB MRM3 07.01 E
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 Thermal Image
4.3 Requirement on the Main Current
Transformers
5 Operation and Adjustments
5.1 Displayed text for parameter settings
5.2 Settting 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 Indictation of the Activation Store
5.3.6 Parameter Set Changeover Switch (P2)
5.4 Protection Parameters
5.4.1 Thermal Overload Protection (k x IB)
5.4.2 Heating Period Constant τWand
Cooling-Down Time Factor τC
5.4.3 t2x and t6x Minimal Trip Time During
the Starting Process.
5.4.4 Phase Undercurrent Element (I<)
5.4.5 Phase Overcurrent Element (I>)
5.4.6 Trip Characteristics for the Phase Over-
current Element (I>+CHAR)
5.4.7 Tripping Time or Time Factor for the
Phase Overcurrent Element (I>+t>)
5.4.8 Reset Mode for the Trip Characteristics
in the Phase Current Path (I>+CHAR+t>)
5.4.9 Phase Short-Circuit Trip (I>>) and
(I>>+Start)
5.4.10 Negative Phase Sequence
5.4.11 Earth Fault Element (IE>)
5.4.12 Trip Characteristics for the Earth Fault
Element (IE>+CHAR)
5.4.13 Tripping Time or Time Factor for the
Earth Fault Element (IE>+t>)
5.4.14 Reset Time for the Earth Fault Element
(IE>+CHAR+t>)
5.4.15 Tripping Time for the CB Failure-Protec-
tion (CB+t>)
5.4.16 External Trip (delayed) (Trip+t>)
5.4.17 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 Maximal Start Time (Start+t>)
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 Fault Recorder (FR)
5.7.1 Fault 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

TB MRM3 07.01 E 3
6 Notes on Relay Tests and Commissioning
6.1 Connection of the auxiliary voltage
6.2 Testing of Output Relays and LEDs
6.3 Test circuit for MRM3
6.3.1 Checking of Input Circuits and of the
Measuring Values
6.3.2 Testing the START-STOP-RUNNING
Recognition
6.3.3 Testing the Pick-Up and Disengaging
Values
6.3.4 Testing the thermal image
6.3.5 Testing the Control Inputs
6.3.6 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 Thermal image
7.4.2 Initial load factor
7.4.3 Tripping of t2x and t6x - times
7.4.4 Inverse time overcurrent protection
7.5 Trip characterisitcs
7.6 Output relays
8 Order form

4TB MRM3 07.01 E
1 Introduction and Application
The motor protection relay MRM3 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 recognises the “Start-Up“ and “Motor Run-
ning“ 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 current
transformer.
The motor can be stopped in delayed or undelayed
mode via digital inputs.
The MRM3 is available with rated currents of 1A or
5A.
Important:
For additional common data of all MR-relays please
refer to manual "MR - Digital Multifunctional relays".
On page 45 of this manual you can find the valid
software versions.
2 Characteristics and Features
•Microprocessor technology with self-supvervision,
•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 overcurrent
protection (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-circuit
free operation,
•Blocking of the individual protective elements or the
trip elements can be set freely,
•The protective functions can be freely allocated to
the output relays. (RelayMatrix),
•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-Data
Protocol or Modbus Protocol.

TB MRM3 07.01 E 5
3 Design
3.1 Connections
Figure 3.1: Connection Diagram MRM3
P1
P2
S1
S2
P1
P2
S1
S2
P1
P2
S1
S2
I1
I2
I3
IE
L1.1
B3
B4 L1.2
L2.1
B5
L2.2
B6
L3.1
B7
L3.2B8
B1
B2
L
1
L2
L3
Figure 3.2: Measuring of phase currents and earth current detection
in Holmgreen connection (IE)
This kind of connection can be used where three
phase CTs are available and a combination of phase
and earth current measuring is required.
Figure 3.3: Measuring of earth current with core-type CT (IE)
With the combination of phase and earth current
measuring, CTs to be connected according to Figure
3.2. and Figure 3.3.

6TB MRM3 07.01 E
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 separate
input 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 has 5 output relays. Two of these relays
with two change-over contacts and three relays with
one change-over contact each are used for signalling.
The protective functions can be freely allocated except
of 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 has 7 digital inputs with fixed functions.
All inputs have a common reference point : Terminal
D8. (See Chapter 3.1)
No Terminal Function Coding
Plug
1C8 Externalreset 2
2 E8 External blocking 1
3 A2 Parameter set change-
over switch
3
4 A5 External trigger for the
fault recorder
4
5 A6 Identification „Motor
Running“
7
6 A7 Ext. trigger, undelayed 6
7 A8 Ext. trigger, delayed 5
3.1.4 Low/High Range of the Digital
Inputs
The MRM3 is equipped with a wide-range power
supply 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 be
adjusted:
Range Plug U not active U active
Low Plugged in <= 8V >= 10V
High Open <= 60V >= 70V
Figure 3.4: Coding Plug

TB MRM3 07.01 E 7
3.2 Front plate
Figure 3.5: Front plate MRM3-IE
Figure 3.6: Front plate MRM3-I
The LEDs ϑ, h, RS and FR on the MRM3 emit a yellow
light, all other LEDs are bi-coloured. The LEDs at the left
next to the alphanumerical display give a green light
during measuring and a red one when a fault signal
occurs.
The LEDs underneath the <SELECT/RESET> - push but-
ton emit a green light during adjustment and inquiry of
the setting quantities left to the LEDs. They show a red
light if the printed setting quantities right to the LEDs
are activated.
3.2.1 Indicating LEDs
L1, L2, L3 Indication of the phase currents
E Indication of the earth current
I2 Indication of the unbalanced load
current (NPS)
ϑIndication of the temperature equivalent
h Operating hour meter
!Date and time
3.2.2 Adjusting LEDs
IB> Rated motor current
K Constant quantity (k*IB = 100%
thermal load)
τWHeating period constant
τCCooling down factor
t> Tripping times, generally
ϑ> Switching threshold of the thermal
overload alarm
No. Number of motor starts
CHAR Characteristics setting
I< Undercurrent setting
I> Overcurrent setting
I2> Load unbalance setting (NPS)
I>> Short-circuit setting
IE> Earth current setting
CB CB failure protection
Block Start blocking/Protective blocking
0 Current>0/<0 START/STOP
recognition
Start Start blocking/Start time
Trip External trip
FR Parameter for the fault recorder
RS Setting of the relay address
P2 Parameter set 2 is active
S/R Motor starting/Motor running

8TB MRM3 07.01 E
3.3 Analog part
The alternating currents injected by the CTs are con-
verted into galvanical isolated voltages via input
transmitters 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 into
digital signals by means of sample and hold circuits.
These digitized values are then used for further proc-
essing. The measuring values are acquired at fn = 50
Hz (fn = 60 Hz) with a sampling frequency of 800 Hz
(960 Hz), and thus the instantaneous values of the
measured 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 protection
unit. With this micro-controller all tasks are completely
digitally processed, from discretization of the measur-
ing quantities to protective tripping.
With the protection program, stored in the program
storage (EPROM), the micro-processor processes the
voltages applied to the analog inputs and from this
calculates 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 used
in the process.
The micro-processor compares the existing current with
the 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 than
the trip delay or if the thermal image exceeds its rated
value, a fault signal occurs. Dependent on their set-
tings, the output relays pick up as well. When setting
the 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 is
signalled by the “Selfsupervision” output relay.
Figure 3.7: Block Diagram of Protective Functions

TB MRM3 07.01 E 9
4 Working Principle
4.1 Start Recognition
The MRM3 monitors the flow of the current from which
the following operational conditions of the motor 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 the
stop time.
Start/Stop Threshold
This threshold is fixed at 2% of IN
Stop time:
The Stop time is adjustable in order to tolerate
a brief off-time of the current flow (e.g. change-
over Star/Delta) from the START or RUNNING
conditions. STOP is only indicated if the current
was under 2% INfor longer than the stop time.
Based on this time the running down period
can be considered in a certain way for the LED
indication.
START-Condition:
START is only recognised if the previous condition was
STOP and the motor current has exceeded the start
threshold. If the STOP or RUNNING conditions are
recognised, 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 that
the RUNNING conditions are indicated too
early in advance.

10 TB MRM3 07.01 E
•No exeeding of the start threshold during pony mo-
tor start-up or when soft starters are used.
•Multistage resistance start where the start threshold is
either exceeded several times or not at all.
The time is running from the instance the start threshold
is exceeded. RUNNING is only accepted by the su-
pervision after the time has elapsed or the overload
threshold is undershot. If the overload threshold is not a
clear criterion, the time has to be set at least for so
long 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 dropped
below k x IB and the start recognition time has
elapsed. (direct start)
or
•if the motor is connected across several resistance
steps, it is possible that the start threshold is
passed through repeatedly. RUNNING conditions
are recognised when the start recognition time has
run out after the last step and a current has settled
between 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 time
has elapsed. The overload threshold has not nec-
essarily to be exceeded.
(soft start)
•If the «Motor Running» input was activated but the
overload 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 is equipped with a flexible supervision
element which can limit the sequence of possible
starts.
A start should be prevented if it is obvious that it is
likely to be interrupted due to overload so that in total
the down-time can be curtailed. If a start is not rec-
ommendable at a certain time (with the motor
switched off), the MRM3 activates an allocated output
relay until the waiting time has elapsed. Irrespectively
of the adjustment of this element, the thermal image is
always activated and shuts the motor down as soon as
the thermal overload threshold is reached (due to a
start or overload).
The protective element can either be tied to the thermal
image or be manually defined by the number of starts
and cycle duration.