Seg HighTECH MRU3-2 User manual

MRU3-2 -Voltage relay with evaluation of symmetrical
components

2TB MRU3-2 12.00 E
Contents
1 Introduction and application
2 Features and characteristics
3 Design
3.1 Connections
3.1.1 Analog input circuits
3.1.2 Blocking input
3.1.3 External reset input
3.1.4 Output relays
3.1.5 Fault recorder
3.1.6 Parameter settings
3.2 Display
3.3 LEDs
3.4 Front plate
4 Working principle
4.1 Analog circuits
4.2 Digital circuits
4.3 Selection of star or delta connection
4.4 Voltage supervision
4.4.1 1-phase/3-phase supervision
4.4.2 Principle of the voltage unbalance
protection
4.4.3 Measuring principle
4.4.4 Negative sequence system of a
symmetrical voltage system
4.4.5 System with voltage unbalance
4.4.6 Zero sequence system
5 Operations and settings
5.1 Display
5.2 Setting procedure
5.3 System parameter
5.3.1 Display of residual voltage UEas primary
quantity (Uprim/Usec)
5.3.2 D/Y – Switch - over
5.3.3 Setting of nominal voltage
5.3.4 Display of the activation storage
5.3.5 Parameter set change-over switch/
external trigger for the fault recorder
5.4 Protection parameters
5.4.1 1-phase or 3-phase U</U>- tripping
5.4.2 Parameter setting of over- and under-
voltage supervision
5.4.3 Positive sequence system voltage
(U1<, U1>)
5.4.4 Negative sequence system overvoltage
(U2>)
5.4.5 Zero sequence system overvoltage (U0>)
5.4.6 Adjustment of the slave address
5.4.7 Setting of Baud-rate (applies for Modbus-
Protocol only)
5.4.8 Setting of parity (applies for Modbus-
Protocol only)
5.5 Parameter for the fault recorder
5.5.1 Adjustment of the fault recorder
5.5.2 Number of the fault recordings
5.5.3 Adjustment of trigger occurences
5.5.4 Pre-trigger time (Tvor)
5.6 Date and time
5.6.1 Adjustment of the clock
5.7 Indication of measuring values
5.7.1 Measuring indication
5.7.2 Unit of the measuring values displayed
5.7.3 Indication in faultless condition
5.7.4 Indication after pickup/tripping
5.7.5 Indication of the phase sequence
5.8 Fault memory
5.9 Additional functions
5.9.1 Setting procedure for blocking the
protection functions
5.9.2 Reset
5.9.3 Erasure of fault storage
6 Relay testing and commissioning
6.1 Power-On
6.2 Testing the output relays
6.3 Checking the set values
6.4 Secondary injection test
6.4.1 Test equipment
6.4.1 Example of the test circuit
6.4.2 Checking the input circuits and
measuring functions
6.4.3 Test of the symmetrical components
values
6.4.4 Checking the operating and resetting
values of the over/undervoltage
functions
6.4.5 Checking the relay operating time of the
over/undervoltage functions
6.4.6 Checking the external blocking and reset
functions
6.5 Primary test
6.6 Maintenance
7 Technical Data
7.1 Measuring input circuits
7.2 Common data
7.3 Setting ranges and steps
7.3.1 Interface parameter
7.3.2 Parameter for the fault recorder
7.4 Output relays
8 Order form

TB MRU3-2 12.00 E 3
1 Introduction and application
The MRU3-2 is a relay for voltage supervision with
universal application, it protects the three-phase net-
work against voltage unbalance or earthfaults in iso-
lated networks. Beside the pure rms value measure-
ment of the line voltage the MRU3-2 evaluates the
symmetrical components (positive-, negative- and zero
sequence system). By evaluating these components re-
lay MRU3-2 can detect the phase sequence, voltage
unbalance and earthfaults.
Important:
For additional common data of all MR-relays please
refer to technical description "MR - Digital Multifunc-
tional Relays".
2 Features and characteristics
•Microprocessor technology with watchdog,
•digital filtering of the measured values by using dis-
crete Fourier analysis to suppress higher harmonics
and d.c. components induced by faults or system
operations,
•analog low pass filter,
•two parameter sets,
•voltage supervision each with two step under-/ and
overvoltage detection,
•Voltage supervision for each phase separately
•Completely independent time settings for voltage su-
pervision
•separate tripping elements for over- and undervolt-
age and positive sequence system
•overvoltage detection in negative- and zero se-
quence system,
•display of measuring values of the line voltages and
system voltages U0, U1 and U2 as rms values
(zero-, positive- and negative sequence system)
•alternatively connection and measurement of the
phase-to-neutral or phase-to-phase voltage
•display of the phase sequence,
•display of all measuring values and setting parame-
ters for normal operation as well as tripping via a
alphanumerical display and LEDs,
•display of measuring values as primary quantities,
•tripping memory for all line voltages and the volt-
ages of the symmetrical components,
•storage and display of tripping values in a fault
memory (voltage-failure safe),
•recording of up to eight fault occurences with time
stamp
•for blocking the individual functions by the external
blocking input, parameters can be set according to
requirement,
•suppression of indication after an activation
(LED flash),
•free assignment for output relays,
•display of date and time,
•in complience with VDE 0435, part 303 and IEC
255,
•mains frequency is adjustable to 50 Hz or 60 Hz or
variable from 40 - 70 Hz,
•RS485 interface for communication with master sys-
tems
•serial data exchange via RS485 interface possible;
alternatively with SEG RS485 Pro-Open Data Proto-
col or Modbus Protocol.

4TB MRU3-2 12.00 E
3 Design
3.1 Connections
Figure 3.1: Star connection of the voltage transformers
E8
D8
Blocking
Blockier-
C8
external
eingang
externer
Reset
Reset Input
D1
D2
D3
C1
C2
C3
E1
E2
E3
D4
C4
E4
Selbstüberwac ung
selfsupervision
D9
E9
C9
L+/L L-/N
~
=Relais 1
Relay 1
Relais 2
Relay 2
Relais 3
Relay 3
Relais 4
Relay 4
L1 L2 L3
t
U
A
B
C
a
b
c
tU1< / tU1>
tU2>
tU0>
U1< / U1>
U2>
U0>
A3
A5
A7
A8
Serielle Sc nittstelle
Serial Interface
N
G
P
N
G
P
SELECT/
RESET
+
-
ENTER
TRIP
Power
Supply
Hilfs-
Spannung
D5
C5
E5
D6
C6
E6
D7
C7
E7
A4
A6
t
U
tU< / tU>
U< / U>
Figure 3.2: Delta connection of the voltage transformers
Attention !
If the input transformers are connected in delta circuit
no detection of zero phase sequence (U0) is possible.

TB MRU3-2 12.00 E 5
3.1.1 Analog input circuits
The analog input voltages are galvanically decoupled
by the input transformers of the device, then filtered
and finally fed to the analog digital converter. De-
pending upon the demands the MRU3-2 can be con-
nected directly to the mains or via external voltage
transformers in star- or delta connection. The priority
should be given to the star connection, because of the
ability to detect a sero sequence system.
3.1.2 Blocking input
When the voltage, which must be in the admissible
range of the auxiliary voltage, is connected to termi-
nals D8/E8, the following tripping functions are
blocked undelayed:
•undervoltage U</U<<
•overvoltage U>/U>>
•positive sequence system undervoltage U1<
•positive sequence system overvoltage U1>
•negative sequence system overvoltage U2>
•zero sequence system overvoltage U0>
Blocking can be freely selected via the allocation
mode. (refer to chapter 5.9).
Input D8 is the ground (L- or N) for blocking and the
external reset. The blocked functions are again re-
leased undelayed when the auxiliary voltage is dis-
connected from the terminals D8/E8.
The above mentioned functions remain blocked for 2 s
after the supply voltage had been applied.
3.1.3 External reset input
Refer to chapter 5.9.2
3.1.4 Output relays
The MRU3-2 is equipped with 5 output relays.
•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; Signal self-supervision (internal failure of
the unit ) C7, D7, E7
All trip and alarm relays are working current relays, the
relay for self supervision is an idle current relay.
3.1.5 Fault recorder
The MRU3-2 has a fault value recorder which records
the measured analog values as instantaneous values.
The instantaneous values
UL1; UL2; UL3 for star connection
or U12; U23; U31 for delta connection
are scanned at a raster of 1.25 ms (at 50 Hz) and
1.041 ms (at 60 Hz) and saved in a cyclic buffer.
Storage division
Independent of the recording time, the entire storage
capacity can be divided into several cases of distur-
bance with a shorter recording time each. In addition,
the deletion behaviour of the fault recorder can be in-
fluenced.
No writing over
If 2, 4 or 8 recordings are chosen, the complete
memory is divided into the relevant number of partial
segments. If this max. number of fault event has been
exceeded, the fault recorder block any further record-
ings in order to prevent that the stored data are written
over. After the data have been read and deleted, the
recorder to ready again for further action.

6TB MRU3-2 12.00 E
Writing over
If 1, 3 or 7 recordings are chosen, the relevant num-
ber of partial segments is reserved in the complete
memory. If the memory is full, a new recording will
always write over the oldest one.
The memory part of the fault recorder is designed as
circulating storage. In this example 7 fault records can
be stored (written over).
Memory space 6 to 4 is occupied.
Memory space 5 is currently being written in
Figure 3.3: Division of the memory into 8 segments, for example
Since memory spaces 6, 7 and 8 are occupied, this
example shows that the memory has been assigned
more than eight recordings. This means that No. 6 is
the oldest fault recording and No. 4 the most recent
one.
trigger occurence
recording duration
Tpre
[s]
Figure 3.4: Basic set-up of the fault recorder
Each memory segment has a specified storage time
which permits setting of a time prior to the trigger
event.
3.1.6 Parameter settings
System parameters
Uprim/Usek Primary/secondary measured value
display of the voltage transformers
D/Y Selection of switching groups
fNRated frequency
LED-Flash Suppression of LED flashing after
activation
P2/FR Parameter switch/external trigger for the
fault recorder
Protection parameters
1/3 1-phase or 3-phase U</U> tripping
U< Pickup value for undervoltage
tU< Trip value for undervoltage low set element
U<< Pickup value for undervoltage
tU<< Trip value for undervoltage high set element
U> Pickup value for overvoltage
tU> Trip value for overvoltage low set element
U>> Pickup value for overvoltage
tU>> Trip value for overvoltage high set element
U1< Pick-up value for undervoltage in positive-
phase sequence system
tU1< Trip value for undervoltage in positive-
phase sequence system
U1> Pick-up value for overvoltage in positive-
phase sequence system
tU1> Trip value for overvoltage in positive-
phase sequence system
U2> Pick-up value for overvoltage in negative-
phase sequence system
tU2> Trip value for overvoltage in negative-
phase sequence system
U0> Pick-up value for overvoltage in zero-
phase sequence system
tU0> Trip value for overvoltage in zero-phase
sequence system
Parameters for the fault recorder
FR Number of disturbance events
FR Trigger events
FR Pre-trigger time Tvor
Date and time
Year Y = 00
Month M = 04
Day D = 18
Hour h = 07
Minute m = 59
Second s = 23
Additional functions
Blocking function
Relay configuration
Fault memory

TB MRU3-2 12.00 E 7
3.2 Display
The display is used for indicating all setting- and
measuring values. The actual measuring values as also
the fault values can be indicated. In faultless operation
the indicated value of the normal operation can be
called by pressing the <SELECT> and <ENTER> push-
buttons.
After tripping the display changes into the tripping
mode from where fault data can be called.
3.3 LEDs
LEDs L1, L2, L3, U1 and U2 left from the display are
two-colored and indicate the measured quantities;
green for measuring values and red for fault indication.
LED U0 lights yellow which normally indicates (relay
not tripped) that the measuring value of the zero se-
quence system and in case of tripping the tripping
value of the zero sequence system is shown in the dis-
play.
The LED marked with the letters RS lights up during set-
ting of the slave address for the serial interface
(RS 485) of the unit.
The LED marked with "FR" lights up during parameter
setting at the fault recorder. When LED !lights up,
date and time are displayed. LED "PS" indicates the
phase sequence.
The 9 LEDs below the <SELECT/RESET> pushbutton
signalize the parameter of the individual tripping ele-
ments. In case of tripping they indicate, together with
the upper LEDs, the respective kind of fault.
A permanent red light indicates tripping. When the
tripping delay has not elapsed the LEDs of the corre-
sponding combination (at pickup) are flashing.
If one of the limit values is exceeded for only a short
time before the set tripping delay is not expired, the
corresponding LED combination flashes. This flashing is
shorter than for warning. This pickup warning signal
can be switched off with a reset. This activation signal
can be shut-down with the "Reset" key (refer to chapter
5.9.2) or suppressed by the FLASH/NO_FLASH func-
tion. The active parameter set is indicated by LED "P2".
LED D/Y lights up during parameter setting for the in-
terlinking of the input voltage CTs.
3.4 Front plate
Figure 3.5: Front plate MRU3-2

8TB MRU3-2 12.00 E
4 Working principle
4.1 Analog circuits
The input voltages are galvanically insulated by the in-
put transformers. The noise signals caused by inductive
and capacitive coupling are supressed by an analog
R-C filter circuit.
The analog voltage signals are fed to the A/D-
converter of the microprocessor and transformed to
digital signals through Sample- and Hold- circuits. The
analog signals are sampled with a sampling frequency
of 16 x fN, namely, a sampling rate of 1.25 ms for
every measuring quantity, at 50 Hz.
4.2 Digital circuits
The essential part of the MRU3-2 relay is a powerful
microcontroller. All of the operations, from the analog
digital conversion to the relay trip decision, are carried
out by the microcontroller digitally. The relay program
is located in an EPROM (Electrically-Programmable-
Read-Only-Memory). With this program the CPU of the
microcontroller calculates the three phase voltage in
order to detect a possible fault situation in the pro-
tected object.
For the calculation of the voltage value an efficient
digital filter based on the Fourier Transformation (DFFT -
Discrete Fast Fourier Transformation) is applied to sup-
press high frequency harmonics and d.c. components
caused by fault-induced transients or other system dis-
turbances. The microprocessor continuously compares
the measured values with the preset thresholds stored
in the parameter memory (EEPROM). If a fault occures
an alarm is given and after the set tripping delay has
elapsed, the corresponding trip relay is activated.
The relay setting values for all parameters are stored in
a parameter memory (EEPROM - Electrically Erasable
Programmable Read Only Memory), so that the actual
relay settings cannot be lost, even if the power supply
is interrupted.
The microprocessor is supervised by a built-in "watch-
dog" timer. In case of a failure the watchdog timer re-
sets the microprocessor and gives an alarm signal via
the output relay "self supervision".
4.3 Selection of star or delta
connection
All six connections of the input voltage transformers are
led to screw terminals. The nominal voltage of the de-
vice is equal to the nominal voltage of the input trans-
formers. Dependent on the application the input trans-
formers can be connected in either delta or star. The
connection for the phase-to-phase voltage is the delta
connection. In star connection the measuring voltage is
reduced by 1/ 3 . During parameter setting the con-
nection configuration either Y or ∆has to be adjusted.
)!
)"
)#
)$
)%
)&
7
7 !
7!
Sec. winding of
mains V.T.
=
>
?
Figure 4.1: Input v.t.s in delta connection (D)
)!
)"
)#
)$
)%
)&
7
7
7!
Sec. winding of
mains V.T.
=
>
?
Figure 4.2: Input v.t.s in star connection (Y)

TB MRU3-2 12.00 E 9
4.4 Voltage supervision
4.4.1 1-phase/3-phase supervision
The voltage relay MRU3-2 protects electrical genera-
tion systems, consumers and appliances in general
against over- and/or undervoltage. The relay is
equipped with an independent, 2-step over- (U>, U>>)
and undervoltage supervision (U<, U<<) with sepa-
rately adjustable tripping values and delay times. Volt-
age measuring is 3-phase. In this process there is a
continuous comparison of the line conductor voltages
in case of a delta connection and of the phase volt-
ages in case of a star connection with the pre-set limit
values.
With the MRU3-2 the highest voltage is always evalu-
ated for overvoltage supervision and the lowest volt-
age for undervoltage supervision.
A distinction is made between 1-phase and 3-phase
tripping. (1/3 – Parameter)
With 1-phase tripping the voltages are evaluated as
follows:
U</U<</U</U>>: Activation cum tripping takes
place if at least one phase has fallen short of the trip-
ping value.
With 3-phase tripping the voltages are evaluated as
follows:
U<: Activation cum tripping takes place if all three
phases have fallen short of the tripping value.
U<<: Activation cum tripping takes place if one phase
has fallen short of the tripping value.
U>: Activation cum tripping takes place if all three
phases have exceeded the tripping value.
U>> Activation cum tripping takes place if one phase
has exceeded the tripping value.
4.4.2 Principle of the voltage unbalance
protection
The principle of this procedure is to detect faults which
effect an asymmetry of the voltage vector.
A single-phase line interruption can for instance cause
voltage unbalance in the mains which does not guar-
antee that the voltage will be zero in the faulty phase.
Especially in higher impedance networks the missing
phase can partly be rebuilt through running engines or
transformers. A pure undervoltage protection cannot
detect this condition, however, the rebuilt phase does
not coincide with its old position in amount and phase.
So an asymmetrical voltage vector system is formed.
In a compensated or isolated grid a single-phase
earthfault will hardly cause a significant earth current.
Because, however, the faulty phase takes on the earth
potential the entire voltage vector system is shifted by
the amount of the faulty phase and does not rotate
anymore around the initial star point (earth). The rela-
tive position of the voltage vectors between each other
is hereby not changed. Also this vector system is not
symmetrical anymore in relation to the earth potential.
The MRU3-2 can detect such asymmetry.

10 TB MRU3-2 12.00 E
4.4.3 Measuring principle
Any rotating three-phase system (original system) can
be replaced by three symmetrical systems acc. to the
method of the "symmetrical components", a positive
sequence system, a negative sequence system and a
zero sequence system.
Positive sequence system U1:
The rms value of the positive sequence system repre-
sents the component of the original system which is
symmetrical and rotates in the positive direction acc. to
its definition. A pure symmetrical voltage vector system
consists only of its positive sequence system.
The residual voltage in the positive sequence system is
calculated by:
U1 = 1/3| ( U1+ a1U2+ a2U3) |
Negative sequence system U2:
The rms value of the negative sequence system de-
scribes the component of the vector system which ro-
tates in negative direction. The rotating field, which ro-
tates in the mathematical sense in the negative direc-
tion (so-called "left rotating field"), consists only of a
negative sequence system. A measure for the size of
the asymmetry of the original system represents the re-
sidual voltage in the negative sequence system.
The residual voltage in the negative sequence system
is calculated as follows:
U2 = 1/3| ( U1+ a2U2+ a1U3) |
Zero sequence system U0:
The zero sequence system describes the displacement
of the vector star point from the reference star point.
This reference star point is generally the earth poten-
tial.
The residual voltage in the zero sequence system is
calculated as:
U0 = 1/3| ( U1+ U2+ U3) |
Used variables:
(complex vectors are underlined)
U1rms value vector of phase voltage L1
U2rms value vector of phase voltage L2
U3rms value vector of phase voltage L3
U0 rms value of the zero sequence
system
U1 rms value of the negative sequence
system
U2 rms value of the positive sequence
system
a1= e i120° rotation operator for 120o
a2= e i240° rotation operator for 240o
Explanation:
a2U2means:
Rotate the voltage vector U2by 240oin positive direc-
tion (to the left).

TB MRU3-2 12.00 E 11
4.4.4 Negative sequence system of
a symmetrical voltage system
Figure 4.3: Graphical determination of the negative sequence system in a symmetrical system
Figure 4.3 shows a symmetrical vector system. As in-
dicated in the calculation the MRU3-2 forms the nega-
tive sequence system. For this it rotates per software
both voltage vectors U2by 240o and U3by 120o
and adds them. Acc. to definition the result of the vec-
tor must be multiplied by 1/3. In this example the sum
equals zero. Conclusion: the source system is symmet-
rical.
4.4.5 System with voltage unbalance
Figure 4.4: Graphical determination of the negative sequence system in an asymmetrical system
Figure 4.4 shows the voltage vectors of an asymmetri-
cal grid. A residual negative sequence system voltage,
which is not zero, is calculated in this example. Should
this residual voltage exceed the set treshold, which is
indicated as rms value, the relay trips after the prese-
lected time delay.
For the exact rotation of the current vectors by 120oor
240othe system frequency has to be pricisely ad-
justed.

12 TB MRU3-2 12.00 E
4.4.6 Zero sequence system
To decide whether a vector system is symmetrically,
the point, the symmetry has to refer to, is always to be
mentioned. Usually this point is the earth potential.
When an earthfault occurs in an isolated or compen-
sated grid, it does not influence the relative position of
the three voltage vectors to each other, mains opera-
tion can be maintained. The vector peak of the missing
phase is forced on the earth potential. For an observer
who takes the earth potential as reference, the star
point shifts by the amount of the missing phase. For
him the voltage vector system is not anymore symmetri-
cal. The exact measure of the shifting results from re-
placing this system in symmetrical components in the
developed zero sequence system.
Note:
Shall the relay evaluate the zero sequence system it is
absolutely necessary that the voltage transformers and
the MRU3-2 are wired in star connection. The star
points must be earthed, furthermore the MRU2-2 must
be set to Y-connection. In delta connection no zero
sequence system evaluation is possible and thus no
earthfault detection.
When only the phase-to-phase voltages are measured,
the vector star point is not known, thus also the posi-
tion of the star point in regard to the earth potential
cannot be defined.
Symmetrical vector system Vector system with earth fault
U0~0V U0~230V
Phase-to-phase voltage
400 V
Phase-to-phase voltage
400 V
star point star point
Figure 4.5: Zero point shifting after earthfault in the isolated grid

TB MRU3-2 12.00 E 13
5 Operations and settings
5.1 Display
Function Display shows Pressed pushbutton Corresponding LED
Normal operation SEG
Measured operating values Actual measured value <SELECT/RESET>
one time for each value
L1, L2, L3, U1, U2,
U0
Phasenfolge 123; 321 PS
Transformer ratio of the CT’s (SEK) 1.01-6500=prim <SELECT/RESET><+><-> L1, L2, L3
Setting values
Star/delta connection
Y/DELT <SELECT/RESET><+><-> D/Y
Mains frequency f = 50 Hz, f = 60 Hz
v = 50 Hz, v = 60 Hz
<SELECT/RESET><+><-> fN
Parameter switch/external trig-
ger for the fault recorder SET1, SET2, B_S2, R_S2,
B_FR, R_FR, S2_FR
<SELECT/RESET><+><-> P2
Switch-over LED flash
No LED flash
FLSH
NOFL
<SELECT/RESET><+><->
U</U> 1-phase/3-phase
tripping
U<>1/U<>3 <SELECT/RESET><+><-> 1/3
undervoltage (low set)
tripping delay of low set element
Setting value in volt
Setting value in seconds
<SELECT/RESET><+><->
one time for each value
U<
tU<
undervoltage (high set)
tripping delay of high set element
Setting value in volt
Setting value in seconds
<SELECT/RESET><+><->
one time for each value
U<<
tU<<
overvoltage (low set)
tripping delay of low set element
Setting value in volt
Setting value in seconds
<SELECT/RESET><+><->
one time for each value
U>
tU>
overvoltage (high set)
tripping delay of high set element
Setting value in volt
Setting value in seconds
<SELECT/RESET><+><->
one time for each value
U>>
tU>>
positive-phase sequence system un-
dervoltage U1<; trip delay tU1<
Setting value in volt
Setting value in seconds
<SELECT/RESET><+><->
one time for each value
U1<
tU1<
positive-phase sequence system
overvoltage U1>; trip delay tU1>
Setting value in volt
Setting value in seconds
<SELECT/RESET><+><->
one time for each value
U1>
tU1>
negative-phase sequence system
overvoltage U2>; trip delay tU2>
Setting value in volt
Setting value in seconds
<SELECT/RESET><+><->
one time for each value
U2>
tU2>
zero-phase sequence system U0>
trip delay tU0>
Setting value in volt
Setting value in seconds
<SELECT/RESET><+><->
one time for each value
U0>
tU0>
Function blocking EXIT <+> until max. setting
<-> until min. setting
LED of blocked pa-
rameter
Slave adresse of serial interface 1 - 32 <SELECT/RESET><+><-> RS
Baud-Rate 1) 1200-9600 <SELECT/RESET><+><-> RS
Parity-Check 1) even odd no <SELECT/RESET><+><-> RS
Recorded fault data:
Star-connection: L1, L2, L3
Symmetrical components:
U1, U2, U0
Tripping values in volt <SELECT/RESET><+><-> one
time for each phase
L1, L2, L3; U1, U2,
U0, U<, U<<, U>,
U>>, U1<, U1>,
U2>, U0>
Delta-connection: L1/L2, L2/L3,
L3/L1
symmetrical components: U1, U2
Tripping values in volt <SELECT/RESET><+><->
one time for each phase
L1, L2, L3, U1, U2,
U<, U<<, U>, U>>,
U1<, U1>, U2>
Save parameter? SAV? <ENTER>
Save parameter! SAV! <ENTER> for about 3 s
Delete failure memory wait <-> <SELECT/RESET>
Enquiry failure memory FLT1; FLT2..... <-><+> L1, L2, L3
U<, U<<, U>, U>>
Trigger signal for the fault recorder TEST, P_UP, A_PI, TRIP <SELECT/RESET> <+><-> FR
1) only Modbus

14 TB MRU3-2 12.00 E
Function Display shows Pressed pushbutton Corresponding LED
Number of fault occurences S = 2, S = 4, S = 8 <SELECT/RESET> <+><-> FR
Display of date and time Y = 99, M = 10,
D = 1,
h = 12, m = 2, s = 12
<SELECT/RESET> <+><-> "
Software version First part (e. g. D02-)
Second part (e. g. 6.01)
<TRIP> one time for each part
Manual trip TRI? <TRIP> three times
Inquire password PSW? <SELECT/RESET>/
<+>/<->/<ENTER>
Relay tripped TRIP <TRIP> or fault tripping
Secret password input XXXX <SELECT/RESET>/
<+>/<->/<ENTER>
System reset SEG <SELECT/RESET>
for about 3 s
Table 5.1: Possible indication messages on the display

TB MRU3-2 12.00 E 15
5.2 Setting procedure
In this paragraph the settings for all relay parameters
are described in detail. For parameter setting a pass-
word has to be entered first (please refer to 4.4 of de-
scription "MR-Digital Multifunctional Relays").
5.3 System parameter
5.3.1 Display of residual voltage UE
as primary quantity (Uprim/Usec)
The residual voltage can be shown as primary measur-
ing value. For this parameter the transformation ratio of
the VT has to be set accordingly. If the parameter is set
to "sec", the measuring value is shown as rated secon-
dary voltage.
Example:
The voltage transformer used is of 10 kV/100 V. The
transformation ratio is 100 and this value has to be set
accordingly. If still the rated secondary voltage should
be shown, the parameter is to be set to 1.
5.3.2 D/Y – Switch - over
Depending on the mains voltage conditions, the input
voltage transformers can be operated in delta or Y
connection. Change-overs are effected via the <+>
and the <-> keys and stored with <ENTER>.
5.3.3 Setting of nominal voltage
For proper functioning it is necessary to first adjust the
rated frequency (50 oder 60 Hz).
It can be selected between „f = 50 Hz“, „f = 60 Hz“
or „v = 50 Hz“, “v = 60 Hz”.
The difference lies in the method of voltage measuring.
With the setting "v = 50 Hz“ or “v = 60 Hz” voltage
measuring is independent of the existing frequency.
This means, the voltage value can be correctly meas-
ured between 40 Hz and 70 Hz without adverse ef-
fects from the frequency.
With the setting "f“ = 50/60 Hz the measured voltage
value is influenced by the frequency. (see Table 5.2)
Declination of measuring value at 50Hz
97,5
98,0
98,5
99,0
99,5
100,0
100,5
44 46 48 50 52 54 56
[%]
[Hz]
Declination of measuring value at 60Hz
97,5
98,0
98,5
99,0
99,5
100,0
100,5
54 56 58 60 62 64 66
[%]
[Hz]
Table 5.2: Impairment of voltage measuring
This difference in settings is required for the fault re-
corder. If the fault recorder is to be used, the setting
must be f = 50 Hz or f = 60 Hz.
At 50 Hz or 60 Hz the fault recorder determines 16
measured values per period. With the setting "v = 50
Hz" or “v = 60 Hz” 16 measured values of the pres-
ently measured frequency would always be deter-
mined. The disturbance recorder would not indicate
any frequency changes and thus render incorrect
measuring results.
Setting v = 50 f = 50 v = 60 f = 60
Rated frequency 50 Hz 50 Hz 60 Hz 60 Hz
Influence on voltage
measurement
none 0,5..1%/Hz
(refer to table 5.1)
none 0,5..1%/Hz
(refer to table 5.1)
Fault recorder Recording
distorted**
Recording
correct**
Recording
distorted**
Recording
correct**
Influence on all other
functions
none none none none
Table 5.3: Deviation of measured value at 50 Hz or 60 Hz
* Setting is important for correct recording of fault recorder
** Sample rate is variably adjusted to the momentarily measured frequency. 16 samples are always measured in one period.
*** Sample rate setting is fixed to 50 Hz or 60 Hz. 16 samples per 20 ms or 16.67 ms are always measured.

16 TB MRU3-2 12.00 E
5.3.4 Display of the activation storage
If after an activation the existing current drops again
below the pickup value, e.g. U<, without a trip has
been initiated, LED U< signals that an activation has
occured by flashing fast. The LED keeps flashing until it
is reset again (push button <RESET>). Flashing can be
suppressed when the parameter is set to NOFL.
5.3.5 Parameter set change-over
switch/external trigger for the
fault recorder
By means of the parameter-change-over switches it is
possible to activate two different parameter sets. Swit-
ching over of the parameter sets can either be done
by means of software or via the external inputs RESET
or blocking input. Alternatively, the external inputs can
be used for Reset or blocking of the triggering of the
fault recorder.
Software-
parameter
Blocking input
used as
RESET input
used as
SET1 Blocking input RESET input
SET2 Blocking input RESET input
B_S2 Parameter switch RESET input
R_S2 Blocking input Parameter
switch
B_FR Externe Trig-
gerung des Stör-
schreibers
Reset input
R_FR Blocking input External trigger-
ing for the fault
recorder
S2_FR Parameter switch External trigger-
ing for the fault
recorder
With the settings SET1 or SET2 the parameter set is
activated by software. Terminals C8/D8 and D8/E8
are then available as external reset input or blocking
input.
With the setting B_S2 the blocking input (D8, E8) is
used as parameter-set change-over switch. With the
setting R_S2 the reset input (D8, E8) is used as para-
meter-set change-over switch. With the setting B_FR the
fault recorder is activated immediately by using the
blocking input. On the front plate the LED FR will then
light up for the duration of the recording. With the set-
ting R_FR the fault recorder is activated via the reset
input.
With the setting S2_FR parameter set 2 can be activa-
ted via the blocking input and/or the fault recorder via
the reset input.
The relevant function is then activated by applying the
auxiliary voltage to one of the external inputs.
Important note:
When functioning as parameter change over facility,
the external input RESET is not available for resetting.
When using the external input BLOCKING the protec-
tion functions must be deactivated by software block-
ing separately (refer to chapter 5.9.1).
5.4 Protection parameters
5.4.1 1-phase or 3-phase U</U>-
tripping
Switching-over of the parameter permits selection be-
tween 1-phase and 3-phase tripping of the U</U>
steps.
Keys <+> or <-> are used to change the value and
<ENTER> to store it.
Note
When the MRU3-2 is to be used for measuring the re-
sidual voltage in systems with isolated or compensated
neutral or as generator earth fault protection, the
measuring voltage has to be applied to terminals
A3-A4. Undervoltage functions U< and U<< have to
be set to "EXIT" and overvoltage functions U> and U>>
have to be adjusted to the required pickup values.
The frequency must be set to 50 or 60 Hz. The pa-
rameter 1-phase or 3-phase tripping mut be set to
U<>1 (1-phase tripping).

TB MRU3-2 12.00 E 17
5.4.2 Parameter setting of over- and
undervoltage supervision
The setting procedure is guided by two coloured
LEDs. During setting of the voltage thresholds the LEDs
U<, U<<, U> and U>> are lit green. During setting of
the trip delays tU>, tU>>, tU< and tU<< the according LEDs
light up red.
Thresholds of the voltage supervision
During setting of the threshold U>, U>>, U< and U<<
the displays shows the voltages directly in volt. The
thresholds can be changed by the <+> <-> push but-
tons and stored with <ENTER>.
The undervoltage supervision (U< and U<<) as well as
the overvoltage supervision (U> and U>>) can be de-
activated by setting the threshold to "EXIT".
Tripping delay of voltage supervision
During setting of the tripping delays tU<, tU<<, tU> and tU>>
the display shows the value directly in seconds. The
tripping delay is changed via the push button <+>
and <-> in the range of 0,04 s to 50 s and can be
stored with the push button <ENTER>.
When setting the tripping delay to "EXIT" the value is
infinit meaning only warning, no tripping.
5.4.3 Positive sequence system
voltage (U1<, U1>)
Rms values and tripping delays can be set in the simi-
lar manner as described for the normal under-/over
voltage settings. Both elements can be blocked or set
as alarm stages.
5.4.4 Negative sequence system
overvoltage (U2>)
This parameter determines the treshold for the rms
value of the negative sequence system. As described
in 5.4.2, the entire stage can be blocked or set as
alarm element.
5.4.5 Zero sequence system
overvoltage (U0>)
The treshold for the rms value of the zero sequence sys-
tem can be set with this parameter. Also here it is pos-
sible, as described in chapter 5.4.2, to block the en-
tire element or to set it only as alarm element.
5.4.6 Adjustment of the slave address
By pressing push buttons <+> and <-> the slave ad-
dress can be set in the range of 1 - 32. During this ad-
justment the LED RS lights up.
5.4.7 Setting of Baud-rate (applies for
Modbus-Protocol only)
Different transmission rates (Baud rate) can be set for
data transmission via Modbus Protocol.
The rate can be changed by push buttons <+> and
<-> and saved by pressing <ENTER>.
5.4.8 Setting of parity (applies for
Modbus-Protocol only)
The following three parity settings are possible :
•"even" = even
•"odd" = odd
•"no" = no parity check
The setting can be changed by push buttons <+> and
<-> and saved by pressing <ENTER>.
5.5 Parameter for the fault recorder
5.5.1 Adjustment of the fault recorder
The MRU3-2 is equipped with a fault recorder (refer to
chapter 3.1.5). Three parameters can be determined.

18 TB MRU3-2 12.00 E
5.5.2 Number of the fault recordings
The max. recording time is 16 s at 50 Hz or 13.33 s
at 60 Hz.
The number of max. recordings requested has to be
determined in advance. There is a choice of (1)* 2,
(3)* 4 or (7)* 8 recordings and dependent on this the
duration of the individual fault recordings is defined,
i.e.
(1)* 2 recordings for a duration of 8 s (with 50 Hz)
(6.66 s with 60 Hz)
(3)* 4 recordings for a duration of 4 s (with 50 Hz)
(3.33 s with 60 Hz)
(7)* 8 recordings for a duration of 2 s (with 50 Hz)
(1.66 s with 60 Hz)
* is written over when a new trigger signal arrives
Caution:
If the fault recorder is used, the frequency should be
set to f = 50 Hz or f = 60 Hz (refer to chapter 5.3.3).
5.5.3 Adjustment of trigger occurences
There is a choice between four different occurences:
P_UP (PickUP) Storage is initiated after recognition
of a general activation.
TRIP Storage is initiated after a trip has
occured.
A_PI (After Pickup) Storage is initiated after the last
activation threshold was fallen
short of.
TEST Storing is activated by simultaneous
actuation of the keys <+> and <->.
During the recording time the
display shows “Test”.
5.5.4 Pre-trigger time (Tvor)
By the time Tpre it is determined which period of time
prior to the trigger occurence should be stored as well.
It is possible to adjust a time between 0.05s and the
max. recording interval (2, 4 and 8s at 50 Hz and
1.33; 3.33 and 6.66 s at 60 Hz). With keys <+>
and <-> the values can be changed and with
<ENTER> be saved.
5.6 Date and time
5.6.1 Adjustment of the clock
When adjusting the date and time, LED "lights up.
The adjustment method is as follows:
Date : Year Y=00
Month M=01
Day D=01
Time : Hour h=00
Minute m=00
Second s=00
The clock starts with the set date and time as soon as
the supply voltage is switched on. The time is safe-
guarded against short-term voltage failures (min. 6
minutes).
Note:
The window for parameter setting is located behind
the measured value display. The parameter window
can be accessed via the <SELECT/RESET> key.

TB MRU3-2 12.00 E 19
5.7 Indication of measuring values
5.7.1 Measuring indication
In normal operation the following measuring values
can be displayed.
•Voltages (LED L1, L2, L3 green)
•In star connection all phase-to-neutral voltages
•In delta connection all phase-to-phase voltages
•Phase sequence (LED PS yellow)
5.7.2 Unit of the measuring values
displayed
The measuring values can optionally be shown in the
display as a multiple of the "sek" rated value (x ln) or
as primary current (A). According to this the units of the
display change as follows:
Indication as Range Unit
Sec. voltage 000V - 999V V
Primary voltage .00V – 999V
1k00 – 9k99
10k0 – 99k0
100k – 999k
1M00 –-
3M00
V
kV
kV
kV
MV
Table 5.4: Units of the display
5.7.3 Indication in faultless condition
In normal operation the display always shows |SEG.
After pressing the pushbutton <SELECT/RESET> the
display switches cyclically to the next value. After the
measuring values had been indicated the setting pa-
rameters are displayed. Hereby the LEDs in the upper
section signalize which measured value is indicated,
the LEDs in the lower section signalize which setting
parameter is indicated on the display. Longer actuat-
ing the pushbutton resets the relay and the display
changes into normal operation (|SEG).
5.7.4 Indication after pickup / tripping
In tripped condition "TRIP" appears on the display and
the LEDs of the operating measuring data light up red
together with the LEDs of the tripping parameter (U0:
yellow). All operating data, which were measured at
the moment of tripping, can now be called one after
another by pressing pushbutton <SELECT/RESET>. (re-
fer to chapter 5.8). By pressing the <-> key, the fault
memory can be retrieved. If in this condition setting
parameters are to be indicated, pushbutton <ENTER>
has to be pressed.
The graphic below shows again the difference be-
tween the different display modes.

20 TB MRU3-2 12.00 E
<SELECT>
<SELECT>
<SELECT>
<ENTER>
|SEG TRIP
<SELECT>
<SELECT>
<ENTER>
<SELECT>
Display after tripping
Display in normal operation
Tripping
<RESET>
Measuring data
Parameter Parameter Failure data
Figure 1.1: Switching over of the display in dependence of the operating mode.
5.7.5 Indication of the phase sequence
The indication refers to the designation of the voltage
input terminals. The sequence can be "123" or "321".
Which phase sequence is the correct one depends
upon the given case of application. But in any case
the assignment has to be met which phase sequence
shall correspond to the positive sequence system.
Display "123" means that the connected rotating field
has the positive sequence system of unit MRU3-2 and
thus is considered as correct. If these voltages are ad-
ditionally symmetrical, there will be no negative se-
quence system and the positive sequence system has
the same rms value as the phase voltages.
If the phase sequence "321" is indicated the assign-
ment could be wrong. This has to be checked whether
the applied voltages show a wrong phase sequence
or whether there is a fault in the connection. When
"???" is indicated the unit signalizes that no clear
measurement of the phase sequence is possible.