Seg MRU3-1 User manual

MRU3-1 –AC voltage relay

2TB MRU3-1 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 Reset input
3.1.4 Output relays
3.1.5 Fault recorder
3.1.6 Parameter settings
3.2 LEDs
3.3 Front plate
4 Working principle
4.1 Analog circuits
4.2 Digital circuits
4.3 Voltage supervision
4.3.1 Selection of star or delta connection
4.4 Blocking function
5 Operations and settings
5.1 Display
5.2 Setting procedure
5.3 Systemparameter
5.3.1 Display of residual voltage UEas
primary quantity (Uprim/Usec)
5.3.2 ∆/Y – Switch over
5.3.3 Setting of nominal frequency
5.3.4 Display of the activation storage
5.3.5 Parameter switch/external triggering 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 Adjustment of the slave address
5.4.4 Setting of Baud-rate (applies for Modbus-
Protocol only)
5.4.5 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 (Tpre)
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 of fault memory data
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
6.4.2 Example of the test circuit
6.4.3 Checking the input circuits and
measuring functions
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 MRU3-1 12.00 E 3
1 Introduction and application
The voltage supervision relay MRU3-1 protects electri-
cal power generators, consumers or operating com-
ponents generally against over- or undervoltages.
Among other applications the relay can be used:
•for detection of over- or undervoltages in power gen-
rating plants and energy supply systems
•to protect generators against critical overvoltages in
case of defective voltage regulators
•as undervoltage protection for motors
•as generator stator earth fault protection
•as over- and undervoltage protection with evaluating
the symmetrical components (MRU1-2, detailed in-
formation on this type can be found in the relevant
technical description)
There is also a similar protection relay IRU1 available
in a more simpler design, i.e. with less function, with-
out display and without serial interface.
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,
•two parameter sets,
•voltage supervision each with two step under-/ and
overvoltage detection,
•Completely independent time settings for voltage su-
pervision
•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
•1-phase or 3-phase tripping criterion for the U</U>
step,
•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,
•serial data exchange via RS485 interface possible;
alternatively with SEG RS485 Pro-Open Data Proto-
col or Modbus Protocol.

4TB MRU3-1 12.00 E
3 Design
3.1 Connections
Figure 3.1: Connection of the MRU3-1 to phase-to-phase voltage
Note: Connection of phase-to-neutral voltage is possible too.
Figure 3.2: Voltage transformer in V-connection
3.1.1 Analog input circuits
The external wiring of the measuring circuits are shown
in the connection diagram. The analog input voltages
are galvanically decoupled by the input transformers of
the device, then filtered and finally fed to the analog
digital converter. The measuring circuits can be con-
nected in star or delta connection.
3.1.2 Blocking input
When required to inhibit functions of the relay, the
auxiliary voltage has to be switched to D8/E8. Please
refer to chapter 4.4.
3.1.3 Reset input
Please refer to chapter 5.9.2.

TB MRU3-1 12.00 E 5
3.1.4 Output relays
The MRU3-1 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 MRU3-1 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; U21 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. It is
possible to store 1 - 8 fault occurences with a total re-
cording time of 16 s (with 50 Hz) and 13.33 s (with
60 Hz) per channel.
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.
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.

6TB MRU3-1 12.00 E
3.1.6 Parameter settings
System parameters
Uprim/Usek Primary/secondary measured value
display of the voltage transformers
∆/ Y Selection of switching groups
fNRated frequency
P2|FR Parameter switch/ext. triggering for the
fault recorder
LED-Flash Suppression of LED flashing after
activation
Protection parameters
1/3 1-phase U</U> or 3-phase U</U>
tripping
U< Tripping value for undervoltage low set
element
tU< Tripping delay time for undervoltage low
set element
U<< Tripping value for undervoltage high set
element
tU<< Tripping delay time for undervoltage
high
set element
U> Tripping value for overvoltage low set
element
tU> Tripping delay time for overvoltage low
set element
U>> Tripping value for overvoltage high set
element
tU>> Tripping delay time for overvoltage high
set element
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
3.2 LEDs
All LEDs (except LED RS, FR and P2) are two-coloured.
The LEDs on the left side, next to the alphanumerical
display light up green during measuring and red after
tripping.
The LEDs below the push button <SELECT/RESET> are
lit green during setting and inquiry procedure of the
setting values which are printed on the left side next to
the LEDs. The LEDs will light up red after parametrizing
of the setting values next to their right side.
The LED marked with letters RS lights up during setting
of the slave address of the device for serial data com-
munication.
The LED marked with the letters FR is alight while the
fault recorder is being adjusted.
If the ! LED is displayed, date and time are shown.
3.3 Front plate
Figure 3.5: Front plate MRU3-1

TB MRU3-1 12.00 E 7
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 MRU3-1 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 Voltage supervision
The voltage relay MRU3-1 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 preset limit
values.
With the MRU3-1 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 or tripping takes place
if at least one phase has fallen short of the tripping
value.
With 3-phase tripping the voltages are evaluated as
follows:
U<: Activation or tripping takes place if all three
phases have fallen short of the tripping value.
U<<: Activation or tripping takes place if one phase
has fallen short of the tripping value.
U>: Activation or tripping takes place if all three
phases have exceeded the tripping value.
U>> Activation or tripping takes place if one phase
has exceeded the tripping value.

8TB MRU3-1 12.00 E
4.3.1 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 delta has to be ad-
justed.
)!
)"
)#
)$
)%
)&
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)
4.4 Blocking function
No. Dynamic Behaviour U</<< U>/>>
1 voltage to external
blocking input is ap-
plied
free pro-
gramma-
ble
free pro-
gramma-
ble
2 blocking input is
released
released
instanta-
neously
released
instanta-
neously
3 supply voltage is
switched on
blocked
for
200 ms
blocked
for 200
ms
4 3ph measuring volt.
is suddenly applied
released released
5 one or several meas-
uring voltages are
switched off suddenly
(phase failure)
released released
Table 4.1: Dynamic behaviour of MRU3-1 functions
Blocking function set in compliance with require-
ments:
The MRU3-1 has an external blocking input. By apply-
ing the auxiliary voltage to input D8/E8, the re-
quested protection functions of the relay are blocked
(refer to chapter 5.9.1)

TB MRU3-1 12.00 E 9
5 Operations and settings
5.1 Display
Function Display shows Pressed pushbutton Corresponding LED
Normal operation SEG
Measured operating values Actual measured values <SELECT/RESET> one time
for each value
L1, L2, L3,
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><+><-> ∆/Y
Parameter switch/ext. triggering
for the fault recorder SET1, SET2, B_S2, R_S2,
R_S2, B_FR, R_FR, S2_FR
<SELECT/RESET><+><-> P2
Switch-over LED flash
No LED flash
FLSH
NOFL
<SELECT/RESET>
<+><->
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>>
rated frequency setting value in Hz <SELECT/RESET><+><-> fN
U</U> 1-phase/3-phase U<>1/U<>3 <SELECT/RESET><+><-> 1/3
Blocking function EXIT <+> until max. setting value
<-> until min. setting value
LED of blocked
parameter
Slave address 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: U1, U2, U3
tripping values in Volt <SELECT/RESET><+><->
one time for each phase
L1, L2, L3, U<, U<<,
U>, U>>
delta-connection: U12, U23, U31 tripping values in Volt <SELECT/RESET><+><->
one time for each phase
L1, L2, L3, U<, U<<,
U>, U>>
Save parameter? SAV? <ENTER>
Save parameter! SAV! <ENTER> for about 3 s
Delete fault memory wait <-> <SELECT/RESET>
Enquiry fault 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
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-)
Sec. 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
1) only Modbus
Table 5.1: Possible indication messages on the display

10 TB MRU3-1 12.00 E
5.2 Setting procedure
For parameter setting a password has to be entered
first (please refer to 4.4 of description "MR-Digital Mul-
tifunctional Relays").
5.3 Systemparameter
5.3.1 Display of residual voltage UEas
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 is used for 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 frequency
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]
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 presently
measured frequency would always be determined. 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
(see table 5.1)
none 0.5..1%/Hz
(see table 5.1)
Fault recorder Recording
distorted**
Recording
correct***
Recording
distorted**
Recording
correct***
Influence on all other
functions
none none none none
Table 5.2: 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.