Seg MRN3 User manual

MRN3 -Mains decoupling relay

2TB MRN3 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
3.2 Parameter settings
3.3 LEDs
3.4 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 Principle of frequency supervision
4.5 Measuring of frequency gradient (MRN3-2)
4.6 Vector surge supervision (MRN3-1)
4.6.1 Measuring principle of vector surge
supervision
4.7 Voltage threshold value for frequency
measuring
4.8 Blocking function
5 Operation and setting
5.1 Display
5.2 Setting procedure
5.3 Systemparameter
5.3.1 Display of residual voltage UE as 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
(FLSH/NOFL)
5.3.5 Parameterswitch/external trigger for the
fault recorder
5.4 Protection parameters
5.4.1 Parameter setting of over- and under-
voltage supervision
5.4.2 Number of measuring repetitions (T) for
frequency functions
5.4.3 Threshold of frequency supervision
5.4.4 Tripping delays for the frequency elements
5.4.5 Parameter setting of vector surge
supervision (MRN3-1)
5.4.6 Parameter setting of frequency gradient
(MRN3-2)
5.4.7 Voltage threshold value for frequency
and vector surge measuring (df/dt at
MRN3-2)
5.4.8 Adjustment of the slave address
5.4.9 Setting of Baud-rate (applies for Modbus
Protocol only)
5.4.10 Setting of parity (applies for Modbus
Protocol only)
5.5 Adjustment of the fault recorder
5.5.1 Number of the fault recordings
5.5.2 Adjustment of trigger occurences
5.5.3 Pre-trigger time (Tpre)
5.6 Adjustment of the clock
5.7 Additional functions
5.7.1 Setting procedure for blocking the
protection functions
5.8 Indication of measuring values
5.8.1 Measuring indication
5.8.2 Min./Max.- values
5.8.3 Unit of the measuring values displayed
5.8.4 Indication of fault data
5.9 Fault memory
5.9.1 Reset
5.9.2 Erasure of fault storage

TB MRN3 12.00 E 3
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
6.5 Example of test circuit
6.5.1 Checking the input circuits and
measuring functions
6.5.2 Checking the operating and resetting
values of the over/undervoltage functions
6.5.3 Checking the relay operating time of the
over/undervoltage functions
6.5.4 Checking the operating and resetting
values of the over/underfrequency
functions
6.5.5 Checking the relay operating time of the
over/underfrequency functions
6.5.6 Checking the vector surge function
6.5.7 Checking the external blocking and reset
functions
6.6 Primary injection test
6.7 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 Parameters for the fault recorder
7.4 Output relays
8 Order form

4TB MRN3 12.00 E
1 Introduction and application
The MRN3 is a universal mains decoupling device and
covers the protection requirements from VDEW and
most other utilities for the mains parallel operation of
power stations.
•Over/ and undervoltage protection,
•over/ and underfrequency protection,
•extremely fast decoupling of generator in case of
mains failure (MRN3-1) or
•rate of change of frequency df/dt (MRN3-2)
Because of combination of three protectional functions
in one device the MRN3 is a very compact mains de-
coupling device. Compared to the standardly used sin-
gle devices it has a very good price/performance ratio.
For applications where the single protection functions
are required SEG can offer the single MR-relays as fol-
lows:
•MRU3-1 four step independent over-/ and under-
voltage protection (also used for gene-
rator earth fault protection).
•MRU3-2 two step independent over-/ and under-
voltage protection with evaluation of the
symmetrical voltage components.
•MRF3 four step independent over/ and under-
frequency protection and two step
frequency gradient supervision df/dt.
•MRG2 generator mains monitor / vector surge
detection.
Important:
For additional common data of all MR-relays please re-
fer to technical description "MR - Digital Multifunctional
Relays".
2 Features and characteristics
•Microprocessor technology with watchdog,
•effective analog low pass filter for suppressing har-
monics when measuring frequency and vector surge,
•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 op-
erations,
•integrated functions for voltage, frequency and vector
surge in one device as well as single voltage, fre-
quency and vector surge devices,
•two parameter sets,
•voltage supervision each with two step under-/ and
overvoltage detection,
•frequency supervision with three step under-/ or over-
frequency (user setting),
•completely independent time settings for voltage and
frequency supervision,
•adjustable voltage threshold value for blocking fre-
quency and vector surge measuring,
•display of all measuring values and setting parameters
for normal operation as well as tripping via a alpha-
numerical display and LEDs,
•display of measuring values as primary quantities
•Storage of trip values and switching-off time (tCBFP) of 5
fault occurences (fail-safe of voltage),
•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,
•user configurable vector surge measurement 1-of-3 or
3-of-3,
•reliable vector surge measuring by exact calculation
algorithm,
•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 Protocol
or Modbus Protocol.

TB MRN3 12.00 E 5
3 Design
3.1 Connections
Figure 3.1: Connection diagram MRN3-1 and MRN3-2
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. The measur-
ing circuits can be applied in star or delta connection
(refer to chapter 4.3.1).
3.1.2 Blocking input
The blocking function can be set according to require-
ment. By applying the auxiliary voltage to D8/E8, the
previously set relay functions are blocked (refer to 4.8
and 5.7.1).
3.1.3 Reset input
Please refer to chapter 5.9.1.
3.1.4 Output relays
The MRN3 is equipped with 5 output relays. Apart from
the relay for self-supervision, all protective functions can
be optionally assigned:
•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.

6TB MRN3 12.00 E
3.1.5 Fault recorder
The MRN3 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 influ-
enced.
No writing over
If 2, 4 or 8 recordings are chosen, the complete mem-
ory is divided into the relevant number of partial seg-
ments. If this max. number of fault event has been ex-
ceeded, the fault recorder block any further recordings
in order to prevent that the stored data are written over.
After the data have been read and deleted, the re-
corder to ready again for further action.
Writing over
If 1, 3 or 7 recordings are chosen, the relevant number
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).
Figure 3.2: Division of the memory into 8 segments, for example
Memory space 6 to 4 is occupied.
Memory space 5 is currently being written in
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 3.3: 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.
Via the interface RS485 the data can be read and
processed by means of a PC (HTL/PL-Soft4). The data is
graphically edited and displayed. Binary tracks are re-
corded as well, e.g. activation and trip.

TB MRN3 12.00 E 7
3.2 Parameter settings
System parameters
Parameter settings MRN3-1 MRN3-2
Uprim/Usek XX
∆/Y XX
fN X X
P2/FR X X
LED-Flash X X
Table 3.1: System parameters
Protection parameters
Setting
parameter
MRN3-1 MRN3-2
U< X X
tU< XX
U<< X X
tU<< XX
U> X X
tU> XX
U>> X X
tU>> XX
TXX
f1XX
tf1 XX
f2XX
tf2 XX
f3XX
tf3 XX
df X
dt X
1/3 X
∆Θ X
UB<XX
RS485/Slave X X
Baud-Rate* X X
Parity-Check* X X
Table 3.2: Protection parameters
*only Modbus
Blocking functions
Parameter settings MRN3-1 MRN3-2
U< X X
U<< X X
U> X X
U>> X X
f1 X X
f2 X X
f3 X X
∆θX
df/dt X
Table 3.3: Blocking functions
Parameters for the fault recorder
Parameter setting MRN3-1 MRN3-2
Number of fault
events
XX
Trigger events X X
Pre-Triggerzeit Tpre XX
Table 3.4: Parameters for the fault recorder
Additional functions
Parameter settings MRN3-1 MRN3-2
Ralay assignment X X
Fault recorder X X
Table 3.5: Additional functions
Date and time
Parameter settings MRN3-1 MRN3-2
Year Y = 99
Month M = 03
Day D = 16
hour h = 07
minute m = 29
second s = 56
X
X
X
X
X
X
X
X
X
X
X
X
Table 3.6: Date and time
The window for parameter setting is located behind the
measured value display. The parameter window can be
accessed via the <SELECT/RESET> key.

8TB MRN3 12.00 E
3.3 LEDs
All LEDs (except LED RS, min. and max.) are two-
coloured. The LEDs on the left side, next to the alpha-
numerical 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 set-
ting 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 communi-
cation.
The LED marked with the letters FR is alight while the
fault recorder is being adjusted.
3.4 Front plate
Figure 3.4: Front plate MRN3-1
Figure 3.5: Front plate MRN3-2

TB MRN3 12.00 E 9
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 measur-
ing quantity, at 50 Hz.
4.2 Digital circuits
The essential part of the MRN3 relay is a powerful mi-
crocontroller. All of the operations, from the analog digi-
tal conversion to the relay trip decision, are carried out
by the microcontroller digitally. The relay program is lo-
cated in an EPROM (Electrically-Programmable-Read-
Only-Memory). With this program the CPU of the mi-
crocontroller calculates the three phase voltage in order
to detect a possible fault situation in the protected ob-
ject.
For the calculation of the voltage value an efficient digi-
tal filter based on the Fourier Transformation (DFFT - Dis-
crete Fast Fourier Transformation) is applied to suppress
high frequency harmonics and d.c. components caused
by fault-induced transients or other system disturbances.
The microprocessor continuously compares the meas-
ured values with the preset thresholds stored in the pa-
rameter 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 element of MRN3 has the application in
protection of generators, consumers and other electrical
equipment against over-/and undervoltage.
The relay is equipped with a two step independent
three-phase overvoltage (U>, U>>) and undervoltage
(U<, U<<) function with completely separate time and
voltage settings.
In delta connection the phase-to-phase voltages and in
star connection the phase-to-neutral voltages are con-
tinuously compared with the preset thresholds.
For the overvoltage supervision the highest, for the un-
dervoltage supervision of the lowest voltage of the three
phases are decisive for energizing.

10 TB MRN3 12.00 E
4.3.1 Selection of star or delta
connection
All connections of the input voltage transformers are led
to screw terminals. The nominal voltage of the device is
equal to the nominal voltage of the input transformers.
Dependent on the application the input transformers 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 connection con-
figuration 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 (
∆
)
)!
)"
)#
)$
)%
)&
7
7
7!
Sec. winding of
mains V.T.
=
>
?
Figure 4.2: Input v.t.s in star connection (Y)
4.4 Principle of frequency supervision
The frequency element of MRN3 protects electrical
generators, consumers or electrical operating equipment
in general against over- or underfrequency.
The relay has independent three frequency elements
f1- f3with a free choice of parameters, with separate
adjustable pickup values and delay times.
The measuring principle of the frequency supervision is
based in general on the time measurement of complete
cycles, whereby a new measurement is started at each
voltage zero passage. The influence of harmonics on
the measuring result is thus minimized.
J
KJ 6
6
Figure 4.3: Determination of cycle duration by means of zero
passages.
In order to avoid false tripping during occurence of in-
terference voltages and phase shifts the relay works with
an adjustable measuring repetition. (refer to chapter
5.4.2)
Frequency tripping is sometimes not desired by low
measured voltages which for instance occur during al-
ternator acceleration. All frequency supervision functions
can be blocked with the aid of an adjustable voltage
threshold UBin case the measured voltages value is be-
low this value.
4.5 Measuring of frequency gradient
(MRN3-2)
Electrical generators running in parallel with the mains,
e.g. industrial internal power supply plants, should be
separated from the mains when failure in the intrasystem
occurs for the following reasons:
•It must be prevented that the electrical generators are
damaged when mains voltage recovering asyn-
chrone, e.g. after a short interruption.
•The industrial internal power supply must be main-
tained.