Combined overvoltage and undervoltage
relay
REU 523
1MRS 751123-MBG
3
The start and the tripping of the undervoltage
stages can be set to be internally blocked
when the measured value falls below 0.2 x
U
n
. This function is selected in switchgroup
SGF. In addition, the tripping of stage U< can
be set to be blocked by the start of stage U<<.
The selection is made with a switch in one of
the software switchgroups. The start and the
tripping of an undervoltage stage can also be
blocked by applying an external binary input
signal to the relay.
High-set stage U<< can be set out of opera-
tion. This state will be indicated by three
dashes “---” on the LCD and by “999” when
the set start value is read via serial communi-
cation.
Circuit breaker failure
protection (CBFP) unit
The CBFP unit will generate a trip signal via
power output 2 (PO2) if the fault has not been
cleared on expiration of the set operate time
0.10 s...1.00 s
Normally, the CBFP unit controls the up-
stream circuit breaker. It can also be used for
tripping via redundant trip circuits of the
same circuit breaker provided that the circuit
breaker has two trip coils. The circuit breaker
failure protection unit is activated via a soft-
ware switch.
Disturbance recorder
T
he REU 523 includes an internal distur-
bance recorder which records the momentary
measured values, or the RMS curves of the
measured signals, and up to eight user-select-
able binary signals: the external binary input
signal and the states of the internal protection
stages. The disturbance recorder can be set to
be triggered by a start or a trip signal from
any protection stage and/or by an external
binary input signal, and either on the falling
or rising trigger edge. The ratio of the pre-
and post-triggering of the recording can be
set.
The recording length varies according to the
selected sampling frequency. The RMS curve
is recorded by selecting the sampling fre-
quency to be the same as the nominal fre-
quency of the relay. See the table below for
details:
HMI module
The HMI of the REU 523 is equipped with
six push-buttons and an alphanumeric 2 x 16
character LCD. The push-buttons are used for
navigating in the menu structure and for
adjusting set values.
An HMI password can be set to protect all
user-changeable values from being changed
by an unauthorised person.
The REU 523 offers you multi-language sup-
port. The following languages are available
for HMI menu: English, German, French,
Spanish, Italian, Swedish and Finnish.
Self-supervision (IRF)
The REU 523 is provided with an extensive
self-supervision system which continuously
supervises the software and the electronics of
the relay. It handles run-time fault situations
and informs the user about an existing fault
via a LED on the HMI and a text message on
the LCD.
Communication capabilities
The REU 523 can be connected to a substa-
tion automation or monitoring system using
either the SPA bus communication protocol
or the IEC 60870-5-103 remote communica-
tion protocol. Both protocols are supported in
the same device.
The SPA bus communication protocol is an
asynchronous serial communication protocol
(1 start bit, 7 data bits + even parity, and 1
stop bit) with a selectable data transfer rate
(default 9.6 kbps). It is a master/slave proto-
col supporting one master device and several
slave devices. The SPA bus protocol can be
used to transfer data , e.g. measured currents,
registered values, events, and relay settings,
between the master and the slave device.
The REU 523 supports the IEC 60870-5-103
remote communication protocol in the unbal-
anced transmission mode with a data transfer
Nominal
frequency
Hz
Sampling
frequency
Hz
Recording
length s
50
800
0.60
50
400
1.20
50
50
9.60
60
960
1.00
60
480
2.00
60
60
16.00
Nominal
frequency
Hz
Sampling
frequency
Hz
Recording
length s
