Combined overvoltage and undervoltage
relay
REU 523
1MRS 751123-MBG
3
addition, the tripping of stage U< can be set
to be blocked by the start of stage U<<. The
tripping of an undervoltage stage can also be
blocked by applying an external binary input
signal to the relay.
The high-set stage can be set out of operation.
This state will be indicated by dashes on the
LCD and by “999” when the set start value is
read via serial communication.
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. The CBFP unit is acti-
vated with a soft-ware switch.
Disturbance recorder
The REU 523 includes an internal distur-
bance recorder which records the momentary
measured values, or the RMS curves of the
measured signals, and eight digital signals:
the external binary input signal and the states
of the internal protection stages. The distur-
bance 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 triggering 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
characters’ 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 the 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 manages 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
rate of 9.6 kbps. The IEC 60870-5-103 proto-
col is used to transfer mesurand and status
data from the slave to the master. Disturbance
recorder data, however, cannot be transferred
using this protocol.
The REU 523 is provided with two serial
communication ports, one on the rear panel
and the other on the front panel.
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
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