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7UT51 v3
19
Maintenance and Servicing
The 7UT51 relays has measurement and signal
processing circuits that are fully solid state and,
therefore, completely maintenance-free. However,
there are basic maintenance procedures that can help
solve problems if the performance of the relay is
suspect. These procedures assume that the relay is
operating in its intended environment and has been
correctly set and configured.
If the device is equipped with a backup battery for
saving of stored events and the internal time clock, the
battery should be replaced after at least five years of
operation. This recommendation is valid independent
on whether the battery has been discharged by
occasional supply voltage failures or not.
As the protection is almost completely self-monitored,
from the measuring inputs to the trip contact outputs,
hardware and software faults are automatically
alarmed. This ensures the high availability of the relay
and allows a more corrective rather than preventive
maintenance strategy. With detected hardware faults
the relay blocks itself; drop-off of the availability relay
signals "equipment fault". If there is a fault detected in
the external measuring circuits, generally an alarm is
given only.
Recognized software faults cause the processor to
reset and restart. If such a fault is not eliminated by
restarting, further restarts are initiated. If the fault is
still present after three restart attempts the protective
system will switch itself out of service and indicate this
condition by the red LED "Blocked" on the front plate.
Drop-off of the availability relay signals "equipment
fault".
The reaction to defects and indications given by the
relay can be individually and in chronological
sequence read off as operational alarms
(Address 5100) for defect diagnosis. The relay's event
log and target log data may be useful for maintenance.
The event log is under Address Block 5100, and the
target logs for the last three faults are under
Address blocks 5200, 5300, and 5400, respectively.
If the relay is connected to a local substation
automation system (LSA), defect indications will also
be transferred via the serial interface to the central
control system.
PRIM-2330C
Maintenance and Servicing
19.1
Troubleshooting Tips
If the relay indicates a defect but none of the
programmable LEDs on the operator panel are lit, then
perform the following checks:
•
Are the modules pushed in and locked properly?
•
Is the On/Off switch on the operator panel in the
"On" position?
•
Does the input power have correct polarity and
voltage?
•
Is the input power connected to the proper relay
terminals?
•
Has the minifuse in the power supply section
blown?
•
Is the relay correctly set and configured?
If the red Blocked LED is lit and the green Power LED
is not lit, the device has recognized an internal fault.
To reinitialize the unit, turn the DC auxiliary voltage off
then back on using the operator panel On/Off switch.
When the DC auxiliary voltage is off, the relay will lose
any event log data, target log data, and configuration
settings that have not been saved.
19.2
Routine Checks
Routine checks of characteristics or pickup values are
not necessary as they form part of the continuously
supervised firmware programs. The planned
maintenance intervals for checking and maintenance
of the plant can be used to perform operational testing
of the protection equipment. This maintenance serves
mainly for checking the interfaces of the unit, that is
the coupling with the plant. The following procedure is
recommended:
•
Readout of operational values (Address Block
5700) and comparison with the actual values for
checking the analog interfaces.
Simulation of an internal short-circuit with 4 x IN for
checking the analog input at high currents.
19
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