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8.2
Routine checks
8.2.1
7SS601 measuring system
8.2.2
Peripheral modules
Trip circuits
Isolator status
feedback signals
Isolator replica
Current
transformer
circuits
7SS60 Manual
E50417-G1176-C132-A2
Routine checks of characteristics or pick-up values are not necessary as they are part
of the continuously supervised firmware programs. The planned maintenance inter-
vals for checking and maintenance of the plant can be used to perform operational
tests of the protection equipment. This maintenance serves mainly for checking the
interfaces of the unit, i.e. the coupling with the plant.
The following procedure is recommended. If the result of one or more of the above
steps suggests that there is a fault, please proceed as described in chapter 8.4.
q
Check that the green LED Service/Betrieb on the front panel of the 7SS601 mea-
suring system is on and that the red LED Blocked/Störung is off.
q
Check whether the LED indications on the front panel show a plausible current sta-
tus of the measuring system and the station.
q
Press the N key. All LEDs (with the exception of the red LED Blocked/Störung)
light up.
q
Read out the measured values (refer to Section 6.1). The differential current must
be low, and the restraint current must be equal to the summated amounts of the cur-
rents of all feeders that are connected to the measuring system.
q
Read out the operational annunciations (refer to Section 6.1). Check that they do
not contain any entries on faults in the system, in the measured values, or any other
kind of implausible information.
q
Check the trip circuits for controlling the circuit breakers. Where service conditions
do not allow to trip a circuit breaker, you can proceed e.g. by switching off the
breaker control voltage and checking the trip function as far as the circuit breaker
coil.
q
Check that isolator states are correctly detected. To do so, perform an isolator
switching operation and check the feedback signal in OPEN position. If there is no
checkback signal (because of wire break or auxiliary power outage), the isolator is
assumed to be CLOSED, so that instabilities of the measuring system when a cur-
rent flows are efficiently counteracted.
q
Check the correct allocation of the feeder currents to the measuring system (isolator
replica) using load currents or secondary test equipment.
The transformer currents of feeders which do not carry a sufficient load current should
instead be checked with primary testing equipment.
Maintenance and Troubleshooting
8-3
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Table of Contents
Troubleshooting
