Capacitor Test; Figure 5.8-1 Capacitor Test Timing Diagram - Siemens 7SR224 Technical Manual

7SR224 Argus Description of Operation
5.9

Capacitor Test

The actuator mechanism of the recloser can be driven from a charged capacitor network. The condition of the
capacitors is monitored externally to the relay and the interface to the relay is in the form of two binary signals
which are driven by undervoltage detectors as shown below. These inputs are CapMon Input 1 and CapMon
Input 2.
In the quiescent state, both logical inputs should be in the '1' state and the detection of '0' on both inputs will
trigger the CapacitorSupplyFail output.
In addition to the monitoring during quiescent conditions, the state of the inputs can be monitored to assess
capacitor condition during an externally applied discharge test. When the Cap Element setting is Enabled, the
sequence is executed automatically, 30 minutes after completion of a successful battery test. The sequence can
be started manually on demand by energising the Capacitor Test binary input. If any protection element pickup
occurs at any time during the capacitor test sequence, the sequence will be terminated.
Figure 5.9-1 Capacitor Test timing diagram
When the test is required, the output Cap Test Active is raised. This is used externally to start the discharge test.
When the voltage reduces to the higher voltage detector, the relay binary inputs CapMon Input 2 will change to
state '0' from the quiescent '1'. CapMon Input 1 will remain at the '1' state. The relay recognises this 1-0
condition and starts a timer which runs for the Cap Holdup Time. If the CapMon Input 1 changes state to '0'
during this time, the test is recorded as a fail and the relay goes to the recovery state as described below. If the
timer expires with the 1-0 condition still maintained, the test is considered as a pass. The sequence now enters
the recovery state and the Cap Test Active output is cleared causing the external discharge test to end The
Capacitor voltage will now recover and the quiescent 1-1 state for CapMon Input 1 and CapMon Input 2 will be
re-established. If the 1-1 state is not achieved at the end of the 10 second recovery time, the Cap Recovery Fail
output and the Capacitor Only Trip output are raised and the reclose function of the relay are internally blocked.
Normal continuous monitoring of the quiescent state will be resumed 10 seconds after the reset of the Cap Test
Active output.
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