Capacitor Test; Figure 5.8-1 Capacitor Test Timing Diagram - Siemens 7SR224 Description & Operation

Recloser controller

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(1) Description of Operation 7SR224

5.8

APACITOR

EST

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 5.8-1

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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