7
Continuous mode
operation
In the continuous mode operation the closing
signal output of the synchro-check relay is ac-
tive as long as the closing conditions are ful-
filled and disappears when the conditions cease.
The operation of the supervising stage can be
blocked by applying a blocking signal to the
stage. The function of the blocking input is se-
lected by means of selector switchgroup SGB.
The activated output of the synchro-check re-
lay delivers a command signal to the control
module for the closing operation and the final
closing operation is performed by the control
module. Beside the closing conditions in force,
the only thing affecting the continuous mode
operation is an external blocking signal applied
to the synchro-check relay. When the blocking
signal is activated the control output resets even
if the closing conditions are valid. Should the
blocking signal be active at the moment when
the closing conditions come into force, no clos-
ing signal will be delivered. The principal reali-
zation of the closing operation system with the
synchro-check relay in the continuous mode
operation is presented in figure 4.
SC Synchro-check relay
CM Control module
Command signal
CM
SC
Closing signal
Fig. 4. A simplified block diagram of the synchro-check relay in continuous mode operation.
At great frequency differences the closing con-
ditions are valid for a short time and the length
of the closing signal pulse is becoming shorter
and shorter with increasing frequency difference.
The closing signal should be at least 70 ms, ap-
proximately, in the continuous mode operation.
Hence, time calculated from frequency and
phase angle difference for valid closing condi-
tions shall be about 70 ms longer than the op-
erate time of the circuit breaker, before a clos-
ing signal is released.
