FIELD: electrical engineering.
SUBSTANCE: after appearance of first short-circuit current surge at transformer buses, count down of time is started that is equal to that of sectionalising switch (SS) protection operation. Note that moment of short-circuit current surge cut-off is recorded and, if said moment complies with the moment of short-circuit current surge cut-off, then first, SS cut-off state is registered and, further, after moment of short-circuit current surge cut-off, total time equal to delay time of automatic repeated cut-in of given circuit breaker and time of operation of circuit breaker protection operation with acceleration, then second short-circuit current surge origination and time of its protection operation with acceleration is controlled. Then if after its origination, at the moment of termination of total time count down no cut-off of second short-circuit current surge cut-off occurs, then SS repeated cut-off failure is registered. If the moment of termination of the main switch protection operation complies with the moment of second short-circuit current surge cut-off, then line main switch is considered cut-off in its repeated cut-in at stable short-circuit condition in circular circuit.
EFFECT: expanded performances.
2 dwg
