FIELD: electrical engineering. SUBSTANCE: required effect of action of device for failure redundancy of switch is obtained thanks to insertion of relay of testing decrease of short-circuit current through stand-by switch for interlocking of operating circuits of device for failure redundancy with reduced time delay due to exclusion of tuning away from total time of operation of switch. Relay of testing current decrease is placed into directed differentiating circuit of output of relay testing current of substation switch. EFFECT: improved operational reliability. 2 dwg
