Polarizing potential transfer switch circuit for use with power transmission lines

Claim 1

A polarizing potential transfer switch system which is useful with a power transmission line protective system which includes a loss-of-potential circuit and a protective relay circuit which produces circuit breaker trip signals in response to possible fault conditions, wherein sources of trip signals include true fault conditions, wherein sources of trip signals include true fault conditions on a transmission line and transfer switch operations, comprising: a polarizing potential transfer switch for switching power between first and second polarizing potential bus lines in which the transfer switch includes an open position between contact with the first bus and the second bus; means providing an indication of when the transfer switch is moved to its open position; a first timer means responsive to said indication for producing a first timer output signal for a first interval of time, in the absence of a trip signal during a previous first period of time; first gate means for producing a first gate output signal upon the coincidence of the first timer output and a trip signal; a second timer means responsive to the first gate output signal to produce a second timer output for a second interval of time sufficient to permit a loss-of-potential circuit to block a trip signal; and a second gate means responsive to the coincidence of a trip signal and the lack of a second timer output signal to produce a circuit output signal which in turn will be used to open a circuit breaker.