Abstract: A microprocessor based recloser control has a microcomputer for causing trip and close operations of a recloser in response to the conditions of the power distribution lines being protected and operator commands. The microcomputer may be overridden by a mechanical switch in the recloser control. If power to the recloser control is lost, the microprocessor will continue to function with power storage means for a limited duration. Towards the end of that duration, this microcomputer will power down the microprocessor in an orderly manner allowing automatic return to its functions when power is restored. After the microprocessor is no longer functioning, a secondary overcurrent trip circuit is relied upon to cause a trip operation of the recloser for extended durations of power outage. The secondary overcurrent trip circuit can be disabled by the microprocessor.

Abstract: A three-phase power supply has a current transformer in each power line. The transformer secondary winding is connected to a load. Generally, the load is a control means responsive to the current being sensed. A triac in parallel with the secondary winding and load has its gate connected by a voltage sensitive circuit to sense the corresponding secondary winding voltage and to conduct and protect the transformer in the event of load loss. The gate circuit includes a metal oxide varistor and a linear resistor in series connected in parallel with the secondary winding. A second linear resistor is connected to the common node of the first linear resistor and metal oxide varistor. The second linear resistor is in series with a diac and connects the gate to the common node of the varistor and first resistor. A trigger capacitor is connected between the common node of the second resistor and diac and the opposite end of the first linear resistor.