Circuit Breaker and Protective Relay Economisation Employing Logic Sequence Switching

The authors have considered a typical radial distribution substation which is being fed by a single high tension feeder and have shown that individual circuit breakers associated with different outgoing distributors can be totally dispensed with by the use of two suitably placed autoreclosing circuit breakers. This economisation has been achieved at the cost of interruptions of supply either in all or in half of the distributors for a very short duration, which may be tolerated in most of the cases of rural areas, for faults in any distributor. Different logical and switching schemes to be used have been developed by writing different constrained equations, and then solving them with the help of boolean algebra. Semi-conductor switching, counting and logic circuits have been used to control the sequential and interlocked mode of operations for the two circuit breakers and isolators. Provision has been made to isolate each C.B. from supply for maintenance and repair work during which period the other C.B. will maintain the continuity of entire supply.