This standard is applicable to all types of circuit-breakers having rated voltages exceeding 72.5 KV, and specifies the field-testing of such circuit-breakers for proving their ability to switch three-phase overhead lines on no-load under normal service condition. A series combination of an overhead line with short lengths of cable is covered by this standard.
Notes—(1) Cables are considered to be short if their total charging current does not exceed 20 per cent of the overhead line-charging current and the charging current of any cable adjacent to the circuit-breaker does not exceed 10 per cent of the overhead line-charging current. In any case the total current should not exceed the assigned line-charging breaking current.
(2) Circuit-breaker for use with overhead lines which include series capacitors are not within the scope of this standard.
(3) Tests to prove the performance un default conditions and other abnormal conditions should be subject to agreement between the manufacturer and user. Such abnormal conditions are, for instance, those where the voltage is higher than the higher rated voltage of the circuit-breaker, conditions which may occur due to sudden loss of load on long lines.
PS 387-1964 history
1964PS 387-1964 Alternating-current circuit-breakers (field testing to the switching of over-head on no load)