This standard is applicable to all types of circuit-breakers having rated voltages exceeding 12 kV, intended to be used for switching cables of appreciable length in earthed neutral systems. It con cerns the testing of such circuit-breakers for proving their ability to switch cables on no-load under normal service conditions. A series combination of a cable with a short length of overhead line is covered by this standard.
Notes.—(1) This standard presumes that, at voltages exceeding 12 kV, cables have an earthed screen on each phase.
(2) An overhead line is considered to be short if its charging current does not exceed 1 % of the cable-charging current.
(3) Test to prove the performance under fault conditions and other abnormal conditions should be subject to agreement between 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 cables.
(4) The user shall specify in the enquiry that the circuit-breaker is intended to be used for switching of cables on no-load.
PS 388-1964 history
1964PS 388-1964 circuit-breakers (testing of circuit-breakers with respect to the switching of cables on no-load).