Minimum no. of CB opening on full SC current w/o maintenance
Minimum no. of CB opening on full SC current w/o maintenance
(OP)
Is there any national or international standard manufacturers of switchgear should comply with, that specifies some minimum number of operations at full short circuit current for a circuit breaker before it requires maintenance? While my question is a general one for all types of circuit breakers, I am specifically interested in MV and HV SF6 and vacuum interruptors.






RE: Minimum no. of CB opening on full SC current w/o maintenance
Manufacturers typically provide a recommended number of *mechanical* operations between maintenance, but if you are interrupting heavy current, your maintenance cycle may be less than this. For vacuum breakers there is typically a contact wear gauge or indicator that must be checked periodically.
Quick check of GE literature for 15 kV vacuum breakers indicates 10,000 operations (1 open and 1 close) before servicing. I don't know if this is a standard value or not.
Sorry this doesn't help much, but maybe someone has the C37 standards open and can check on this.
RE: Minimum no. of CB opening on full SC current w/o maintenance
RE: Minimum no. of CB opening on full SC current w/o maintenance
Therefor manufacturers and independent test institutes usually perform additional tests on HV circuit breakers after a number of SC interuptions. These are
- closed contact restistance
- overtemperature of contacts at nominal rated current
- dielectric withstand test across the open pole
- optical inspection of the contacts and arc chamber
all done with SC-stressed poles.
High voltage SF6 CBs like SIEMENS 3AQ and 3AT were rated at 10 SC interuptions until maintainance, and at type tests one pole often saw 30 SC interuptions before replacement. I don't know today's situation, but in the past these figures were leading edge on the market.