Minimum no. of CB opening on full SC current w/o maintenance

[omara]

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.

 

[dpc]

I do think this is covered in ANSI C37, but I don't have it in front of me.

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.

 

[GordS]

I would recommend inspection / servicing after every short circuit operation. There are excessive mechanical and thermal forces involved with short circuit interruption which just may impact the breakers ability to properly function. ANSI C37.06 (AC High Voltage Circuit Breakers Rated on a Symentrical Current Basis - Preferred Ratings and Related Required Capabilities) Table 8 (Schedule of Operating Endurance Capabilities for Circuit Breakers) has a note 11 which states "If short-circuit operation occurs befor the completion of the listed operations, maintenance is recommended and possible functional part replacement may be necessary...". I have seen this same requirement echoed in the breaker maintenance manuals.

 

[gunter]

10 years ago I was with a CB manufacturer and I like to comment this matter. Both ANSI C37 and IEC56 are not very specific on this topic of CB condition after SC interuption.

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.