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Testing breakers

Testing breakers

Testing breakers

I was wondering if I could get some advice on preforming the following test on electrical equipment/breakers? I will list them as they were listed to me. Please referrance the numbers in your responces.

#1  Preform time-current characteristic test on the time delay element at three times the rated current.

#2 Check the contact resistance in micro-ohms and the dielectric strengthin meg-ohms.

#4 If the breaker has an instantaniouse element, check the trip setting and test accordingly.

Thanks in advance Scott                                                            

RE: Testing breakers

The tests that you describe would generally be performed as follows -
#1 - Use a high current injection test set with a timer (can be integral or separate) to check the operating time of the breaker. Note that if this is a thermal magnetic breaker, there is a wide tolerance band in the curve and that operation is dependent on temperature - allow cooling period between tests.
#2 - Check the contact resistance using a micro-ohmmeter or a DC current injection set (measure voltage drop across the circuit & calculate resistance); compare to manufacturer's spec values &/or use to establish a database to trend condition.  Use a megohmmeter to measure insulation resistance - measure each phase to the other two & ground; record values for trending & check absolute value (recommended minimum 100 MOhms for 600V equipment tested at 1000V)
#3 - Same test equipment as #1 above, or higher rated test set, depending on breaer rating; use short pulses of test current to avoid overheating of test set; ensure the test leads are short and low reactance type to avoid excessive voltage drop & consequent overduty of the test set.
Assuming that you are talking about molded case breakers, you should also do a mechanical inspection and operation check, as well as tighten all connections - use a torque wrench if correct value is known.

RE: Testing breakers

Excellent post peterb (complete and concise). If specific information is needed on time-current curves or acceptable values of contact resistance please respond with the breaker nameplate information (ie. manufaturer, model number, current rating, etc.)

RE: Testing breakers

The breakers in question are GE SPECTRA series. They are in the high voltage panel(480/277). I am guessing they range from 70 to 100 amp. I have tried to locate the info that rhatcher has metioned, but have had no luck. Any additonal info would be appreciated.

RE: Testing breakers

1. Refer to General Electric Spectra RMS(TM) Molded Case Circuit Breakers Type SE (Frame 100) or SF (Frame 250)
2. GET-7002C "Spectra RMS(TM) Molded Case Circuit Breakers Application and Selection" (It has many useful references inside, e.g. GEA-11884 "Spectra RMS(TM) Circuit Breakers, etc.)
3. Contact:
GE Industrial Systems, P.O. Box 2913, Bloomington, IL 61702-2913, USA
Fax 309-662-9660
for more info/literature.
4. This is a more sophisticated molded case circuit breaker with many features, e.g. "undervoltage release," which have not been addressed in above postings.
5. Contact the manufacturer: GE Co., 41 Woodford Av., Plainville, CT 06062, USA for more info.

RE: Testing breakers

jbartos's recommended pub GEC-7002C is available on the web. You should definitely become familiar with it if you plan to do anything more than turn on one of these breakers:


Select pub# GEC-7002C.

Page 27 has a chart with the instantaneous trip settings by frame size. Page 44 shows a chart for selection of the time-current curves. If you need curves for your breakers please provide either the curve # from the chart or the frame size and current rating (check page 8 for current rating info).  

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