Testing breakers 1

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

 

[jbartos]

Suggestion: Please, notice that circuit breaker tests do vary with voltage levels and current ratings. Visit

http://www.nema.org

http://www.ieee.org

http://www.ul.com/

for industry standards covering circuit breakers or switchgear and their testing.

 

[peterb]

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.

 

[rhatcher]

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.)

 

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.

 

[jbartos]

Suggestions:
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.

 

[rhatcher]

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:

http://www.geindustrial.com/industrialsystems/circuitbreakers/applicat/cb-pd-et/index.htm

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).