Circuit Breaker Maintenance in regards to Safety and Arc Flash

Debbie Mann Consulting, Inc.

My company does Arc Flash Safety Consulting. As part of this consulting, we try to identify areas where a problem, not limited to arc flash, could occur and we submit a list of comments including urgent alerts to dangerous conditions that present themselves.

In the course of this work, we have become aware of circuit breakers that should have opened that did not because they could not. Also, in the various courses that I have taken, it has been discussed that opening a breaker or disconnect can cause an arc flash strong enough to explode the cabinet, even though opening a breaker or disconnect is generally a Category 0 event. The only reference that I find to this issue in NFPA 70E is:

NFPA 70E 225.3 - Circuit Breakers that interrupt faults approaching their interrupting ratings shall be inspected and tested in accordance with the manufacturer’s instructions.

However, the NETA MTS standard recommends doing extravagant tests on breakers yearly, including taking hot voltage readings. I think these recommendations are prohibitive. Here is a description of some of the requirements from a previous Mike Holt Newsletter:
It is recommended that at least once a year a properly trained and equipped qualified electrician perform the following maintenance task:

• Visually inspect the case to determine if any portion indicates overheating; replace the breaker if overheating indications are found.
• Check connections for indications of overheating.
• Cycle the breaker five times manually.
• Check and record the voltage drop across the breaker using a calibrated digital voltmeter (capable of reading three places to the right of the decimal point).
• The load should be operated at full load for three hours, or until the breaker reaches normal load temperature; scan the breaker with an IR type non-contact thermometer and record the readings.
• Record voltages and note any voltage imbalance from phase to phase.
• Current readings should be taken with a true RMS type meter due to the increasing harmonic content in many electrical systems in commercial/industrial facilities today.
• Current readings on equipment grounding conductors (where required) for specific machines should be noted. Clamp on type ground-rod circuit resistance reading meters should be used for this task as they can detect both the impedance and the level of current on the conductor if any is present, as other clamp on type amp-meters will not indicate Ma levels.

Breaker test sets are commercially available from several sources (AVO Multi Amp is one source 800.723.2861). Testing of circuit breakers is a very specialized area requiring special training and test equipment and should be conducted only by competent personnel. NEMA has published a valuable guideline (AB-4-1991) that should be consulted when testing MCCB’s.
NFPA 70E doesn’t even require maintenance unless the fault rating is high relative to the rating. Manufacturers’ requirements seem to just require operating the breaker and doing a basic visual inspection once a year – certainly a lot more doable than what NETA recommends.

As part of a training program, I would like to recommend that facilities disconnect power to a panel, go through the 6 step process to make sure that it is really and truly deenergized, and then operate the breaker, clean the breaker, operate it several more times and give it a good visual inspection. The thing is, if I recommend this level of service when NETA recommends a much higher one, it may expose me to a liability. Imagine that we all banded together and got every owner in the country to do this level of minimal maintenance on breakers and half the deaths were averted. The remaining widows and widowers would likely sue us because they found the maintenance to be inadequate since it didn’t meet NETA. But I believe that very few people will perform the NETA recommended maintenance. And performing a more minimal maintenance even every 5 years would probably avert not only many arc flash incidents, but also fires – I know personally of one that likely would have been prevented.

I have the following questions for the readers of this column:

1. Do you perform or require preventative maintenance of breakers at any regular interval?
2. When you have a shutdown, do you operate and inspect breakers affected by the shutdown that are not directly involved in any problem?
3. Do you feel that performing breaker no-load operation and cleaning would be beneficial? Rephrasing that: Is there an interval where the cost and disruption of cleaning and operating the breakers would be considered of value to you relative to the increase in safety both due to Arc Flash Safety and risk of fire?
4. Do you find the NETA requirements to be reasonable?
5. Do you feel that the NETA requirements would serve as a legal liability, causing the risk of making these recommendations to be too great to make you willing to make a recommendation for less than the full NETA boatload of maintenance?
6. Do you have experience in this area? Have you experienced damaging events that could have been prevented by this kind of maintenance?
7. Do you have other recommendations for a sufficient level of maintenance? Or other comments on this issue?

Complying with NFPA 70E does not guarantee that a worker won’t be injured. The gear will not prevent second degree burns or temporary sight or hearing loss. Being blown across a room when wearing appropriate gear will still cause injury. Is circuit breaker maintenance a way to minimize the number of such injuries? And what should the recommended maintenance be?

Please post your comments.

Deborah J. Mann, PE
Debbie Mann Consulting, Inc.
121 N. 4th  St.
Lafayette, IN 47901