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 Post subject: Breaker Maintenance
PostPosted: Tue Nov 04, 2014 5:58 am 

Joined: Tue Nov 04, 2014 5:53 am
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Does anyone know what IEEE 1584 says regarding the condition and maintenance of breakers that the calculation assumes in order to determine clearing times from manufacturer's TCC's? especially when the breakers are old... Thank you.


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 Post subject: Re: Breaker Maintenance
PostPosted: Tue Nov 04, 2014 8:32 am 
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I don't think there anything specific in IEEE 1584 regarding maintenance but the results of the clearing time depend on the device functioning properly. The argument and good engineering judgement would say that unless a device is maintained, there is no guarantee it will operate as designed.

NFPA 70E specifically states that condition of maintenance must be considered.

This is particularly important on older LVPCB where grease hardening can occur and if they still have non SST devices such as ones that have oil dashpots and small timing orifices.

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 Post subject: Re: Breaker Maintenance
PostPosted: Mon Nov 10, 2014 11:06 am 

Joined: Mon Nov 10, 2014 11:01 am
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ANSI NETA mts-2007 is a good reference for judging how often you need to maintain circuit breakers and the like to keep them in good working order which is what is required by NFPA 70E.


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 Post subject: Re: Breaker Maintenance
PostPosted: Tue Nov 11, 2014 1:15 pm 

Joined: Tue Nov 04, 2014 5:53 am
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Thank you.

This issue seems to be under addressed / under considered as engineers totally rely on manf's TCC's for circuit breakers, sometimes without knowledge of whether or not the MCCB or LVPCB has been exercised, tested, and maintained (where possible). As mechanical devices with lubrication etc it seems a leap of faith to trust they will operate as designed after 5, 10, 15, 20+ years.....

Of course, the TCC determined clearing time is perhaps the most critical leg of the "power, distance, time" triangle affecting incident energy and PPE category.

Does any one know if there have been studies where vintage MCCB and LVPCB breakers (maintained/exercised or not) have been injected tested to see how the actual clearing times compare to the manf TCC at the time of manufacture?

Love this forum - great way to help us keep people safe!


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 Post subject: Re: Breaker Maintenance
PostPosted: Tue Nov 11, 2014 1:55 pm 
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Location: Port Huron, Michigan
I always try to maintain a 3 to 5 year rotation of testing and maintenance of all feeder breakers. Then you can be a little more confident that they will operate as designed.


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 Post subject: Re: Breaker Maintenance
PostPosted: Tue Nov 11, 2014 2:17 pm 
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Location: North Carolina
ANSI NETA mts-2007 is a good reference for judging how often you need to maintain circuit breakers and the like to keep them in good working order which is what is required by NFPA 70E.


Really? Do you unwire all your control wiring and megger it every 24 months? For the small number of failures that this might detect, isn't it going to cause more than it detects? How about the one that recommends using a torque wrench to test for torque on a fastener, which flies in the face of "fasteners 101"?

I like NETA-MTS from the point of view that it is one of the most clearly written standards. However, the inspection frequencies and many of the recommended tests are not appropriate. It has a more aggressive testing schedule than any other standard out there and there is no justification for it. It appears that this standard is written by a group of electrical equipment testing companies as a way of self-promoting requiring as much testing as possible. Perhaps that would explain why NETA stands for (inter)National Electrical Testing Association.

I was not a big fan of 70B in earlier editions than the current one either because it was full of just plain typos and spelling errors that was not a quality document. The current version is much improved in this regard.


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 Post subject: Re: Breaker Maintenance
PostPosted: Wed Nov 12, 2014 6:53 am 

Joined: Mon Nov 04, 2013 2:36 pm
Posts: 4
Do you have you car inspected yearly as required by several states? Several years ago, my company was asked to have a small pump station tested to return it to service after a period of little use. We found the main breaker and several large breakers did not trip at 200%. The plant manager mentioned that one night the telementry indicated the power was off in the pump-station. The utility was called and replaced there transformer fuses several times. as the fuses continued to blow. An electrician was called and found the electrical heater in the plant was shorted, but the breakers had not tripped. He opend the heater breaker and power was restored. Apparently the the heaterbreaker, the MCC breaker and the main breaker failed to trip. Moisture in an off-line station apparently swelled the arc chutes. This same company had a 1200 ampere feeder come loose and damag a MCC bus. it took over 12 hours to repair. Meanwhile a large city almost run out of water while the plant was down. I recommand that any large system should have a themo-testing done annually and the main and all large feeder breakers tested regularly. Any problems found on testing must be fixed. I have run across cases where testing was done, and the problems were not addressed. NETA has many recommadations and test procedures.


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 Post subject: Re: Breaker Maintenance
PostPosted: Thu Nov 13, 2014 7:37 pm 

Joined: Thu Jun 05, 2014 5:52 pm
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Fuse was blown and CB wasn't tripped can be mis-op or mis-coordinated. RCA need to carry out rather than assume that CB not trip at 200%. NFPA 70B provides general maintenance guide line but how much maintenance need is depend on who you talk to. Old car, old school use time base for oil change but most of new car use condition base. Likewise, testing and maintaining CB can be run to failure, Preventive, Proactive or Predictive.

Back to the original question, If CB is designed to trip at least 1 in 6 months then exercise is not a really need. Otherwise, plan to exercise CB to ensure it will operate when called, on a critical system. If the concern is on clearing time then Kelman test is the answer. In fact, annual Kelman test results can be analyzed and trended to determine whether CB need to have major maintenance or overhaul as need.
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 Post subject: Re: Breaker Maintenance
PostPosted: Fri Nov 14, 2014 6:32 am 

Joined: Tue Nov 04, 2014 5:53 am
Posts: 14
Thanks - this Kelman test - does it apply to Molded Case Circuit Breakers?


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 Post subject: Re: Breaker Maintenance
PostPosted: Thu Nov 20, 2014 10:38 am 

Joined: Thu Sep 27, 2012 3:02 pm
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Location: Washington
EPRI also has some great documents on breaker maintenance, including a database to help determine maintenance frequency based on conditions, importance of the equipment, etc. The PEARL folks have some great documents as well. In my experience I have found that the basic manufacturer recommendations are not sufficient for low voltage power breakers and medium voltage breakers (air and VCB). We most typically saw breakers failing to close due to hardened grease in areas not addressed in the basic maintenance. We also saw issues with breaker failing due to wear on mechanical parts, which required a tear down and re-build. There are a number of users-groups for specific breaker types where maintenance issues are discussed that are very helpful.


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 Post subject: Re: Breaker Maintenance
PostPosted: Sat Nov 29, 2014 7:56 pm 
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Back to the original question, a breaker consists of a trip unit and the breaker itself. In smaller breakers the trip unit is integrated. An output from the trip unit energizes the trip coil in the breaker. The breaker mechanical system most often suffers lubrication issues which cause it to seize up or operate slowly. The trip coils sometimes fail but not often. The trip units come in three varieties. First generation are electromechanical. I would say bad things about them but in some applications they are very reliable (molded case breakers). Second generation is solid state. Basically analog electronics. Did not turn out to be much more reliable than the older stuff. Third generation is microprocessor. They are much more reliable but partly because they replace 2-6 older trip units with a single one.

Breaker testing is really about breaker exercising, inspection and lubrication, and testing the system end-to-end. If it passes this, no reason it can't be trusted.


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