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 Post subject: Circuit Breaker Maintenance
PostPosted: Wed Aug 10, 2016 2:07 pm 
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Apologizes if this topic is covered elsewhere in the forum. If so, please point me in the right direction.

We are having some arc flash studies completed for buildings across our campus. The consultant is recommending that fuses be replaced with current limiting type fuses and also that breaker settings be dialed down to be more conservative. Adjusting our old breakers is something that we are nervous about doing and so I wanted some reactions from this group.

I know NFPA 70B has guidelines about exercising/cleaning breakers every couple of years but of course we, like every other building owner I have ever ran across, don’t regularly maintain our low voltage circuit breakers. We are not staffed to regularly clean & exercise the plethora of breakers across of 100+ buildings, nor do we have funds lying around to replace the vintage to middle aged breakers should they be discovered as prone to failure.

We are worried that by adjusting the breakers as recommended by the studies that we are asking for them to nuisance trip or perhaps malfunction in some unforeseeable way, causing widespread building outage or expensive parts replacements. Of course, if we run across breakers that are clearly on the their last leg or are an immediate threat to personnel they should be addressed right away. It's those "dark horse" breakers that concern us.

Do folks have recommendations for what to do or have similar situations? Are there simple ways to inspect breakers to see if they appear to have useful service life remaining / can be exercised or adjusted without worry of problems in doing so? Any tips and tricks that don't involve a lengthy outage to building power? What are your other large campus type clients doing in regards to maintenance and testing of breakers? Is this something anyone does that you are aware of?

Any feedback is appreciated.


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 Post subject: Re: Circuit Breaker Maintenance
PostPosted: Wed Aug 10, 2016 3:20 pm 
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Location: Folsom, Ca
DMB5mil,

This is a fairly common conundrum that comes up during studies. The best thing I could recommend is acquiring the services of a NETA certified electrical testing company, obtaining or having on short order some replacement breakers, and scheduling a maintenance shutdown.

Now I know that this sounds like a lot of work and costly, but hear me out. If you schedule a maintenance shutdown you eliminate the chance of an unplanned outtage, and you can have backup plans in place in case something major fails (but that's also why you have the spares on hand). The arc flash studies that you're having performed right now are based on equipment that is operating within the manufacturers clearing times. Without maintenance and testing being performed, it is not possible to know whether or not the equipment is working properly, which invalidates the study. So by doing this you're implementing your settings (validating arc flash study), maintaining/inspecting your electrical equipment (increasing reliability), and avoiding any possibility of major costs associated with an unplanned outtage.

This has been the approach I've used with many large clients (data centers, hospitals, office buildings, etc.), but it does take time and planning. As far as the breaker testing, if you have older style power circuit breakers I would make sure the testing company uses primary injection testing on them. Its the most reliable way of testing them out. Anyways hope this helps.


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 Post subject: Re: Circuit Breaker Maintenance
PostPosted: Thu Aug 11, 2016 8:39 am 
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Posts: 439
Location: Wisconsin
DMB5mil wrote:
Adjusting our old breakers is something that we are nervous about doing and so I wanted some reactions from this group.


From a maintenance standpoint your old equipment either works or it doesn't. Changing the breaker settings does not affect that.
Poor maintenance can defeat the best design.

If you are happy with the incident energy results of your existing installation, then don't make any setting changes.
If you want the results 'lower values' in your study, you have no choice but to adjust the settings.
Your call.

Except for malfunctioning equipment, breakers do not 'nuisance trip' (yes, any trip can be a nuisance to operations). The breaker tries to open because some equipment is failing, causing too much current to flow. For most situations, the faster the fault, failed equipment, is removed from service the less collateral damage is incurred. Less damage means a faster return to service and a lower mean time to repair. Properly coordinated breakers usually reduce the area affected by a fault.

Line to Ground faults (GF) may be the most likely type of fault to occur in an operating power system.
Minimizing protection (e.g. GF only on main device) here is most likely to have an impact on the overall system.
Set too high and a fault can result in severe equipment damage.
Set too low and total UPS outage can occur.

Better to minimize the area affected by the most likely occurrence (GF on feeders and branches, like in hospitals).
Of course, minimizing by eliminating ‘energized’ work would be ideal.


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 Post subject: Re: Circuit Breaker Maintenance
PostPosted: Sun Aug 14, 2016 12:58 am 
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You can't eliminate ALL energized work. In order to lock it out and comply ith OSHA, you have to test for absence of voltage and up until that point, equipment is considered live until proven dead. Thus voltage testing, even if it is testing for the absence of voltage, is energized work.

Second, the idea that you can change breaker settings on a breaker and it won't trip is simply not true. There are a few manufacturers especially with the old solid state (not microprocessor based) types that will actually trip when you attempt to change settings. This was touted as a "feature". Generally what happens is that pulling the pin to change a tap setting or a range setting causes the breaker to default to it's lowest settings. If this happens and the breaker is energized, quite often it causes a trip. This has come up on this forum before and been confirmed by multiple people.

If you read the manufacturer's instructions some place in almost all breaker and/or trip unit manuals it will say something to the effect that online changes may cause a trip. This does not mean that it WILL happen as it seems to be hinting at.

Furthermore, a malfunctioning breaker can nuisance trip on normal operating current, as can one that is not configured properly. Or it can trip much more slowly than it should or perhaps not at all. And if the malfunctioning breaker is the upstream overcurrent protective device that opens under an arcing fault, it can cause the incident energies to be much higher than predicted.


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 Post subject: Re: Circuit Breaker Maintenance
PostPosted: Mon Aug 15, 2016 6:40 am 
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Joined: Tue Jan 19, 2010 2:35 pm
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As you said, your problem is common.
Here's how I'd treat this.
1. Your consultant probably wants to lower the breaker settings to reduce the possible arc flash energy at these breakers or those down stream. Ask him and if that's the case and then look at where the really hazards are. Then consider how often you access those areas. Once you decided if it's frequent enough to justify reducing the settings, adjust as you will but -
2. Paul's idea of planning an outage is excellent advice. This is the best and safest way to address your issues. But an outage takes some serious planning on your part.
3. If you can sell a planned outage to your managers, then game out different possible problems before you write up a MOP.
4. Do a written method of procedure (MOP). Do not skip this step, it's critical and worth the effort.
5. If you have an electrical contractor you know and trust, get them involved upfront and get them to help with the MOP.
6. Your contractor may have a testing organization they trust or can recommend.
7. Another option is to hire an engineer familiar with old equipment. They're out there - just look for gray hair and wrinkles. These people are often excellent resources and can help you with difficult decisions.
8. Companies like Cooper-Bussman and other publish charts to help with selecting fuses to reduce let thru currents. Something I imagine is a problem in some of your buildings.
9. Lastly, if you haven't read your arc flash reports, do that before you do anything more. If there are areas you don't understand, ask the consultant to explain. He'll likely be happy you actually read the report and be more than willing to explain anything that's confusing.

Good luck,


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 Post subject: Re: Circuit Breaker Maintenance
PostPosted: Mon Aug 15, 2016 8:56 am 
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Thanks everyone. As always good conversation & points to consider.


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 Post subject: Re: Circuit Breaker Maintenance
PostPosted: Mon Aug 29, 2016 5:37 am 
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Lots of good useful replies. I won't repeat this useful information but want to reinforce one concept. If you don't maintain your breakers and apparently don't "trust" them, then you are wasting your money doing an AF study. In order to perform normal operation of these devices and utilize the calculated values from the study, the devices must be: 1. Properly installed, 2. Properly maintained, 3. Doors closed/secure, 4. Covers in place/secure, 5. No evidence of impending failure. If these conditions are not met, then you cannot use the AF study values. Remember, the IE values calculated are based on operating time of the breakers. If they are not maintained, they likely won't operate according to expected opening times and the IE energy will be much greater than calculated.


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 Post subject: Re: Circuit Breaker Maintenance
PostPosted: Tue Aug 30, 2016 7:04 am 
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spark wrote:
In order to perform normal operation of these devices and utilize the calculated values from the study, the devices must be: 1. Properly installed, 2. Properly maintained, 3. Doors closed/secure, 4. Covers in place/secure, 5. No evidence of impending failure. If these conditions are not met, then you cannot use the AF study values. Remember, the IE values calculated are based on operating time of the breakers. If they are not maintained, they likely won't operate according to expected opening times and the IE energy will be much greater than calculated.


I am unsure of where you got that you cannot use the AF study values. It seems like you are utilizing what is stated in NFPA 70E Table 130.7(C)(15)(A)(a) which merely states whether you need Arc Flash PPE. It says nothing about what level of PPE is needed.

_________________
Barry Donovan, P.E.
www.workplacesafetysolutions.com


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 Post subject: Re: Circuit Breaker Maintenance
PostPosted: Tue Aug 30, 2016 7:55 pm 
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wbd wrote:
spark wrote:
In order to perform normal operation of these devices and utilize the calculated values from the study, the devices must be: 1. Properly installed, 2. Properly maintained, 3. Doors closed/secure, 4. Covers in place/secure, 5. No evidence of impending failure. If these conditions are not met, then you cannot use the AF study values. Remember, the IE values calculated are based on operating time of the breakers. If they are not maintained, they likely won't operate according to expected opening times and the IE energy will be much greater than calculated.


I am unsure of where you got that you cannot use the AF study values. It seems like you are utilizing what is stated in NFPA 70E Table 130.7(C)(15)(A)(a) which merely states whether you need Arc Flash PPE. It says nothing about what level of PPE is needed.


It's a recipe for disaster because if you don't start somewhere, what pray tell do you use? Theoretically we'd jump start it like this. We'd start by getting to the first piece of equipment that is properly maintained, even if it's the utility's cutouts. We can short circuit this somewhat by realizing that fuses are almost always going to function as well so the idea that the incident energy values get thrown out only applies when the circuit breaker is the OCPD. Then starting from the electrical power source(s), we can move down the "tree" providing proper maintenance as we go until everything is properly maintained.

The interesting part though is that incident energy is determined by the next upstream device, not the one being worked on. So in the event of a fault as long as the next upstream device is properly maintained, the incident energy values still hold true. So for instance if a piece of equipment faults, then obviously we can't go with the idea that there is no evidence of impending failure. An electrician I know of repeatedly reset a circuit breaker (and so did the operator) troubleshooting a pump. Once it was recognized that the motor was burned up the electrician replaced it. The final action to close the breaker back in to put it back in service triggered an arc flash which severely burned the electrician. Lesson learned: NEMA AB-4 for molded case breakers specifically states that it needs to be visually inspected after a fault. Breakers are designed to trip/survive a very limited number of faults (3-50 depending on the design). After that, all bets are off.

However that doesn't mean that the incident energy from an arc flash study doesn't apply because the upstream equipment is still operating normally assuming that everything is maintained properly. But if it isn't being maintained, then given the 10-20% failure rate of circuit breakers observed by both studies published in the IEEE Gold book as well as more recently by NETA, it's not looking good for reliability if the breakers aren't maintained.


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