Main Breaker Exercise

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bridcarp

Member
Got a question for you Guru's.. We have a new procedure at my facility, where every month we will be checking our generator's by opening the main breaker. which will simulate a power outage. My concern is with my Arc flash study being done and my cat for this breaker being Extreme Danger, what would be the procedure for operating this breaker? With the covers on the switch gear,is it safe to open and close this breaker monthly? Any help would be appreciated. Thanks Brian in Salinas CA
 

iMuse97

Senior Member
Location
Chicagoland
The covers on the switchgear just become large projectiles if you have an arc flash. You need a remote racking device. Zog would probably like to sell you one. :)

Do you really want to do this, significantly shortening the usable life of that thing? Where's Zog when you really need him?
 

drbond24

Senior Member
Do you really want to do this, significantly shortening the usable life of that thing? Where's Zog when you really need him?

If Zog talks him out of flipping the breaker a million times, he'll lose the sale on the remote racking device! ;)

I agree with the life shortening comment, though. That breaker only has so many operations before it is junk, and you (the OP) will be killing it slowly by doing this testing. I'd take it to once a year at least, if not every 5 years. There is no need to do it monthly.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
Check with the manufacturer of the equipment.

I know of at least one manufacturer that says their equipment has been tested for normal operation (i.e. on-off but not reseting after a trip), per UL 891 standards and therefore poses little to no hazard. they base their opinion on the fact that UL 891 and UL 489 standards requires the devices to operate up through many operations without damage that would cause them to become inoperable. This type of reasoning has some validity, but it cannot be used when the device is being closed onto a fault. This is why breakers are not to be reset without determining why they have tripped.

Another issue though, is the relatively limited electrical life of some devices. Few breakers larger than 200A are rated for "hundreds" of operations, this means you may need to replace or rebuild your breaker every few years.
 

tryinghard

Senior Member
Location
California
In a perfect arrangement the equipment is labeled accordingly revealing the arch flash rating. This may not be as dangerous as you think if labeled, and with covers on.
 

cowboyjwc

Moderator
Staff member
Location
Simi Valley, CA
I agree that you need to operate the breaker from time to time and annualy might be enough. He also is required to do what he is doing per the code for the generator.
 

zog

Senior Member
Location
Charlotte, NC
Sorry I am late, busy at the Breaker Conference. What type of breaker is this?

Most OEM's will recommend manual operation annually, and actual testing every 2-3 years. Breakers are usually rated for a certian number of fault interuptions (Usually 2 or 3) and a number of normal operations (Usualy more like 2,000).

We have wireless remote operators for 97 different applications. We can operate about anything from 150ft away and is portable and easy to use.
 

mcclary's electrical

Senior Member
Location
VA
Do you really want to do this, significantly shortening the usable life of that thing? Where's Zog when you really need him?

I worked at a very large sawmill when I was in my teens and twentys. One of the buildings had an 800 amp 480 volt 3 phase service. EVERYDAY, at the end of the day, they manually tripped the MAIN BREAKER by hand with the test button. I used to raise cain at them for the longest time on how they were going to ruin that breaker. I stayed on them about it, yet they were still doing it everday. After about 5 years of telling them it was gonna damege it, I quit trying and gave up. (They didn't believe me when they first started, they really don't belive me 5 years later.) The thing is still in operation today.
 

zog

Senior Member
Location
Charlotte, NC
I worked at a very large sawmill when I was in my teens and twentys. One of the buildings had an 800 amp 480 volt 3 phase service. EVERYDAY, at the end of the day, they manually tripped the MAIN BREAKER by hand with the test button. I used to raise cain at them for the longest time on how they were going to ruin that breaker. I stayed on them about it, yet they were still doing it everday. After about 5 years of telling them it was gonna damege it, I quit trying and gave up. (They didn't believe me when they first started, they really don't belive me 5 years later.) The thing is still in operation today.


"Being in operation" means nothing, how do they know this breaker will trip if a fault occurs??? When was the last time it was tested, I am guessing never.
 

iMuse97

Senior Member
Location
Chicagoland
just goes to show you, when it comes to breakers, if you think you know something, you still better run it by someone like Zog first.:) In situations with equipment like this, I haven't been the one to know, but I've kept my ears open and am still learning a thing or two.
 

zog

Senior Member
Location
Charlotte, NC
Hey Birdcarp.

If you want any real answers to your questions you need to tell us the actual breaker type, pictures help.
 

mcclary's electrical

Senior Member
Location
VA
"Being in operation" means nothing, how do they know this breaker will trip if a fault occurs??? When was the last time it was tested, I am guessing never.

I'm sure your guess would be correct, but I haven't been there in years. But I've got a question for you, I at least wanted them to manually open the breaker without the trip button. If load was shed, and opened by hand, would that hurt it over years and years?
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
I'm sure your guess would be correct, but I haven't been there in years. But I've got a question for you, I at least wanted them to manually open the breaker without the trip button. If load was shed, and opened by hand, would that hurt it over years and years?
It depends on the size of the breaker and if it is a molded case or power circuit breaker design.

A 1200A molded case breaker, like Square D I-Line, are rated for about 2 full rated fault current, 500 full load current, and 2,000 no-load operations.
 

bridcarp

Member
Hey Birdcarp.

If you want any real answers to your questions you need to tell us the actual breaker type, pictures help.

Pics on the way... I have two different senerios... I have a 3000amp 480v and a 4000a 480v breakers. both are bolted to buss. not rackable. The second way would be to shut off the 1200a 12KV vaccum breaker, which all of these where tested 2 months ago. I really don't want to do either, and with all this infomation you guys are giving me, I'm forwarding on to senior management and Critical Environment Operations Manager. I'm hoping they will change there minds. Also thinking about calling in utility power company to shut off 12kv into building at the switch, and then returning power back on after testing is complete. this way we will be producing a power failure, and no one will even have to suit up.
 

jmd445

Senior Member
An excerpt from NFPA 110
8.4.9.3 The test shall be initiated by operating at least one transfer switch test function and then by operating the test function of all remaining ATSs, or initiated by opening all switches or breakers supplying normal power to all ATSs that are part of the EPSS being tested.

and

8.4.7* EPSS circuit breakers for Level 1 system usage, including main and feed breakers between the EPS and the transfer switch load terminals, shall be exercised annually with the EPS in the ?off? position.

If your ATS is supplied with a test switch I would do it from the ATS. Cycling the circuit breaker is suicidal.

Jim



 

renosteinke

Senior Member
Location
NE Arkansas
Talk to your transfer switch maker. "Exerciser" units are made specifically to do this: to transfer the building to generator power on a regular basis, just to keep the generator in good shape.
 

zog

Senior Member
Location
Charlotte, NC
Pics on the way... I have two different senerios... I have a 3000amp 480v and a 4000a 480v breakers. both are bolted to buss. not rackable.

What is the breaker type????????????

The second way would be to shut off the 1200a 12KV vaccum breaker, which all of these where tested 2 months ago.

Chances are that is safer from an arc flash point of view.

Also thinking about calling in utility power company to shut off 12kv into building at the switch, and then returning power back on after testing is complete. this way we will be producing a power failure, and no one will even have to suit up.

You still need to suit up to verify absence of voltage, plus the power company will charge you to do that, and change you to sit there and wait.
 
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