Danger of resetting a 400 amp 480 volt breaker with a dead short

[zog]

at age 65 with my experience (and attitude).... take the time to check...
when I was younger (and faced those situations)...a long stick

Or remote operators http://www.remoterackingsolutions.com/remote-switch-operators.htm

 

[Fulthrotl]

Lets consider a 2000 amp main installed in a high rise office building. The breakers feeds the upper half of the building via bus duct. The breaker has ground fault protection. It's 9:00am on Monday. Whats your call?????

ghostbusters?

if the breaker in question feeds the bus duct, ya can't megger it without
opening all the bus taps. i'd want to megger it before i blew something, maybe
myself, up.

everyone's gonna scream like a mashed cat at the delay. ok.
they are gonna want in on, NOW. ok.
opening 10 floors of disconnects is gonna take half an hour. best to start at
the top floor, and work your way downward. it's faster that way.
and make sure you have enough locks... everyone is gonna be flipping stuff,
trying to get it back on...

to do it correctly, parts of that building are gonna be off for at least 2 hours.
if the bus is ok, you can start meggering each floor, and turning it back on,
but it's gonna take a while, unless you have a crew helping you. you're gonna
have to turn off all the breakers in each panel, megger the feeders and
bus tap, light it back up, and close all the branch breakers.
if the bus duct is shorted.... well..... you're gonna have a busy day...:smile:
ever try to pull a bad section of bus duct out of the middle of a vertical riser?

even if you had a remote recloser, and were under no danger personally.
do you want your name written all over a huge emergency repair bill?

a guy who was my journeyman in my second year, went to work 15 years
ago for DWP. smart, brilliant at times, he did some really nice work there.
and one day, his crew had removed personal shorts and grounds, at a
powerhouse, and he went to light up a can. the breaker relayed. often times,
some of the equipment in service is old, and problematic. if it's been off for
10 months, like this situation, it'll have to be push started, so to speak, and
so instead of checking, he threw the switch a second time.

someone had added a SECOND set of shorts and grounds, and had tucked
them nicely out of the way, so they were easy to miss. how thoughtful.
repairing the damage was approx. $2M. a black mark in the copy book,
to say the least. thank god nobody was hurt.

 

[zog]

I have always had a very strict policy on personel protective grounds, controlling them is very important, I use additional tags on the LOTO point that says "Warning, PP Grounds installed" and include the assigned number for that ground set (The ground cluster is tagged with a number also).

I have seen similar things happen, whole plants go dark because someone forgot grounds, no one was hurt, but production went down, some minor equipment damage and the guy was fired. Same guy did it again at another company that hired him, fired him also, he now installs sprinkler systems.

 

[charlie b]

From what I remember of my Navy training, a tripped breaker can be reset one time. If it trips again, it must be tagged out and the circuit repaired. That might not have been the best process, and it might not be what the Navy is teaching today.

 

[zog]

From what I remember of my Navy training, a tripped breaker can be reset one time. If it trips again, it must be tagged out and the circuit repaired. That might not have been the best process, and it might not be what the Navy is teaching today.

Different world, navy procedures are designed with battle conditions and operations in mind over safety. I am sure they are still teaching the same thing today. Plus on a naval system, the operator could check for grounds on any bus from the EPCP before re-energizing the bus, and that was part of the procedure if you recall.

 

[zbang]

the Riot Act

the Riot Act

By the way, what is the 'RIOT ACT'.

Wikipedia is your friend

"Read the Riot Act"
Because the authorities were required to read the proclamation that referred to the Riot Act before they could enforce it, the expression to read the riot act entered into common language as a phrase meaning "to reprimand severely", with the added sense of a stern warning.

 

[zbang]

I somewhat fondly remember the head electrician at the college I attended... during a half-campus outage caused by the PoCo, he patiently explained to a group of us students that when something like this happens, you don't just flip the campus main back on. During the outage, he and his crew had gone to each building and pulled their mains, and was now bringing up a couple of buildings at a time. Some of this also might have had to do with the 50+ yr old distribution system

 

[charlie b]

Wikipedia is your friend

Wikipedia is a waste of valuable Internet web space.

Use it, if you must, to gain a vague notion of the answer to your question. But believe nothing you read therein, unless and until you find at least one, and preferably two, reliable and authoritative information sources that confirm what it says. Better yet, just go to a reliable and authoritative information source to begin with, and don't bother with Guess-a-pedia.

JMHO, of course. :roll:

 

[weressl]

How long does that take, five minutes? If the breaker tripped there was a reason. Your playing with alot of calories.....

It doesn't matter if you're fat when you're dead

 

[weressl]

I was NOT asking in jest, I was just getting some clarity. I have been on other jobs where i see other electricians resetting (high amperage) breakers that have malfunctioned. Fortunately, there wasnt a 'bang' and no one got hurt.

The most recent incident was several months ago, there was this 800 amp 'power breaker'( the one you have to charge with handle and then close) that when it was opened to kill power to the disco we were working on, would NOT reclose at first. Most of this was because there havent been proper pm's done on this power breaker. I stood back and watch my co worker, (without ppe) take a few cranks at it to get charge so it can be closed.

I was going to leave it in that condition until the next day so the boss can get someone in to repair it, but he decided to go head and see if he can get to close, and it did. Fortunately no 'bangs' or booms.

Just trying to spread safety awareness and increase/better my own safety. I think the springs in these power breakers had jammed or whatever.

By the way, what is the 'RIOT ACT'.

I don't care how many empty chamber a revolver has, I will not pull the triger.:smile: Anyone who does just plain stupid.

 

[weressl]

Since Don already mentioned OSHA, I'll add NEMA AB-4 and IEEE 1015. Both are ANSI documents. The NEMA document is available as a free download at their site. Unfortunately, the IEEE document is only available by purchase (or descrete quotes like that below). It is one of the "Color" series - the IEEE Recommended Practice for Applying Low-Voltage Circuit Breakers Used in Industrial and Commercial Power Systems (Blue Book).

In the NEMA AB-4 Introduction, third paragraph, it mentions the rigorous UL testing the circuit breakers go through. Still, it ends with the statement: ?Thus circuit breakers have an extensive but finite interrupting capability, and breakers that experience multiple high short-circuit-current faults should receive a thorough inspection with replacement if necessary.

The IEEE document considers two (2) ?high short-circuit-current faults? sufficient to warrant replacement:


The trips your colleague experienced were probably not rated maximum level faults as indicated by the time delay in tripping. The problem is that he no longer has any idea what service life is left or that it will safely interrupt another fault - and neither does NEMA nor UL.

That and some other reasons fuses are still SAFER than circuit breakers.

 

[zbang]

Wikipedia is a waste of valuable Internet web space.

Use it, if you must, to gain a vague notion of the answer to your question. But believe nothing you read therein, unless and until you find at least one, and preferably two, reliable and authoritative information sources that confirm what it says. Better yet, just go to a reliable and authoritative information source to begin with, and don't bother with Guess-a-pedia.

Wikipedia can be an excellent starting point and many of it's topics are spot-on accurate (and have the backup citations). Just like any source, don't blindly believe what you read in one place, check some others. While it isn't so good on constantly changing topics, printed books aren't either.

As it happens, the article on the Riot Act is correct and has enough citations to satisfy most skeptics. It also agrees with some books that I have.

FWIW, the WP article on Split Phase looks quite correct to me, as does the one on the National Electrical Code. Check 'em out.

 

[charlietuna]

To properly megger this feeder you have to disconnect the ground fault sensor circuit along with every bus tap disconnect...

 

[augie47]

To properly megger this feeder you have to disconnect the ground fault sensor circuit along with every bus tap disconnect...

charlie, you are probably right, but when I read that, my first reaction isthat nothing on the service GF system would be affected on the load side of a tripped feeder breaker.

 

[rbalex]

I'm not so much a fan of fuses as I just want the fact known that MCCBs aren't nearly as robust many think they are after clearing a fault. They do fine with overloads and are sufficently proof-tested for that.

I'm surprised no one has mentioned IEEE 1548 Recommended Practice for the Selection, Field Testing, and Life Expectancy of Molded Case Circuit Breakers for Industrial Applications. It was the working group I finally quit after 8 years of non-production. It took 6 years for the Project Action Request (PAR) approval (it was ad hoc before that) and another 9 to get IEEE Standards Board approval.

Project scope: To provide the user with a recommended procedure that is safe and easily understood, for the selection, application, and determination of the remaining life in molded case circuit breakers.
Project purpose: Project is necessary because there is widespread misunderstanding on this subject. Because of these misunderstandings, users are unintentionally installing and applying molded case circuit breakers in situations that are potentially dangerous. The proposed recommended practice will provide suggested recommended practices to safely apply and test molded case circuit breakers. [rbalex underline italics mine]

 

[augie47]

I'm not so much a fan of fuses as I just want the fact known that MCCBs aren't nearly as robust many think they are after clearing a fault. They do fine with overloads and are sufficently proof-tested for that.

I'm surprised no one has mentioned IEEE 1548 Recommended Practice for the Selection, Field Testing, and Life Expectancy of Molded Case Circuit Breakers for Industrial Applications. It was the working group I finally quit after 8 years of non-production. It took 6 years for the Project Action Request (PAR) approval (it was ad hoc before that) and another 9 to get IEEE Standards Board approval.

Bob, I'd like to read it. It is available without being an IEEE member ?

 

[rbalex]

Bob, I'd like to read it. It is available without being an IEEE member ?

Unfortunately, I don't believe so. I'm also afraid I don't have a copy either. I just know it exists.

 

[IMM_Doctor]

Nfpa 70e

Nfpa 70e

And note that there are OSHA rules that prohibit the resetting the breaker after a trip unless you have checked the circuit first.

See NFPA 70E 130.6 (K)

 

[brian john]

All the pictures shown here have been posted before.

Closed into a fault Bolted pressure switch.

Closed into a fault circuit breaker.

 

[Fulthrotl]

All the pictures shown here have been posted before.

sorrry, but you are gonna have to refurbish that one a bit more before
sliding it into that square D box........ it doesn't look "reconditioned" enough
at first glance.......