Lights went out in Walmart

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carlos cainas

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At a Walmart working on the pole lights we had a short in the wire and caused my two pole 20 amp breaker to trip, it also went through the 200 amp fuses, the 200amp main breaker at the panel, causing the 200 amp breaker that feeds that panel at the switch gear to trip, causing the whole panel to shut down. We tried it again with the same results. I will give you more details of the GE 3 phase panel when I go back tomorrow.
 
carlos cainas said:
At a Walmart working on the pole lights we had a short in the wire and caused my two pole 20 amp breaker to trip, it also went through the 200 amp fuses, the 200amp main breaker at the panel, causing the 200 amp breaker that feeds that panel at the switch gear to trip, causing the whole panel to shut down. We tried it again with the same results. I will give you more details of the GE 3 phase panel when I go back tomorrow.
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Yes, it can cause the main to trip. Hopefully you isolated out the fault prior to resetting the breaker. A few ways to do that - but did you reset any breakers?
 
Most likely you took out the GFP main, Settings are as GENERALLY as low as 100 amps and as high as 1200 amps with Time Delay (TD) at Instantaneous to 1.0 seconds. If the GFP is set at or around 200 amps with a low TD it is feasible the GFP operated.

1. The GFP should be set per the coordination study (which few owners/electrical engineers bother with.

2. You should not be working on anything while energized.
 
how to test

how to test

hello, I am the service man that got the call, been doing service now for about 12 yrs, electrical to long, it was late in the day I did not check the settings on the panel 200 amp breaker,but lets say it was at 200 or I will set it to 200 how would I check for this not to happen again Walmart hates going dark.
 
I sure wouldnt go changing settings on breakers.... I dont mean to sound rude so please dont take it that way, but I think you need to learn about GFP, coordination, etc. I hope you didnt close those breakers 'to try it' before confirming you cleared the fault. I also think you need to watch some arc flash videos.
 
Good idea...

Good idea...

wireguru said:
I sure wouldnt go changing settings on breakers.... I dont mean to sound rude so please dont take it that way, but I think you need to learn about GFP, coordination, etc. I hope you didnt close those breakers 'to try it' before confirming you cleared the fault. I also think you need to watch some arc flash videos.
Click to expand...

May I suggest THIS ONE to start?

And THIS ONE....
 
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need a solution not an explanation

need a solution not an explanation

our company requires us to wear a suit any time we open a panel,now that we got all the safety issues out of the way,this has happen to many of service tech including me and have corrected the breaker tipping leaving the panel as is.
 
First I doubt that breakers of this size have any type of adjustable trip settings or has a ground fault setting. The trip curves of molded case breakers from 15 amp to 200 amp can easily overlap for ground faults or short circuits.
 
to the GURRO or is it BURRO

to the GURRO or is it BURRO

before you call anybody stupid,take a good look at your self on that DIRT BIKE GOOD LUCK ON IT.
 
While this is area is a bit out of my league and gladly admit it (i am residential and light commercial) I don't think that anyone said anything out of line, or do I think anyone called you "stupid".

c2500
 
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carlos cainas said:
before you call anybody stupid,take a good look at your self on that DIRT BIKE GOOD LUCK ON IT.
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Carlos...relax....he didn't call YOU stupid...it's called a signature line...shows up on every post....his happens to be on the bottom left, mine happens to be on the bottom right.
 
carlos cainas said:
before you call anybody stupid,take a good look at your self on that DIRT BIKE GOOD LUCK ON IT.
Click to expand...

I can see you are a new member here, and just keep this in mind. This forum is here to help others in the trade. I don't believe anyone's calling anybody anything, here. If they were, the moderators would shut this down before you knew what hit ya. People here are here to help. Safety is #1. Helping others in the trade has to have that in mind 1st. Keep things civil here, and you will find a wealth of info. Abuse it, and you will find no help. Above all, safety is #1. Resetting a tripped breaker w/o verifying that it is safe to do so is not only an OSHA violation, but also asking for trouble, (i.e. someone can get hurt.)
Welcome to the forum.:smile:
 
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sorry for the oversight

sorry for the oversight

you know electrician sometime have a very short fuse, sorry about that,just kind of fustrated on this issue.
 
For the record, Carlos and I have chatted by PM and it's all ok. :)

Moving forward, one of the possible causes of what happened at his Walmart is simply a coordination issue between the main and downstream breakers. It is quite a formidable task to properly coordinate overcurrent devices in a large system with lots of short circuit current available.

Bob (iwire) has extensive experience in commercial, he may have a better answer.. :)
 
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I am too lazy to do a search so I am posting this again I apologize to the members for being redundant.

Carlos PLEASE read this is from a previous post I put together as a service electrician this may HELP you and save your life, or at a minimum knocking a valuable customer off line. If this bores you (and my writing can be boring) skip too the 3rd post HOW TO SAFELY RESET GFP PROTECTED MAIN LINE SWITCHES:


Electricians are often faced with having to close/shut/reenergize Main Line Switches (either bolted pressure Switches High Pressure Contact switches or Circuit breaker) after opening due to a Ground Fault. When care is not taken in closing a Main Line Switch the electrician exposes himself to possible dangerous sustained arcing faults with personal injury or equipment damage for the facility owner with the liability for the damage. What I have listed below is the approach I have utilized over the years for a safe, effective fairly fast method to restore power to a facility.

What I have outlined below describes Ground Fault on Main Line Switches (I use this term loosely to include various styles of devices), but the type of systems discussed and the procedures for locating faults can be utilized on distribution systems with multiple levels of Ground Fault Protection.

WHAT IS GROUND FAULT PROTECTION OF DISTRTIBUTION EQUIPMENT:

1. The Ground Fault Protection (GFP) system is designed for equipment protection, NOT PEOPLE PROTECTION as some may think.
2. GFP was first adopted into the NEC in 1971 NEC article 230.95. The reason for this new Article was the increase in sustained arcing ground faults resulting in system burn down that accompanied the increase in the use of 480/277 distribution systems.
3. The basic NEC rule for the mandatory installation of GFP is on Main Line Switches 1000 amps and larger and more than150 volts to ground.
4. Setting for the GFP relay is a maximum of 1200 amps with a maximum of 1.0 second delay.
5. While arc faults occur at all voltage levels sustained arcing ground faults occur at a voltage above 370 VAC. The peak voltage of 208/120 VAC system to ground is 169 VAC, while for a 480/277 VAC system the peak voltage is 391 VAC above the 370 VAC threshold. 120 X 1.414=169 and 277 X`1.414=390 (numbers are rounded off).
6. The nature of this sustained arc is the impedance of the arc is high and the fault does not generate enough current to operate the OCP. But this arc has damaging energy and can burn down switchboards, turn busways into a mass of molten metal and KILL IN the preverbal flash of less that a second.
7. Switchboards AIC ratings are designed for the worse case fault, this is a bolted phase to phase fault, in reality this type of fault, bolted; is rare. Studies have shown most faults start as ground faults and then if the OCP does not clear the fault they may become phase to phase but not bolted.
 
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TYPES OF GROUND FAULT PROTECTION SYSTEMS:

1. There are 3 basic types of GFP in use these are Zero Sequence, Ground Return and Residual.
2. Early GFP systems utilized the Ground Return. This was a Current Transformer (CT) usually with a 600 to 5 ratio mounted on the neutral to ground bond. The 5 amp secondary operated a dash pot and this in turn operated to open the Switch. There were several problems with this system, the first being the neutral ground bond exist at the main service and at the utility transformer; this dual path desensitized the GFP system as there were two ground return paths to the source. Additionally the dash pot had inherent time delay. Then there was the Main Line Switches, early Switches utilized linear motors and circuit breakers utilized motor operators, both considered slow. Therefore, these early systems had three factors that could delay their operation under ground fault. Ground Return type GFPs are still in use with the newer style relays, typically this type of GFP is utilized with double ended Switchboards (two or more feeds).
1. Manufactures were working on large window CTs (12’-36’X8-16”) to provide a faster safer more reliable cost effective solution. These CTs encompass the phase and neutral/grounded bus/conductors. This system is refered as a Zero Sequence system, this system coupled with the advent of new electronic relays and Shunt trips for circuit breakers and spring opening bolted pressure Switches resulted in VERY FAST clearing of Ground Faults. Zero Sequence systems measure all current leaving and all current returning to the Main source the sum of these is effectivly “0” amps (there may be a small amount of leakage current). If there is a ground fault the current takes an alternate path (multiple ground paths) bypassing the Zero Sequence CT and result in current on the CT secondary, when this current reaches the preset current threshold of the GFP relay and meets the time delay the contacts close to operate the Main Line Switch or CB. These CTs are actually called current sensors this has to due with the secondary output or the ration is not given in ration like standard CTs. I am no CT expert and state this here only for educational purposes.
2. Residual GFP systems utilize 2 to 4 CTs, wired in such a manner to a GFP relay that mirrors operation of the zero sequence system.
3. While different manufacture offer different settings typically the basic GFP relay has settings between 100-1200 amps, with delay from instantaneous-1.0 seconds.
 
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