# Ground fault protection at crusher/pavement plant



## te12co2w (Jun 3, 2007)

I have not been in this yard. This is from one of the owner's employees. There are a lot of flexible cords going everywhere in this yard for motors, cabinets, control room, etc. They have a mix of grid power and generator power. This employee said he saw a blue flame/spark shoot out of the ground or someplace else. He gestured with his hands about 2-3 feet long. That was the length of the flame. Ground was wet. He was standing in water in close proximity to the flame. He is concerned about his own safety. He said he brought it up with his supervisor. They brushed him off. He asked me how he might install ground fault protection on these cord sets. He said that the flame he saw was on a 480v circuit. I don't know what brand of equipment they have down there. Has anyone here ever dealt with this? I will not be installing any electrical there myself. Sorry if this is too unclear, but I haven't been on the grounds.


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## micromind (Aug 11, 2007)

Cord is VERY common at crush plants and hot plants. A lot of it is several hundred feet long and some of it is undersized. 

When a cord blows up, the fine strands will make a spectacular spark/flame. 

The last one I saw that blew up like this was a 6/4 feeding a 75HP motor. I happened to be looking in the general direction and saw a plasma ball about 8" in diameter which quickly became somewhat similar to a lightning bolt. It extinguished itself after it got to be about 15" long. 

The 250 amp breaker feeding it never tripped..........

Getting the company to install ground-fault on anything in a crush plant would be an exercise in futility.........


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## joebanana (Dec 21, 2010)

It only takes one wrongful death lawsuit to change a companies safety policy.


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## tates1882 (Sep 3, 2010)

Requiring the workers to wear electrical rated footwear and having a safety program in place would be a good start. I can't imagine the headache involved in maintaining ground fault protection at crusher 


Sent from my iPhone using Tapatalk


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## RePhase277 (Feb 5, 2008)

I think better cable protection would be more effective than ground fault protection... less headache at least. But there are many off-the-shelf ground fault solutions for 480 V circuits, but he better get some running shoes because he will be chasing something every day.


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## Big John (May 23, 2010)

There are a ton of stand-alone ground fault relays out there for $150-$200. 

I'd think a 100mA trip threshold would be a good compromise to prevent chasing faults everywhere.

But if the guy who owns the gear doesn't want to spend that money, there's not much you're gonna do.


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## Wiresmith (Feb 9, 2013)

ground fault relays on main's that trigger alarms, like what they use with high impedance neutral systems


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## brian john (Mar 11, 2007)

You can use a current relay and size your CT's for the load, configure as a Zero Sequence GFP, trigger an alarm or operate a Shunt Trip CB


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## Wiresmith (Feb 9, 2013)

management will probably be very angry the second time a loaded conveyor is shut down for nuisance trips. some conveyors in plants like that have to be unloaded to start back up. but they would have bigger problems if someone is hurt, i recommend alarms.


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## John Valdes (May 17, 2007)

I had several aggregate plants, two separate companies and have never seen a group be as excitable as these guys.
To me, an emergency is when I see doctors walking around in white coats and nurses helping them.
Not a motor that will not start.

They actually thought the sun came up each morning for them!

There are a couple of them I would love to run into today.


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## mitch65 (Mar 26, 2015)

I have worked on several crusher plants, have never seen ground fault protection on any of them. Any GF protection would soon be bypassed. The operations I have seen do most of their electrical work themselves and only call someone when they f&*k something up so badly that they can't fix it. I think if someone got killed, they would throw them in the bush, say they never came back from days off and hire another skid to fill his boots.


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## micromind (Aug 11, 2007)

mitch65 said:


> I have worked on several crusher plants, have never seen ground fault protection on any of them. Any GF protection would soon be bypassed. The operations I have seen do most of their electrical work themselves and only call someone when they f&*k something up so badly that they can't fix it. I think if someone got killed, they would throw them in the bush, say they never came back from days off and hire another skid to fill his boots.


This is a pretty accurate description of every crush plant I've ever worked on. 

I think every apprentice should go on a few service calls to crush plants........if nothing else, they'd learn just exactly how hard you can push stuff until it blows up. 

And yes, they absolutely WILL bypass any and every safety thing that shuts any part of the plant down.


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## te12co2w (Jun 3, 2007)

Thanks for the replies everyone. I suspect the owners will not want to spend much, if any money on ground fault protection. Maybe I could sell some kind of alarm, but as mentioned, any attempts would soon be bypassed. Thanks again.


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## JRaef (Mar 23, 2009)

I too have done a lot of crushing plant work, and yes, GFP is non-existant, other than what the NEC requires (and sometimes the portable plant guys claim they don't need to meet NEC requirements...).

The situation you described is something that happens when the ground conductor is cut, disconnected, or NEVER connected on one of those portable cables strung out to a piece of machinery. What happens is that a motor winding fails or a cable wears through from vibration against a bracket, then there is a ground fault. But the ground out there is often so incapable of conducting current (because it's dry and rocky) that because the ground conductor is not connected, nothing trips and the whole frame is energized, until SOMETHING conductive gets close enough to complete the circuit, and it all goes at once. TECHNICALLY, they are required by MSHA to have "continuous ground conductor monitoring" devices installed at each piece of machinery. The problem is, MSHA is very lax about gravel operations, they are typically overwhelmed by actual production mines. So in 20+ years of working in rock plants, I saw exactly ONE ground monitoring system in use, and that was at a plant that had an accident, so they were investigated by MSHA and were told to install it.

https://arlweb.msha.gov/S&HINFO/TECHRPT/ELECTRICAL/groundwiremonitors.pdf


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