Gold mine grounding issues, and harmonic problems.

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SILVERFOX907

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Hello everyone, and im hopping to received help.

I started working at a gold mine, because of the recession. Its been a month now, but I noticed a lot of dirty power. Its a large open pit mine, with 13.8v feeding it. It takes about 40 minutes to drive around, with step down transformers along the way. 13.8v to 4160v or 480v.

Some things I’ve noticed is grounding, and bonding problems. Or lack of. Most of the structures don’t even have a main bonding jumper, or a GEC. It just Armored cable running everywhere, with out ground bushings entering an enclosure. They have had problems with well pump failures for awhile now, and replacing them.
480v some of them are 2,000’ + down a 6” or 8” hole.

One well had isn’t pump motor replaced 4 times this year. All the motors are 480v with different hp.
My question is can the grounding and bonding issues create harmonic issues, stressing out the motor. Creating a negative, or positive additional harmonic frequence, causing more torque on the rotor?

Some of the lift stations I can hear the a sound that i can’t explain, I want to say it’s dirty power, and the harmonics of it. Electricity doesn’t make noise, but you can hear a motor cooling fan.
 
I don't believe any amount of grounding will reduce harmonics.

The noise you may be hearing from the motor is possibly caused by the frequency of the PWM output of the VFD if you are using a VFD. Usually this can be adjusted at the VFD to something that doesn't make as much noise.

It's also possible that the pump is running dry. This is a big problem with underground pumps because they rely on water flowing through them to cool the motor.

In any case as I understand it, mines are exempt from complying with the national electrical code and have to comply with different standards which I am unfamiliar with.

If you find my response helpful, feel free to send me a sample of the output of your mine. :)
 
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petersonra said:
In any case as I understand it, mines are exempt from complying with the national electrical code and have to comply with different standards which I am unfamiliar with.
Click to expand...
MSHA is the safety governing body, but it’s my understanding also mines don’t have to follow NEC
 
In my classes I had some mine electricians, yes they MSHA uses the NEC. And they are required to do a yearly fall of potential test on ground rods. Do you see MSHA or OSHA on site? Or perhaps you are back in the bush, and could have grounding and bonding issues.
 
petersonra said:
I don't believe any amount of grounding will reduce harmonics.

The noise you may be hearing from the motor is possibly caused by the frequency of the PWM output of the VFD if you are using a VFD. Usually this can be adjusted at the VFD to something that doesn't make as much noise.

It's also possible that the pump is running dry. This is a big problem with underground pumps because they rely on water flowing through them to cool the motor.

In any case as I understand it, mines are exempt from complying with the national electrical code and have to comply with different standards which I am unfamiliar with.

If you find my response helpful, feel free to send me a sample of the output of your mine. :)
Click to expand...
 
Yes they do have problems with water flow in winter, because its not a wet season. They run the motors , and neck back valves in the discharge water at the local well. To keep it from drying up, and freezing There are 50+ wells here.
I believe it quits too much pressure on the motor rotor. They have nonlinear loads like a comm shack, and VFD’s without filters.

Im trying to talk them into buying a thermal imaging camera, so I can look for potential problems coming up this winter.
This place is a mess, and the have lift stations, and leave the door wide open. The VFD’s are filthy, and filters are plugged.
So much cleaning to do.
This is one of my projects id like to tackle before winter hits.

My opinion is they have had super lazy electricians, and now im cleaning up the mess.
I honestly thought Grounding and bonding was for 3 things.

-Life safety
-Equipment protection
-And reduce noise and harmonics.
 
petersonra said:
I don't believe any amount of grounding will reduce harmonics.

The noise you may be hearing from the motor is possibly caused by the frequency of the PWM output of the VFD if you are using a VFD. Usually this can be adjusted at the VFD to something that doesn't make as much noise.

It's also possible that the pump is running dry. This is a big problem with underground pumps because they rely on water flowing through them to cool the motor.

In any case as I understand it, mines are exempt from complying with the national electrical code and have to comply with different standards which I am unfamiliar with.

If you find my response helpful, feel free to send me a sample of the output of your mine. :)
Click to expand...
The problem is management doesn’t know, or capital projects either. Contractors come here, and do what they want. Cash out, and leave.

For any contractor , this is their gold mine.
Free money.
 
tom baker said:
In my classes I had some mine electricians, yes they MSHA uses the NEC. And they are required to do a yearly fall of potential test on ground rods. Do you see MSHA or OSHA on site? Or perhaps you are back in the bush, and could have grounding and bonding issues.
Click to expand...
Most MSHA inspectors come from a different area.
It will slowly get better here, but it’s going to take time and effort on my part.
 
SILVERFOX907 said:
.
I honestly thought Grounding and bonding was for 3 things.

-Life safety
-Equipment protection
-And reduce noise and harmonics.
Click to expand...
If by grounding you mean an actual connection to Earth, it does none of these things.

Bonding is important so that you have a low impedance path so that a ground fault can be cleared by the circuit over current protection device. That is mostly a life safety issue. I suppose it could also be an equipment protection issue because potentially you could get an arc if you don't have an adequate low impedance fault path to allow the overcurrent protection device to clear the fault.

But neither grounding nor bonding will do much for noise or harmonics.

Incidentally if you look in the national electrical code and article 250, I forget exactly where, there is a paragraph that describes exactly why we have a grounding electrode system and a connection to it. To be candid, in my opinion, there's nothing in there that's really worth the effort that people put into their grounding electrode systems. They make a big deal of it but for the most part it doesn't actually do anything I can't imagine what it would do underground that would be useful.
 
I'm a water well pump contractor in Washington State. We are licensed as specialty electricians, restricted to pumps and irrigation systems.

Until the mid 1980's we didn't ground submersible well pumps, they didn't even have a gec wire. Then we started adding them to existing pumps and new installations.

A submersible pump motor, whether it's a Franklin, Hitachi, or other brand has a Kingsbury thrust bearing in the bottom of the motor. It takes the entire thrust of the pump and weight of the water in the column pipe. It is a frictionless flat carbide bearing that has a film of water between the two plates. It needs to run a minimum of 30 hz to develop this water film.

A pump motor actually uses less amps as the discharge is throttled back. There can be as much as a 50 % reduction in amps at deadhead. Increased flow takes more amps than incresed pressure. However a submersible motor is cooled by the water flowing past it. It has minimum flow requiement to keep the motor cooled. This means that the water has to come from below the pump setting, not above it. If the sub pump is top fed, the motor recelves no cooling flow. If you don't have one, get a copy of the Franklin AIM manual. If can be downloaded free on Franklin's website.

Yes harmonics can be a big problem with submersible motors. Are these pumps being run on VFD's? On 460 volt motors, they need an output filter if there is more than 50 feet between the vfd and the motor. More than a few hundred feet I change to a dv/dt filter. Over 1,000 feet is going toneed a pure sine wave filter. I use either TCI or MTE brand filters. None of the submersible motor manufacturers will warranty a 460 volt motor on a VFD, without the proper filter.
 
Another option if you are running the pumps on VFD's. A pressure transducer can be installed down hole with the pump in the well. The VFD can then be programmed to maintain a set pumping water level, and will automatically reduce the speed of the pump to maintain the desired dewatering level. The pump will run at full speed intil the water level drops to the desired depth then automatically maintain that water depth.

Some drives can also be programmed to sense the drop in amps when the water level reaches the pump intake. It then shuts the pump down for a predetermined amount of time to allow the water level to recover. There are also controls that we can add to a non vfd system to sense the drop in amps. I install these on low producing wells.
 
Hv&Lv said:
I don’t think that’s the NEC. It’s a CFR code. Probably based on the same thing, but not the same (I don’t believe)
Click to expand...
That's correct it is 30 CFR Part 56, the electrical portions are largely based off the 1968 NEC with additions for mine specific conditions. Part 56 covers surface metal/nonmetal mines. Part 57 applies to underground metal/nonmetal mines.
 
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