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 Post subject: Temp Protective Grounding
PostPosted: Mon Feb 21, 2011 1:48 pm 
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Location: Lawrenceburg KY
I remember GE Servicing our Switchgear (cleaning and checking) in the past and using protective grounding cables several years ago.

My memory is failing and I need some confirmation on the use of grounding cables for a 15KV to 480V Switchgear system.

1. We opened and locked out the poles HV switches, simple single fed system.
2. We tested to verify the 15KV system was de-energized.
3. This is the part I am vague on. I remember they GE guy attaching the cable to ground and dangling the cable near the HV Pri lead and watching it arc.
4. He did this to all three phases to remove any static charge in the line.
5. Now, would he have removed the leads from the transformer and grounded the cables? Or would he have not dis-connected the leads and grounded the transformer leads with the HV cable attached?
6. Is it proper protocol to ground the secondary also?

I cannot find a best practice for installing temp protective grounding while servicing a simple single service switchgear. Any info or reference document would be great.
Thanks


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PostPosted: Tue Feb 22, 2011 6:48 am 
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Location: Spartanburg, South Carolina
Quote:
5. Now, would he have removed the leads from the transformer and grounded the cables? Or would he have not dis-connected the leads and grounded the transformer leads with the HV cable attached?
6. Is it proper protocol to ground the secondary also?

Temporary grounds are required when it is possible that a voltage could reappear at the point of work. If there are cables connected that can have voltage induced on them or if they could be connected to another source, then they should be grounded before working on them. This needs to be established by company safety procedures. Often procedures call for grounding all MV and HV equipment while working on it.

It is probable that once the single feed cable capacitance was discharged, no voltage could appear. If you have the temporary ground set there, I would recommend connecting it to the primary while the work is being performed, even if the cable is in a location where no voltage can be induced on it.


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