Personal safety grounds

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101010

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What is your procedure for personnel safety ground while working on a transformer after you test to make sure transformer is denergized ? 480 v to 208 v trans. Does connecting the proper size ground wire connected to the grounding system and a across the 3 phases suffice. I know you connect to the ground first then to the phases and disconnect in the opposite order. any other suggestions?
 
101010 said:
What is your procedure for personnel safety ground while working on a transformer after you test to make sure transformer is denergized ? 480 v to 208 v trans. Does connecting the proper size ground wire connected to the grounding system and a across the 3 phases suffice. I know you connect to the ground first then to the phases and disconnect in the opposite order. any other suggestions?
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I would verify voltage reading on line side of transformer, then proceed with connection. I have used a special 4/0 grounding conductor to connect all 3 phases to each other then to ground upstream from where I am working...
 
I am dead set against making a short circuit in 600 volts and below.

I lock out tag out and go to work.

OSHA is fine with that.
 
101010 said:
What is your procedure for personnel safety ground while working on a transformer after you test to make sure transformer is denergized ? 480 v to 208 v trans. Does connecting the proper size ground wire connected to the grounding system and a across the 3 phases suffice. I know you connect to the ground first then to the phases and disconnect in the opposite order. any other suggestions?
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"Proper size" means your groud set it tested and rated for the avialble fault current at the connection point. ASTM F 855
 
zog said:
"Proper size" means your groud set it tested and rated for the avialble fault current at the connection point. ASTM F 855
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Back when I started, it was common to see things like jumper cables and log chains used for this purpose in 480 switchgear. I understand why that is not correct, but it was a common practice, at least around here.
 
iwire said:
What is mandatory?

LOTO is, grounding out is not. At least at the voltage levels I work with.
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Not OSHA required, but may be mandatory under an entities documented safe work procedure. It is an additional safety measure to mitigate residual charges, such as a system with capacitors or other load equipment with the potential to backfeed the system (wind-milling fan motors?).
 
Smart $ said:
Not OSHA required, but may be mandatory under an entities documented safe work procedure.
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Of course, but I was responding to a post about OSHA.

It is an additional safety measure to mitigate residual charges, such as a system with capacitors or other load equipment with the potential to backfeed the system (wind-milling fan motors?).
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I think it is ridiculous under 600 volts and is more likely to lead to a injury if someone leaves it in place.
 
iwire said:
Of course, but I was responding to a post about OSHA.
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I know. Just seemed like best place to post what I had to say at the time. Sorry if I inconvenienced you. ;)

I think it is ridiculous under 600 volts and is more likely to lead to a injury if someone leaves it in place.
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While I agree with the underlying reason, each situation should be analyzed independent of others, prior to performing work, with precautionary measures acted on accordingly. While I don't care to admit it, I've been shocked by a 144VDC system that made me me stop and re-evaluate.
 
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