Switch Grounding Mats

Brian H.

New Member
Dec 30, 2016
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#1
I have a manually operated 345 KV, 3-phase, ganged disconnect switch that isolates the Main Transformer from the Switchyard. At one point the operator would stand on a ground mat (metal grate with a bonding jumper that runs to the switch handle) while opening or closing the switch. Somewhere along the way the mat was removed and now needs replaced.

Is there an OSHA 1910.269, NESC, or IEEE standard requiring the mat?
Is there an IEEE, NESC standard that dictates the size of the mat, size of the bonding jumper and attachment hardware?

Thanks,
Brian
 
#2
Re: Gang Operated Switch Ground Mat

Dear Brian,

Firstly, we apologize for the delayed response – this one slipped below the radar.

OSHA 1910.269 requires that employees must not handle equipment which could become exposed to dangerous voltages unless they are in an equipotential zone or protected by insulating equipment. We recommend using both the equipotential mat and insulating equipment (in the form of gloves and EH Shoes). Consider a DI rated over boot (rated 20kV) and class 4 gloves.

For the equipotential mat, you would want to make sure that the operator has enough room to maneuver without stepping out (thus entering a step potential zone). Remember the workers heart will say run but the brain needs to say “stay!” – think carefully about the size of the mat in the context of a fault condition. OSHA requires that you use bonding cables to connect the equipotential mat to the ground mat or ground grid. I would standardize and use the same bonding cable that was used throughout the yard. OSHA requires that all connections be tightened and free from corrosion – so don’t forget to ensure your PMs are in place after the installation is completed. Have a look at 1910.269 Appendix C Paragraph III.C. 1 and III.D.2.i.

If you have gone ahead and installed the mat already, we would love to see a few pictures.
 

Hugh Hoagland

Moderator
Staff member
Dec 30, 2016
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Louisville, KY
www.arcwear.com
#3
Re: Gang Operated Switch Ground Mat

The standards unfortunately are very vague in this account.

OSHA 1910.269 requires protection from shock and arc flash but doesn't force specifics for shock.

Isolation is the real protection in your example but because of potential failures many companies require mats, gloves and shoes. If a worker is not shocked, there is no specific requirement. Our recommendations are based on experience in many companies of touch and step potential. These are best practices Zarheer listed above and they have been shown to save lives in some of the possible failures in overhead switching.
 

Sepulveda

New Member
May 25, 2018
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#4
So not much has changed over the years? Do you think there will be some stricter regulation regarding this in the future, Hugh?