Applying distribution protective grounding methods to MV industrial equipment

[jtinge]

All of the guidance that I am aware of for personal protective grounding of medium voltage circuits and equipment for maintenance is specific to substations and transmission and distribution circuits. Is anyone aware of similar guidance for medium voltage circuits and equipment in industrial facilities? Industrial facilities have similar substation and distribution circuits for which the previously referenced personal protective grounding requirements are applicable and can easily be applied. However, MV metal-clad switchgear, motor starters and motors in industrial plants often have insulated terminals and bus for which protective grounds cannot be applied. Many new MV switchgear designs include the means to install personal protective grounds during maintenance of the MV circuit parts. However, existing installed MV switchgears and motor starters do not have these provisions. Is there any guidance or best practices available for establishing an electrically safe work condition for MV switchgears, motor starters and motors when personal protective grounds cannot be applied?

 

[zog]

NFPA 70E is your guidance, I would take the time to do an outage and install ground balls in your gear so this is never an issue again.

 

[jtinge]

We've thought about adding grounding balls to the switchgear bus and that addresses the safety concern when we have to take down and work on a whole switchgear. But more routinely we only have to rack out an individual breaker to isolate a MV motor and there is no where to place grounds on the MV motor cables or cable terminations and on older gear, no where to add grounding balls. I'm sure we are not the only ones who have this situation.

 

[zog]

Use a ground and test device, what type of breakers are your MV feeders?

 

[jtinge]

Use a ground and test device, what type of breakers are your MV feeders?

It varies as a lot of our switchgears in facilities date back to 1960's. But GE, Westinghouse, Siemens Allis, ITE, ABB, Allis Chalmers, Cutler Hammer, and Square-D are the main ones off the top of my head. I appreciate your insight and have initiated further discussions with our HV maintenance group to investigate the addition of grounding balls where feasible and grounding test carts if available.