Ground Check vs. Ground Fault

[dconnors]

Reading up on grounding of mobile equipment. I am curious the take on NEC 250.188 D (see below)? The way I read this is ground fault is required, which is a given. I do not read this to imply ground check is required. But the continuity statement has me curious.

What does the thread community think?


250.188 Grounding of Systems Supplying Portable or Mobile Equipment

(D) Ground-Fault Detection and Relaying

Ground-fault detection and relaying shall be provided to automatically de-energize any component of a system over 1000 volts that has developed a ground fault. The continuity of the equipment grounding conductor shall be continuously monitored so as to automatically de-energize the circuit of the system over 1000 volts to the portable or mobile equipment upon loss of continuity of the equipment grounding conductor.

 

[EC Dan]

It seems to be requiring de-energization if either of two things happens: 1) an ungrounded conductor comes in contact with a grounded conductor ie. ground fault, and 2) the grounding path has been interrupted. So I would say a ground check is required.

 

[paulengr]

The only way to test ground conductor continuity is with a circuit running current through the grounding conductor. You need an extra wire to complete the circuit. That’s what the ground check wire is for.

 

[dconnors]

I agree with both assessments, it is appreciated. Now my next query.

I've got an existing 5kV system in which a new mobile piece of equipment is to be installed. I've always implemented a neutral grounding resister (NGR) and ground check as part of the system feeding the mobile equipment. However, this system is existing and the step down transformer is owned by the utility.
A electrical vendor has informed me a dedicated transformer with NGR is required for ground check, which is not conducive at this site. As such:
1. Is the transformer/NGR requirement correct for ground check?
2. Are there any other ground check options that do not require a dedicated transformer/NGR?

Again, thanks for the input!

 

[tom baker]

Is this a mine application? Mines are not under the scope of the NEC, but our members here always surprise me with their knowledge.