Grounding vehicle at far end of extension cord

[Goofy256]

Hello,
I am providing advice to a manufacturer of a vehicle carrying explosive items, along with related electrical equipment. Normally, the equipment is powered by the engine alternator, but a 120 volt connection to a portable generator is possible for longer-term use. I have advised the manufacturer that installing a ground rod at the vehicle is a violation of the NEC, because cord-and-plug connected equipment may only be grounded through the grounding conductor in the extension cord. Improper grounding could affect the ability of the circuit breaker to trip when certain types of faults occur. One of several reasons for grounding, according to the NEC, is to facilitate the operation of a circuit protective devices under ground-fault conditions. However, a static discharge ground wire may be attached to the vehicle, because this is common practice in explosives safety. The instructions to the people operating the equipment are unclear at this time, they simply warn to "properly ground the equipment". What is the proper method of grounding a vehicle at the far end of an exension cord, and what is prohibited?
Thank you.

 

[petersonra]

Re: Grounding vehicle at far end of extension cord

Think about it this way.

In general, the EGC is required to be run with the power wires. Since the power is fed through the cord, therefore the EGC also needs to come the same way.

This does not mean that you cannot also have a supplemental ground rod attached to the vehicle frame for the purposes of static reduction or a path for lightning to take to earth, or that you are prohibited from running a bonding conductor from your vehicle ground rod back to the service ground point.

[ October 19, 2004, 04:38 PM: Message edited by: petersonra ]

 

[dereckbc]

Re: Grounding vehicle at far end of extension cord

Goofy, It is not a violation to add a ground rod at the point of use, this would be the staic ground you are refering too. It does not impede the operation of a circuit breaker. If the generator is portable, I assume it is not grounded, adding a ground rod (static ground as you called it) would give some static and lightning protection. As far as a fault clearing path for the source of power (generator), the EGC provides that path, earth ground has nothing to do with it.

Edited for clarity.

[ October 19, 2004, 04:58 PM: Message edited by: dereckbc ]