2-wire System Grounding

[supernibs2000]

My company has a system that taps directly off of the power pole and is contained in a metal box on the pole. The tap is less than 5 feet and in most cases only Line and Neutral are brought into the box. The L-N connection goes through a surge suppressor/filter and then attaches to a transformer which steps down the voltage 10X. This reduced voltage is rectified and converted into 12 V for the system. Other configurations of this module uses a solar panel instead of an AC line tap (still on a pole).

My question is in regards to safety and grounding... Is there an applicable NEC section that deals with this type of system? There wouldn't be multiple ground loops and in most cases, there isn't a ground wire run into the box. Would this box be agnostic to ground fault currents? Should there be an Earth ground attached to the box (in either configuration)?

My gut tells me that there should be a good ground on any metal box hanging out on a telephone pole and that the system (as a 2-wire system with galvanic isolation) is inherently agnostic to L-G or N-G disturbances, but I could be wrong there. Looking for some direction from folks with more experience than me

Thank you for your time!

 

[kwired]

My company has a system that taps directly off of the power pole and is contained in a metal box on the pole. The tap is less than 5 feet and in most cases only Line and Neutral are brought into the box. The L-N connection goes through a surge suppressor/filter and then attaches to a transformer which steps down the voltage 10X. This reduced voltage is rectified and converted into 12 V for the system. Other configurations of this module uses a solar panel instead of an AC line tap (still on a pole).

My question is in regards to safety and grounding... Is there an applicable NEC section that deals with this type of system? There wouldn't be multiple ground loops and in most cases, there isn't a ground wire run into the box. Would this box be agnostic to ground fault currents? Should there be an Earth ground attached to the box (in either configuration)?

My gut tells me that there should be a good ground on any metal box hanging out on a telephone pole and that the system (as a 2-wire system with galvanic isolation) is inherently agnostic to L-G or N-G disturbances, but I could be wrong there. Looking for some direction from folks with more experience than me

Thank you for your time!

Still not sure of exactly what you are describing, but if it is in a metal housing you at least want a bond from either equipment grounding conductor or grounded service conductor to exposed non current carrying metal components. This may be accomplished simply by using metal raceway.

Can you paint us a better picture of what you have, is the "power pole" you mention a utility company pole or something else?

 

[JoeStillman]

Welcome to the forum.

If you're connected to a neutral, you're not Ground Agnostic. The surge suppressor needs a low-impedance connection to ground in order to protect your hardware from common-mode overvoltage due to lightning strikes.

NEC articles 200 (grounded conductors, i.e. neutrals) and 250 (grounding and bonding) are the Gospel that will overcome your agnosticism.

 

[al hildenbrand]

Indeed, Welcome to the Forum.

I agree with Joe that what you are describing is already referenced to Earth by the current carrying neutral, almost certainly.

You seem to be describing an assembly that is related to either communication utility or electric utility. Article 90.2 of the National Electrical Code excludes most of these assemblies from its Scope.

Regardless of statute, understanding the electrical circuit of your assembly and the supply it is connected to will be important.

For starters, on the utility side of a Premises Wiring (System) {SEE Article 100 Definition of this three word term} the equipment grounding conductor that is tied to exposed conductive surfaces, and the insulated neutral (the grounded conductor) are bonded together by the Main Bonding Jumper in the Service Disconnect into a single conductor, most commonly called the Grounded Service Conductor. At the supply source, usually an electric utility transformer, the Grounded Service Conductor is bonded, by the utility, to the exposed metal body of the transformer, and that body is, in turn, bonded to a connection to Earth at the base to the utility pole, AND, is bonded to the primary transformer supply conductor's grounded conductor.

It's a convoluted interconnection.