separate static ground for military communications trailer

[shade23]

I have been asked to drive a ground rod for static grounding of a military communications trailer. The trailer can be used in the field with a generator or it can be supplied by a facility electrical system.
The trailer now is plugged into a facility power system. Everything is new and properly grounded at the facility and the power cord is a factory cord designed for the trailer.
On the exterior of the trailer next to the power inlet is a frame and trailer body ground connection.
The cable from the trailer body ground is routed to the ground at the disconnect which the trailer is connected to. The ARMY wants a separate ground rod installed for the trailer body and frame. They do not want the facility ground and trailer body ground at the same termination.
I say that they will not get a better ground than the facility ground and I say the grounds need to be bonded at the disconnect. The trailer disconnect is only used for the trailer and nothing else. It is 100 amp 120/208 3 phase.
The ARMY can do whatever they want but I would appreciate any input.
Thank You

 

[cuba_pete]

Tell them that they need to review MIL-HDBK-411B:

"Grounding of power distribution equipment must strictly follow MIL-STD-188-124 and NEC Section 250 criteria. Proper grounding is essential for personnel and equipment safety, as well as control of static electricity, and noise."

Similar, if not identical intent, is identified in MIL-HDBK-419A, and MIL-STD-188-124B. The manuals and standards reference each other for specific sections.

...and stop telling people to do work that is unsafe.:rant:

There are a lot of misconceptions about electrical and electronic theory in the government and military...we're not all dunces, however.

BTW: If you provide an NSN/NIIN or nomenclature for the MILVAN, i.e., AN/TSC-xxx I may be able to find an implementation guide for the equipment. I highly doubt it was spec'd for the method that they want

Detailed information should have been provided in the contract, but if you are a sub then you may not have even seen the contract and the contracting officer's representative (COR) may be directing you to do it. Often times, the COR is not technically...shall I say...competent when it comes to implementation.

More often than not, the COR never even makes an appearance and the role is delegated to someone who may know even less.
.

 

[winnie]

All grounds must be bonded together and all grounds must be bonded back to the electrical system neutral at the disconnect.

With that said, there is no prohibition to having _additional_ ground rods that are only indirectly bonded, say through separate connections to the chassis.

Ground rods that are not bonded together introduce all sorts of issues, including conducting ground currents up through one rod, through equipment, and back down through another rod. So they _must_ be bonded together somehow.

Grounding for communications equipment may be required to function at communications frequencies as well as at power frequencies. This opens up transmission line and antenna effects, and a _fantastic_ ground at power frequencies might be horrible for radio frequencies.

-Jon