Fences around MV Deadfront Switchgear

[haze10]

250.194 ... a substation with exposed electrical conductors and equipment.

I'm really confused with regards to whether or not it is necessary to ground the metalic fence around deadfront switchgear. In an industrial setting (not utility) where you have an outdoor substation, say with medium voltage padmount transformers and metal clad switchgear, and you put a fence around the equipment to limit access - do you have to ground the fence?

250.194 uses the condition of 'exposed conductors', but with deadfront pad mounts and metal clad switchgear there is NO exposed conductors. This Article appears to me to reference substations which are more utility in nature where you have crib poles with exposed wiring and transformers with top mount exposed bushings.

In some forums there is reference to 'stray and touch voltages' and that ground of fences around deadfront equipment is required. Yet NEC is always using the word 'exposed'.

So not sure if it is or is not required to ground the fence.

Also 110.31 refers to fences and then to Table 110.31, but the title is ...minimum distance to live parts... But deadfront doesn't have live parts. So I'm thinking that for deadfront you would be following the min working clearances as in Table 110.34A with the metal fence being Condition 2 as its conductive with the earth, just like a concrete wall.

Does anyone fully understand this.

 

[JezNZ]

I do not know your code requirements.

However if the fence is within the earth grid zone, then typically speaking it should be bonded.

If the fence is outside the earth grid zone, then by bonding it to somewhere else you risk the transfer of earth potential rise and creating a dangerous conditions in a fault scenario. This case needs to be more closely looked at.

I'm aware of some instantances, where to simplify the scenario the fence is installed insulated from earth, for example through the use of wooden or plastic fence posts.

 

[Palletjack]

How many MV dead front pad mount transformers do you see in neighborhoods and front yards?
How many have fences? I don’t recall ever grounding one yet.