Entering wet MV transformer vault

[electrofelon]

What is the standard protocol for entering an MV transformer vault that has just been pumped out? Does this situation differ from a dry or above ground MV vault?

 

[ramsy]

Confirmed shutdown for me.
Completly de-energed before entry, or Megger testing.
Never heard of moon suite shoes rated for medium voltage with wet floors.

 

[electrofelon]

Confirmed shutdown for me.
Completly de-energed before entry, or Megger testing.
Never heard of moon suite shoes rated for medium voltage with wet floors.

Thanks. Also just to clarify these are submersible transformers, does that change anything?

 

[Hv&Lv]

We had those a few years back. We got rid of them and pulled all them above ground.
I realize it can’t be done everywhere, but pumping vaults down for entry was de-energized and grounded operation for me.
after all, once it’s pumped down and you get in there, what are you going to do??
the submersible transformers are nothing more that UG elbows on the top bushings. The common elbows about everyone uses for UG installations are rated for 6’ deep.

 

[electrofelon]

We had those a few years back. We got rid of them and pulled all them above ground.
I realize it can’t be done everywhere, but pumping vaults down for entry was de-energized and grounded operation for me.
after all, once it’s pumped down and you get in there, what are you going to do??
the submersible transformers are nothing more that UG elbows on the top bushings. The common elbows about everyone uses for UG installations are rated for 6’ deep.

Right I guess it depends what is going on. Like you say, presumably one is going in the vault to fix something where it will need to be de-energized anyway, so why not just kill it in the beginning....

So another question I have always been unclear on: What about touching/working near concentric neutral MV cables not in a raceway, in general? IS that considered safe and acceptable?

 

[Hv&Lv]

I have no problem doing that. I’m a little more wary of CN cable vs jacketed cable simply because there’s a jacket that will take some abuse such as dropping a tool on it.
when my guys (or me, just not so much anymore....)work around concentric cable that’s hot, we are aware that it’s hot and only move it or touch it with PPE. the risk of a blowout at the spot we are working is rare, but still...

I have cut it hot (7.2kV years ago) and put hot cable on grounding bushings. It’s not loud at all. Just spits to ground. If it’s on a fuse you hear the fuse blow from across the neighborhood.