Electric Grade Mineral Oil

FaradayFF

Senior Member
Location
California
Hi Guys,

I've got an oil filled distribution transformer located indoors that utilizes electrical grade mineral oil. The transformer will be placed on a concrete pad. I'm looking at NEC 450.23, it requires an automatic fire extinguishing system and a liquid confinement area. Is mineral oil considered a "less-flammable liquid that has a fire point of not less than 300C"?.
It seems an overkill to provide a vault for a 25kvA xfmr installed in an enclosure.

Any ideas?

Thanks,
EE
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
Conventional mineral oil Won’t work.
the fire point is around 175c

Cooper has a bio temp oil that’s over 300c, there are others also.

somewhere I’ve got a downloaded paper on it. I’ll look in my computer...

another edit...
I didn’t think a transformer with standard mineral oil could go inside, regardless of fire suppression and containment...
 
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FaradayFF

Senior Member
Location
California
Well, it's not a typical residential building that needs to comply with IBC. It's an utility owned enclosure that houses electrical equipment and is supervised by trained personnel..

Regards,
EE
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
Well, it's not a typical residential building that needs to comply with IBC. It's an utility owned enclosure that houses electrical equipment and is supervised by trained personnel..

Regards,
EE
Doesn’t that still fall under the NEC?
is it an “integral part of” the substation or generation plant?
 

FaradayFF

Senior Member
Location
California
Hi Hv&Lv,

It's located on premises of a maintenance& support facility. The facility, though, is owned by the generating utility.
That begs the question if they have to adhere to NEC, or they may have their own quality plans that they follow.

Regards,
EE
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
Hi Hv&Lv,

It's located on premises of a maintenance& support facility. The facility, though, is owned by the generating utility.
That begs the question if they have to adhere to NEC, or they may have their own quality plans that they follow.

Regards,
EE
I work for a utility, Even our control house in a substation is under the NEC...
who owns it isn’t the question here, it’s what it is used for
I would take a look at 90.2(A)(4)
 
I've got an oil filled distribution transformer located indoors that utilizes electrical grade mineral oil.
...
It seems an overkill to provide a vault for a 25kvA xfmr installed in an enclosure.
This is a new installation? For something that small, can you use a dry transformer? (Granted that there may be technical reasons for oil, I just don't know what applies here.)
 

kwired

Electron manager
Location
NE Nebraska
I work for a utility, Even our control house in a substation is under the NEC...
who owns it isn’t the question here, it’s what it is used for
I would take a look at 90.2(A)(4)
Control house general wiring yes.

The control circuits themselves should be exempt from NEC per 90.2(A)(4).
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
Control house general wiring yes.

The control circuits themselves should be exempt from NEC per 90.2(A)(4).
Yes, I know. Thanks...
the OPs question is regarding a 25kVA oil filled transformer in an enclosure,
I agree with another post. Dry pack would be the way to go.
 

kwired

Electron manager
Location
NE Nebraska
Yes, I know. Thanks...
the OPs question is regarding a 25kVA oil filled transformer in an enclosure,
I agree with another post. Dry pack would be the way to go.
So it comes down to is it the "service transformer" and is under control of the utility or is it a "separately derived system beyond the service point"? First one is outside scope of NEC second one is not.
 

FaradayFF

Senior Member
Location
California
I think it would be considered a service transformer, as it is served by overhead line on the primary. The whole installation is located on Utility's premises and is owned by the Utility. It sounds this being the case, the NEC doesn't apply to the transformer and Utility standards would govern.

Thanks all.
EE
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
I disagree with your reasoning, but whatever...

we own our office. It is served by our transformer coming off our primary served by our secondary to our breaker and outlets.., all on our premises...

we still had to have inspections because it isn’t an integral part of a generation facility.
the same for our control houses in the substation.
mall the wiring that is integral to our generation or distribution is not covered. Breaker panels, switches, lights, etc that are part of the “convenience package” , are covered by NEC...
 
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