Live front or dead front transformer

[steve66]

Specified a medium voltage transformer (13.2KV to 480) and the vendor asked if it should be a live front or a dead front.

I didn't know that was an option on xformers.

Every transformer I've seen has locked doors on the front that prevent access to the high and low voltage connections. Open one door, and the low voltage connections are accessible. Open another door and the High voltage connections are accessible. Does that make it a dead front, or a live front??

 

[barclayd]

Live front means the medium voltage terminations are bolted, with stress cones. When you open the door, the medium voltage is present at the termination point. Dead front means the terminations utilize molded, load-break elbows, which enclose the actual termination point.
db

 

[kingpb]

Live front is in simple terms, the cables terminate in the open air onto the porcelain bushing attached to the transformer wall.

For deadfront the cable are connected to bushing wells, that are loadbreak inserts for connection.

FYI the HV side (13.2kV) is the only part this terminology applies too.
The LV (480V) is typically spade connected.

 

[steve66]

That makes sense.

This must be a deadfront, with loadbreak elbows, correct?

http://i568.photobucket.com/albums/ss124/myphotobucket2221/P1010279.jpg

Are there any advantages to a live front? It seems like a dead front would be the way to go.

Steve

 

[tkb]

I can't tell if this one is live front or dead front.

 

[rcwilson]

Are there any advantages to a live front? It seems like a dead front would be the way to go.

Steve

Load Break elbows have limited ampacity - 200 Amps with some newer products for 600 A. The 200 A is about 5 MVA at 13.8 kV or 1400 kVA at 4.16 kV. Multiple cables per phase requires some special jumper devices to parallel the cables. Checkout the Cooper on line catalog for examples. There are other suppliers also.

Load break, dead front systems appear to be safer but I worry that in an industrial situation an inexperienced person who would shy away from open high voltage terminations, might try to unplug or touch an elbow without the proper equipment. I know this happened at a nearby college campus.

Some engineers believe the elbows are not as reliable long term as a stress cone and bolted connections. My instinct is to agree with them, but my experience indicates the elbows serve quite well for distribution to smaller transformers.

 

[iMuse97]

I can't tell if this one is live front or dead front.

IMHO, that one's dead. Otherwise they wouldn't have called you. Or is this the type of PM jobs you get on a regular basis?

 

[templdl]

It Looks as if it was a victim of the Phoenix, Az dust storm.

 

[steve66]

Load Break elbows have limited ampacity - 200 Amps with some newer products for 600 A. The 200 A is about 5 MVA at 13.8 kV or 1400 kVA at 4.16 kV. Multiple cables per phase requires some special jumper devices to parallel the cables. Checkout the Cooper on line catalog for examples. There are other suppliers also.

Load break, dead front systems appear to be safer but I worry that in an industrial situation an inexperienced person who would shy away from open high voltage terminations, might try to unplug or touch an elbow without the proper equipment. I know this happened at a nearby college campus.

Some engineers believe the elbows are not as reliable long term as a stress cone and bolted connections. My instinct is to agree with them, but my experience indicates the elbows serve quite well for distribution to smaller transformers.

Thanks.

Aren't there also non-load break elbows??

 

[rcwilson]

There are dead-break elbows and connectors with higher current ratings.