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Thursday, 10 September 2009 00:00

OPEN LEG STILL HOT

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Author - rich ouellet

Submitted By -  it was during a heat storm, we go to a call for  a bad can.

 single phase primary, 50 kva transformer with a cutout. The triplex has one leg burned off where it connects to the trans lead.

 we see that the burned off leg is being energized by the connected one. Thinking its gotta be a bad spot somewhere in the span of triplex.
 
  making sure theres no backfeed or other can phased in.
 we could see that the entire span had got really hot,melted in some spots.
Both legs are showing  nothing to each other, 120v to neut and both are showing 240v to the bushing that has burned itself free.We decide to try to isolate where the bad spot is on the triplex.
no matter where we opened up the triplex the unconnected lead stayed hot. now were really scratching our heads.

then I remembered that like 20 years ago I encountered the same thing ,the old timer there said "watch this kid" after killing the can he reconnected the triplex to where it used to be,

keep in mind that the open leg had been showing opposite polarity .

As he closed the cutout we all expected to see sparks
but low and behold held and the legs were back to normal
I hope I explained this ok.

Dose anybody know why 1 minute they were opposite then when reconnected they were back normal?
This has been bugging me ever since.

take care guys   rich
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