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Post  topgroove on Thu Apr 26, 2012 6:29 pm

had this call Monday night, just as the heavy wet snow intensified. It was on a 4.8kv delta feeder up in some hills. I get to the address and see two blown fuses feeding the single phase tap off the three phase.

Over a foot of snow in the customers narrow driveway that curved up hill. It went five sections back to a single 25kva csp. I figured I better walk back and take a look. the top of a pine tree had broke off and had both phases pinned down. got my stick saw and after a little work, freed up both phases. Looked everything over and everything was clear.

Got back to the road and refused the cut-outs with 25k's and threw it in, picking up load on both doors. walked back up the driveway and tested voltage at the meter channel. Uh Oh! 57 volts 57 volts 118 phase to phase? Could see lights on inside the house but they were dim. Had the customer open-up the mains, till I could figure this out. The transformer was really old but to have balanced voltage like that I figured we had a dead phase on the primary.

Sure enough Phase 3 on the main three phase was dead. This was the only customer that called on the entire feeder. With Delta feeders, every three phase bank and single transformer will backfeed the dead phase. Most customers will never notice a problem, except those toward the end of the feeder.

Now I had to find the open. I got the feeder maps out and started patrolling back to the substation in a blinding snowstorm. Found nothing, but every once in awhile took primary voltage readings. Phase three was showing open. Got to a point where the road became a seasonal access road and even my truck would get stuck in the snow . Last thing I wanted to do was get stuck.

I drove a 7 mile detour and got to the substation from the other direction. One section outside the station at the three phase disconects, Phase two switch was arcing bad and the door to phase three was gone, completely missing???

waited for help and replaced all three switches in the snowstorm. Than I called the original customer and had him close his mains. All was well.

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Join date : 2012-01-29

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