wtdoor67
06-16-2010, 11:11 AM
I put this up a long time ago but I thought some might enjoy it again if they remember.
It was a Muni, so Swimpus might be comfortable here.
The system was 7200/12470. I ran an overhead crew. The asst. supt. contacted me via phone. He said that the service crew supervisor had reported a location with a "weak transformer". He asked if I had ever encountered such. I said no, I hadn't.
He explained the location was a water well of the city's, and it was currently served by a 2 pot open bank with 480 volt secondary. The source consisted of 2 phases of the circuit. Some call it open Wye. The asst. said, well I'll just have your crew go out, add the third phase and hang another pot to close the delta etc.
The following day we drug in a third phase. Upon arriving at the bank I could tell by eye ball it was far too large a load for a 2 pot bank. We had killed out the whole mess, so we just pulled up the wire, sagged and dead ended it and hung a new 3 pot bank. Seems like it was 3 fifty KVA's, and heated it all up. The voltage was still screwy. I went nearby and bumped a single phase pot over to the other phases and got an extremely low reading on one phase.
At this point I called and told my supervisor that there was something wrong between this location and the sub. The aforementioned service supervisor overheard the conversation and of course being unsure, immediately had his hands start patroling that section of the feeder. Soon someone found a broken jumper that went to a gang switch, that was in the feeder.
My crew went to the location and reattached the jumper. I think it was 477 ACSR. This put the voltage at the new waterwell bank to normal.
The puzzler for me was this feeder with the broken jumper fed a large portion of downtown. Not a large city, about 45000 at the time. However some of the customers were 3 phase and one in particular was the newspaper which had several computers and sensitive equipment. As far as I knew they had never complained.
We figured it out. Any guesses? No Swamp, I'm not laying out ever detail so any apprentice could guess. It really wasn't complicated, but it was aggravating.
It was a Muni, so Swimpus might be comfortable here.
The system was 7200/12470. I ran an overhead crew. The asst. supt. contacted me via phone. He said that the service crew supervisor had reported a location with a "weak transformer". He asked if I had ever encountered such. I said no, I hadn't.
He explained the location was a water well of the city's, and it was currently served by a 2 pot open bank with 480 volt secondary. The source consisted of 2 phases of the circuit. Some call it open Wye. The asst. said, well I'll just have your crew go out, add the third phase and hang another pot to close the delta etc.
The following day we drug in a third phase. Upon arriving at the bank I could tell by eye ball it was far too large a load for a 2 pot bank. We had killed out the whole mess, so we just pulled up the wire, sagged and dead ended it and hung a new 3 pot bank. Seems like it was 3 fifty KVA's, and heated it all up. The voltage was still screwy. I went nearby and bumped a single phase pot over to the other phases and got an extremely low reading on one phase.
At this point I called and told my supervisor that there was something wrong between this location and the sub. The aforementioned service supervisor overheard the conversation and of course being unsure, immediately had his hands start patroling that section of the feeder. Soon someone found a broken jumper that went to a gang switch, that was in the feeder.
My crew went to the location and reattached the jumper. I think it was 477 ACSR. This put the voltage at the new waterwell bank to normal.
The puzzler for me was this feeder with the broken jumper fed a large portion of downtown. Not a large city, about 45000 at the time. However some of the customers were 3 phase and one in particular was the newspaper which had several computers and sensitive equipment. As far as I knew they had never complained.
We figured it out. Any guesses? No Swamp, I'm not laying out ever detail so any apprentice could guess. It really wasn't complicated, but it was aggravating.