Single phasin'

[rcdallas]

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[T-Man]

On a 120/208 4 wire grounded wye three phase the elevator and A/C is out, maybe no heat. But we would disconnect and isolate so the repairs could be made on the secondary. If the primary had a phase out we might open three phase breakers till we could find the primary problem, Maybe a jumper open or line fuse blown. If it was underground bad then we'd have to take that out ground and tag it so a crew could get in and fix it. It really depends what ya have to decide what yer gonna do. If you can keep the lights on their refrigerator working, keep em happy till the heavy crew shows up then blame them for the outage. . . .LOL:eek:

[Lineman North Florida]

If it's not gonna be an extremely long outage I'm opening them up and not dealing with backfeed most of the time, if it's something like a power pot out on a 2 pot bank, I will lift the tie leg and they can keep single phase till I get another power pot to change it out, on underground I'm opening them up as on our system all 3 phases are gonna be in 1 conduit and until I'm sure what all kind of damage I have it's coming open.

[topgroove]

I Totally agree with T-man ! If the customer is willing to open all there three phase breakers I wouldn't have a problem giving them 120/208. Of cource if the dead leg is also one of the double pole hotlegs you'ld have to isolate the dead leg and jumper from the dead leg to the remaining hotleg. ( I hope that make sence). I would not let their three phase equipment single phase. It will cause damage to the equipment if left that way for awhile.

[wtdoor67]

I would discuss it with my supervisor and make sure everybody in the area does about the same thing.

It's always been my understanding that most regulations etc. require the customer to provide their own protection for single phase conditions. Power co's etc. cannot be liable for such. Most fall under the act of God rule. If a condition is cause by and "Act of God" they're usually clear. To me that Blue Bonnet thing falls under that. I don't have sympathy for power co's but I also realize no one can prevent a tree from being blown over by the wind etc. I've seen several grass fires started by sparking from lines etc. You can't prevent it. I remember once a farmer lost a lot of hay. Stacked all his bales right under the 3 phase line. Bad insulator caught one bale on fire and of course spread to the rest.

Single phasing is sometimes alright. If you have somebody from the customer on the premise sometimes you can go in and get them to shut off their 3 phase breakers and explain to them what's gonna happen.

I remember dinking with a couple of restaurants once. They were 208. One just had a 3 phase dishwasher and the other's only 3 phase was that blower vent that took away the cooking smoke etc. They were fine with it.

I remember talking to an oil field electrician once. I think he said their protection covered everthing except overvoltage.

[Pootnaigle]

Ummmmmmm I bleve most utilities have it in their contract with 3 phase customers that they wont be responsible for any damages incurred due to single phasing. there is single phase motor protection on the market but most fore go it. If its on a single bank I would speak with the 3 phase customer and advise they turn off all 3 pole breakers. In the event it was on a 3 phase tap with a phase of primary down I would make sure it was safe for a backfeed condition and leave the other 2 working until the line crew arrived.

[topgroove]

NO.

And I don't think any company would allow their crews to do something like this. AND Shouldn't.

Your "senerio" lacks....all sorts of information. The only "Critical Customers" I know of...have Generator Backup, for serious outages. I'll say again. "NO".:mad:

I've done it Swamp. Its the life of a troubleman, sometimes we do whatever we have to,

to get the lights back on. As long as it can be done safely, and you get the blessing of the on call supervisor everyone is good with it.


It dosen't take long to isolate the bad cable, Open all the three pole breakers, and jumper a couple hotlegs if ya have to.


In in out in less than 30 minutes. Sometimes a little customer service goes along way.

[rcdallas]

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[topgroove]

Okay, I appreciate all of the information. Swamp again I can't just dive into all the specifics as I have a job and this is a public forum. I can only highlight key points.

Though I wonder how this equipment protection actually works, some kind of a relay controlled deal with contactors where if it sees a zero on a phase it'll open the contactor? Hmmm...Exaxtly... with a isolation switch,,, or with a transfer switch it sences low or high voltage to switch to generator power

[climbsomemore]

NO.

And I don't think any company would allow their crews to do something like this. AND Shouldn't.

Your "senerio" lacks....all sorts of information. The only "Critical Customers" I know of...have Generator Backup, for serious outages. I'll say again. "NO".:mad:

Not only is it allowed Swampy... it is taught. We just never did it very often. More than one "3 phase customer has limped through the weekend "one lunged" with the power pot on a 4 wire delta bank out... or partial lights and NO AC or fire pumps etc if they were fed from a Wye bank.

The customer has to under stand that elevators, AC and fire pumps will be out of service. If it's OK with them ...be sure they lock out the disconects on their side that feed the 3 phase motors in question untill repairs are made.

[MI-Lineman]

We could but don't? Usually the whole service is burned into one big gob anyway!:rolleyes: Primary faults? Nope! Still don't do it here? You could but again we don't usually?

[ntxhand]

Did they end up jumpering it and run the cable across the parking lot and send a crew out later when the place closed???

[rcdallas]

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[ntxhand]

I see, well simliar situation happened just north of Dallas. They dug up the primary faulted cable which was direct buried, meanwhile another crew was making up terminations for the jumpers. The job started at 3pm they finished "jumpering" it to the transformer across the parking lot about 5, finished splicing the faulted cable, where it had been spliced 3 times already at 6 pm. Because they didnt want to shut the restaurant down twice they didnt return to remove the jumpers till 2 when it closed.