hockeyoligist2
Senior Member
- Location
- close to greenville sc
We have a 6% or more current imbalance at one of our sewer plants, every motor in the plant has lower amperage on C phase.
It started on Nov. 21 as far as we know, the blowers started shutting down every few hours because of it. The operator just reset them from a remote computer and didn't call in any of our electricians since the backups would start and we all went home early for the holiday. Then there was a power outage on the 22nd for about 1 hour, the plant switched to generator power,no electricians were called in. So we didn't know about the imbalance or outage until Fri. after I got called in.
The the voltage had went up to as much as 507v phase to phase, with spikes as high as 511v according to our trend monitor. It's a 480v system and the voltage has been a little high for 2 years, since the new generator and transformer was installed, around 488v.
We had them to do a tap change today to lower the voltage and we are back to 480v with a load on it, 490v with no load.
We hadn't been able to do a closed transition, the generator wouldn't sync with the utility because of the high voltage. And due to DEHEC regulations we didn't want to do an open transition. We did get it to sync before he made the tap change.
The current imbalance went away on generator power.
POCO has been saying it's on our side and that they are within their perimeters. The guy that did the tap change left as soon as he was finished so I didn't get to talk to him and let him know that the imbalance went away on generator power. It only took him 2 or 3 minutes.
If it is on our side it would have to be in the 2 year old breaker for the utility or the 2 year old wires running 20' from their transformer. Doubtful.
I don't have a clue what could be causing it on the POCO side and I doubt that they will admit that it is on their side since they are within their perimeters.
Any ideas?
It started on Nov. 21 as far as we know, the blowers started shutting down every few hours because of it. The operator just reset them from a remote computer and didn't call in any of our electricians since the backups would start and we all went home early for the holiday. Then there was a power outage on the 22nd for about 1 hour, the plant switched to generator power,no electricians were called in. So we didn't know about the imbalance or outage until Fri. after I got called in.
The the voltage had went up to as much as 507v phase to phase, with spikes as high as 511v according to our trend monitor. It's a 480v system and the voltage has been a little high for 2 years, since the new generator and transformer was installed, around 488v.
We had them to do a tap change today to lower the voltage and we are back to 480v with a load on it, 490v with no load.
We hadn't been able to do a closed transition, the generator wouldn't sync with the utility because of the high voltage. And due to DEHEC regulations we didn't want to do an open transition. We did get it to sync before he made the tap change.
The current imbalance went away on generator power.
POCO has been saying it's on our side and that they are within their perimeters. The guy that did the tap change left as soon as he was finished so I didn't get to talk to him and let him know that the imbalance went away on generator power. It only took him 2 or 3 minutes.
If it is on our side it would have to be in the 2 year old breaker for the utility or the 2 year old wires running 20' from their transformer. Doubtful.
I don't have a clue what could be causing it on the POCO side and I doubt that they will admit that it is on their side since they are within their perimeters.
Any ideas?