Utility Power Issue...Cleaning Up Dirty Power 277/480 WYE ?

[PatriotIII]

Have a facility here in Eastern TN with an interesting issue. 277/480v wye 1600A surge protected GFCI MCB...After consulting with an EC from the area and monitoring incoming power for a week, we have discovered that the utility power has voltage fluctuations from 502V to 318V. Before I present these findings to the power company I was wondering if anyone has experienced similar issues and any possible solutions you may have come across for this. We have a Number or VFD's on site and are also experiencing issues with these as well, perhaps the voltage issue correlates with the VFD issues.

 

[kwired]

Have a facility here in Eastern TN with an interesting issue. 277/480v wye 1600A surge protected GFCI MCB...After consulting with an EC from the area and monitoring incoming power for a week, we have discovered that the utility power has voltage fluctuations from 502V to 318V. Before I present these findings to the power company I was wondering if anyone has experienced similar issues and any possible solutions you may have come across for this. We have a Number or VFD's on site and are also experiencing issues with these as well, perhaps the voltage issue correlates with the VFD issues.

That severe of drop is more than just a dirty power problem. Connection failure somewhere? You would think if that bad it totally fails or would have already. Severely undersized components for the load supplied somewhere on distribution side? I doubt it is even a failing tap changer or controls, lowest setting probably not possible to be that low.

Has more load been added (even if over some time) yet POCO never notified so never upgraded the supply, transformer, etc? just because one installs a 1600 amp service doesn't mean POCO will supply you equipment that can deliver that if your expected load is only say 500 or 600 amps. You talking a difference of maybe a 500 kVA vs a 1500kVA transformer being needed to supply the actual load here.

 

[PatriotIII]

That severe of drop is more than just a dirty power problem. Connection failure somewhere? You would think if that bad it totally fails or would have already. Severely undersized components for the load supplied somewhere on distribution side? I doubt it is even a failing tap changer or controls, lowest setting probably not possible to be that low.

Has more load been added (even if over some time) yet POCO never notified so never upgraded the supply, transformer, etc? just because one installs a 1600 amp service doesn't mean POCO will supply you equipment that can deliver that if your expected load is only say 500 or 600 amps. You talking a difference of maybe a 500 kVA vs a 1500kVA transformer being needed to supply the actual load here.

We have no load on the transformer. After the 6th VFD failure we basically shut production down and that’s when the data was acquired on the utility power.

 

[hillbilly1]

I’m trying to remember, I know somebody will chime in if I’m wrong, but if the amperage and voltage drops, it’s on the power company’s end, if the amperage rises, and the voltage drops, it’s on your end.

 

[infinity]

utility power has voltage fluctuations from 502V to 318V

With these numbers at the incoming service I would look no further than the POCO.

 

[kwired]

I’m trying to remember, I know somebody will chime in if I’m wrong, but if the amperage and voltage drops, it’s on the power company’s end, if the amperage rises, and the voltage drops, it’s on your end.

When drop is only by maximum of 10% probably mostly true.

When it drops by nearly 40% there is a serious problem, if it is a bad connection you would think it wouldn't take very long for total failure of the connection. This almost has to be a POCO issue whatever is going on or at least severely undersized service transformer for the load supplied even if nothing else is wrong.

 

[Jraef]

Utilities are required to deliver +-5%, so on a 480V service, that is 456 to 504V at the service terminals*. You are within the upper limit, but at 318V you are WAY BELOW the lower limit. So I agree, this is likely a PoCo problem.

* But if you are taking measurements at some distance down stream of the service terminals, then that might not be them, it might be a local issue. Their responsibility stops at your service entrance terminals.

 

[PatriotIII]

I agree also. An oscilloscope was placed on the service entrance terminals