Active Harmonic Filter on Utility WYE-WYE Transformer

[smoothops10]

Details below but main question, has anyone successfully seen active harmonic filters on 480/277V 3phase system supplied from a WYW WYE utility transformer (not the more common delta-wye)?


I have a site with two MCCs, each with 300hp and 100hp VFDs. The drives are the older SqD Altivar 61 6-pulse with 3% line reactors.
Each MCC has two (2) 100A Accusine PCS active harmonic filters. All four units are inoperable.
V THD readings at <2%. I THD readings at 20%.
Utility transformer is WYE-WYE 1500kVA, 5.99%IZ.

All 4 accusine units are inoperable. No one knows why or if they were ever started up at all 10 years ago.
I recall hearing about a past job that had specified the accusine filter units and the electric supplier in the area was a small electric cooperative that had installed a Y / Y utility transformer. When the filters operated, significant noise or issues were injected back into the cooperative’s distribution system affecting other supplied customers. I don't have all the details. My understanding is the Δ primary windings trap much of the noise (3rd harmonics) from being injected back whereas the Y windings do not. The cooperative made the site turn the filters off and I do not believe a resolution was ever reached.

Maybe this site turned these off for the same reason? Thoughts appreciated.

 

[jim dungar]

The vast majority, I would say over 75%, of 480Y/277 services are supplied by utilities using wye-wye transformers.
My experience is limited, but I never heard of active filters as being a source of 'noise'.

With only a 2% THDv, I am not surprised the filters are not being used.

 

[smoothops10]

The vast majority, I would say over 75%, of 480Y/277 services are supplied by utilities using wye-wye transformers.
My experience is limited, but I never heard of active filters as being a source of 'noise'.

With only a 2% THDv, I am not surprised the filters are not being used.

Thanks for the reply. You may be right but in the locales I have worked, the delta-wye has been prevalent.
As for 'noise', the filters provide harmonic correction and power factor correction by injecting currents to cancel out harmonics and adding VARs as needed. My theory is they either may have been set up wrong, along the lines of CT(s) installed backwards or parameter inputs left at factory default, or the filters are being too aggressive and trying to correct harmonics or power factor on the distribution network - as postulated the 3rd harmonic typically the largest harmonic produced may have the correction current going in to the distribution circuit whereas on delta-wye it would have circulated in the delta winding.

Or maybe they were just never turned on, wouldn't surprise me.

 

[smoothops10]

Jim, just saw your comment on the low V THD %. I agree, have seen the V distortion level is more important the I THD reading.
IEEE 519 calls for <5%V and <8%I. That said, we have low V reading, high I reading - you see limited potential issue in this case? Looking to add 150 hp 6-pulse drive.

 

[D. Castor]

At those fairly low distortion level, they probably decided that active filter weren't needed and didn't want to pay for the power they required. Probably 95% of the utility pad-mount transformers out here in the Pacific Northwest are wye-wye.

If no problems are being reported, and the utility isn't complaining, I wouldn't be overly concerned with meeting the IEEE 519 guidelines. They are just numbers. I wouldn't do anything until there's a complaint or problem. Unless there are other utility customers on this transformer, your point of common coupling is really on the transformer primary and the transformer provides substantial buffering impedance.