Grounding transformer placement 1

[Chebahtah]

Project consists of a 3-phase 95kW solar PV plant connected to a 12.47kV distribution line. The 480V inverter's isolation transformer is connected delta-wye with high-resistance grounding.

PV setup:

http://i1245.photobucket.com/albums/gg581/jchebahtah/inverter.png

simplified single-line:

http://i1245.photobucket.com/albums/gg581/jchebahtah/singleline.png

It was determined that a grounding transformer is needed to prevent possible overvoltages during a ground fault (if feeder breaker opens and PV remains in-service forming an island).

Any preference of where to install the grounding transformer (480V or 12.47kV level)?

It would certainly be cheaper to throw the xfmr on the 480V...

Justin Chebahtah

http://www.justinchebahtah.com

 

[davidbeach]

If the wye-wye transformer is solidly grounded on both sides it should be possible to achieve an effectively grounded system on the high side using a grounding transformer on the low side. If either side of the wye-wye is not solidly grounded the grounding transformer must be on the high side to become effectively grounded.

 

[Chebahtah]

Thank you very much for the prompt, concise, and informative response. Enjoy the star!

Justin Chebahtah

http://www.justinchebahtah.com