msheets
PE Electrical
- Location
- Salt Lake City, UT, USA
- Occupation
- Electrical Engineer
We completed a small commercial PV system last month, but the POCO has not yet approved the net metering agreement, and just yesterday told us that due to the requirements of IEEE Standard 1547.7, we will have to install a transformer grounding bank before we can start generating. For those unfamiliar with 1547, the relevant portion essentially states that if the generating facility is connected to a 3ph 4W system, and the total generating peak power is more than 10% of the minimum load on the circuit, then the generating facility has to be effectively grounded. Solectria wrote an interesting paper on the subject: http://solectria.com//site/assets/files/1484/solectria_effective_grounding_for_pv_plants.pdf. Quite a bit of PV has gone up in the area lately, and the POCO just realized that they are at or near that 10% limit.
The prospect of adding the transformer grounding bank doesn't bother me too much, but due to the lead time of some of the components, we may have to put off generating another two months. I can't imagine our client is too happy about that. With that in mind, I'd like to know whether this applies to this project. The transformer feeding the building is 12470Y-Ground / 208Y. I can't think of any reason why this transformer should not be solidly grounded. If that is the case, is it safe to assume that the "effectively grounded" portion of the 1547 requirement is satisfied, and we therefore do not need the transformer grounding bank? Am I missing anything?
The prospect of adding the transformer grounding bank doesn't bother me too much, but due to the lead time of some of the components, we may have to put off generating another two months. I can't imagine our client is too happy about that. With that in mind, I'd like to know whether this applies to this project. The transformer feeding the building is 12470Y-Ground / 208Y. I can't think of any reason why this transformer should not be solidly grounded. If that is the case, is it safe to assume that the "effectively grounded" portion of the 1547 requirement is satisfied, and we therefore do not need the transformer grounding bank? Am I missing anything?