Section Puc 905.03 - Configuration of the Transformer Serving the Customer-Generator's Facility Site(a) The existing site transformer serving the customer-generator load may be used if its use will not significantly degrade the power quality or voltage regulation on the secondary distribution system and if such usage will not create problems for distribution utility system relaying.(b) For single-phase distributed generation facilities connected to 4-wire multi-grounded neutral systems, the high side of the step-up transformer shall be connected phase-to-neutral.(c) A phase-to-phase high side connection shall be allowed if it does not degrade power quality or voltage regulation on the distribution system.(d) For single-phase distributed generation facilities connected to 3-wire or 4-wire impedance grounded systems, the step-up transformer high-side winding shall be connected phase-to-phase.(e) For 3-phase distributed generation facilities connected to 4-wire multi-grounded distribution systems, the step-up transformer may be an existing grounded-wye to grounded-wye transformer. The term "wye," as used in this paragraph, means the configuration in which one end of each transformer winding is connected to a common point and the other to its appropriate line terminal, resembling the letter "Y."(f) In cases as described in (e) above, the generator shall be impedance grounded as necessary to achieve effective grounding but limit the desensitization of the distribution utility system ground fault relaying.(g) The net-metered facility site shall be impedance grounded, as described in (f) above, if necessary, in a manner adequate to assure that the facility does not: (1) Significantly degrade the power quality or voltage regulation on the distribution system;(2) Create significant safety problems; or(3) Create problems for distribution utility system relaying.(h) To guard against over-voltages on the unfaulted phases of a 3-phase utility primary, if the transformer serving the customer-generator site is ungrounded, over-voltage protection shall be used to:(1) Detect a situation in which the utility has tripped due to a phase-to-ground fault, and the connected ungrounded generator might not yet have tripped; and(2) Trip the generator at high speed.(i) The cost of any improvements necessary to the site transformer serving the net-metered facility shall be borne according to the distribution utility's approved tariff on file with the commission.N.H. Admin. Code § Puc 905.03
INTERIM #5921, eff 11-7-94, EXPIRED 3-7-95
New. #7424, eff 1-12-01; ss by #9353, INTERIM, eff 1-12-09, EXPIRED: 7-11-09
New. #9515, eff 7-18-09; ss by #9998, eff 9-20-11
Amended by Volume XL Number 33, Filed August 13, 2020, Proposed by #13080, Effective 9/14/2020, Expires 9/14/2030