(1) The norms of operation for hydro generating stations shall be as under-
(a) Normative Annual Plant Availability Factor (NAPAF) for hydro generating stations shall be determined by the Commission as per the following criteria:-
(i) storage and pondage type plants with head variation between Full Reservoir Level (FRL) and Minimum Draw Down Level (MDDL) of up to 8%, and where plant availability is not affected by silt : 90%
(ii) storage and pondage type plants with head variation between FRL and MDDL of more than 8%, where plant availability is not affected by silt:
Plant-specific allowance to be provided in NAPAF for reduction in MW output capability as reservoir level falls over the months. As a general guideline the allowance on this account in terms of a multiplying factor may be worked out from the projection of annual average of net head, applying the formula:
(Average head / Rated head) + 0.02 Alternatively in case of a difficulty in making such projection, the multiplying factor may be determined as:
(Head at MDDL/Rated head) x 0.5 + 0.52
(iii) pondage type plants where plant availability is significantly affected by silt : 85%
(iv) run-of-river type plants: NAPAF to be determined plant-wise, based on 10- day design energy data, moderated by past experience where available/relevant;
(b) Auxiliary Energy Consumption:
Surface hydro electric power generating station With rotating exciters mounted on the generator shaft
0.7% With static excitation system 1% 1 Add. vide Not. No. HPERC-F(1)-2/2018 dated 22 nd November, 2018 published in the R.H.P. 27 th November, 2018 at p. 6249-6255.
22 Compendium of HPERC Regulations, March 2021 Underground hydro electric power generating station With rotating exciters mounted on the generator shaft
0.9% With static excitation system 1.2%
Provided that the Commission, may for sufficient reasons to be recorded in writing, after exercising due diligence and applying prudency check, deviate from the above ceiling norm.
(2) A further allowance may be made by the Commission in NAPAF determination under special circumstances, e.g. abnormal silt problem or other operating conditions, and known plant limitations.
(3) In case of a new hydro electric project the developer shall have the option of approaching the Commission in advance for fixation of NAPAF based on the principles enumerated in clause (a) of sub-regulation of this regulation.
(4) The Commission may lay down relaxed operational norms including the norms of NAPAF and auxiliary consumption contained in these regulations for a generating station, and these relaxed norms shall be applicable for determination of tariff for such generating station during the control period.
(5) The norms of operation under these regulations shall be ceiling norms and shall not preclude generating companies and the beneficiaries from agreeing to improve norms of the operation. If the PPA stipulates better norms of operation then such norms provided in the PPA shall be considered.
(6) In case of renovation and modernisation, de-rating or re-rating of the generating station, norms of operation shall be reviewed and modified accordingly.