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1 'l:l1w m:q;n: government of India ~~gtf'~ Central Electricity Authority ~m~~ ~~I Western Regional Power Committee IS/ISO: q;:fi-3, t:;i1.~ Wr, 3iirfr(' ), ~ F-3, MIDC Area, Andheri (East), Mumbai ~ Phone: , ; ; ~ Fax: Website: prc-wrpc@nic.il!protectionwrpc@tgail.com NO. WRPC/Protection/2017/ To, - _ B (2 0 ~~ Date: or Executive Director, WR-I, NTPC Ltd., WR HQ-I, Mumbai Fax Executive Director, (WR-I), PGCIL, Sampriti Nagar, Nagpur , Fax ~ GM(CTU-Plg.), PGCIL, Saudamini Plot No.2, Sector-29, Gurgaon Fax GM, WRLDC, POSOCO Mumbai. 5. ChiefEngineer(SLDC), MSETCL, Airoli. Sub: SPS for evacuation of power from Mouda STPS(Unit#2 of Stage-II). Sir, Please find enclosed herewith record notes of the meeting on review of SPS for evacu tion of power from Mouda STPS,held on at WRPC Mumbai/or further necessary action. Enc!': as above. J.K.Rathod, OLJ - J Engineer (P) 0 j I ")

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9 Record notes of the meeting on Review of SPS for evacuation of power from Mouda STPS held on at WRPC Mumbai A meeting on review of SPS for evacuation of power from Mouda STPS was held at WRPC Mumbai on The list of participants is enclosed at Annex Shri Satyanarayan S., SE(C & O), WRPC welcomed the participants. He welcomed Shri A. Balan Member Secretary WRPC and requested him to chair the meeting. He informed that the SPS for evacuation of power on declaration of Commercial Operation (CoD) of NTPC Mouda Stage-2 Unit No.1 (Unit No.1 capacity 660MW and the total Installed capacity at NTPC Mouda after CoD of Unit No. 1 of Stage -2 became 1660MW), through 400kV Mouda-Wardha D/c, was finalized in the meeting held on 01 st Feb.2017 at Diu (enclosed at Annex-2). 2. NTPC vide letter dated (copy enclosed at Annex-3), have informed that the 2 nd Unit (660MW) of Mouda Stage-2 have been successfully commissioned and they are in the advance stage for trial run operation of the unit prior to CoD of the Unit. 3. The total Installed Capacity after CoD of 2 nd Unit of Stage-2 at NTPC Mouda would become 2320MW and the ex-bus capacity would be around 2120MW. The ATS for Mauda State-2 evacuation i.e 400kV Mouda-Betul D/c lines are expected to be commissioned by June 2017 end. Since there is a restriction to inject infirm power from 2 nd unit of Mouda Stage-2 during testing including full load testing and trial run of this unit, the trial run and the CoD of this unit may be affected. 4. In response to the above NTPC letter, CTU vide letter dated (Annex-4) have intimated that system studies were carried out by them for evacuation of power from Mouda STPS (2x500+2x660MW) through the existing 400kV Mouda-Wardha D/c(quad) line(ats for Mouda Stage-1). It has been observed that with evacuation of about 2120 MW, the line loadings are generally in order under normal conditions. Further based on the stability studies, it has been observed that the system remains stable even under the outage of one circuit of 400kV Mouda-Wardha D/c line after a line fault close to the bus is cleared in 100ms with opening of faulted line.

10 5. In view of the CTU letter following facts and issues were discussed; a) PGCIL representative stated that the ATS for Mouda Stage-II, i.e. 400kV Mouda-Betul D/c lines would be commissioned in July b) The existing evacuation system i.e. 400kV Mouda-Wardha D/c (quad) is in service for more than 2 years and the line length is 124km/circuit. The maximum conductor design temperature is 75 degree Centigrade. The thermal loading limit of the single ckt line is 1748MW, as per CEA Transmission Planning Criteria document. c) The CTR at Mouda end has been changed to 3000/1A. d) As per the stability studies carried out by CTU, the system remains stable even under the outage of one circuit of 400kV Mouda-Wardha D/c line, after a line fault close to the bus is cleared in 100ms with opening of faulted line. e) The CTU study suggests that there is no need of instantaneous tripping of the generating units, since even after a fault on one of the 400kV Mouda-Wardha circuits, the system remains stable if the line trips and isolates the fault within 100msec. The thermal loading limit of the single circuit is 1748MW and therefore it can carry the full dispatch of Mouda STPS for shorter periods. f) Therefore there is no need of instantaneous tripping of generating units at Mouda STPS. However NTPC is required to back down the generation to a tune of MW immediately through coal mill tripping. 6. Till the start of the trial run of the 2 nd Unit of Stage-2, the SPS formulated on (enclosed at Annex-2) would continue. 7. The following SPS scheme shall be implemented by NTPC at Mouda STS before the commencement of the trial run of the 2 nd Unit of Stage-2. If felt necessary the same would be reviewed after commissioning of the 400kV Mouda-Betul D/c lines; a) Under normal conditions when both the circuits are in service there is no backing down required. b) If the Ex-bus generation is more than 1500MW (the SPS would be active) and one of the 400kV kv Mouda-Wardha line trips, the Ex-bus generation at Mouda should be restricted to 1500MW immediately by backing down the quantum over and above 1500MW before tripping of the line. For simplicity if the Ex-bus generation is more than 1500MW and one of the

11 400kV kv Mouda-Wardha line trips, then automatic backing down of around MW should be done immediately through coal mill tripping (NTPC may take an appropriate call of either immediate automatic back down of generation or trip the unit, whichever is convenient to them). The loss of line sensing logic to be implemented would be fulfillment of either of the 400kV Mouda-Wardha breaker tripping of any line or the flow on the 400 kv Mouda-Wardha tripped line is less than 100MW. After the automatic action of the SPS, WRLDC would advice NTPC further action required to control the Ex-bus generation at Mouda depending on the real time system condition. 8. The SPS for Wardha gate flow already implemented would remain unchanged. The above SPS would be implemented by NTPC at Mauda before commencement of the trial run operation of the 2 nd unit of Stage-2 of Mouda STPS. The same shall be reviewed, if felt necessary after commissioning of the 400kV Mouda-Betul D/c lines. 9. In view of extreme loading of the healthy circuit of 400kV Mouda- Wardha for a short duration after tripping of other faulty 400kV Mouda-Wardha circuit, NTPC and POWERGRID shall ensure that there is no load encroachment in Z-3 settings of Main-I & Main-II line protections at both ends of the 400kV Mouda-Wardha D/c. The meeting ended with the thanks to the chair. *********************