Maharashtra Electricity Regulatory Commission expresses concern over 
failure of city’s  islanding scheme

Maharashtra Electricity Regulatory Commission at the suo-moto hearing, on Wednesday, on the power grid failure that occurred on October 12, expressed its concern and displeasure over the failure of Mumbai islanding system and asked the utilities to pull up its socks and take corrective measures. Free Press Journal broke the story on MERC’s decision to hold a suo moto hearing on the power outage in the Mumbai Metropolitan Region (MMR). The regulator is expected to soon issue its order.

MERC members Mukesh Khullar and IM Bohari, during the virtual hearing, sought clarification from the power utilities on how all the systems failed at the same time, what lapses in maintenance led to the tripping of transmission lines and why there was sudden fall in Mumbai’s power generation. Maharashtra State Load Dispatch Centre (MSLDC), MahaTransco, Tata Power and Adani Electricity were among those who took part in today’s virtual hearing.

MSLDC said that the power failure was due to the tripping of the 400kV Padghe-Kalwa circuit II and the subsequent hand tripping of 400kV Talegaon-Kharghar, which resulted in the complete failure of power supply to the 400 kV Kalwa and Kharghar substations. “This nonavailability of 400 kV sources resulted in the shifting of the complete load of the lower 200 kV network to other sources, including Padghe, Uran, Boisar and Koyna circuits and the Mumbai generators. The load generation imbalance persisted in the Tata Power network (demand 1033mw, generation 864 mw). With this, there was a large dip in frequency in the isolated Tata Power network. Thus, the Trombay units 5 and 7 tripped on under frequency, resulting in total blackout in the Tata Power and BrihanMumbai Electric Supply and Transport (BEST) networks,” said MSLDC.

On its part, Tata Power argued that all the protection schemes related to under frequency relay and islanding operated correctly and isolated the Mumbai system with MahaTransco. Rate of frequency drop was very high due to fault being close to Tata System.

Further, Tata Power said the hydro power stations were ready within 24 minutes to be connected to the grid for extending supply to Mumbai. However, on the account of overvoltage while charging the Karanjade-Chembur transmission line, connectivity to the grid could not be established.

Tata Power made a strong case for the review of Mumbai islanding scheme, especially when the generation and incoming power ratio is changing.

Adani Electricity said its distribution system operated an islanding facility and continued power supply to vital installations with the help of the Dahanu thermal power station.

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