Tata Power, MahaTransco trade charges over Mumbai power disruption

State govt orders high probe to fix responsibility, as outage brings trains and other critical services to a grinding halt

Tata Power and the Maharashtra State Electricity Transmission Company (MahaTransco), a state government-owned electricity distributor, have blamed each other for the power outage in Mumbai on Sunday due to which trains and other critical services came to a grinding halt in the city.

While Tata Power has blamed the massive voltage fluctuations in MahaTransco's transmission lines for the incident, government officials said Tata Power plant was operating at half of its capacity and failed to ramp up electricity generation on Sunday despite instructions from the State Load Dispatch Center -- the apex body which ensures integrated operation of the power system in the state.

The Maharashtra Energy Minister Nitin Raut has asked officials to probe the reasons behind the power outage including, non-compliance of SLDC directions and short-term cost-saving actions taken by the utilities.

Giving details about the Sunday shutdown, MahaTransco officials said all stakeholders including Tata Power were informed that two of its transmission lines were under planned shut down since February first week for work related to Mumbai metro.

“Despite incoming power supply to Mumbai being limited due to the planned outages, embedded generating companies should have ramped up electricity generation to maximum capacity.  But Tata Power acted in a surprising deviation to this by operating at less than half of its capacity,” said an official.

Tata Power instead was importing cheaper power from the market to maintain its competitive position which put additional burden on the transmission system and Trombay plant failed to enter the "islanding mode". The islanding method ensures uninterrupted supply in Mumbai in case of any voltage fluctuations in the rest of the grid. The average cost of power production at Trombay, a coal based power station, is Rs 6 a unit -- almost double the cost of power procured from the spot market.

On Sunday, MahaTransco officials said the Mulund-Trombay line tripped because of technical snag and the State Load Transmission Centre asked the Tata Thermal Power and Tata Hydro- Electricity Power Company to increase their capacity around 9:00 a.m. but Tata Power demanded an email in order to increase its capacity. “Had the Tata Power increased the power generation with immediate effect, this situation would have been averted,” MahaTransco said in a statement.

“It was a time critical delay which plunged Mumbai into darkness,” the official said.

Tata Power officials, on the other hand, said when the lines tripped, it created a disturbance in Tata Power’s system and there was a reduction in demand to the tune of 850 MW. The total demand of Mumbai fell from 2,000 MW to around 1,200 MW and different parts of Mumbai were affected including South Mumbai, Chembur, and suburban areas.

“We restored the power supply within one hour and stepped up our hydro generation to full capacity and avoided much larger damage,” said Sanjay Banga, President of Tata Power.

Tata Power said its Trombay Units were generating electricity at 52% of their capacity as per the SLDC instruction though they are capable of generating a full capacity of 930 MW. On February 27, its generation was as per demand and had nothing to do with the outage, the company said.