According to a statement from MSETCL, which operates four 400kV transmission lines fetching power to Mumbai, it could not complete ongoing maintenance work on two of these four lines to fix a broken conductor and an obstructed insulator
Mumbai was brought to its knees on Monday morning by an unprecedented power blackout that disrupted suburban railways and emergency services and forced offline thousands of remote-working bankers, stock traders and technology professionals.
Just as Mumbai was beginning its new work week, the city and its suburbs suffered a massive outage at 10am that lasted at least two hours in some places, and continued up to eight hours in others.
According to a statement from the Maharashtra State Electricity Transmission Co. (MSETCL), which operates four 400kV (kilo-volt) transmission lines fetching power to Mumbai, it could not complete ongoing maintenance work on two of these four lines to fix a broken conductor and an obstructed insulator. “At 9.58am on Monday, one of the two remaining lines, Padgha-Kalwa Vahini-2 transmission line carrying 633MW tripped and was shut due to a technical failure," it said.
“The flow on Pune-Kharghar (the last remaining line) rose up to 900MW and tripped at 10am, resulting in load drop in Mumbai system," a statement from Tata Power Ltd, one of the three distribution utilities in Mumbai, said.
“The power demand on Monday morning from Mumbai was about 2,400MW (megawatts)," a senior official at a power utility said. “Half of this is generated by plants near Mumbai, and the rest comes from MSETCL’s transmission lines. So, when the MSETCL transmission lines tripped, and the 1,400MW that was coming from MSETCL went off grid, it was such a sudden demand in load for the rest of the city’s network that Mumbai’s islanding system failed."
The city’s power islanding system, built by Tata Power in 1981, is designed to isolate its electricity network from the rest of the national grid during widespread external grid disturbances. Under the system, power plants within Mumbai continue generating electricity during grid failures, supplying power for rail transport and essential category consumers such as hospitals. The islanding system, which has held up even during massive grid failures of the past, will now be re-evaluated to see how it can be improved, the official cited above said.
The blackout impacted mobile networks, telecom operator Vodafone Idea Ltd said. With over 90% of staff across tech firms working from home due to covid and Mumbai hosting businesses across information technology, banking and financial services, the prolonged outage affected productivity. Mumbai and its suburbs are home to major technology companies like Tata Consultancy Services, Tech Mahindra, Accenture and Capgemini, apart from hosting 40% of the country’s data centre facilities.
Even though stock exchanges functioned with uninterrupted power supply, stockbrokers working from home were affected. “Trading continued at the main office since all our systems are backed up by inverters," a primary dealer at a private bank’s treasury department said on condition of anonymity. “A few traders were asked to go to the main office immediately. The volume of trade was less on Monday compared to Friday, and part of the reason could be the power outage."