MUMBAI: Tata Power on Monday said there was "simultaneous substation tripping" at state-run MSETCL's two facilities, which led to a major power outage in the financial capital and surrounding areas.
It said the tripping at the Kalwa and Kharghar sub-stations at 1010 hours caused a huge dip in frequency in the Mumbai transmission system, leading to the tripping of power supply.
Trains came to a halt and other activity was also grounded due to what was labelled as a grid failure by officials.
"Restoration work is in progress to bring supply from the 3 Hydro units and Trombay units once the MSETCL (Maharashtra state electric transmission company) transmission lines are connected," the Tata Power statement said.
Earlier, Western Railway and state-run discom BEST Electricity had said there was a failure at Tata Power's end, leading to the outages.