A major fire at the Srisailam Left Bank Hydel Power Station in India’s Telegana state on August 20 killed nine people and seriously injured three others. There is now a wide-ranging federal investigation into its cause.
According to plant owner and operator, Telangana State Power Generation Corp. Ltd. (TSGenco), the tragic accident occurred at about 10:30 p.m. on the left bank of the 900-MW hydropower plant on the Srisailam reservoir. The reservoir is part of a joint irrigation project on the Krishna River shared by the Indian south-central states of Telangana and Andhra Pradesh.
The hydropower plant on the Telangana side comprises six 150-MW turbines housed in a four-story facility that reaches a depth of 1.2 kilometers (km) underground. TSGenco said the plant has only one entry and exit point; the exit tunnel is reportedly 2-km long. The incident reportedly began on the top floor of the facility, which houses six control panels linked to the six turbines and generators. The floors below house the generators, turbines, and water inlet valves.
In a statement Friday, the day after the incident, TSGenco said 17 people were in the plant when the incident began. Eight escaped, but nine were trapped. “The fire broke out in the panels in unit 1 of the power station which led to the accident. The employees tried to put off the fire and save the plant from burning. The employees tried their level best till 12 a.m. [on Friday], but in vain,” the statement read.
“As fire and dense smoke spread, it was not possible to go inside for a very long time. The teams could enter the plant by the afternoon of Friday,” it said.
A reported short-circuit caused fire accident in Hydro Electric Project at Srisailam Left Bank (Telangana), 9 believed to have trapped inside the plant & are being rescued. @thenewsminute pic.twitter.com/s7qRdveYul— CharanTeja (@CharanT16) August 21, 2020
Harrowing footage of the fire incident shows plant workers attempting to put out the fire.
The deceased include seven TSGenco employees: Deputy Engineer Srinivas Goud, Assistant Engineers Venkat Rao, Mohan Kumar, and Uzma Fathima; Plant Attendant Rambabu; Junior Attendant Kiran and Sundar Kumar. Two employees of Hyderabad-based automative battery company Amaron Batteries were also among the fatalities: Vinesh Kumar and Mahesh Kumar.
A Possible Cascade of Events
Preliminary reporting as of August 25 suggests the incident may have stemmed from a cascading emergency, which ultimately led to the explosion of an auxiliary transformer as the fire spread to the panel board. Authorities have also since determined that the exhaust fans inside the plant malfunctioned “due to technical reasons.”
TSGenco Chairman and Managing Director D. Prabhakar Rao on Sunday told reporters that further investigations are warranted because the plant did not function as designed. Two of the six units at the plant should have tripped automatically as soon as the fire broke out. “But it did not happen. We are unable to understand why it did not happen as the plant is equipped with the latest technology,” Rao told The Times of India. “The isolation was done from outside and vibrations were being felt. The power supply went off as fire engulfed and smoke filled up the tunnels.”
Dispelling rumors that the “mishap” resulted from overproduction, Rao also noted the hydropower plant had functioned as designed over the past month. However, he noted “power supply to the hydel station was switched off by the load dispatch center in Hyderabad.” He added: “When power was switched off, the ventilation stopped and the emergency exit also could not be opened.” TSGenco is now scrutinizing why the maintenance team failed to trip the unit when they discovered the fire in the control panel, he said.
So far, the state has dispatched a five-member high-level committee comprising senior engineers to inquire into the circumstances, Rao said. A committee report, which will include specific recommendations to prevent future incidents, is expected within two weeks.
Federal Investigation Takes Shape
Meanwhile on August 24, media widely reported that the Indian government had also launched an investigation into the incident led by the federal Crime Investigation Department (CID). Investigators are reportedly looking to determine whether cause of the fire was electrical or “something else,” as a forensic official told The Economic Times. Investigators have reportedly surveyed CCTV footage, maintenance records, and employee logs, and are collecting statements of survivors and employees.
The incident has also since taken on political weight as a number of high-profile Indian politicians have stepped into the fray. On Monday, A. Revnath Reddy, the working president of the Telangana Congress and a minister of parliament representing Malkajgiri, a suburb in Telangana’s capital Hyderabad, in a letter to Prime Minister Narendra Modi urged an “impartial inquiry.”
Revnath alleged that over the past several years, “multiple red flags were raised about the poor maintenance of accompanying structures, including the structural integrity of the dam itself, on which the plant is built. Concerns were also raised at the 39th meeting of the National Committee on Dam Safety in February 2019 but the State Government of Telangana failed to act.”
More details are certain to emerge over the coming weeks. Telugu news channel HMTV reported that a team of experts, which was finally able to reach the scene of the incident on Monday, are still assessing the damage.
Fire Risks at Hydropower Plants
While widespread safety protocols have generally served to prevent severe incidents, power plant fires are not uncommon. On Monday, for example, fire crews battled a “stubborn” fire on the upper floors of a turbine building at Talen Energy’s 1.7-GW Martins Creek plant in Pennsylvania. The plant, which ceased burning coal 13 years and has since switched to natural gas and oil, experienced a transformer fire in 2016.
The blaze on Monday is believed to have begun when lubricating oil leaked from a turbine. The fire burned through the roof of the facility’s six-story building and required numerous ladder trucks to fight it from above and below. Talen Energy said all employees were evacuated from the plant, and everyone has been accounted for.
As POWER has reported, while hydropower plants face perhaps the lowest fire risk among electric generating facilities, they are not without risk, as history has shown. A fire was complicit, for example, in the cascading events that led to the Russian Sayano-Shushenskaya Hydro Power Plant accident in August 2009, which claimed the lives of 75 workers.
Common hazards at hydropower plants include oil-filled transformers, electrical cables and switchgear, air-cooled generators, and large quantities of combustible hydraulic oil. Common fire hazards include hot work, smoking, general storage, and temporary construction/overhaul materials.
—Sonal Patel is a POWER senior associate editor (@sonalcpatel, @POWERmagazine).