150 MW Unit 4 At Srisailam Hydroelectric Station Rejoins Grid After Six Years

Unit No. 4 of the 900 MW Srisailam Left Bank Hydro Electric Station in Nagarkurnool district was successfully synchronised with the state grid at 3.21 am on August 11. The 150 MW power generation unit returned to operational status following a six-year cycle of fire damage, repeated repair attempts, and trial failures that began in August 2020. With this synchronisation, all six 150 MW units at the hydro complex are now functional, boosting peaking power support for state power generation corporation TS-Genco.

The trouble began on August 20, 2020, when a major fire broke out at the unit, causing severe damage to its stator and rotor. To restore the damaged unit, repair work was split between two firms. Noida-based Voith Hydro Pvt Ltd was awarded work in August 2021, while Shree Abirami Engineering Works was brought in during February 2022.

Following the first round of repairs, the unit was commissioned on July 29, 2023. However, it tripped within a few weeks due to a stator earth fault that damaged the stator bars and the core. Because the machine was still under guarantee, Voith agreed to redo the stator rewinding work free of cost. However, the firm sought an additional ₹2.95 crore for rotor lowering, alignment, and the installation of online air-gap and partial discharge monitoring systems. Work on this phase started in April 2025.

The unit was recommissioned on October 2, 2025, but tripped the following day due to an air-gap protection alert. Technical inspections carried out by Voith alongside Japanese firm HM Hydro discovered loosened rotor poles in addition to other operational issues.

Following an official review in January 2026, Voith was directed to carry out all required rectification works. After obtaining clearance from the chief electrical inspector, power officials successfully completed the synchronisation on August 11.

Engineers are now conducting fine-tuning processes, including dynamic balancing and turbine auto-tuning, to ensure continuous and stable plant operations. TS-Genco expects the full operation of all six units to deliver improved peaking power support and allow for enhanced utilisation of water releases from the Srisailam reservoir.