Trishuli Hydropower Station will be shut down for a major overhaul as age is catching up with the venerable plant. Built more than half a century ago, the 24 megawatt station is racked by fire incidents, grid failures, equipment breakdown and falling output.

"We have seen frequent fires at the switchgear which controls the electrical equipment of the plant, and the other half-century-old structures are also disintegrating," said Tara Dutta Bhatta, chief of the station.

"A rehab of electrical equipment, including transformers and civil structure, must be carried out, and the plant will go for a complete shutdown for nearly two months or as per need basis once work begins."

The Rs224 million hydel scheme, commissioned in 1967 with financial assistance from India, has seen four fire incidents in just a year owing to high current fluctuation, prompting officials to call for global bids for its refurbishment.

According to the Nepal Electricity Authority, it has decided to restore and modernise the power station in 30 months and has invited global tenders.

"With high silt deposit in the balancing reservoir, the plant does not operate to its designed peaking feature. Choking of the valves is also a common issue during the monsoon. This obstructs discharge into the canal and reduces generation," said the state-owned power utility.

In recent years, the run-of-the-river scheme has seen regular grid failures and water leakages causing seizure of electrical equipment, depriving the electricity authority of sellable power during peak hours.

The power plant has also seen a series of fire incidents causing losses amounting to millions. In October 2018, high voltage caused severe damage to the electrical system of the plant; and in January this year, the switchgear of one of the seven turbines caught fire, forcing a shutdown of other units.

At present, the plant is churning out less than 21 megawatts from six units while one unit awaits repair, and the governor system of the power station is in poor shape. The fault in the governor system has been cited as the cause of multiple fire incidents at the plant in the last fiscal year.

The governor system senses and regulates the speed and power of the generating units, and keeps the engine running at the desired level to produce the required amount of energy.

"Extensive work has been put into analysing the prospects and options of rehabilitation and modernisation of the power station in this fiscal year," said Madan Timsina, officiating deputy managing director of the Generation Directorate of the Nepal Electricity Authority.

The power utility plans to open the bids on September 8, and as per preliminary estimates, the rehabilitation project funded by the government and power utility will cost Rs600 million to Rs800 million.

This is the second time the plant will be switched off for rehabilitation after it was commissioned in 1967. It was first upgraded in 1995 from a 21 megawatt plant to a 24 megawatt plant with seven units, six units generating 3.5 megawatts each and one unit generating 3 megawatts.

Also, because of massive accumulation of sand in its intakes, the station has not been able to operate at optimum capacity.

Due to silt issues, the station is feeding only 75 percent of its total annual output of 163 gigawatt hours into the national grid. In the last fiscal year, the project, despite being run at full capacity, was able to relay only 123 gigawatt hours.

While the plant is closed for repairs, the power grid will lose 38 megawatts as its cascade project Devighat Hydropower Station will be switched off too. Once the electrical equipment at the Trishuli station is replaced, the output of its cascade project is also expected to improve.

The Nepal Electricity Authority has also planned to repair the powerhouse at Devighat in the next fiscal year.

"The Devighat powerhouse is facing problems in its governor and other systems. The faults need to be identified and repair work needs to be done, which will be carried out by suitable experts in the next fiscal year," said the power utility. "Repair work to stop water leakage from the lower part of the escape gate will be carried out while the Trishuli powerhouse is shut down."

With both the Trishuli and Devighat stations closed for maintenance while the festival and dry seasons are coming up, electricity imports from India are set to increase unless new power projects roar into life.