… the plant is expected to resume operations today

MB Subba 

The 1,020MW Tala hydroelectric plant has been completely shut down since 6pm of July 19 with a daily revenue loss of around Nu 55 million (M).

Large chunks of debris due to continuous rainfall during the past few days clogged the gates of the intake tunnels.

At this time of the year, the Tala power plant with the monsoon rains would be generating the rated capacity of 1,020MW and an additional 10 percent overloading capacity, altogether amounting to 1,122 MW, according to the Druk Green Power Corporation (DGPC). This is equivalent to a daily generation of about 26 million units.

“If one were to consider that 100 percent of the generation from Tala to be exported to India, the daily revenue loss would be approximately Nu 55M,” DGPC managing director (MD), Dasho Chhewang Rinzin said.

However, officials are working round the clock to complete the restoration works at the dam intake gates. The DGPC MD said that all six generating units had been out of operation and that only once the free flow of water is restarted from the dam intake gates, generation will be restarted.

The project had planned to start filling the reservoir by late night yesterday.

Dasho Chhewang Rinzin said that power generation would resume today if things go as per the plan. Electricity generation in the country’s biggest plant would have been shut down for three days if generation resumes as expected.

The DGPC MD said that the accumulated debris that was clogging the intake gates were being cleared and the debris in the desilting gates chamber are also being cleared. He said that on July 19, the Tala generating units started to experience some problems in generating at full capacity.

Since the pressure gauge readings at the Main Inlet Values were found to be slightly lower than rated, the generating units were shut down, according to him. After shutting down two of the generating units, the remaining four generating units also tripped in the evening at around 6pm, he added.

“When the generating units tripped, there was water outflow from the adit tunnel to the dam desilting gates chamber accompanied by some noise,” he said. On inspection, it was found that the desilting gates had been dislodged from their docking place with some damages to the rope-drum hoisting mechanism and the supporting steel beam I-sections.

On the causes of the damage, the DGPC MD said that from the review of the sequence of events, it appeared that the penstock pressure loss and subsequent events could have been caused by air suction into the water conductor system due to choking at the dam intake gates.

“To ascertain this, the Tala reservoir was emptied to get access to the intake gates. On completing the lowering of the water level in the reservoir, the intake gates were found to be clogged with debris thus impacting the flow of water into the water conductor system,” he said.

All resources of Tala and Chhukha power plants have been mobilised for cleaning of the intake gates and to lower the reservoir level to get access to the intake gates. The desilting gates chamber is also being cleared of any debris to allow free flow of water into the headrace tunnel.

The DGPC MD said that the desilting gates, rope-drum hoisting mechanism and the supporting structures will take some more time to restore but these are required only for maintenance works and not for operating the powerhouse.

However, he added that there are no problems with the generating units. “The problem is with the dam intake gates only, which are being cleared of the accumulated debris to allow free flow of water into the water-conducting system.”

While almost all the sectors of the economy took a severe hit in 2020 due to the Covid-19 pandemic, hydropower saw significant growth with energy generation increasing by 31.45 percent.

According to DGPC, the country exported a total of 9,121 million units (MU) of electricity worth more than Nu 27.042B in 2020.

The total generation from the six hydropower plants that are in operation increased to 11,364 MU in 2020 from 8,645 MU in the previous year.

Edited by Tshering Palden