Incessant rain disrupts power generation at Tala

As intake tunnels gets clogged due to debris from the surging river, millions of revenues are lost in a day

By Tashi Namgyal

Tala Hydroelectric Plant suffered a daily revenue loss of around Nu 55 million since 6PM of July 19 when the plant had to be completely shut down due to debris from incessant rainfall over the past week clogging the gates of the intake tunnels.

On July 19, the generating units started to experience some problems in generating at full capacity.

The generating units were shut down after readings from the pressure gauges at the main inlet vaults were found to be slightly lower than rated. The remaining four generating units also tripped at around 6PM that evening, following the shutting down of two generating units before that.

Upon inspection, it was found that water outflowed from the adit tunnel to the dam desilting gates chamber accompanied by some noise when the generating units tripped. Some damages were also reported on the rope-drum hoisting mechanism and the supporting steel beam I-sections when the desilting gates got dislodged from their docking place.

Preliminary assessments pointed out that air suction into the water conductor system and choking at the dam intake gates was caused by pressure loss and consequent events.

It was ascertained when the intake gates were found clogged with debris which impacted the flow of water into the conductor system.

According to the Druk Green Power Corporation (DGPC), the plant is slogging off a daily energy generation of around 26 million units. Fueled by the monsoon rains and strong river currents, the plant would actually be generating at its peak of 1,020MW and an additional 10 percent overload capacity amounting to 1,122MW altogether.

This means that if the entire energy generated is to be exported to India, the revenue loss per day would accumulate to approximately Nu 55 million, officials from DGPC opined.

Resources from both Tala and Chhukha power plants have been amassed to clean the intake gates and to lower the reservoir level to get access to the intake gates, while the chambers are also being cleared of any debris to allow free flow of water into the headrace tunnel.

Project officials are however working to reinstate the six generating units which had been put out of operation. The energy generation will be restarted once the water flows freely from the dam intakes.

The main works of the project started in early 1999. Despite many adverse geological problems encountered in many components of the project and the extensive damages caused by the unprecedented rains of 2000, the first unit of the project was commissioned on July 31, 2006.

Meanwhile, hydropower sector in the country saw a significant growth in 2020 although other sectors of the economy suffered a severe blow from the Covid-19 pandemic.

Records with DGPC show Bhutan’s energy generation increased by almost 32 percent in 2020, exporting a total of 9,121 million units of electricity worth more than Nu 27 Billion.

With the six hydropower plants currently in operation, the country generated 11,364 million units of electricity in 2020 from 8,645 million units in 2019.