Power: The two power outages on March 15 and 16 that left the western parts of the country in darkness for an hour caused no revenue loss, said Bhutan Power Corporation (BPC) officials.

Nine western dzongkhags lost power supply for about an hour on March 16. On March 15, power outage lasted about half an hour.

BPC officials said that the valves of water tunnels to turbines automatically shut, cutting the flow of water. This is a typical case in winter.

“So, there is no loss in generation of power or revenue,” said Ujjwal Deep Dahal, Bhutan Power System Operator’s General Manager.

“The outages were result of system disturbance on the Indian grid due to which the operational system of the power plants were constrained,” said Ujjwal Deep Dahal.

BPC was carrying out scheduled outage for maintenance of the transformer at Malbase near Phuentsholing because of which the restoration of the power system took some time, he added.

The Indian and Bhutanese grids operate at the same frequency. When the larger system shuts down or falls in frequency, the other system does not function.

“It’s better to shut down the system because it could lead to a much larger damage to the system,” Ujjwal Deep Dahal said.

The transmission lines connected to the Chukha hydropower plant were disturbed and disrupted power connections in the dzongkhags.

“We have to restore the system together with the Indian authorities in Delhi and Chukha hydropower plant, which takes time,” he said.

“They’ve been very cooperative.”

Basochhu hydropower plant came back faster than Chukha to light some parts of the city.

BPC officials said that usually most of the transformers undergo maintenance in winter, which could add pressure the other transformers in operation, causing them to fail.

The latest outage is the first of such duration in the past three years. The longest power outage was in 2012 that lasted about six hours.

On both occasions, the eastern region had uninterrupted power supply. There were no complaints from any industries.

Tshering Palden