The Bhutanese Leading the way.
On 15 May 2025 Unit IV of the 1,020 MW Punatsangchu II project had to be shut down during the trial run due to overheating.
The project has 6 units of 170 MW each and is currently generating power on 3 commissioned units of around 500 to 560 MW.
An official of the Ministry of Energy and Natural Resources (MoENR) said, “After the assembly and erection of Unit IV, the machine was subjected to trial operation to check for vibrations and to stabilize the bearings. During mechanical spinning, a rising trend in bearing temperature was observed, indicating the need to review the bearing gap settings. Consequently, the bearing housing must be overhauled to adjust the thrust and lower guide bearing settings.”
The bearing plays an important part for the unit to be able to spin at high speed, and so any heating of the bearing is an issue.
A source said that the targeted date is to get the unit up by 25 May but this is uncertain.
An official said that considering the quantum of work involved, such as draining and refilling, approximately 12,000 liters of oil, removal of oil coolers and bearing setting from the unit, the activity is expected to take around 5 to 6 days.
Following the necessary rectifications, the unit will be put into trial operation. Once the bearings and vibration levels stabilize, the unit will proceed to the next phase of electrical testing.
The Bharat Heavy Electricals Limited (BHEL) that supplied the units has staff at the site who is involved in the repair work. The exact cause of the issue will be given in a separate report later.
The MoENR official assured there will be no revenue loss as the machine is still in the testing phase and has not yet been cleared for commercial operation. Moreover, the current river discharge is only sufficient to operate three units.
The generation of three units varies and is regulated by Bhutan Power System Operator (BPSO), based on the system demand, grid requirements and as per river inflow. Currently, each of the three units is generating between 170 MW or to a 10% overload of 187 MW each.
In terms of the commissioning plan for the remaining units, the official said the project is making all out effort to commission the remaining units as soon as possible.
“Considering the quantum of works involved and quality requirements, and assuming no unforeseen issues arise during erection and testing of the remianing units, the project is targeting to commission all units by September 2025 in all respects,” said the official.
The above is the official timeline. Another MoENR official said the internal timeline or aim is to get the Unit IV online by 25 May, commission the Unit V within June and get the Unit VI commissioned by July 2025 leading to full generation of 1,020 MW or even more.
