The Bhutanese Leading the way.
As per reports from the Ministry of Energy and Natural Resources (MoENR), the water seepage issue in Punatsangchu Hydropower Project Authority II (PHPA II) near the control system has reduced.
The drilling of drainage holes around the pressure shaft bottom is ongoing, with 55% of the work completed so far. To prevent further seepage from reaching the control system, CGI sheet cladding has been installed, extending from the machine hall spring level to the turbine floor. About 80% of this installation has been completed.
There were concerns that if the seepage persisted, it could cause the control system to malfunction, potentially jeopardizing the operation of the two units that were exporting electricity. The Direct Current (DC) system, which powers control panels, sensors, and switches, also faced a ground fault issue. Ground faults, which occur when electricity escapes its normal route and flows into the earth, can lead to hazards such as shocks or fire risks.
The project has not reported any direct damage to the control system or electrical panels due to seepage and the ground fault in the DC system has been successfully identified and resolved without causing any electrical shocks, fires, or further malfunctions.
The project had also faced water shortages, impacting its ability to operate both units at full capacity. While one unit was running at full capacity, the available water inflow was insufficient to support both units. For full capacity operation of both units (170 MW), approximately 155 cubic meters of water was required, whereas the available inflow was only around 84-85 cubic meters.
Given that the project would face penalties if it did not maintain consistent electricity supply after its Commercial Operation Date (COD), the units were managed accordingly. One unit was supplying around 130 MW, and the other was supplying approximately 50 MW, totaling 180 MW as of early 2025.
MoENR stated that regarding power generation, the limited water inflow during the lean season has allowed only one unit to operate. The average power output for the past month was approximately 170 MW. MoENR noted that river inflows are at their lowest during January and February but are expected to improve from March or April onwards.
Despite the challenges, MoENR stated that the project has been managing generation schedules in accordance with guidelines and has not faced major challenges for inconsistent power supply. To prevent similar seepage and electrical issues in the future, drainage holes have been drilled in the tunnel leading to the auxiliary power system (APS) to tap seepage moving towards the powerhouse cavern walls and ceiling.
In a hydropower plant, an APS refers to a separate electrical system that provides power to operate the plant’s non-generating equipment, like pumps, valves, control systems, and lighting, essentially powering all the necessary functions to run the hydropower station itself, distinct from the main power generated by the turbines; it acts as a backup power source in case of a main power disruption.
MoENR also confirmed that the powerhouse cavern is being monitored through installed instruments, with the National Institute of Rock Mechanics (NIRM) analyzing data to ensure stability. Given the approaching monsoon season, the project has installed a CGI sheet false ceiling to protect electrical equipment, and no major issues are anticipated.
In terms of operations, the first two units have been running smoothly without significant challenges. Preventative maintenance is being carried out per the operation and maintenance manual provided by the Original Equipment Manufacturer.
Since the CGI sheet false ceiling on crown and cladding on walls were installed to protect the electrical equipment from seepage falling from crown and walls, the project does not anticipate any problem with regard to the upcoming monsoon season.
