MHPA awaits grid sync

May 9 | Kuensel
By Nim Dorji, Trongsa

While one unit of the 720 MW Mangdechhu Hydro Power Authority (MHPA) has successfully tested, a temporary arrangement has been made to evacuate power to India using the transmission line of Punatshangchhu I and II.

This is because the transmission lines in the bordering Indian state of Assam, spanning 45KM, falls in the Manas Tiger Reserve. The project’s Managing Director, A K Mishra said that the Assam government took some time to resolve the issue. “But it will be ready in a few months’ time,” he said adding that for the time being, power would be transmitted through Punatshangchhu lines via Lamoizingkha to Alipur Duar.

The project, he said will take over the transmission lines from Bhutan Power Corporation and would be handed back after the commissioning. Counterparts in Alipur Duar were also asked to charge the lines. “Once the frequency matches, grids would be synchronised and power would be exported,” A K Mishra said.

The joint managing director of the project, Chencho Tshering said that the circuit testing was successfully carried out. Each unit, which is capable of generating 180 MW produce 13.8 KV of current. This was further stepped up with the help of transformers to 400 KV.

“We achieved the required voltage. It is a good sign of successful commission,” Chencho Tshering said.

Testing of generating units was carried out prior to filling the reservoir, by diverting a seepage into the pressure shaft.

While testing the water conductor system, including the intake tunnel, headrace tunnel and tailrace tunnel, three minor leakages were spotted at the adit tunnels.

Adit tunnels are tunnels excavated to access the central point from where the hydro tunnels like headrace and tailrace tunnels are constructed. After the construction of main tunnels, adit tunnels are plugged and concreted.

The joint managing director said the leakages would be repaired by dewatering the tunnel. Draining of water from the tunnel began on May 7 and three meters of water is being depleted every day. This will take 27 days.

In adit-5, A K Mishra said that there are 135 bolts of which four bolts were broken. This resulted in small leakage and that the project is rectifying those. “This is nothing new in a project of such magnitude,” he said.

Simultaneous to the rectification works, he said testing of other units would be done. The butterfly valve chamber below the two pressure shafts will be filled with water and the mechanical testing of unit three and four will be carried out.

Dewatering from the HRT is a critical job and if it is not performed as per the guideline, there are chances of crack and collapsing of the tunnel.

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