The diversion tunnel of the 720MW Mangdechhu hydropower project will be plugged between September 15 and October 15. This entails filling the dam with the water and is usually the last activity in hydropower projects.
As of May 31 this year, 96.5 percent of the works have been completed including the transmission lines.
The project’s managing director, A K Mishra said that long-term data of Mangdechhu River reveals a discharge of 100 cumecs (cubic meters per second) during monsoon. By mid September, he said it drops to 58 cumecs, which is more manageable to control the water discharge in a channelised manner.
After filling the dam, the intake tunnels will be opened, diverting the water into the desilting chamber and then to the headrace (HRT) tunnel. “It will take 15 days to fill the tunnel,” he said.
“After filling the pressure shaft and surge shaft with water, each turbine would be tested, one by one,” A K Mishra, said. “Similarly each machine will have to be synchronised with the Indian grid.”
The whole process will consume about a month. “If everything goes smooth, commissioning date of November is achievable,” he added.
All major civil, hydro-mechanical, electro-mechanical and transmission lines & its ATS of Mangdechhu Project are nearing completion.
Concrete lining works in the headrace tunnel is currently ongoing. About 94.6 percent of the works in the HRT is completed. The remaining work is expected to complete by August end. The HRT Concrete Lining works is getting affected due to the financial crunch and shortage of skilled and unskilled workers. Eight gantries are deployed in the HRT to expedite the work.
In the dam, 99.7 percent of the works are completed. The intake tunnel and disilting chambers are already completed last year. In April this year, installation of floodgates began and is progressing smoothly.
Works in the powerhouse are also nearing completion with a physical progress of 95 percent of the electromechanical component as of May 31. The powerhouse cavern itself is a size of an eight-storied building. All four transformers have already reached the site.
The third revised cost estimate of Nu 52.709B at December 2017 price level was submitted by the MHPA management in March this year to the government of India. As of May 31, the project has received Nu 45.35B from GoI, of which Nu 44.3B has been spent.
After commissioning, the project will generate 3B units of energy in a year.
“As per the data available, Mangdechhu Project if compared with the contemporary Hydroelectric Projects recently commissioned, is the cheapest and also executed in the optimum time frame in-spite of difficult terrain and logistics,” A K Mishra said.
Mangdechhu project transmission lines will also be transmitting the power of 118 MW Tansibji Hydro Project after its commissioning to Alipurduar Sub-station, West Bengal.