Technical Information
The principal components of the Project consists of a main large reservoir impounded by a dam on the Xe-Namnoy River, a long underground waterway to develop a high head of some 650m, an open air switchyard and a powerhouse at the base of the Bolaven Plateau and a straight tailrace channel that connects the powerhouse to the Xe Kong River.
Supplementing the volume of water in the Xe-Namnoy Reservoir for power generation purposes is achieved by diverting the run-off from two neighboring sources, the Houay Makchanh and the Xe-Pian Rivers. The diversion is made in cascades which starts from the Houay Makchanh to the Xe-Pian catchment which likewise stores water from the Houay Namliang and thence to the Xe-Namnoy Reservoir. The structures for this diversion system are a bottom intake on the Houay Makchanh and a dam and intake in the Xe-Pian River. Two underground water conduits, one working under free flow from the Houay Makchanh to the Xe-Pian Reservoir, and the second one under both pressurized and free flow conditions from the Xe-Pian Reservoir to the Xe-Namnoy Reservoir, ensures the transfer of water to the Xe-Namnoy Reservoir.
From the Xe-Namnoy Reservoir, water is conveyed to the powerhouse units by means of a power intake, a 13.7 km. of low pressure headrace of concrete lined tunnel, 550m concrete lined vertical shaft, 1,300m of steel lined high pressure headrace tunnel, 750m penstock and steel water flow distribution manifolds. At the powerhouse, one Pelton and three Francis units are in charge of power generation. Plant output at rated net head is 410MW. After power generation, water is released into the tailrace channel which conveys the flow some 6 km. downstream and discharged to the Xe Kong River. Ninety percent of the power generated is exported to Thailand by a 500kV and 230kV transmission line and the rest to the local grid by a 115kV transmission line, respectively.
