147MW Patrind Hydropower Project
The run-of-river Patrind Hydropower Project has been constructed on river Kunhar. With a capacity of 147MW (Net), the Project shall generate, on average, 632 GWh of electricity annually during the concession period of 30 years. Since the Project has been developed by SHPL as an IPP, the SHPL has entered into a 30 year Power Purchase Agreement with National Transmission and Dispatch Company (NTDC), Pakistan's grid system operator, for the sale of electricity generated from the Project.
The Project is located on the boundary of Azad Jammu & Kashmir (AJ&K) and District Abbottabad of Pakistan, near the city of Muzaffarabad. The majority of the Project structures, including the powerhouse, are located in the territory of AJ&K. However, the diversion tunnel, flushing tunnel and a part of the weir are located within territorial limits of District Abbottabad.
The weir side of the Project can be reached through Boi Road on right side of river Kunhar at a distance of approximately 12.3 km from Garhi Habibullah, a small town in District Mansehra. The powerhouse side of the Project is accessible from lower Chattar, Muzaffarabad where a class 70 bridge has been constructed across river Jhelum as part of the Project for access to the powerhouse.
The Project diverts the waters of river Kunhar through a weir, located near village Patrind, and a left bank conveyance system of headrace tunnel to the right bank of river Jhelum, near the city of Muzaffarabad, where a powerhouse has been built. The natural difference of elevation between river Kunhar and river Jhelum, along with a 43.5 meter high weir provides a suitable head to set up a 147MW power project.
Major Project components include a weir structure, an upstream concrete cofferdam and a flushing tunnel for sediments flushing, an intake structure slightly upstream of the weir leading to the headrace tunnel. The headrace tunnel passes through a ridge towards river Jhelum. It connects to an underground surge shaft via link tunnel and further opens into vertical pressure shaft, which connects with a horizontal pressure tunnel. The penstock divides into three manifolds conveying design discharge to a surface type powerhouse located on the right bank of the river Jhelum.
Since river Kunhar is a river with high concentration of sediments, proper and effective sediment management scheme has been priority for SHPL. An Optimal Hybrid Desander System (OHDS)/ Rearranged Sandtrap has been preferred for the Project over any scheme involving surface or underground sandtrap. OHDS is composed of a flushing tunnel and a modified pool. Flushing tunnel of suitable dimensions (tested in numerical and physical modelling) is provided at upstream of the concrete cofferdam, located upstream of the weir, to flush out the sediments from the reservoir when the inflow is more than 200mᶟ/sec. The pond between upstream cofferdam and the weir will be used as the natural sandtrap for settling down particles The settled particles shall be flushed out using under-sluice radial gates provided in the weir structure. The OHDS scheme has been tested through numerical modelling by HR Wallingford and physical modelling at ETH, Zurich, Switzerland.
Sediment management system also relies on proper reservoir operation procedure. SHPL has prepared a comprehensive plan for reservoir operation, which has also been made part of the Operating Procedure of the Project in consultation with the power purchaser.
While the OHDS has been shown to be effective in managing sediments at the reservoir, SHPL has also opted for HVOF coating for its three 50MW francis turbines as added protection against adverse impacts of any particles flowing into the power intake.
The Project is connected to Pakistan’s national grid through 132 kV double circuit transmission line.