Transient processes and optimization of HPP hydraulic structures

Abstract

In the scope of Hoabinh HPP extension an additional powerhouse is being designed on the common reservoir with two units 240 MW each and two pressure tunnels 765-785 m long. Due to unfavorable geological conditions the design organization made the decision to abandon the construction of the compensating reservoirs on the tunnels. To reduce the hydraulic hammer the current speed in tunnels was decreased to 3 m/s which is half as much of the speeds normally accepted in energy conduits. The article presents a set of calculations of transient processes required for feasibility study of decreasing the internal diameter of the head conduit in abandonment of the construction of the compensating reservoir. The calculations were performed using the specialized program of calculations of the transient processes of HPP. There were considered the processes of load rejection, frequency regulation in allocation to the isolated energy district and power regulation at constant frequency in the power grid. There is presented the system of limitations of the parameters of transient processes which permitted to justify the decrease in the internal diameter of the conduit from 11.5 to 10.5 m. It is shown that with decrease of the pressure tunnel diameter there are fulfilled the given guarantees of regulation in pressure and in rotation frequency, the conditions of fluctuation stability in frequency regulation, specific speed of power regulation.