Hydroelectric Generator

Overview

A hydroelectric generator converts the potential energy of stored water into electricity. Water falling through a head of about 120 m drives a Francis reaction turbine, which spins a vertical synchronous generator producing 50 MW at 11 kV. The Francis runner suits medium-head sites and extracts energy from both the pressure and velocity of the water as it passes through. The unit runs at a fixed 300 RPM to deliver 50 Hz from its 20-pole generator.

Construction

Water enters through the Main Inlet Valve, the main shutoff that isolates the unit for maintenance, then passes into the Francis Water Turbine. The spiral casing distributes flow evenly around adjustable wicket gates, which meter water onto the runner; the runner's curved blades turn the flow's energy into shaft torque before the water exits down the draft tube.

The turbine shaft drives the Synchronous Generator, a vertical synchronous machine whose excited rotor poles induce three-phase voltage in the stator. Rotating mass is supported by the Guide & Thrust Bearing Assembly assembly, which carries both the radial guide bearings and the thrust bearing that bears the entire rotating weight plus hydraulic down-thrust. A Main Shaft Seal prevents water leakage where the shaft passes out of the turbine.

Output power is delivered through the Generator Busbar Terminal to the step-up transformer. Speed and load are regulated by the Hydraulic Governor, a hydraulic actuator that positions the wicket gates to hold frequency as load changes, supervised by the Control & Protection System protection system.

Auxiliaries keep the machine healthy: the Cooling Water System system removes heat from the generator and bearings, the Lubrication System supplies oil to the bearings, and the Foundation & Pit Liner pit liner anchors the unit in the powerhouse.