6.2.4.4 Control equipment

SHP schemes are normally unattended and are operated through an automatic control system. Because every power plant is different, it is almost impossible to determine here the extent of automation that should be included in a given system. Automatic control systems can significantly reduce the cost of energy production by reducing maintenance and improving reliability, while running the turbines more efficiently and producing more kilowatts from the available water.

A governor that usually controls a turbine is a combination of devices and mechanisms that detect speed deviation and convert it into a change in servomotor position. Governors can be mechanical or electronic. In the mechanical type, the speed sensor is a fly-ball mechanism that controls a hydraulic oil system to operate, through servomotors, the guide vanes or the runner blades. Electronic governors control the turbine through power amplification stages, which normally incorporate a hydraulic power unit. If the generator is connected to a large network, the network provides frequency regulation and a governor is unnecessary.

On the other hand, in every country the electricity supply regulations place a statutory obligation on public electric utilities to maintain the safety and quality of electricity supply within defined limits. Switchgear is then required to control the generators and to interface them with the grid or with the isolated load. It must provide protection for the generators, main transformer and station service transformer.