In hydropower stations, water is the source of energy and electricity is the target of production. The electrical system is the main facility for the rational conversion, transmission and distribution of energy. Generally, the hydropower station's electrical system can be divided into hydro generator, generator voltage equipment, main transformer , high-voltage power distribution equipment and power supply system, grounding system and other parts, as shown in the solid line box below. Hydrogenerators and electrical main wiring are the same as the heart and aorta of the electrical system. Turbine generator Turbine output of rotating machinery can be converted into electrical energy, is the source of hydropower output power. Large hydro-generator efficiency generally up to about 98%. At present, China has put into operation the maximum capacity of hydro-generator 889MVA. The main electrical connection is to connect hydro generator, generator voltage equipment, main transformer, high-voltage power distribution equipment, power system and other functions together in an appropriate way so as to realize the functions of transmitting, boosting, collecting, distributing and sending of electric energy . The generator voltage equipment transmits the energy generated by the hydroelectric generator to the main transformer. The return current has the characteristics of high voltage and large current. The power supply system is usually connected to the power supply system of the plant, the excitation unit of the generator and the like. Has been put into operation hydropower station voltage level up to 24kV. Taking into account the hydropower station to participate in peak regulation, frequent unit switching and other factors, hydro generator outlet often installed generator circuit breakers . Large-capacity generator voltage loop of the connecting conductor is usually used to close the busbar. Main transformer is a combination of generator voltage equipment and high-voltage power distribution device, the generator voltage is raised to the transmission voltage to reduce the transmission current, thereby effectively reducing transmission losses and material costs of the grid. Under normal circumstances, the larger installed capacity, the transmission distance, the higher the transmission voltage. At present, China's hydropower transmission voltage level up to 750kV. The high-voltage power distribution unit is used to collect the electric energy sent from the main transformer and send it out to the power system through the outgoing line, mainly including open distribution equipment, gas-insulated metal-enclosed switchgear (GIS) and hybrid power distribution equipment. Due to the fact that hydropower plants are mostly located in mountain valleys and high voltage power distribution facilities are often restricted, the GIS with the highest reliability and the most compact layout but with the highest cost has become the first choice of high voltage distribution equipment for hydropower stations in China and its highest voltage level has reached 800kV. High-voltage power stations for hydropower stations usually use high-voltage power cables or gas-insulated metal enclosed transmission lines (GIL). The power supply system of the plant obtains the power supply from the unit, the power grid, etc., and provides power to the load (point) of the power station such as unit operation, lighting , public facilities and dam area electrical equipment according to the requirements of the power utilization facilities. Grounding system to ensure the normal operation of the hydropower station electrical system and personal, equipment safety, hydropower station grounding system to take full advantage of the reservoir water, underwater steel structures and natural grounding to reduce the grounding resistance. The power system of the plant and the earthing system are important safeguards for the safe, reliable and economical operation of the hydropower station. The equipment and wiring are widely distributed in all parts of the hydropower station.