An electrical substation is a part of electric energy conversion and distribution system. Substations are designed for all voltages. They convert voltage from high to low and in reverse.
The electrical network defines the purpose, power and voltage of substations. The loads depend on the consumers. Let’s consider the main types of substations.
Converter stations are used to transmit and receive high voltage current. The main purpose of traction substations is to convert power for public utilities. Transit traction substations convert power for consumers, and transmit the power in the network to neighboring power systems. Intermediate substations convert power to their customers. Terminal substations are positioned near high-voltage lines.
Depending on the design there are indoor and outdoor substations. Outdoor substation equipment is located outdoors. Indoor substations equipment is reliably protected from adverse weather conditions indoors.
Substations for voltage of 6-10 kV are located in cities, towns and villages. They are serviced by mobile service crews.
Substations for voltages of 35kV, 110kV and 220 kV use low voltage controls and distribution gear. Their control panel and alarm is located on the front of the cabinet. These stations do not require constant presence of staff, and can be serviced by mobile service crews or an operator on duty. This is a common type of substations.
Indoor substations with high voltage of 110-220 kV are usually built in densely populated areas in large cities. They bear large electrical distribution loads and have a constantly operator on duty, also they should have noise isolation protecting the local population from the noise generated by the transformers.
Substations with higher voltage of 800 kV and 1500 kV have a large number of complex conversion equipment. They are fewer in number, compared with the other substations listed above.