In general, power stations and substations are complex systems, which consist of many components. The most important ones are:
Synchronous generators. Synchronous generators are used in power plants to produce electricity. Depending on the type of prime engine there are hydro generators and turbo generators
Power transformers and autotransformers (compensators). Power transformers converting voltage from one to another. Three-phase transformers have capacity from 220 kV to up to 1000 MVA, 330 kV – 1250 MVA, 500 kV – 1000 MVA.
Single-phase transformers are used less frequently, usually because it is impossible to manufacture a suitable three-phase transformer or to transport it to the place of future operation. Maximum capacity of the group of single-phase transformers for voltage of 500 kV is 3 * 533 MVA, voltage 750 kV – 3 * 417 MVA and voltage 1150 kV – 3 * 667 MVA.
Synchronous compensators. The synchronous compensator provides an optimal level of voltage in power system. Typically, it operates in motor mode with no load on the shaft with alternate exciting current. Depending on excitation current, synchronous compensator can give or take reactive power into/from the network