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Electrical installations comprise various sets such as electrical generators, transformers, electric motors and facilities for the transmission, distribution and delivery of electricity. These systems are vital for the operation of the plant; hence we take special care of each one.

The transformers are static electrical devices that transform voltage between two electrical circuits and are needed to adapt the voltage to the needs of the users. To connect to the transmission network, the voltage of the current from the generator must be raised to the voltage of the transmission system. In Slovenia, there are three levels of high-tension lines; 110kV, 220kV and 400kV, which transmit and deliver energy or supply large customers directly.

The transformer of the main line of the generating unit is located behind the generator and serves to transfer the electricity to the transmission network. The generator output also has a directly connected transformer that supplies the needs of the generating unit itself. We call this kind of device connection a generating unit circuit and its operation is both the safest and the cheapest.

At the Šoštanj thermal plant, we have different transformers, classified according to purpose: gen. unit output transformers, gen. unit own needs supply transformers and transformers dedicated to other general purposes and common devices. To supply electric devices and machines using low-voltage electricity, we have transformers which lower the voltage, for example from 10kV to 0.4kV, 220V or even lower.

Transformers also have their peculiarities and demand proper care. They are protected from internal electric errors and overheating. They are cooled by ventilation with the air from the environment or with the flow of oil from the oil reservoir through the water coolers. Smaller transformers have coil insulation provided by thermo-insulating materials and are air ventilated. 0.5 percent or more of the power output is lost due to the operation of the transformers.