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.