A transformer substation is a device designed to convert the electrical energy of one voltage into the electrical energy of another voltage. The main element of each substation is a three-phase transformer.
The basis of the transformer is a closed magnetic circuit, consisting of three rods. There are two windings on each transformer rod. The transformer winding, to which the supply voltage is supplied, is called primary, and the winding to which the load is connected is called secondary.
The principle of operation of the substation transformers is based on the phenomenon of mutual induction. When the primary winding of the transformer is connected to an alternating current network, the current begins to flow through the winding, which creates an alternating magnetic flux F. In the core, penetrating the coils of the secondary winding, the flux induces an EMF U2 in it, which can be used to power the load.
- where w is the number of turns of the primary and secondary windings.
- For k> 1, the transformer is step-down, and for k <1 it is step-up.
- three phase transformer
Three-phase power transformer:
During the operation of the transformer due to currents in the windings, magnetization reversal of the magnetic circuit and the presence of eddy currents, heat is generated in it. Therefore, in powerful transformers, a magnetic circuit with windings is immersed in a tank filled with transformer oil. Oil removes heat through convection or forced circulation. To increase the cooling surface, steel pipes or radiators are welded into the walls of the tanks. Transformer oil not only cools the transformer, but also serves as a good insulator. Low power transformers (up to 10 kV-A) are air-cooled.
Figure 2 shows the main characteristics of power transformers. It can be seen from the figure that there is a certain load power at which the efficiency of the transformer is maximum. This power is called the rated power of the transformer. Since the transformer windings have resistance, the voltage on the secondary winding depends on the transformer load and is equal to the rated voltage only at the rated load power. With a decrease in load, the voltage increases, and with an increase, it decreases.
In addition to the transformer, the necessary switching equipment, control and metering devices are installed at the substation.
Transformer substations are distribution and consumer. In distribution (district) substations, electricity is transformed from a voltage of 500 kV to a voltage of 110 kV, and in consumer substations, from 10 kV to 380/220 V and supplied directly to consumers.
By design, consumer transformer substations are open (outdoor) and closed. The design of the substation depends on the power of the transformer. With low power, mast substations are used when a transformer and all equipment are placed on a pole. With a transformer power of more than 100 kV · A, in stand-alone brick or metal buildings, complete transformer substations of the KTP type are installed, which are fully assembled at the factory and delivered assembled.