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Home / Download Center / Electrical Engineering Books and Technical Guides / Power substation guides / The basics of power transformers in electrical T&D grids

Introduction to power transformer

A transformer is a four-terminal device that transforms an AC input voltage into a higher or lower AC output voltage. It transforms power from a particular circuit to another with no frequency changes regardless of the voltage levels.

The essentials of power transformers in electrical transmission and distribution grids
The essentials of power transformers in electrical transmission and distribution grids

Transformers are important component in our current life and they make large power systems possible. To effectively transfer hundreds of megawatts of power over long distances, very high line voltages are required – in the range of 161 to 1000 kV. However, the highest practical design voltage for large generators is about 25 kV.

How can electrical power be generated at 25 kV and transmitted at a much higher voltage?

Transformers can provide the solution to this problem. They can step voltages up or down with a very small loss of power. Connecting a step-up transformer between the generator and a transmission line allows the creation of a practical design voltage for the generator and at the same time an effective transmission line voltage.

With step-down transformers connected between the transmission line and the various electrical loads connected to it, it is allowed to use the transmitted power at a safe voltage.

Without them, it would be impossible to develop large power systems that exist today.

The essentials of power transformers in electrical transmission and distribution grids
Figure 1 – Typical power transformer

The transformer consists of three main components: primary winding, which acts as an input, the second coil secondary winding, which acts as the output, and the iron core, which serves to strengthen the magnetic field generated.

Transformer has no internal moving parts, and it transfers energy from one circuit to another by electromagnetic induction. External cooling may include heat exchangers, radiators, fans, and oil pumps. Transformers typically used because a change in voltage is needed.

Power transformers are defined as transformers rated 500 kVA and larger (In figure 1 is shown typical power transformer).

Transformers transfer electrical energy between circuits completely insulated from each other and this allows using very high (stepped-up) voltages for transmission lines, resulting in a lower (stepped-down) current. Higher voltage and lower current reduce the required size and cost of transmission lines and reduce transmission losses.

They do not require, as much attention as most other devices. Nevertheless, the care and maintenance, which they really require, is absolutely necessary.

Because of their reliability, maintenance is sometimes ignored, which reduces service life and sometimes outright failure.

Title: The basics of power transformers in electrical T&D grids (Bachelor’s Thesis) – Aidana Ibatullayeva, Faculty of Electrical Engineering, Power Engineering Department
Format: PDF
Size: 2.2 MB
Pages: 52
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The basics of power transformers in electrical T&D grids
The basics of power transformers in electrical T&D grids

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