All About Distribution Transformers

Distribution transformers are used commonly in the electrical system. These transformers are responsible for the final voltage transformation in the system. Since it is where the voltage is stepped down to meet domestic requirements, the distribution transformer is an essential part of our own consumption. Distribution transformers India can be pole-mounted or placed underground.

A distribution transformer is converts high voltage electricity into lower voltage, making it viable for residential or commercial purposes. It is an electrical isolation chamber. It has two main functions:

  • To step down the voltage
  • To provide isolation between primary and secondary.

Because it converts the electrical energy into a form that is usable, distribution transformers are found in almost every consumable electrical system. In other words, every appliance we have, gets it energy only after it has been routed through a distribution transformer. The number of transformers will depend o the area of coverage and the number of users within. In urban areas where we have dense population distribution, one transformer may serve a number of households. In isolated areas where households are more scattered, the number of houses served by one transformer may be much smaller. A large industrial or commercial compound, on the other hand, may have multiple transformers.

Functions of distribution transformers:

Some specific function for distribution transformers include:

  • Domestic power supply
  • Pumping stations where the voltage level is low
  • Power supply for the railways
  • Power supply for industrial and commercial purposes.
  • At power generating plants like wind farms

Types of distribution transformers:

There are different ways of classifying distribution transfers. They could be classified according to location, insulation, phases, voltage and BIL.

According to location:

The transformer could be above ground or it underground. If it is mounted on a utility pole, it is known as pole-mount transformer. Transformers on ground are installed on concrete pads. These are known as pad-mounted transformers. Finally, there are the underground transformers that are located under the earth.

Type of insulation:

The insulation in the transformer can also vary. There are two broad categories here – dry type and liquid immersed. Liquid immersed transformers usually use oil for cooling and heating. Dry type transformers, on the other hand, are air cooled. The dry transformer is compact in size and hence, easily mounted. It also requires minimum servicing, capable of running for long periods without servicing. This is why a dry type transformer is considered safer and more efficient in certain settings. It is the more commonly found transformer in an indoor location.

Nature of supply:

The type of electrical supply is another way of categorizing these transformers. A Transformer oil purification can be single phase three phase. A single phase transformer one conductor and one neutral wire where a three phase transfer has three conductors and one neutral wire. The single phase is used where the power requirement is not heavy, such as for domestic use. A three phase transformer is used when we need a large supply of power, such as in a large industry.


Transformers can also be categorized according to voltage level – low or medium voltage. Low voltage transformers are used to step down voltage quite low, while medium-voltage output is a bit higher. So, a low voltage transformer could be used for a domestic appliance, while a medium voltage transformer is installed for higher output.

Selecting a distribution transformer for domestic use

When it comes to domestic use, we are looking for transformers that are suitable for low voltage networks that range from 50 to 2500 kVA. There are some essential criteria:

Operational safety:

We have to ensure that the transformer has gone through proper testing for operational safety. There are certain specific tests to ensure this. Routine tests are done for voltage test and losses. Type testing is for heating and surge testing. For noise generation and short circuit strength, you can conduct special tests.

Electrical conditions:

Find out about the short circuit voltage and the transformation ratio.


The location of the transformer while have an impact on how we mount it. Is it indoor or outdoor? Are there environmental conditions that we must factor in, such as a shed in outdoor locations to protect the transformer from rain? Are you allowed to mount the transformer in said location as per rules?

Operating conditions:

The factors we must consider here are the estimated hours of operation, loading capacity, fluctuations, efficiency and voltage requirement. You should also find out if there is a parallel distribution transformers India servicing the same area.

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