All we knows that a transformer works as a heart of an electrical system and it is responsible for transfer the electrical energy from one place to another place with required voltage level.As we all knows that an electrical system can be divided in three parts which are as below :

a) Generation

b) Transmission

c) Distribution

As the name suggests above, Generation indicates the generation of electrical power through various resources like Thermal energy ,Wind enegry,Hydro energy etc. After generation of electrical power,it needs to transmit the same to final destination i.e user end. Before electricity is supplied at homes offices it travels a long distance from the power generation plant and this travel cost is most important and plays a vital role in the economy of any country.

Generally electrical power is generated at 11 KV level; current rating at this point is very high.Now if we plan to transmit the energy at this current level ,material cost will be on higher side therefore the voltage level when power leaves the power plant is very high to reduce the travelling cost of power .The power reduced to a lesser voltage  when it reaches the electricity poles which make it  less dangerous .Finally it reaches its destination such as the appliances we use at home ,where power transformers are employed to lower the voltage further down in order to bring it to a more manageable state for use.

Therefore from above we can divide the transformers in two parts one is Step Up Transformer and second one is Step Down Transformer.