Fungsi utama dari kekuasaan transformer is to transmit electric energy, so the rated capacity is its main parameter. Therefore the power transformer in the substation is also playing the same role and the transmission of electrical energy power transformer is one of the main equipment of power plants and substations. The role of the transformer is various, not only can raise the voltage to send electrical energy to the area of use, but also to reduce the voltage for all levels of use. Therefore, the power transformer in the substation plays a relatively important role in the working system of the substation.