Most of large power transformers are inflated during transportation due to the large weight. If the transformers could not be installed on time

it is quite possible for them to be affected by moisture during the long time storage. In this research

a winding heating method of low frequency current is applied in a certain 500 kV transformer by choosing appropriate voltage and frequency combined with certain parameters.After the heating

the transformer has made significant improvements in multiple insulation parameters which safeguard the normal operation of nuclear power plant. The result shows that the winding heating of low frequency can solve the problem of transformer affected with damp efficiently. Therefore

it also provides abundant references for similar issues in the future.