Study on the on-site heating method for large-scale power transformers

Moisture is one of the most important factors that can largely affect the insulation of large-scale power transformers, especially converter transformers. At present, the on-site drying method for the power transformers is still hot oil circulation method using vacuum oil filter, which costs a long time and has poor effect when the environment temperature is low. In order to meet the requirement of on-site heating for large-scale power transformers, short circuit method was proposed as the on-site drying method. The LV winding is short-circuited, and ac current equal to the nominal current is applied to the HV winding. The heat produced by the load loss can heat the winding insulation uniformly to the designated temperature uniformly so as to dry the insulation. A set of short circuit heating device was developed. The method and the device had been applied on the UHV converter transformer, and had achieved remarkable effects. All applications indicate that short circuit method is a proper method for on-site heating of large-scale transformers for its high heating efficiency and perfect drying effect.