This paper analyzes and discusses the partial overheating problem affecting normal operation of Primary evaporator' s heater from the aspects of reasons and harmfulness, and proposes the corresponding control countermeasures.

In this dissertation, a research is made not only on the 3D steady and transient eddy current fields in large transformers,but also on stray losses, the local overheating as well as the mechanical strength of structures after the occurrence of sudden short circuit, using electromagnetic theory and modern numerical methods.

The causes are H2S corrosion and partial overheat.

Since the 500 kV parallel reactors that are made in China or in Japan for the Gezhouba Power Plant were put into operation, the local overheat has occurred in every reactor.

The results showed that plunger bushing took place local overheat in heating process.