Recent diagnostic technology on oil-immersed power transformers in Japan

There are two kinds of diagnoses about oil-immersed power transformers. One is the method to detect inner fault of transformers. The other is the method to estimate the lifetime of transformers. Many diagnostic methods on transformers have used decomposed components from organic materials in insulating oil. A new technology on diagnosis of transformers by using gas chromatograph mass spectrum was introduced. The high boiling point decomposed components are indices in this technology. This paper discusses transformer gas-in-oil analysis, and lifetime diagnosis.