Development of the portable decomposed gas analyzer for gas insulated transformers

Gas insulated transformers are usually installed at underground substations located in the urban area, and it is worried that abnormalities caused by the progress of deterioration may soon start to appear as 30 years have passed since the first gas insulated transformer was installed in Japan. Therefore, the diagnostic technique without stopping the gas insulated transformer operation has become necessary. Authors focused on decomposed gas components in gas insulated transformer: F^-, SO₂ and CO, and have developed and introduced an in-vehicle decomposed gas analyzer with gas sensors that has been used as the primary equipment for diagnosis of gas insulated transformers since 1993. The necessity of prompt arrival at small substations in case of accidents, as well as the demand of higher diagnostic accuracy, has been increasing recently. Thus, authors have newly developed a decomposed gas analyzer, which applies the standard criteria for decomposed gas. This analyzer is so portable that a person can carry on the shoulder. The performance of this analyzer was verified through field tests of transformers in service. This has resulted in an establishment of diagnostic system for gas insulated transformers.