Experimental Study on Gas Relay Operation Characteristics of On-load Tap Changer

In recent years, there are many accidents of gas protection misoperation caused by normal switching of on-load tap changer. In order to explore the cause of misoperation, an experimental platform for the study of gas relay action characteristics was built based on 2XCMDI-1000/126C-10193W on-load tap changer. Different working conditions were made inside the tank by means of pressure injection by air compressor, and the operation characteristics of different types of gas relay under various pressure and oil flow conditions were tested. By comparing and analyzing the experimental results, it was found that with the increase of the pressure value of the pressure source, the oil flow velocity corresponding to the action time of the baffle-type gas relay used in the on-load tap changer had a gradually decreasing trend, while the oil flow acceleration increased gradually. Based on the theory of fluid mechanics, it is considered that the action of baffle in gas relay is the result of the combined action of "dynamic pressure" corresponding to oil velocity and "static pressure" in insulating oil liquid. This also partly explains that the gas protection of on-load tap changer misoperates when the oil flow velocity does not reach the setting value.