Gas protection is the main element in transformer internal fault. It is better for transformer interturn, interlayer short circuit, iron core fault, branch pipe internal fault. When the back of oil immersed transformer fails, the arc make insulation material break down to create abundant gas. The gas protection make use of gas relay of reactant gas condition to protect the transformer internal fault.
In the gas keep relay, the top is a sealing keg float, the bottom is a metal baffle. Both of them are equipped with sealing quick silver junction. The keg float and baffle could revolve around each axis. When it operate normally, the interior of keep relay is filled with oil and the keg float in the oil which is in the place of come-up, the quick silver junction open and the baffle droop, the quick silver junction also opens. When there is a slight fault in the transformer, the gas production speed is relatively slow. On the way of rising to the oil storage tank, the gas is first stored in the upper space of the gas relay, so that the oil level will drop and the keg float will drop accordingly to make the mercury contact close and put on the delay signal, which is the so-called light gas.