Abstract: This paper introduced the working principle of oil discharge and nitrogen injection fire extinguishing device of oil immersed transformer and described the shortcomings of the traditional oil discharge and nitrogen injection fire extinguishing device based on the heavy hammer mechanism. In view of the shortcomings of traditional oil discharge and nitrogen injection fire-extinguishing device, a design scheme of oil discharge and nitrogen injection fire-extinguishing device based on pneumatic was proposed. The pneumatic ball valve was used as the oil drain valve and nitrogen injection release valve to solve the problem of oil and nitrogen leakage in the oil discharge and nitrogen injection fire extinguishing device. The combination of pneumatic and electric control mode can effectively reduce the risk of misoperation of oil discharge and nitrogen injection fire extinguishing device. The sealing diaphragm is added in the oil discharge pipeline, which effectively guarantees the sealing of the oil discharge pipeline, and at the same time, it can realize the effective simulation operation of the system. Thus, the operation safety and reliability of the oil immersed transformer oil discharge and nitrogen injection fire extinguishing device are improved.

Key words: oil-immersed transformer, pneumatic, oil dischargeand nitrogen injection, fire extinguishing-equipment