SDJD-100/350 potential equalizer is used to provide lightning protection for the erected and surface regional overhead ground wires of railway system, and prevent against the outdiffusion of stray current and the connection between the ground-terminal equipment of overhead contact system and the grounding grid in case of lightning instant short circuit. It can apply to the equipotential connection of protective grounding, anti-lightning grounding, functional grounding and other independent systems, as well as to the bridge connection or grounding of disc insulator and insulating flange in cathodic protective pipeline. The product has the features of high discharge capacity, reliable protection, fast response, excellent insulation performance, long service life and good sealing performance. According to demand, it can also be configured with no residual voltage counter to record the number of actions. Featured by reliable protection performance and stable operation, the product has been widely used in the rail transit systems of major cities such as Shenzhen, Nanjing, Changsha, Chengdu, Guiyang, Hangzhou, Qingdao and Zhengzhou, as well as a number of petroleum pipelines of PetroChina Co Ltd.