Dalian No.1 instrument transformer Co., Ltd.,(DYH hereafter) former Dalian No.1 instrument transformer works, was founded in 1972, which is a Chinese leader in instrument transformer with more than 1500 employees and more than thirty years manufacturing history. The enterprise occupies an area of 150,000m2, the building area is 80,000m2.DYH's headquarter located in Dalian is the manufacture base of high voltage instrument transformer, medium voltage instrument transformer, insulated busbar, vacuum breaker and other power equipments. The sub-company and branch company located in Xiamen in China, Shanghai in China are mainly manufacturers and provide medium voltage series current and voltage transformers.With more than 180 engineers, the technical center in Dalian is responsible for MV and HV products, long term development and research of new products and new technique, and also provide technical support to all subcompanies and branch companies.The company has advanced epoxy resin vacuum casting production line, oil-immersed and SF6 gas insulated high voltage production line, epoxy immersed paper insulated busbar production line and silicone rubber composite material dry type wall bushing production line. Also the company has established medium and high voltage (instrument transformer, fully insulated busbar) insulation test lab, epoxy resin material and molding part physical-chemical test lab, oil and gas insulation test lab, which are all equipped with advanced domestic and foreign test equipments and have the ability of processing the test about corresponding material and technical research. The high voltage test lab is equipped with 1100kV power frequency test transformer and 3000kV impulse voltage generator, which has the ability of processing all type tests except rated dynamic and thermal current for 500kV and under 500kV instrument transformers.The major products include 0.5~500kV current and voltage transformer, 6~35kV vacuum breaker, 35kV and under 35k