The Arcing Fault Analysis And Reinforced Design For 27.5kV Voltage Transformer

The voltage classes are different in the transmission & distribution system so we need to make relevant low voltage voltmeters and other equipment according to the values of voltage for measurement and to measure voltage in this system.The voltage transformer is one of the electrical element parts which can transform high voltage to low voltage in electric power system.Nowadays,current voltage transformers operated in Chinese railway lines include traditional oil-immersed type,SF6 gas insulated type,Epoxy electric-magnetic and so on.However,the safety of the operation of high-speed rail power grid is so serious because of the overvoltage,harmonic distribution,frequent operation of circuit breakers,severe external application environment and bad product quality existed in the system.As a result,the reliability of the power grid system and the safety of people and equipment become lower and lower.The below paper mainly focuses on the voltage transformers used in 27.5kV WIG gas insulated switchgears in the railway system.First is to analyze failure cases from 2015 to 2017 aimed at voltage transformers under 35 k V and the key point is the arc fault happened at the scene of the high-speed rail.Optimize it according to the design parameters,external mechanism of the transformer,the working principal of electro-magnetic induction and severe external environment to maximize the operation safety of the transformer under the frequent lightening impulse and the overvoltage in the system to improve the safety of the high-speed rail in Chinese.Focus on the selection of internal iron core,the design and arrangement of winding coil,the design of shielding payer and external structure,and inner cone insulation coordination and application of switchgear to solve the previous problems such as the lack ability of overvoltage resistant and temperature change resistant,small error margin.high partial discharge and the lack of insulation coordination.Utilize “Lab Windows_CVI” partial discharge software to test whether the electric field intensity and distribution meet the requirement and improvingly design the JDZXF3-27.5(CQ)2 railway voltage transformer on the basis used for railway electric.Utilize OMICRON CT/PT Analyzer and Erfi D-72250 power meter to test the excitation characteristic data of the product under different voltage levels to verify whether products meet the requirement of overvoltage.Utilize LRHS-1000D-LJS,industrial frequency withstand voltage equipment and IVMS to modify the limit condition of customer scene.Utilize high voltage shield and impulse voltage measurement system to test the partial discharge level of the transformer.According to the result,product's overvoltage factor is 2.8 times and the partial discharge level is lower than 10 p C when 1.2Um.This product can operate stably lower than 1000 m which is an all-round improvement of the quality of railway electrical operation and the safety of people and equipment and is also positive to promote the development of the transformer in Chinese.