Research On Detection Of Typical Defects Of Surge Capacitors Based On DC Partial Discharge

With the continuous development and practical application of high-power power electronic devices,the advantages of high-voltage and UHVDC transmission technologies for long-distance large-capacity transmission of electrical energy are becoming more and more prominent,and it is particularly important for the energy status of energy and load separation in China.The rapid expansion of power network connections,longer transmission distances,and higher voltage levels also place higher demands on the reliability and robustness of power grid operations.China's conventional DC and UHV DC projects are equipped with neutral line capacitors.The neutral line capacitors in the converter station are installed between the DC neutral line and the grounding grid,also known as impulse capacitors or surge capacitors.Safe and stable operation of the surge capacitors is closely related to the reliability of the entire station operation.The working condition of the surge capacitor is special,but at present,the insulation aging mechanism,insulation state evaluation method and insulation state detection method of the surge capacitor have not been thoroughly studied at home and abroad,and no unified standard has been formed.Therefore,it is necessary to address the special working conditions of the surge capacitor.Insulation state evaluation and detection methods of the surge capacitor are further studied to improve the equipment safety and reliability of the surge capacitor,thereby improving the overall reliability of the HVDC transmission project.This article mainly studies the partial discharge of the surge capacitor under DC high voltage.According to the principle and basic characteristics of the partial discharge of the surge capacitor,a capacitor with a rated voltage of 12 k V and a size of 0.6 ?F was designed and manufactured for the four typical typical defects,internal defects,contact defects,wrinkle defects and oil defects.The internal element model of the capacitor was surgeed,and the four typical electric field distributions in the discharge process were analyzed using finite element simulation.This paper builds a DC partial discharge test and test platform,compares the sensitivity and anti-jamming capability of the traditional RC detection impedance and high-frequency current sensor in partial discharge of the test capacitor,and selects the test method for measuring the partial discharge of the surge capacitor.An adjustable high-frequency current sensor for partial discharge test of capacitors was designed and fabricated.The sensor was used to test the DC partial discharge of the surge capacitor.The measured partial discharge signals were analyzed and processed with MATLAB and EXCEL software.