±1100kV特高压直流换流阀试验用高压直流串级发生器的绝缘耐压分析

Analysis on Dielectric Withstand Cascaded DC High-Voltage Generator for ±1100 kV UHVDC Converter Valve Test

为在实验室条件下进行±1 100 kV特高压换流阀绝缘型式试验,需要对用于试验的高压直流串级发生器能否满足绝缘耐压要求进行分析。利用ANSOFT SIMPLORER软件对装置进行电路理论分析计算以及利用ANSOFTMAXWELL有限元软件对其进行三维结构的电场强度仿真分析。仿真得到最大场强为22.62 kV/cm,与空气击穿场强25 kV/cm较接近,结果与装置输出1 843 kV时,装置顶部与实验室顶部钢梁间的空气间隙空气被击穿相吻合。为进一步降低场强,对装置进行优化分析,并得出优化后的电场强度最大值为20.66 kV/cm,低于空气击穿场强。因此认为,若不考虑空气温湿度等条件的影响,在现有试验室条件下,试验室设备具备±1 100 kV特高压换流阀绝缘耐压试验的能力。

To make the dielectric test on ±1 100 kV UHVDC converter valve in laboratory environment, it is necessary to analyze whether the dielectric withstand of cascaded DC high-voltage （HV） generator used in the test can be met. Based on the principle of the cascaded DC HV generator, its topological model is established by ANSOFT SIMPLORER, and above earth potentials at different positions of metal shield cases of silicon rectifier stacks and those at the tops of insulative posts of the HV generator are obtained; the three-dimensional simulation analysis on the distribution of electric field strength of the generator is performed by FEM software ANSOFT MAXWELL. Simulation results show that the maximum electric field strength around the HV generator is 22.62 kV/cm that is close to 25 kV/cm, the breakdown field strength of air, and such a result conforms to the case that the air gap between the top of the HV generator and the top steel beam of the laboratory was broken down while the output of the HV generator was 1 843 kV. To decrease the electric field strength in the air, optimization analysis on HV generator is performed and the result shows that the maximum electric field strength should be 20.66 kV/cm that is lower than the breakdown field strength of air. Therefore, without considering the impacts of humidity and temperature of air, it is feasible to conduct the dielectric withstand test of ±1 100 kV UHVDC converter valve under existing laboratory condition.