绝缘油介电强度测试仪电极电场计算及其校准方法研究

Calibration of insulation oil tester output voltage based on the electric field calculation for the electrode structure

对绝缘油耐电压能力的考核通常采用绝缘油介电强度测量仪进行测试。采用普通高压分压器对绝缘油介电强度测试仪进行校准会出现2个问题:首先测试仪的带负载能力较弱,当分压器的输入阻抗小于测试仪的带载能力时,输出电压就会发生跌落;其次校准需要模拟测试时仪器的实际使用状态,校准装置需要具有与装有绝缘油油杯相同的阻抗。本文采用有限元分别对不同结构的圆盘电极、球形电极以及球盖形油杯电极进行建模计算,得到了不同油杯的电容量大小,同时用高精度LCR电桥对不同结构电极的电容量进行测量,据此设计了中间接地的双电容分压器的矢量信号测量装置,试验结果表明该校验装置可以有效匹配绝缘油介电强度测试仪的油杯阻抗,并能满足了对于测试仪矢量输出量值的准确溯源。研究了用全绝缘电压互感器对此标准装置进行校准,通过和中国国家高电压计量站的比对证明了用互感器串联加法校准的有效性。

Oil tester is wildly used in the high voltage withstands capability of insulation oil testing.There will be two problems in calibrating such device using high voltage divider.First,the output voltage of oil tester will drop down due to its poor loading ability;second,the calibra-tion process should carried out in tester’s actual working condition.When the oil cup is taken out from the oil vessel,the calibration equip-ment should simulate the effect of oil cup.It is recommended that the calibration apparatus have the same impedance with insulation oil vessel. This paper built models for different-structure oil cup including circle plane electrode,sphere electrode and semispherical electrode.The simu-lation result using finite element analysis method and calculated the capacitance values of different oil vessel structure.Besides,high-precision LCR electrical bridge was used to measure capacitances of different electrode structure.Based on the simulation and measurement result,a middle-grounded double capacitance divider vector signal measurement standard was designed.The experiment results indicated that the de-signed calibration apparatus could effectively match the impedance of the oil cup and satisfied the traceability of vector quantity output value of the insulation oil tester with adequate accuracy.Further research on calibration this standard equipment was also discussed,the comparison re-sult to the China high voltage center show the conformity of using voltage transformer with serial adding method.