变电站绝缘在线监测系统抗电磁场干扰特性

为解决变电站存在严重的电磁场干扰易造成绝缘在线监测系统数据的波动大及不稳定的问题,在硬件与软件的设计上采用了多项抗干扰措施。从硬件信号的实现上,参考信号选自电容式电压互感器(CVT)一次而非电压互感器(TV)二次,增强了数据稳定性;研究并改善了传感器的屏蔽方式与系统接地方式,消除共模干扰;在芯片的电源与地之间加入滤波器,滤除电源中的尖峰和数字芯片的高频电流。在软件设计上选择改进基波法,应用数字滤波、谐波分析与自校正技术,消除了测量的随机误差。在高压试验大厅进行的电磁场干扰模拟试验验证了绝缘在线监测系统的整体抗干扰能力。目前该系统已在湖南省500kV云田变电站成功运行。

Anti-electromagnetic Interference Ability of On-line Monitoring System of HV Capacitive Apparatus

The on-line monitoring system of HV capacitive apparatus in the substation is of great importance for the insulation performance evaluation and early insulation fault detection,which is essential for the transformation from preventative maintenance to condition-based maintenance.However,as the severe electromagnetic interference in the substation,the urgent problem of data fluctuation and instability need to be solved.Therefore,integrated anti-interference methods were achieved in the design of hardware and software.The reference signal was obtained from the primary winding current of CVT instead of from the second winding of the TV,which could greatly improve the precision and stability of monitoring system.Optimization of the sensor shielding method with the grounding method was selected to limit the common-mode interference.Capacitor filter between the chip source and the earth was added to weaken the function of peak amplitude and the high frequency current.In the process of software design,the improved fundamental current measuring method,along with the technique of digital filter,harmonics analysis and self-calibration,was adopted to limit the random error.Simulation tests for the on site electromagnetic interference was carried out in the high voltage experimental hall,showing the excellent anti-interference capability of the on-line monitoring system.The effectivity and reliability of the system are validated by its application in the 500 kV Yuntian substation in Hunan province.