气压和湿度对复合电压下换流阀高压电极起晕电压影响试验

Effects of Air Pressure and Humidity on Corona Onset Voltage of High Voltage Electrode of Converter Valve Under Combined AC and DC Voltage

柔性直流换流阀在运行时,其内部尖端以及钳制电位差较大的相邻屏蔽罩可能由于承受过高的交直流复合电压和局部场强过大而产生电晕放电现象。而气压和湿度因素对起晕电压具有一定的影响。因此根据换流阀内部电极电场的特点设计了换流阀高压电极(棒–板电极和屏蔽罩缩比电极)。采用串联加压的复合加压方式和紫外成像技术,在实验室内搭建了气压和湿度可调的交直流复合电压电晕试验平台。之后基于试验平台研究了气压和湿度对复合电压下换流阀高压电极起晕电压的影响。试验结果表明:随着气压的下降,复合电压下和单一电压下棒–板电极的起晕电压均线性下降;复合电压下屏蔽罩缩比电极起晕电压逐渐下降;单一电压下屏蔽罩缩比电极的起晕电压线性下降。随着相对湿度的增大,正直流–交流复合电压下棒–板电极的起晕电压基本不变;负直流–交流复合电压下棒–板电极的起晕电压逐渐减小;单一电压下棒–板电极的起晕电压均逐渐线性减小。随着相对湿度的增大,正直流–交流复合电压下屏蔽罩缩比电极的起晕电压先减小后增大;负直流–交流复合电压下屏蔽罩缩比电极的起晕电压则逐渐减小;纯正直流电压下,屏蔽罩缩比电极的起晕电压先增大后减小;纯交流和纯负直流电压下,屏蔽罩缩比电极的起晕电压逐渐减小。

Inside a converter vale, the inner tip and the adjacent shield with larger clamping potential difference may cause corona discharge due to withstanding the excessive AC and DC composite voltage and exorbitant local field strength in the operation of the flexible DC converter valve. The air pressure and humidity have some influences on the corona inception voltage. Therefore, we designed a high voltage electrode of converter valve(rod-plate and shield shrink electrode) according to the characteristics of electrode electric field in converter valve. Moreover, we built an AC and DC composite voltage corona experimental platform with adjustable air pressure and humidity in the laboratory, which used the method of applying voltage in series and UV imaging technology. Then,we experimentally researched the effects of air pressure and humidity on the corona inception voltage of high voltage electrode in converter valve under the combined voltage based on experimental platform. The results show that the corona inception voltage of the rod-plane electrode decreases linearly under combined voltage and single voltage with the decrease of the pressure. The corona inception voltage of the scaled shield electrode decreases gradually under the combined voltage, when the air pressure drops. The corona onset voltage of the scaled shield electrode decreases linearly under single voltage. With the increase of relative humidity, the corona onset voltage of rod-plane remains unchanged under positive DC and AC composite voltage. The corona voltage of rod-plane electrode decreases under negative DC and AC composite voltage. The corona inception voltage of rod-plane electrode gradually decreases linearly under single voltage. The corona inception voltage of scaled shield electrode decreases first and then increases under positive DC and AC composite voltage. The corona inception voltage of scaled shield electrode decreases under negative DC and AC composite voltage. The corona inception voltage of scaled shield electrode increases first and then decreases under pure positive DC voltage. The corona inception voltage of scaled shield electrode decreases gradually under pure negative DC and pure AC voltage.