采用马蹄形锌环抑制直流瓷绝缘子铁帽电解腐蚀的可行性研究

Feasibility of Using U-shaped Zinc Ring to Restrain Electrolytic Corrosion of Porcelain Insulators' Iron Caps

针对近年来我国多条高压直流输电线路上瓷绝缘子出现的铁帽腐蚀现象，从电化学角度对马蹄形锌环抑制运行绝缘子铁帽电解腐蚀的有效性进行了理论分析，并通过模拟试验进行了验证。为获得热膨胀时锌环对瓷绝缘子的机电特性的影响，将安装了马蹄形锌环的绝缘子于80℃高温环境中放置50h再测量其机电特性。结果表明，在102.3kPa大气压强、5．4℃环境温度、50％相对湿度条件下，安装了马蹄形锌环的样品瓷绝缘子的绝缘电阻的吸收比〉1．8，外绝缘陡波冲击耐受电压峰值在398～434kV范围内，低于内绝缘陡波冲击耐受电压峰值范围（486～509kV），内、外绝缘均满足运行要求，且能够正确合理地配合。此外，马蹄形锌环能够有效抑制瓷绝缘子铁帽的电解腐蚀，且不会对绝缘子的机电特性和更换作业造成不利影响。

In recent years, electrolytic corrosion appears on the porcelain insulators of HVDC transmission lines in China. Hence, we theoretically analyzed the effectiveness of using U-shaped zinc ring to restrain iron caps＇ electrolytic corrosion from the aspect of electrochemistry, which was also tested by simulative tests. Furthermore, to investigate the influences of zinc ring on mechanical and electrical characteristics of insulators under thermal expansion condition, some insulators with U-shaped zinc rings were placed in 80 ℃ environment for 50 hours and then tested. The test results indicated that, at an atmospheric pressure of 102.3 kPa, environmental temperature of 80 ℃, and relative humidity of 50%, absorption ratio of the tested porcelain insulators was higher than 1.8 and the impulse withstand voltage of outdoor insulation ranged from 398 kV to 434 kV, which was lower than that of inner insulation, from 486 kV to 509 kV. Hence the inner and outdoor insulation levels cooperate well and meet the operation requirements. Moreover, the installation of U-shaped zinc ring can actively restrain the electrolytic corrosion of iron caps, and it is not unfavorable for the mechanical and electrical characteristics and replacing of insulators.