SF6电气设备中微水对固体绝缘材料闪络电压的影响

Influence of Moisture on Flashover Voltage of Solid Insulating Materials in SF6 Electrical Equipment

SF6气体中过量的水分一定条件下会凝露在固体绝缘材料表面,严重降低材料绝缘强度,甚至导致绝缘故障。研究微水量对绝缘材料闪络电压的影响对于科学制订SF6电气设备中微水量控制标准具有重要意义。为此通过实验研究了不同温度条件下SF6气体中微水量的变化规律及微水对固体绝缘材料闪络电压的影响规律。结果显示：环境温度不变时,微水几乎不影响绝缘材料的闪络电压。当环境温度骤变时,SF6气体的相对湿度会出现升高,甚至可以达到100%。微水量在一定范围内对绝缘材料闪络电压没有影响,随着微水量逐渐增大,绝缘材料闪络电压出现降低,且降低程度随微水量的增多而增大。环境温度骤升时绝缘材料闪络电压更易受微水影响,且温度变化范围也对微水的威胁有很大影响,低温范围内温度变化更易使水蒸气凝露。此外,实验结果显示对于大温差地区,现行的水分控制标准过于宽松,对不同温差的地区可以考虑制订不同的微水量控制标准。

Excess moisture in SF6 gas will condense on solid insulating materials under certain conditions and cause the reduction of flashover voltage. Therefore research on the influence of moisture on flashover voltage of solid insulating materials in SF6 will help formulate proper standards of moisture content in SF6 gas. We studied the variation of moisture content with of temperature and its influence on flashover voltages of insulating materials. The results show that moisture hardly affects the flashover voltage of insulating materials at constant ambient temperature. When the ambient temperature changes rapidly, relative humidity in SF6 gas will increase and can even reach 100%. After a sharp change of ambient temperature, moisture within a certain amount have no effect on flashover voltage of insulating materials. When the moisture content reaches a certain value, flashover voltages begin to decrease. The larger the moisture content is, the lower the flashover voltage becomes. And moisture has a more remarkabler influence after a sharp rise of ambient temperature than after a sharp decrease. The range of temperature also has a remarkable influence on the threat caused by moisture, for water vapor is more likely to condense at low temperatures. Moreover, the experimental results show that current standard of moisture content cannot guarantee the normal operation of SF6 electrical equipment. It is suggested that different controlling limits should be used for regions with different climate conditions.