交流550kV SF_6高压套管的绝缘设计研究

Insulation Design of AC 550 kV SF_6-insulated High Voltage Bushing

高压套管是高压开关设备中的一个至关重要的元件,其电场结构是一个典型的极不均匀电场结构,所以在设计中如何使其电场分布合理均匀就成为关键点。笔者从起晕场强及起晕电压入笔,给出了高压屏蔽环的设计思路;为了改善地电位附近场域分布,通过大量的电场解析,揭示了接地内置屏蔽筒的尺寸与瓷套的高度及内径间的关系;详细分析了套管在淋雨及干试状态下,由于瓷套外介质相对介电常数εr的变化所引起场域分布的变化情况及不同试验状态下的关注部位。最后给出了550 kV套管绝缘设计时,空气中各部位场强许可值的确定方法及其数值,为套管的研发提供了具有参考价值的经验数据。

High voltage bushing in high voltage switchgear has an electrical field with typical extremely non-uniform electrical field, so it is very important to design a rational distribution of electric field. The authors give a design thought of the high voltage shield ring through considering the electrical field intensity and voltage for starting corona. For the purpose of the improvement of the field domain distribution near ground potential, a number of numerical simulations on electrical field are conducted to explore the relations of the dimension of the earthed built-in shield cylinder with the height and inner-diameter of the porcelain sleeve. The variation of field domain distribution in the bushing due to the change of relative dielectric constant 8r of the medium out of the porcelain sleeve, as well as the positions that need be regarded, is analyzed in the rainy and dry withstand voltage test conditions. Further, the determination method of allowable SFs-insulated bushing, as well as the value of electrical field intensity for each part of the 550 kV allowable value, is given.