对特高压直流线路绕击屏蔽的一种新观点

New Viewpoint About Lightning Shielding Failure of UHVDC Transmission Lines

随着极线工作电压的提高,以单侧地线、极线及雷先导作为雷屏蔽研究模型已满足不了工程实际的需要。因此,以模拟电荷法为基础,将雷电先导、两侧地线、极线作为整体研究对象,考虑极线工作电压及极线分裂数,计算雷先导垂直下行过程中各导线表面场强变化,并运用Peek判据确定各导线对应的雷先导一级定位高度,合理解释特高压直流线路中存在的正极线绕击概率大的问题,提出了新的绕击屏蔽观点:特高压直流架空线路中仅负极线侧避雷线和正极线产生上行先导竞争拦截雷下行先导,正极线侧的避雷线屏蔽功能被削弱,未起到完全保护正极线的作用。

Along with the increase in working voltage, the lightning shielding failure model which is based on one side of shield wire, transmission line and lightning downward leader will be unable to describe the real circumstance of UHVDC transmission lines. So this model cannot meet the requirements of the engineering field for its difficulty in explaining the polarity effect in the process of shielding failure. This paper bases on a Charge Simulation Method, and takes the lightning leader, two shield wires and bundle conductors as a unified whole to research the lightning shielding failure. Meanwhile, this paper considers the working voltage and conductor bundles to calculate the surface electric field of the conductors and shield wires when the lightning leader develops downwards and to calculate the electric field with the different distance between the lightning leader and overhead lines. When the conductors induce the upward leader which is decided by the Peek equation, the height H that named as the first level away the earth of the lightning downward leader will be determined. Then the paper explains the lightning shielding failure problems in UHVBC rationally. It has more probability for lightning shielding failure if the working voltage is considered, Finally, the paper puts forward a new viewpoint of UHVDC lightning shielding failure： in UHVDC overhead lines, only anode conductor and cathode side shield wire will initiate positive leader to compete with each other to intercept lightning leader, the shielding function of anode side shield wire will be weakened and plays no role in the protection of the anode conductor.