求翻译：从各国的实际运行来看，雷击是危害电网安全可靠运行的主要因素。目前，我国采用的防雷措施为架设耦合避雷线、降低杆塔接地电阻、加强线路外绝缘水平、安装氧化锌避雷器等。其基本原理是提高线路的耐雷水平，减少雷击跳闸率，属于“堵塞式”的防雷措施。但是由于雷电活动的随机性与复杂性，以及电网网架结构越来越强，这些传统的防雷保护措施已不能完全避免雷击跳闸的发生。因此，本文的研究500kV输电线路并联间隙对线路跳闸率的影响分析，对于线路防雷保护具有重要的意义。是什么意思？

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From the perspective of the actual run, lightning strikes against Grid security is a major factor run reliably. Currently, the country adopted the anti-mine-action coupling expensive lightning-rod, and reduce the ground resistance, strengthen lines installed insulation levels, such as zinc oxide lig

Judging from the actual running of the national, lightning is a major factor against power network safety and reliable operation. At present, the coupled lightning, and lightning protection measures for the erection of Tower grounding resistance reduction, enhanced line level of external insulation,