Upper electrode design for scale model experiment of upward leader inception from UHV transmission lines

Scale model experiment is an important way to study the lightning shielding performance and calculation method of UHV transmission line. In order to improve the calculation method and analyze the influence factors about lightning shielding performance of UHV transmission line, a new electrode is proposed to solve the current questions about the scale model experiment on upward leader inception from UHV transmission line. The new electrode composed by a concave plane electrode and a rod electrode. The concave plane electrode used for simulating the intensive electric field distribution in a large space generated by the lightning stepped leader, and it is similar to the effect of the inverted rod to plane. The rod electrode used for controlling the discharge path which makes observation of the high speed CCD camera more effective. The Finite Element Method (FEM) was used to calculate and compare the surface electric field strength at a given conductor generated by the conventional rod electrode, rod plus round plane electrode and the new design electrode under the same impulse voltage level and gap distance. The influence factors about the electrical field strength were analyzed. The results show the new design electrode can generate the most intensive electric field strength compared with the former ones, and it can be used for the larger air gap distance.