Effects of model scale on lightning shielding simulation test of overhead transmission lines

In order to study the effects of model scale on lightning shielding performance of transmission lines in simulative experiments, we performed a series of discharge tests on typical scaled models of 500 kV transmission lines in plain terrain, in which switching impulses were adopted. The model scales were 1:80, 1:40, and 1:25 to actual transmission lines. Based on the test results, the spatial distribution of shielding failure probability with switching impulse voltage was plotted, and the shielding failure probability was calculated by using the area method. Furthermore, the calculation results were compared with the results calculated with other methods, such as the method in the electric power industry guide, the electrogeometric model(EGM) method, and the improved EGM method. The comparison indicated that the distribution rule of the obtained shielding failure probability plot basically agreed with the calculation results from EGM model. Moreover, we observed the residue upward streamer incepted from the surface of conductors which was fail to hit and the primary discharge by using a high-speed camera. Lightning shielding simulative tests using switching impulses were also carried out on the 3 models, and the shielding failure probabilities of each model were quite different from each other, meanwhile the discharge haphazard was obvious. In general, the size of model had significant influence on the tests results.