Effect of the corona shield of the OMNI bipolar conventional air terminals

BCAT(Bipolar Conventional Air Terminal) is a lightning rod to reduce the probability of lightning strikes by inhibiting the increase of electric field caused by earth potential when thunderclouds approach. Corona inception voltage is very important in order to inhibit the increase of electric field as the lower the inception voltage of corona discharge, the greater the effect of inhibiting the increase of electric field. In this paper, the corona inception voltage of a conventional air terminal and 4 types of BCATs are tested with applying DC high-voltage. The test results indicate that the corona inception voltage of the conventional air terminal (Sample 1) was the lowest. In case of the 2 models of BCAT (Samples 2 and 3), corona discharge occurs at 80kV while at the latest models of BCATs (Samples 4 and 5) showed, corona discharge occurring at 70kV and 45kV, respectively. It is verified that lower corona inception voltage of the BCAT can be achieved by modification of the structure and shape of the BCAT to increase the effect of the corona shield. Based on this test result, development of optimal shape of the BCAT is expected to be viable when a corona discharge simulation model for the BCAT is established. As it is difficult to conduct outdoor field tests for the irregular characteristic of lightning occurrence, it is necessary to develop a test method to verify the maximum performance of an air terminal. Because outdoor testing of lightning rods is difficult, the development of outdoor testing method for the lightning rod will also be needed.