Attachment Processes and Influencing Factors in Competition Tests Under Switching Impulse Voltages

Research on the attachment processes in competition tests can provide insights into the influencing factors involved in the selection process that determines the lightning strike point. In this paper, a series of competition tests with a rod-rod gap configuration are designed and carried out. The test results indicate that the strike mechanism is decided by two discharge processes, namely the free development of the downward-propagating discharge and the interception process of the upward and downward discharges. If the first process prevails, the strike probabilities for different grounded rods will tend to be equal. For the second process, the strike probabilities reflect the different performances of the grounded rods for intercepting downward discharges. As the scale of the discharge gap increases, the development of the downward leader becomes more and more dominant in selecting the strike point. In natural lightning strikes, the scale of the downward leader is normally more than 90% of the discharge gap, hence the protective effect of lightning rods with different tips will not be significant for low rod heights and small lightning currents. To reflect the effect of the downward leader development on the choice of the strike point, a minimum discharge air gap of 10 m is suggested.