On the requirment of insulation design at high altitude for Lung-Xi 330KV power transmission line

the tests were performed.The results test are as follows

power frequency average flashover voltage and 50% switching impulse voltage at dry and wet conditions; 50% lightning impulse voltage; and 50% switching impulse FOV of long air gaps （1-5m） on the simulating tower.The regression equations and curves of the FOV are given.