Lightning impulse corona characteristic of 1000 kv UHV transmission lines

The lightning overvoltage is one of key issues to design the insulations of transmission line and power apparatus. Usually, the influence of the impulse corona on lightning overvoltage is ignored. Fully understanding the corona characteristics of 1000 kV UHV transmission line is helpful to understand the actual wave process and realize a suitable insulation design of 1000 kV UHV system. Experiments on the lightning impulse corona characteristic of bundle conductors for 1000 kV transmission lines are carried out in China UHV AC Test Base and the impulse corona Q-V curves of different bundle conductors are obtained. The results show that impulse corona causes the capacitance of the conductor increasing. Analysis on the Q-V curves shows that the positive impulse corona occurs a little time later than the lightning impulse voltage exceeds the corona inception voltage and the delay time is tenth of microsecond.