A lot of impulse discharge experiments are conducted by operation wave that can be more close to natural lightning, in these experiments the proportion of the size of experimental model to that of actual ZBS2 tower is 1:63, and the maximum height of the shielding failure of intermediate phase is obtaine.

According to the operation data abroad,the tripped-out accidents caused by shielding failure amount to a large percentage of the tripped-out accidents caused by lightning strike on the UHV AC transmission lines.

The performance of shielding failure of 500 kV quadruple-circuit overhead AC transmission lines on the same tower with the revised electric geometry model (EGM) method is analyzed, and the problem of shielding for transmission lines by ground wires is discussed.

With the increase of voltage level of transmission line,the proportion of outages because of shielding failure increases,therefore,exactly evaluating lightning-withstanding level of transmission line is especially important for system service and stable operation.

Electro-geometric (EGM) model is now the most popular method for the shielding failure flash-over rate(SFFOR) calculation.

Along with the increase in working voltage, the lightning shielding failure model which is based on one side of shield wire, transmission line and lightning downward leader will be unable to describe the real circumstance of UHVDC transmission lines.