To evaluate the shielding failure trip-out rate of the transmission lines accurately,a new model combining electromagnetic transient program(EMTP) simulation with Monte Carlo method is presented,where all random factors are taken into account and the higher accuracy for electromagnetic transient analysis of EMTP is kept.

This paper presents an algorithm of shielding failure trip-out rate (SFTOR) of overhead transmission line based on Monte Carlo method.

The projection of exposed surface on the ground is adopted to calculate shielding failure trip-out rate.

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

For the transmission lines under operation,lightning outage rate can be converted through frequency of lightning outage and line distance.

Basing on Generalized Integral method,completely reckoning in the tripout by induced lightning, the total lightning outage rate we have obtained.

Evaluation of lightning trip-out rates for Zhejiang Power Grid by using lightning location systems;

There are two indexes to evaluate the power line performance on preventing lightning strikes: the one is the lightning trip-out rate,the other is the lightning withstand level of the power line.

According to these records,the causes of lightning flashover including shielding failure stroke and back-shielding failure stroke were analyzed and therefore shielding-failure stroke rate and lightning trip-out rate were obtained.

One of the main measure to reduce transmission line lightning-stroke trip-out rate is reducing impulse grounding resistance of line tower.