A Simplified Approach for Assessment of Exposure of EHV and UHV Lines to Direct Lightning Strikes

Modeling of lightning attachment to multi conductor transmission lines is made more complex by the effects of mutual conductor proximity, ground field due to cloud charges prior to negative leader descent, and operating voltage of the line. In this paper, it is found that the lateral attractive distanceLdsof any conductor can be expressed by a product of the corresponding valueLds0of a single free conductor and three dimensionless variable functionsFpr,Feg, andFovcharacterizing proximity, ground field, and operating voltage effects, respectively. The method is applied to 345-, 420-, 525-, 765-, and 1150-kV transmission lines and satisfactory agreement is obtained with the results of detailed modeling.