Lightning interception probability and shielding performance of overhead transmission lines

Shielding performance of overhead transmission lines is evaluated by implementing in shielding analysis a statistical model of lightning attachment. The effects of transmission line parameters, lightning peak current distribution and interception probability on shielding failure flashover rate are investigated and discussed. An application has been made to several overhead transmission lines including typical lines the Hellenic transmission system. Results are compared with that obtained by employing in shielding analysis some commonly used electrogeometric models. The estimated shielding failure flashover rate, showing a great variability among lightning attachment models, is much more sensitive to transmission line geometry for the IEEE Standard 1243:1997, which yields the highest values among models. For all lightning attachment models employed in shielding analysis the estimated shielding failure flashover rate of several overhead transmission lines is in qualitative agreement but in quantitative inconsistency with field data.