Shielding failure evaluation by collection surface

Abstract

A new lightning shielding failure evaluation method based on an electro-geometric method aided by 3D graphics technology is introduced. The approach is based on the method of collection surfaces. By using the collection surface of protected equipment instead of the unprotected area, empty areas where no equipment is to be protected are eliminated from contributing to the failure rate. Shielding devices and protected equipment are considered equally as targets for lightning when generating collection surfaces. The collection surfaces are projected to a 2D bitmap, using different colors to represent protected and unprotected areas. An integral is performed on the amplitude of the stroke current (weighted by the probability distribution of this amplitude) to account for the dependency of the shape and size of the unprotected surface on the stroke current. The technique applies to structures or substations of any shape, and can use different striking distances to horizontal and vertical objects. The 69 kV substation example described in IEEE Standard 998 is used to demonstrate usage of this method.