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Lightning protection of substations is a crucial element of the overall insulation coordination approach used in power systems. IEEE Std. 998 (2012) is the world’s leading standard for providing guidance to engineers designing lightning protection for substations. It includes various methods for achieving protection corresponding to the equipment BIL. In this paper, the principles behind one of these methods, the "leader inception theory", are presented. A description is provided of how the method is implemented with a computer program via an example of a real substation. Effective interception of lightning relies not only on the method but also the hardware used. Hence, the paper also discusses the importance of corona minimization from air terminals during the period preceding the descent of the downward leader. The methodology and results of a new series of corona performance testing carried out on a variety of air terminals in a high-voltage laboratory are presented and discussed.

Traditional methods for shielding substations against direct lightning strokes were first published in IEEE Std. 998 in 1996. Several new methods were added to the ensuing 2012 edition. This paper provides an exposition of the key principles and practical implementation of one of those methods, viz. the “leader inception theory”. A novel software implementation of the method is described and the output is illustrated with a case study. Since the efficient interception of lightning involves not only the method used to position protective air terminals but also the characteristics of the air terminals themselves, the paper addresses the importance of space charge and the necessity for minimizing corona discharges during the pre-stroke phase of a thunderstorm. The results of corona discharge measurements made on sharp and blunt air terminals at a state-of-the-art HV facility are presented and discussed.

This paper describes two unprecedented experiments that will answer two of the most fundamental and outstanding questions that remain today regarding the lightning attachment process, namely: (1) Ultra-long, free-ranging sparks that replicate typical “sneak” lightning discharges are used to evaluate and quantify the interception efficiency of the most common LPS's used around the world, and (2) Lightning flash counters and high-speed video cameras are used to make optical observations of natural lightning strikes to a tall structure in order to measure the striking distance and to compare it with current and past models of the lightning attachment process. The quantified outcomes expected from the test campaigns are both profound and of great importance to lightning protection practice, particularly with respect to quantifying the effectiveness of air terminals and lightning protection systems.