The scope of this guide is the identiÞcation and discussion of design procedures to provide direct stroke shielding of outdoor distribution, transmission, and generating plant substations. All known methods of shielding from direct strokes were investigated during the preparation of this guide, and information is provided on two methods found to be widely used: a) The classical empirical method b) The electrogeometric model A third approach, which involves the use of active lightning terminals, is brießy reviewed in clause 6. This guide does not purport to include all shielding methods that may have been developed. The guide also does not address protection from surges entering a substation over power or communication lines or the personnel safety issues. Users of this guide should thoroughly acquaint themselves with all factors that relate to the design of a particular installation and use good engineering judgment in the application of the methods given here, particularly with respect to the importance and value of the equipment being protected.