This application guide covers surges entering an electric generating plant via transmission and distribution lines and methods to reduce them as well as methods of protecting indoor and outdoor equipment@ controls@ and communication systems within the plant switchyard@ the plant proper@ and ancillary facilities within the premises (such as fuel@ ash@ water@ cooling@ weather and warning systems) against direct strokes@ incoming surges@ and internally generated surges. Purpose This application guide aids engineers at all levels of surge protection knowledge to decide whether particular generating plants or parts of plants should have surge protection. The guide may be used in estimating the lightning surge and switching surge exposure of electric generating plants in usual@ not extreme@ exposures. For plants or parts of plants that should be protected@ the purpose of this document is to provide guidance in selecting and applying surge protective devices (SPDs).