This guide summarizes the general considerations in grounding of generating station auxiliary power systems and discusses the factors to be considered in selecting between the appropriate grounding classes and in specifying equipment ratings. This guide applies to both medium-voltage and low-voltage auxiliary power systems. Grounding and bonding to achieve practical safeguarding of persons is fulfillled by electrically connecting equipment frames and enclosures and interconnecting wiring raceways to the station grounding network (see IEEE Std 142-1991 1), as required by ANSI C2-1993. References to safety in this guide mean freedom from equipment damage. The emphasis is on reliability and availability of auxiliary system service achieved through control of ground-fault currents and transient overvoltages. This guide is specifically written for electrical utility systems and does not recognize the neutral grounding requirements for dispersed storage and generation. These requirements must recognize the restrictions imposed by the specific network to which the dispersed storage or generation is connected. Neutral grounding of dispersed storage and generation needs to be coordinated with the electrical utility system.