The scope of the original standard was a guide for acceptable methods and configurations for the protection of shunt reactors. This PAR's intent is to make the existing guide more comprehensive by including reactor configurations and reactor protection schemes not now in the guide. Review and updating of the existing guide is needed to consider protection of shunt reactors with auxiliary power windings, improved turn-to-turn fault protection, use of digital/microprocessor relays and other items specific to shunt reactor protection as brought before the working group. The purpose of the original guide was to provide users of shunt reactors with a complete guide of acceptable methods and configurations for protection of shunt reactors. Several users have indicated the existing guide needs to be revised to cover the protective schemes of other reactor configurations presently in use. Revision Standard - Inactive-Reserved. Reaffirmed March 2012. A comprehensive guide to the methods and configurations for the protection of power system shunt reactors is provided in this guide. The protection of oil-immersed reactors equipped with auxiliary power windings, improved turn-to-turn protection, and use of digital (microprocessorbased) protection for shunt reactors are included. Remarks: Revision of IEEE Std C37.109-1988