Interim Report on Application and Operation of Out-of-Step Protection

Out-of-step protection of synchronous machines and system interconnections is now demanding serious consideration, first because the heavy loading of machines and transmission lines has introduced many stability problems and secondly, because outages resulting from out-of-step conditions may interfere seriously with the war effort. The relay subcommittee has, therefore, considered it timely to prepare a report on the subject and has appointed a working group for that purpose. The report describes briefly out-of-step phenomena, the methods of protection that are available, and a cross section of the practices and requirements of representative utility systems.