Where the ANSI code (81R) protection scheme is used?

The ANSI code 81R protection scheme is used primarily in electrical power systems for the protection of generators and motors against out-of-step conditions. It detects when a machine is losing synchronism with the power system, which can occur during system disturbances or faults. By monitoring the phase relationship between voltage and current, the 81R scheme can initiate disconnection of the equipment to prevent damage and ensure system stability. This protection is commonly implemented in substations and industrial facilities with large rotating machinery.