Some observations on bus relaying

The literature is replete with guidance on the subject of bus relaying. Because of the extremely detrimental results of incorrect operation of bus differential relaying, those giving such guidance have generally leaned in the direction of security. This paper is intended to point out the possibility of easing some of the useful, but not immutable restrictions that have been handed down from generation to generation. In general, the bus configuration does not dictate any particular bus differential relaying concept. Voltage level and importance of the circuits connected to the bus are far more significant criteria. Speed and cost are key factors. Current transformer location and quality are important ingredients in the choice of a bus relaying scheme.