A Pilot-Wire Relaying Scheme Utilizing the Product Differential Relay [includes discussion]

This paper presents a pilot-wire relaying scheme which has been designed to take advantage of the product characteristic of the type-CFD relay. It operates as a variable-percentage differential-relaying scheme on light fault currents, and for all practical purposes as a phase-angle-comparison scheme on heavy fault currents. This scheme permits a wide latitude in the selection of current transformers and types of line terminations. It also provides protection of station equipment against high induced pilot-wire-to-ground voltages.