Protective relay arrangement for short-circuit and earth fault protection in an electricity distribution network

摘要

The invention relates to a protective relay arrangement for the short-circuit and earth fault protection of an electricity distribution network, the arrangement comprising at least two protective relays of the same substation, each adapted to monitor one or more physical variables, such as current and/or its phase angle, of an electricity distribution network line for detecting a short-circuit or earth fault on the line, and comprising means for measuring said physical variables, for comparing the measurement results with corresponding limit values, and, upon detection of a short-circuit or earth fault, for emitting control signals to isolate the faulted line from the electricity distribution network. In accordance with the invention, the arrangement further comprises a data transmission bus within the substation, such as a so-called field bus, and that each relay further comprises means for transmitting the measuring results and information derived therefrom via the data transmission bus to the other relays of the arrangement and means for receiving these measuring results and information derived therefrom from at least one, any other relay of the arrangement, and for using the results when making a decision to emit a control signal.