Protective relay with selective phase selection for double power transmission lines

摘要

Protective relay with selective phase selection in electric power distribution systems with double transmission lines between two stations (TP,TM) and with the ends of the two lines being connected to a common busbar station in each station. The protective device comprise a protection unit, terminal, at both ends of each line. All the terminals (M1,M2,P1,P2) comprises an identical basic design comprising measurement of phase quantities (17), filtering (18) and A/D conversion (19). Furthermore, the identical part comprises a parameter estimator (20) for Fourier series expansion of measured phase signals and generation of the respective residuals. The parameter estimator cooperates with a frequency estimator (21) and a sampling regulator (22). Each basic design also comprises a local logic unit which, by means of a transient and steady state analysis, finds out whether an event on the network is due to a fault or a connection/disconnection of the phase/line and the current direction at each terminal. At one of the terminals, at both stations, there is a station master unit (26) which compiles all information for the station in question, calculates the distance to a fault, etc.. For final decisions as to whether a recorded fault lies between the stations, as to faulty line(s) and phase(s), all information from the two stations is compiled in a superordinate unit (29) in one of the terminals at one of the stations.