Method for locating a fault on a line near to a measuring location with the aid of substitute signals

#The present invention relates to a new and improved method for fault location on a line of the type wherein at least at a measuring location there is formed at least a measurement voltage signal derived from a line voltage and at least a measurement current signal derived from a line current, from such measurement signals there is formed at least one traveling wave signal associated with a traveling wave on the line and its variation with time at the measuring location, and there is formed an evaluation signal characterizing at least the direction of the fault location with respect to the measuring location.

#The method of the present invention is an improvement upon that disclosed in the commonly assigned, copending United States application of Otto Lanz and Michael Vitins, filed Apr. 14, 1976, Ser. No. 676,983, entitled "Method And Apparatus For Locating A Fault On A Line", and the disclosure of which is incorporated herein by reference.

#There are already known techniques for testing for the presence of a line fault, especially a short-circuit within a predetermined line section, which employ traveling wave signals in the sense previously discussed (U.S. Pat. No. 3,590,368). There such traveling wave signals are formed at both end stations of the line section to be monitored and by means of a special line are correlated to one another for the purpose of fault location.

#The following description makes reference to the annexed drawing wherein the single FIGURE illustrates a circuit diagram of apcaratus for locating a fault and providing near or close fault compensation.

#Describing now the drawing, at a line 1 consisting of an above-ground conductor having the longitudinal coordinate x there is provided at x = 0 as the measuring or test location a measuring station 2 comprising a voltage converter 2a and current converter 2b, where there is formed a measurement voltage signal u.sub.m and a measurement current signal i.sub.m. At x = z in the neighborhood of the measuring location it is assumed that there has occurred a short-circuit which causes the line voltage at the measuring location and therefore the original measurement voltage signal to breakdown to values in the neighborhood of the disturbance signal peak.

#In the exemplary embodiment there are provided two evaluation channels, namely a first channel H working with the unchanged or original measurement signals and a second channel H' working with a substitute-measurement voltage signal and corresponding substitute-traveling wave signals.

#The channel H is controlled by the measuring or test station 2 directly by means of the measurement voltage signal u.sub.m and via a constant factor multiplier 3 by the product of the measurement current signal i.sub.m and a resistance or impedance factor R.sub.w --for instance the wave or characteristic impedance of the line and forms therefrom in a summation or adding amplifier 4 and a subtraction amplifier 5 traveling wave signals a(O,t) and b(O,t) associated with two oppositely moving traveling waves on the line. These traveling wave signals characterize the temporal progression or course of such traveling waves at the measuring location x = 0.