Apparatus for localization of a line fault by using traveling wave signals especially for locating faults both near and far from a measuring location

An apparatus for localization of a line fault wherein there is formed at least one signal (traveling wave signal) from the voltage and current at a measuring location and associated with a traveling wave on the line and its variation as a function of time at the measuring location, said apparatus comprising the combination of:

• a. a voltage- and current-measuring circuit provided at the measuring location on the line, said voltage- and current-measuring circuit having outputs which carry a number of voltage-current signal pairs independent of one another with respect to the line inductances and line capacitances and corresponding to the number of phases or conductors of the line;
• b. a summation circuit having at least two outputs;
• c. the summation circuit being connected via at least one voltage signal channel and one current signal channel with the measuring circuit, said summation circuit additively and subtractively superimposing at least one pair of mutually independent voltage and current signals into traveling wave signals related to oppositely moving traveling waves, said traveling wave signals appearing at the outputs of the summation circuit;
• d. an integration circuit for the formation of time integrals of the traveling wave signals;
• e. an evaluation circuit for processing at least two traveling wave-time integrals into an evaluation function selectively characterizing at least any one of the (i) fault direction, (ii) the fault distance from the measuring location, (iii) both the fault direction and fault distance from the measuring location, or (iv) at least a predetermined reference location on the line;
• f. said voltage signal channel comprising two parallel branches, one of said parallel branches comprises an oscillating circuit having a natural frequency contained in the fault-free line voltage.