Arrangement for detecting the direction of a fault from a measuring point

Claim 1

Directional wave detector for determining, with the help of the direction of movement of a transient wave passing a measuring point at a fault in the network, the direction to the fault which has caused the transient wave and which comprises a detector part (R,S,T,) for each phase in the supervised network, each such detector part (R,S,T) having a first band exclusion filter (3) for removing the part of a first signal (Ui), which has the operating frequency of the network, said first signal being proportional to the current at the measuring point, a second band exclusion filter (4) for removing the part of a second signal (Uu), which has the operating frequency of the network, said second signal being proportional to the voltage at the measuring point, a directional detector (13) having first and second pairs of input terminals (9,10 and 11,12) and first and second output terminals (14,15), means to supply a signal from the first filter to one of the first pair of input terminals when the first filtered signal is positive and to the other of the first pair of input terminals when the first signal is negative, means to supply a signal from the second filter to one of the second pair of input terminals when the second filtered signal is positive and to the other of said second pair of input terminals when the second signal is negative, said two filtered signals consisting of those parts of said first and second signals (Ui, Uu) which have passed the filters and which for the main part contain only transients, said directional detector including means to supply a signal to the first output terminal when the signals supplied to the terminals of the first and second pairs of input terminals have different signs and to the second output terminal when the signals supplied to the terminals of the first and second pairs of input terminals have the same sign, a tripping relay (18) conneCted to said first output terminal (14) for producing a tripping signal when a signal is supplied to said first output terminal, and a blocking relay (19) connected to said second output terminal (15) for producing a blocking signal when a signal is supplied to said second output terminal.