Method of testing distance relays
AssigneeBBC Brown, Boveri & Company, Limited
InventorMichael Fiorentzis
Life of this patent
Estimating the term…
Abstract
A method of automatically plotting the loci curves of multi-stage distance relays. The comparison impedances, required for the measurement, are automatically provided for given impedance angle by adjustable currents and voltages. During the determination of the loci curves there is started with a defined, predetermined impedance value which is either greater or smaller than that which is sought to be found. By taking the half of this impedance value or by doubling with subsequent halving, when starting with smaller impedance values, it is possible to incrementally approach the sought of impedance value as a function of whether or not, for the corresponding timing stage of the distance relay, its measuring element responds or does not respond.
Claims16
A method for determining the trip characteristics of distance relays, especially having protection zone switching, for protection of an electrical line by means of variable comparison impedances, wherein the distance relay has a measuring element employed as a comparison instrument, comprising the steps of:
- performing a first relay trip test, with a predetermined phase angle .phi. of the comparison impedance Z.sub.1, said comparison impedance having a magnitude greater than the magnitude of a predetermined image impedance Z.sub.A of the line;
- performing a second relay trip test, with a magnitude of the comparison impedance Z.sub.2 .apprxeq.Z.sub.1 /2 which is at least approximately half as large as the magnitude of the first comparison impedance Z.sub.1 ;
- during each further relay trip test n, wherein the number n of the relay trip tests are selected as a function of the desired accuracy of the trip characteristic to be determined, performing such relay trip test with a magnitude of the related comparison impedance Z.sub.n which has been increased by at least one-half of the impedance change ##EQU6## of the preceding relay trip test when the magnitude of the image impedance Z.sub.A was greater than the magnitude of the comparison impedance Z.sub.n-1 ;
- or
- reducing such comparison impedance at least approximately by one-half of such impedance change ##EQU7## of the preceding relay trip test when the magnitude of the image impedance Z.sub.A is smaller or equal to the magnitude of the comparison impedance Z.sub.n-1 ;
- and
- producing a signal which is proportional to the comparison impedance of the last performed relay trip test.
A method of determining the trip characteristics of distance relays, especially having protection zone switching, for protection of an electrical line by means of variable comparison impedances, the distance relay having a measuring element employed as a comparison instrument, comprising the steps of:
- performing a first relay trip test, with a predetermined phase angle .phi. of the comparison impedance Z.sub.1, said comparison impedance having a magnitude which is smaller than the magnitude of a predetermined image impedance Z.sub.A of the line;
- performing a second trip test, with a magnitude of the image impedance Z.sub.2 .apprxeq.2 Z.sub.1 which is at least approximately twice as large as the magnitude of such first comparison impedance Z.sub.1 ;
- during each further relay trip test n, wherein the number n of such relay trip tests is chosen as a function of the desired accuracy of the trip characteristic to be determined, performing such relay trip test with a magnitude of the related comparison impedance Z.sub.n which is increased by at least approximately one-half of the impedance change ##EQU8## of the preceding relay trip test, when the magnitude of the image impedance Z.sub.A was greater than the magnitude of the comparison impedance Z.sub.n-1 ;
- or
- performing such last-mentioned relay trip test with a magnitude of the comparison impedance Z.sub.n which has been reduced by one-half of such impedance change ##EQU9## of the preceding relay trip test when the magnitude of the image impedance Z.sub.A was smaller or equal to the magnitude of the comparison impedance Z.sub.n-1 ;
- and
- obtaining a signal proportional to the comparison impedance of the last-performed relay trip test.
Dependencies are inferred from the claim text.