Patent ID: 11971440
Assignee: UNIVERSITY OF MANITOBA
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC G  H  Y | IPC G  H

Claim 6:
7. A method for identifying one or more faulted conductors when a fault event has occurred in a power transmission system in which at least two of the conductors transmit power, wherein the power transmission system is a high voltage direct current (HVDC) transmission system having two power-transmitting conductors and a return conductor, the power-transmitting conductors and the return conductor being operably connected between two sets of power converter stations so as to transmit the power along the power-transmitting conductors from a first one of the two sets of power converter stations to a second one of the two sets of power converter stations with the return conductor defining a return path for the current from the second set of power converter stations to the first set of power converter stations, the method comprising:
monitoring current signals which are representative of currents in the conductors at a generally common location within the power transmission system;
filtering the current signals to produce filtered current signals;
determining a maximum rate of change of each filtered current signal within a predetermined time interval after the fault event has commenced;
calculating a ratio of a pair of the maximum rates of change of the filtered current signals; and
comparing the ratio against a threshold value to identify the one or more faulted conductors, wherein the threshold value is a positive constant representative of a minimum ratio of a pair of the maximum rates of change of the filtered current signals based on a fault occurring at a maximum distance from the generally common location at which the current signals are monitored;
wherein monitoring the current signals comprises measuring the current in each one of the conductors at or generally in proximity to a common selected one of the first and second sets of power converter stations;
wherein the ratio of a pair of the maximum rates of change of the filtered current signals comprises (i) a first ratio formed by dividing the maximum rate of change of the filtered current signal of a first one of the power-transmitting conductors assuming a positive current direction through the first power-transmitting conductor so as to be assigned a positive value, by the maximum rate of change of the filtered current signal of a second one of the power-transmitting conductors assuming a negative current direction through the second power-transmitting conductor so as to be assigned a negative value, where the positive current direction through the first power-transmitting conductor is taken as flowing out of the selected set of power converter stations and the negative current direction through the second power-transmitting conductor is taken as flowing into the selected set of power converter stations; (ii) a second ratio formed by dividing the maximum rate of change of the filtered current signal of the first power-transmitting conductor assuming the positive current direction therethrough by the maximum rate of change of the filtered current signal of the return conductor assuming a negative current direction through the return conductor so as to be assigned a negative value, where the negative current direction through the return conductor is taken as flowing into the selected set of power converter stations; and (iii) a third ratio formed by dividing the maximum rate of change of the filtered current signal of the return conductor assuming a positive current direction through the return conductor so as to be assigned a positive value, by the maximum rate of change of the filtered current signal of the second power-transmitting conductor assuming the negative current direction therethrough, where the positive current direction through the return conductor is taken as flowing out of the selected set of power converter stations; and
wherein the threshold value comprises a plurality of threshold values, and wherein comparing the ratio against a threshold value to identify the one or more faulted conductors comprises:
checking whether the first ratio is greater than or equal to a first one of the threshold values, and
if true then determining that the one or more faulted conductors includes the first power-transmitting conductor, or
if false then determining that the one or more faulted conductors includes the second power-transmitting conductor.