DETECTION OF FAULTS ON TRANSMISSION LINES IN A BIPOLAR HIGH-VOLTAGE DIRECT CURRENT SYSTEM

摘要

A method and a device for detection of a fault on a transmission line in a bipolar HVDC installation where, on the basis of the current and voltage of each pole and the impedance of the transmission lines and the ground line, one positive and one negative pole-wave signal and one ground-wave signal are formed and that one first and one second difference signal are formed as the difference between two consecutive samples of the pole-wave signals and that a fault is detected if a first criterion, namely if any of the difference signals is greater than a set value, is fulfilled, and if a second criterion, namely if the numerical value of the difference between the difference signals is smaller than the product of the greatest of the difference signals and a set factor, is fulfilled, and if a third criterion, namely that a ground-wave signal has been detected, is fulfilled.