Research On Fault Location Of ±500kV HVDC Electrode Line

The operation mode of HVDC system is flexible, bipole-grounded return mode and monopole-grounded return mode are the most commom operation modes of HVDC system, at this moment, electrode line and earth are the return line of HVDC system loop. The fault of electrode line would affect the safe and stable operation of HVDC system, especially for monopole-grounded return mode, which could result in monopole block and interrupt power transmission of HVDC system. Therefore, it is significant for the improvement of safe and reliable operation of HVDC system to judge the fault types and calculate the fault distance accurately when electrode line is faulted. The existing PEMO2000 pulse transmitter of electrode line has failed to locate the fault point more than once in practical engineering. So it has important theoretical value and engineering significance to carry out the research about fault location of electrode line.This paper utilizes a ±500kV HVDC PSCAD model of China Southern Power Grid, which simulates the single line grounded fault and single line break fault of electrode line and analyzes fault characteristic. The fault current waveforms of proximal metal fault and break fault of electrode line are similar, “ voltage signal distance” is builded to distinguish two type faults; break-variable of two outlets current are defined to recognize line fault, at the same time a method which could checkout the resistance of electrode is proposed.Electrode line flow heavy current when HVDC system is in monopole-grounded return mode or unbalanced bipole-grounded return mode. Under the circumstances, frequency domain location algorithms based on the dominant characteristic harmonic are proposed, such as improved impedance method, taking transition resistance as pure resistance location algorithm, combined harmonic component and dc component location algorithm. However, as the affect of electrode resistance, those frequency domain location algorithms which only need lower sampling frequency can’t calculate the precise fault distance along full line. Aimed at every location algorithm on the sensitivity of the fault distance is different, this paper proposes a comprehensive selective method based on those location algorithms: divide faulted line into three sections, choose and judge comprehensively location algorithm according every location algorithm on the sensitivity of the fault distance is different, at the same time, check the location result mutually, to meet the accuracy of fault location.Electrode line flow low current when HVDC system is in mode of balanced bipole-grounded return, the time domain voltage method based on translated data-window is employed. This algorithm builds location function according to differentials of distributed voltages is minimal at faulted point along line, and reduces the affect of line frequency varying characteristic, the simulation indicates that proposed algorithm could meet the required precision in condition of higher sampling frequency.