Location of open conductor faults on LCC-HVdc transmission systems

High voltage direct current (HVdc) transmission systems are widely used for bulk energy transmission over large distances and the impact of short circuit faults on dc lines in these systems have been extensively studied. However, a type of fault that has hitherto not widely been investigated is the open circuiting of a conductor, as its occurrence is relatively rare. None of the available literature provides a reasonable discussion on the impact of HVdc open conductor faults on an HVdc system. Using electromagnetic transient (EMT) simulations, this study addresses the void in HVdc fault analysis by giving useful insight into the impact of HVdc open conductor faults on current and voltage transients and their potential impact on the converter operation. A modified empirical arc model with arc length dynamics is developed to model the series open air arc resulting from conductor breaking. The model is implemented as a custom component in the PSCAD simulation platform for conducting simulation studies. Due to the lack of experimental data for HVdc open circuiting faults, the fault induced transients in terminal voltages and currents are studied considering reasonable ranges of arc parameters. Using an EMT model of a point-to-point LCC-HVdc system, the study shows that the dc line overvoltage is highest on the rectifier side and occurs for a conductor break close to the rectifier end. This study also shows that the breaking of conductors generates significant voltage and current travelling waves, which are sufficient to successfully apply the conventional travelling waves-based fault location algorithms to locate HVdc open conductor faults. After evaluating the applicability of the travelling waves-based fault location technique, the achievable accuracy of estimating the location of pole to ground and open conductor faults are evaluated. An improved algorithm is introduced to locate both types of faults with an overall accuracy of ±375 m which is specific to the 1400 km