Online fault location on crossbonded AC cables in underground transmission systems

In this paper, a fault locator system specifically designed for crossbonded cables is described. Electromagnetic wave propagation theory for crossbonded cables with focus on fault location purposes is discussed. Based on this, the most optimal modal component and input signal to the fault locator system are identified. The fault locator system uses the Wavelet Transform both to create reliable triggers in the units and to estimate the fault location based on time domain signals obtained in the substations by two fault locator units.
Field measurements of faults artificially created on a section of a 245 kV crossbonded cable system, connecting the newly installed 400 MW Danish offshore wind farm Anholt to the main grid, are obtained and used to verify the proposed system. Furthermore, extensive simulation data created in PSCAD/EMTDC is used in order to examine the robustness of the system to changes in the fault inception angle, fault resistance and fault location.
It is shown that the fault location can be estimated very accurately using the proposed system and the system will be used to monitor Danish crossbonded transmission cables in the future.