A novel online fault localization technique for HVDC cable transmission systems

In this paper, a modal online fault locator is presented for VSC-HVDC links. The modal theory is applied to the HVDC cable bundles and the decoupled modes are resulted. Each mode has different attenuation, velocity, and characteristic impedance depending on the frequency used. The differenced between the modal velocities is used to design a one-sided fault location algorithm. With the help of Hilbert-Huang transform (HHT) and the instant frequency, the exact arrival times of the different modes are detected and the fault location is determined. CIGRE DCS1 symmetric monopole VSC-HVDC link is modeled in PSCAD and an extruded two pole cable bundle with three conducting layers in each pole is used as the transmission section. The fault location algorithm is designed in MATLAB and is divided into offline and online stages. According to the simulation results, the method is accurate and robust. However, more analysis for different cable parameters, used materials, grounding schemes, and installation considerations are suggested to evaluate the validity of the proposed technique in different conditions.