Travelling-wave-based fault location algorithm for hybrid transmission lines using three-dimensional absolute grey incidence degree

The travelling wave propagation velocities in hybrid transmission lines vary, and the initial travelling wave front and its reflection wave fronts are difficult to distinguish; thus, the traditional travelling-wave-based fault location algorithm for single overhead lines is not suitable. Meanwhile, the faults at submarine cables are random and the weather conditions at sea are variable, which makes the maintenance of these cables extremely difficult. Accurate fault location for submarine cables is important in hybrid transmission lines. A novel travelling wave representation in 3D subspace, called a full waveform, is presented. Based on the transmission characteristics and the refraction and reflection mechanism of the travelling wave, the correlation and difference of the full waveform at different fault points are qualitatively and quantitatively analysed using the three-dimensional absolute grey incidence degree. The one-to-one correspondence relationship between fault locations and single-end measured full waveforms is revealed. On this basis, a single-ended travelling-wave-based fault location algorithm used in hybrid transmission lines is proposed. The proposed algorithm is utilised for a multi-scale travelling wave panoramic waveform, which has a clear physical meaning. There is no need to use the modal component velocities, the initial travelling wave front arrival times, or their subsequent reflection waveforms. The proposed algorithm can be used in multi-section hybrid transmission lines. Transient simulation and postfault analysis are conducted using PSCAD/EMTDC and MATLAB, respectively. The accuracy, limitation, and capability of the proposed algorithm are presented and discussed for different fault conditions.