An Investigation of the Distinct Features of Wavelet Transform Based Protection Strategy for Consideration in HVDC Grids.

Fault vulnerability and protection issues have been identified by systems developers and researchers as one of the major challenges in the drive towards HVDC grids. This is largely due to the relatively low inductance in DC systems, zero crossing issues, selectivity, as well as the vulnerability of the power electronic converters. Therefore, fast and selective protection algorithms are required to prevent both the systems and devices from damage. This paper investigates the distinct features of wavelet transform (WT) in fault identification and discrimination for application to HVDC Grids. In this paper, the simulation results provide relevant evidence of WT ability to detect and discriminate between internal and external faults using WT coefficients and wavelet entropy (WE). The simulation results presented revealed that discrimination was achieved within $(500 \mu s)$ following the arrival of the fault components at the relay terminals; up to a fault resistance of 500 ohms.