Ultra-high-speed travelling wave directional protection based on electronic transformers

Traditional travelling wave (TW) protection is affected by a series of factors such as fault initial angles, grounding resistances, fault locations and bus structures. Especially, limited bandwidth of traditional transformers also restricts the application of TW protection. Hence, to improve the reliability and sensibility of traditional TW protection method, the study designs an ultra-high-speed TW directional protection method based on the output of electronic transformers (ET). First, the study establishes models of ET including Rogowski coil-based electronic current transformer and capacitance divided electronic voltage transformer, and studies their TW transfer characteristics. Second, based on high-frequency band of ET’ secondary output signal, the study can identify fault direction correctly by comparing the similarity between voltage and current TW. Because similarity comparing-based protection method can almost ignore the affection of secondary TW's amplitude, the novel protection method has high reliability and sensibility. Third, in order to test the performance of proposed protection method, a 500 kV power transmission system model in PSCAD is constructed. The simulation results show the proposed protection is not sensitive to fault locations, fault initial angles, grounding resistances and bus structures.