A Novel Grounding Electrode Line Protection Method Based on Harmonic Impedance

In order to deal with the problem of protection dead zone in the grounding electrode line of UHVDC transmission system, a novel method of grounding electrode line protection based on the harmonic impedance is proposed. Firstly, building a distributed parameter model of the line, the expression of harmonic measured impedance of the grounding electrode line under different fault conditions is derived, and the different characteristics of the harmonic measured impedance were analyzed by using the impedance expressions. Based on this, a fault protection criterion based on the impedance amplitude and phase deviation are constructed. The theoretical analysis and simulations results show that compared with the traditional protection scheme, the proposed protection method can protect the entire line reliably and has good tolerance to high transition resistance. Hence, the proposed method has promising prospects for engineering applications.