DC fault analysis of VSC-HVDC and DC cable protection principle

Voltage Source Converter (VSC) based HVDC (VSC- HVDC) transmission technology as a kind of new dc transmission, is attracting more and more research. VSCs are susceptible to cable short-circuit fault and ground fault. This paper focuses on the transient characteristics of electrical quantities in a two terminal VSC-HVDC system after the occurrence of short-circuit fault and ground fault. Equivalent circuits and equations are given to calculate the voltage and over-current in cable. Simulations are undertaken in PSCAD to verify the calculation results, and different fault points and fault resistances are considered. Due to the behaviors of DC voltage and cable over-current in faulty cable and non-faulty cable after the ground fault, a DC cable protection principle was proposed to determine the faulty cable and to decide fault within or outside the protected area.