Effects of Line Length, Fault Resistance and DC Filters on HVDC Line Protection Based on Signum Function of Transient Energy

Abstract

Protection schemes and algorithms of high-voltage direct-current (HVDC) lines are known to be affected by the line length, fault resistance values and dc filter type. The authors have conducted a simulation study on a monopolar HVDC line in order to evaluate the effect of the three parameters on a protection algorithm based on signum function of transient energy. A simulation study has been carried out using PSCAD/EMTDC. The line length has been varied from 200 km to 2000 km, and the fault resistance from 0 Ω to 2000 Ω. Three types of dc filters are considered. The results are presented and analyzed in the paper. For the effect of line length on the fault classification time, the latter varies with the former both for internal and external faults. Increase in the fault resistance leads to a small increase in the fault classification time for internal faults and a larger increase for external faults. Since protection is not to be initiated on external fault, increased classification time for external faults has no bad consequences. Classification time for all the three type of dc filters for internal faults is the same for all the type of dc filters except for sending end dc fault with triple tuned filter.