Evaluation of Short Circuit Currents in Multi-Terminal HVDC Systems

This paper deals with the analysis of short circuit currents in radial HVDC networks. After the occurrence of a short circuit in a HVDC system different sources contribute to the resulting short circuit current. In this paper the various short circuit current sources with their corresponding fault currents are analyzed. The determination of short circuit currents is done by simulation in PSCAD (R). The analysis covers both line-to-line and line-to-earth faults at different fault locations. The dependency of the fault location on the amplitude is shown. The results are verified by an analytical approach to calculate the single short circuit currents of the different sources. A short circuit in a DC system causes transients with high frequencies. Therefore special attention is given to the frequency dependence of transmission lines and their effect on the short circuit current. The paper concludes with general comments on the adaption of the results to meshed DC grids and a perspective to transmission grids in the future.