Analysis of Short-Circuit Current Characteristics and Its Distribution of Artificial Grounding Faults on DC Transmission Lines

Grounding faults are common faults on dc transmission lines. Characteristics of the short-circuit current, such as amplitude and frequency, and its following distribution are very important for analyzing the influence of the fault. Based on the +/- 500 kV Yongfu dc transmission project in China, several artificial grounding short-circuit tests at the terminal or middle of the dc transmission line were carried out. This paper reports the measurement and analysis of the short-circuit current and its distribution in a dc system for the first time. The short-circuit current distribution includes currents in the ground wires of the fault tower and currents in ground wires, which are connected to the converter station grounding grid, such as the optical ground wire (OPGW) currents of ac outgoing lines, neutral point currents of different transformers, and the grounding electrode bus arrester current. In addition, the frequency components of the fault currents are analyzed. Based on the PSCAD/EMTDC software, the current distribution is simulated and discussed. The simulation results are in good agreement with the test results.