直流输电线路短路电流变化特性研究

his paper aims to clarify the variation characteristic of the short circuit current (SCC) in HVDC systems to provide a theoretical support for the system equipment selection, fault identification and protection setting determination. Analysis covers both the natural variation characteristic of the SCC as well as the characteristic that considers the control system influence. Firstly, the analytical expression of the SCC is derived without considering the influence of the control system. Then, the natural variation characteristic of the SCC is analyzed on this basis, clarifying that the SCC increases with oscillations. Subsequently, special attention is given to the control system and its influence on the SCC. It is pointed out that there's no correspondence, under some circumstances that closely related to control delay, between the electrical boundary of the SCC magnitude and the physical boundary of the transmission line. Finally, the variation characteristic of the SCC in real HVDC systems that contain commutation process is studied. It is shown that the magnitude of the SCC at a certain fault distance varies with fault time in a zigzag way.