The complexity of a general AC/DC transmission line is mainly caused by the components such as multi-phase line, non-homogeneous line, partially mutually coupled line and multi-terminal line. This paper proposes a systematic methodology to accurately locate faults in a general complex AC/DC transmission line. Instantaneous measurements only at line terminals are required. First, the modeling methodologies of symmetrical/asym-metrical multi-phase line, non-homogeneous (including partially mutually coupled) line and multi-terminal line are proposed. The distributed parameter line model is fully considered with partial differential equations (PDEs) in time domain. Second, the voltage distribution along the entire line is obtained via numerical solutions. Third, the faulted segment and fault location is determined based on the calculated voltage distribution. The proposed method is carefully designed to ensure applicability for a general AC/DC transmission line, independent of the numbers of phases/poles, non-homogeneous (including partially mutually coupled) sections, terminals, and joint points. Numerical experiments in two example complex transmission lines prove that the proposed method can accurately identify faulted segments and locate faults under different fault conditions. The method works with a relatively low sampling rate of 20k samples/sec and a data window of 5 ms after the fault occurs.
