A novel fault location method for multi-terminal transmission lines based on composite analysis of time-frequency fault traveling waves

In order to solve the problems such as complex fault branch determination, large fault location error and low error tolerance of the existing multi-terminal transmission line (MTTL) fault location method, due to the influence of fault traveling wave (FTW) wave head (WH) time extraction accuracy and network topology structure, a novel fault location method for MTTLs based on composite analysis of time-frequency FTW is proposed. The FTW location mechanism for MTTLs is firstly revealed. According to the characteristic that the FTW natural frequency (NF) is inversely proportional to the transmission distance, the fault branch determination vector is defined, and the corresponding principle is proposed to determine the fault branch. On this basis, the multi-terminal FTW data with adaptive FTW velocity capability are surface-fitted by using the characteristic that the transmission time of FTW is directly proportional to the transmission distance, so as to achieve fault precise location. The PSCAD/EMTDC simulation and laboratory test results show that this method has a simple fault location process and high location accuracy under various fault conditions, effectively reduces the influence of harsh environment, FTW velocity inhomogeneous and WH time extraction error on the location results, and has high error tolerance.