Abstract: In the actual operation of power systems, 500 kV transmission lines often encounter abnormal issues such as excessive distance measurement deviation and unstable distance measurement results, which seriously restrict the efficiency of fault handling in the power grid. Therefore, based on the double-ended traveling wave theory and steady-state impedance analysis theory of fault distance measurement, this paper summarizes typical abnormal phenomena and their evolution patterns, and deeply analyzes the abnormal causes from three dimensions: algorithm defects, transformer characteristics, and system interference. It proposes a comprehensive countermeasure involving multiple links and verifies its effectiveness through a simulation model. The results show that the distance measurement error rate has decreased from 12.8% to 3.5%, and the abnormal occurrence rate has dropped from 18% to 3.4%, providing technical support for improving the reliability of fault distance measurement in 500 kV lines.