The loop operation of distribution lines is expected to reduce power loss and increase the introduction of distributed energy resources as solar power generators and storage batteries. A significant problem during the failure of a section of a distribution line in loop operation is the extension of the failure to other sections due to the wideness of the power supply network area. Currently, there are no methods to easily identify a faulty section using the failure waveform during the loop operation of distribution lines and ground faults; consequently, short‐circuits or disconnections still occur. Therefore, when operating a loop of distribution lines, it is necessary to identify and isolate a faulty section. To solve this problem, we investigate and propose a method to identify the faulty section based on the voltage and current values measured using a switchgear with sensor at the waveform level. By applying the proposed method to identify and isolate faulty sections during distribution line loop operation, power can be transmitted to sections where no fault has occurred at an early stage. The proposed method has a significantly reliable fault detection capability and will help improve the stability of the power supply during loop operation. © 2023 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.