On February 9, 2017, our company's quality control team, together with technical personnel from the Shenzhen power supply section, retested the grounding device of the 10kV overhead power through transformer pole in the Changping section of the Beijing Kowloon line. The grounding resistance value was 2.4 ohms. The project was renovated in February 2015 using a graphite based flexible grounding device. The original grounding test resistance at the construction site from Hengli to Chashan was 43 ohms. After replacing the graphite based flexible grounding device, the completed construction test resistance was 6.3 ohms; After three months of testing, the resistance value was 4.3 ohms, and after one year of operation, the resistance value was retested to be 4 ohms; After two years of operation, a test was conducted in early 2017 to reduce the resistance to 2.4 ohms. After retesting the grounding resistance, we carefully inspected the exposed parts in the air and underground. The exposed parts of the graphite wire in the atmosphere showed no significant changes, no signs of peeling, erosion, or weathering, and the surface condition was as good as new. After excavation inspection, the surface condition of the underground graphite wire is good, and there is no significant difference from the state when it was just completed during construction. According to the technical personnel of the power supply section who participated in the retest, the site was frequently struck by lightning before the renovation, causing equipment damage. Since the renovation more than two years ago, there has been no further equipment damage.