This paper studies the mechanism of graphite fibers damaging the external insulation of electrical equipment. Finite element simulation software is used to establish models and calculate the relationship between the degree of external insulation failure of electrical equipment and graphite fiber parameters. The qualitative and quantitative relationships are explored among factors such as graphite fiber length, distance from insulators, potential, attachment mode to insulators, and attachment degree, and the degree of insulator damage caused by graphite fibers. The danger of graphite fibers and the necessity of preventing graphite fiber attacks on power systems and electrical equipment are demonstrated. A two-dimensional model of three-phase transmission lines is constructed to analyze the law between the intrusion position of graphite fibers and electric field changes. An early-warning method for power systems based on sensing technology is proposed, and protection countermeasures against the impact of graphite fibers on the external insulation of electrical equipment are explored to improve the strain and defense capabilities of resilient power grids.