During the annual maintenance of ultra-high voltage (UHV) lines, there are arc erosion marks on the wire at the grounding clamp. In severe cases, it can lead to strand breakage, wire breakage, and even grounding clamp shedding, which is easy to cause safety accidents. However, the arc ablation characteristics of the wire at the grounding clamp and the process of strand breakage during the maintenance of UHV lines remain unclear. Therefore, based on the induced current calculation result from an actual case of arc ablation on an UHV blackout line, this paper uses the current action integral equivalent method to build a research platform for the arc ablation characteristics of the wire at the grounding clamp. The results show that the discharge arc is accompanied by a large number of heat, light and shock wave effects. The arc generates severe arc ablation along the discharge channel between the lower end of the wire and the clamp, and there are multiple arcing processes. By increasing the contact area between the wire and the grounding clamp, the local arc energy density is reduced, and the ablation degree is obviously weakened. By reducing the gap distance between the wire and the grounding clamp, the arc discharge ablation and impact are more concentrated and severe, and the degree of wire ablation damage is more significant. Under the cumulative effect of arc ablation, the test wire exhibits broken strands, and the fracture is up to 5 mm at the severe melting point, which aggravates the ablation of the adjacent strands. When the arc current action integral is the same, the cumulative effect of wire arc ablation energy under small amplitude, low frequency and long time action current is more obvious, and the damage to wire ablation is stronger. The research results provide a reference for ensuring the personal safety of maintenance staff and prolonging the operating life of transmission equipment.