Abstract: In recent years, incidents of cable insulation breakdown due to the ablation of the insulating layer in high-voltage cables have become increasingly frequent, significantly impairing the safe and stable operation of power grids. The moisture content and external pressure of the insulating layer are crucial factors influencing the development of ablation failures in high-voltage cables. In light of this, we establish a simulation test platform for the ablation of the insulating layer under varying moisture content and different mechanical loads. Moreover, we investigate the temperature, ultrasound, and electrical signals generated by ablation under different conditions and provide insights into the evolution of multiple physical parameters associated with ablation defects. Combining microscopic surface features of the eroded insulating layer and the characterization of ablation product composition, we analyze the mechanisms behind ablation signal generation under different conditions. It is discovered that the localized heating caused by radial current concentration and partial discharge within the insulating layer are the main contributors to elevated temperatures in the insulating layer. Additionally, it is found that partial discharge is the primary cause of ultrasound and electrical signal generation. The study reveals that, compared to dry insulating layer ablation, the presence of moisture in the insulating layer leads to electrochemical corrosion of the aluminum sheath, resulting in increased ultrasound and electrical signals, with occasional minor signal generation in between. This research provides both theoretical and experimental foundations for the development of high-voltage cable insulation ablation detection devices.