Abstract: Currently, multiple failures have occurred in aluminum-core cables of wind farm collector lines, especially in small cross-section aluminum-core power cables. Their disproportionately high failure rate poses great risks to safe and reliable operation of wind farms. In order to deeply analyze the causes of cable faults, three typical fault cases of 26/35 kV small-section aluminum-core power cables were introduced, and cable samples were systematically studied such as anatomical examination, product testing, and simulation tests. Results showed that the direct cause of cable breakdown was that the conductor was damaged and broken due to excessive tensile force, which in turn caused insulation breakdown fault. Combined with conductor manufacturing, cable production process, installation and laying, handover acceptance, and operation & maintenance processes, targeted preventive measures and improvement suggestions were put forward, which could eliminate potential hidden dangers to a certain extent and ensure safe and reliable operation of wind farms.