Abstract: Following adjustments to the transportation organization on the Neijiang-Liupanshui Railway, the down-direction train tonnage rating in the Cangping to Zhaotong section was increased from 2600 t to 3500 t. This section utilizes double-headed SS_3B locomotives operating in multiple units. However, the traction power supply capacity was found to be severely insufficient. The voltage at the end of the traction feeder section dropped to a minimum of 15.6 kV, triggering tripping of the locomotive's main circuit breakers. A detailed analysis was conducted on the problems and causes of the insufficient power supply capacity. The calculation of the proportions of different types of voltage losses revealed that the combined voltage loss from the traction substation and the traction network accounts for approximately 85.5% to 88.2% of the total voltage loss. Proposed engineering implementation measures included optimizing the power supply scheme, enhancing the capacity of the traction substation, and upgrading the traction network. After project implementation, the power supply capacity improved significantly. The voltage at the end of the feeder section increased to above 19 kV, meeting the requirements of design specifications.