Welding of copper rails at HPP Bajina Bašta

Abstract

The paper presents general data on copper as well as specific characteristics encountered during its welding. The initial task was to cut the copper (Cu) busbars in order to remove the existing current-carrying coils and install new ones. The dimensions of the copper busbars are 25 × 200 mm × l. A current of 16,533 A and a power rating of 315,000 kW pass through the specified cross-section. The generating unit was manufactured by Toshiba, Japan.
A specific challenge of this task was the requirement to preserve the insulation on both the busbars and the coils. Simultaneously, it was necessary to preheat the Cu busbar to 700 °C while intensively cooling it at a distance of approximately 300 mm from the weld seam. Welding was carried out using a semi-automatic MIG process. The workspace was extremely confined, which further complicated the operation and demanded strict occupational health and safety measures due to the toxicity of copper fumes. Following welding and the grinding of both the face and root of the weld, the joints were inspected using liquid penetrant and ultrasonic testing methods.