Thermosyphon bushing: design, simulation and implementation

Highlights: • This paper presents a new application of thermosyphons in electrical equipment. • Thermosyphon bushing's performances have been validated by experiments and models. • A thermal network model has been developed for thermosyphon bushings. • Effective thermal conductivities of thermosyphon bushings could be estimated. • The prototypes have been built and tested for a vacuum-insulated disconnect switch. -- Abstract: In order to improve the electric current rating of a vacuum-insulated disconnect switch, a copper-water thermosyphon has been embedded into an electrical bushing to achieve significantly higher effective thermal conductivity and lower hotspot temperatures of the bushing. The temperature profiles of a thermosyphon bushing conductor under different heat loads and filling ratios have been characterized by experiments. For the purpose of estimating the performances of any thermosyphon bushing with various dimensions, working fluids and filling ratios, a thermal network model with lumped thermal capacitors has been established. Characteristic features of thermosyphon bushings like the thick pipe walls and the distributed Joule heat sources are represented in the model. This model successfully predicted the effective thermal conductivity and hotspot temperatures of a thermosyphon bushing prototype designed for a vacuum-insulated disconnect switch. Because of the compact designs of thermosyphon bushings, they can be implemented in a wide range of power equipment, such as vacuum switchgear, disconnect switches, plasma chambers, and high-power physics experiments.