Characterization of Temperature Rise of 550 kV Gas Insulated Busbar Under High Current Working Condition

Objective This study focuses on the temperature rise characteristics of ultra-high voltage, high-current gas-insulated busbars. It investigates the temperature and flow rate distribution of the busbar under 1.1 times the rated current (8 800 A) and 0.3 MPa gas pressure. Additionally, a high-current temperature rise test platform is built to verify the model's validity. Based on this, the study examines the influence of the through-current level, the SF₆ gas pressure, and the contact state on the temperature distribution of the busbar.Methods In this study, the 550 kV gas-insulated busbar is taken as the research subject. The contact resistance is calculated through direct current (DC) low resistance measurement. Electrical and thermal conductivities are the determined using the resistance formula and the Wiedemann-Franz law. These calculations are incorporated into the development of a three-dimensional electromagnetic-temperature-fluid multi-field coupling model of the busbar. The temperature and flow velocity distribution under 1.1 times the rated current (8 800 A) and 0.3 MPa air pressure are calculated, considering factors such as contact resistance, skin effect, natural convection, and thermal radiation. The temperature differences between the busbar conductor, the maximum hot spot, and the shell are analyzed and compared with the temperature difference at the axial section where the basin convex and concave contacts are located. A high-current temperature rise test platform is built to validate the model’s results, and the test measurements align closely with the simulation results. Based on the reliable model verified by the test, the influence of the through-current level, SF₆ air pressure, and contact state on the temperature distribution of the busbar is further investigated. Additonally, a variation diagram showing the maximum hot spot temperature of the busbar with each factor is obtained.Results and Discussions To calculate the bus temperature distribution, it is first necessary to determine its loss size. Considering the skin depth of the conductive rod and basin insert, the total loss of the bus is calculated to be 695.786 W. The primary heat sources are the conductor rod and electrical contact components. The maximum magnetic induction intensity occurs at the basin insert edge, and the current density is mainly concentrated on the surface of the conductor. This loss is mapped to the temperature field to calculate the bus temperature and gas flow rate distribution. The rise in bus temperature is mainly concentrated in the through-flow conductor components. The temperatures at both ends of the contact are significantly higher than at the middle of the guide rod. The highest temperature of the bus, approximately 54 °C, is located at the concave surface of the basin at the top of the electrical contact part. This temperature is about 15 °C higher than the SF₆ temperature at the end of the contact. The temperature rise in the SF₆ is mainly concentrated in the upper part of the cavity. Additionally, the radial temperature gradient of the contact at the concave surface of the busbar is significantly higher than that at the convex surface. Hot air buildup around the shell at the concave surface of the basin is noticeable, showing a radial pattern of higher temperature at the top and lower temperatures at the bottom, with a left–right symmetrical distribution pattern. The location of the busbar conductor hot spot corresponds to the shell, with a clear difference in the temperature gradient at different x-axis locations. The temperature gradient difference between the conductor and the heat near the shell causes the internal SF₆ gas and air to move upward. The external air flow velocity is approximately 0.23 ms⁻¹, creating a circulation along the boundary of the solution domain due to non-isothermal natural convection. The influence of different factors on the bus temperature distribution law is further explored through simulation. As the load current increases, the highest temperature trend for the conductor and electrical contact is almost identical and significantly increases, while the shell temperature increase is much smaller than that of the through-flow conductor. The three highest temperatures rise with the current increase nonlinearly; SF₆ gas pressure per 0.05 MPa shows a roughly linear decreasing trend for both bus conductor and shell temperatures, with the conductor temperature being more sensitive to changes in SF₆ gas pressure than the shell. The abnormal electrical contact temperature increases approximately linearly with the resistance value. The normal electrical contact temperature rise is about 15 ℃. Even when the contact resistance value reaches approximately 70 μΩ the highest shell temperature exceeds the normal temperature of the electrical contact. Finally, the high-current temperature rise test platform validates the constructed model, providing data support for the temperature rise characterization discussed in this study.Conclusions This research delineates the temperature rise characteristics of the electromagnetic-thermal-fluid multi-field coupling model of a 550 kV gas-insulated busbar, considering the influence of contact resistance on the thermal characteristics. It analyzes the temperature rise characteristics under high-current conditions and investigates the influence of current level, SF₆ pressure, and contact state on the temperature distribution of the busbar. These findings have considerable engineering implications, offering valuable references for product design and condition monitoring of gas-insulated equipment, and helping to reduce the occurrence of overheating faults.