Multi-physical Coupling Field Study of 500 kV GIL: Simulation, Characteristics, and Analysis

With the construction of a large number of hydropower stations, transmission lines crossing a river and urban utility tunnels, gas insulated transmission line (GIL) has been applied widely due to its large transmission capacity, low environmental impact and high reliability. Accurate modelling of physical quantities and their characteristics of GIL provides a theoretical basis for its design and operation, which is of great significance to ensure the safety and reliability of GIL operation. The mathematical model and their relationship of GIL multi-physical fields are analyzed at first, upon which simulation model of GIL is built. Secondly, multi-physical coupling field model of electric, magnetic, thermal, fluid and stress field for GIL is studied, while simulation results are basically in consistent with experimental data to verify effectiveness of the model. Thirdly, distribution of multi-physical fields and their relationship are simulated and analyzed, while proximity effect, edge effect and compression factor of GIL multi-physical field are discussed. The results show that the radial temperature inside GIL is higher at the top, lower at the bottom, leading to uneven distribution of thermal expansion displacement, while the axial temperature distribution is basically uniform, which falls firstly and then rises near basin insulator thus results in edge effect. Proximity effect leads to asymmetric distribution and a slight increase of temperature inside GIL as well as a dramatic increase of air velocity around GIL. In addition, when ambient temperature is lower than -5 °C, the compression factor is much lower than 1 and the effect of compression factor should be considered in simulation.