Characterization of internal discharge shock waves of gas-insulated switchgears using shadowgraphy

The gas-insulated switchgear (GIS) is a vital component of a power system, and understanding the shock wave characteristics of its internal discharge is crucial to ensure the safe and stable operation of the entire system. In this study, a high-speed shadowing technique is employed to obtain the shadowgraphs of a typical flow-field evolution of sulfur hexafluoride (SF6) gas following the breakdown of a pin-plate gap inside a GIS. Experimental data were used to derive parameters, including the Mach number, propagation speed, distance of the discharge shock wave, and the temperature, pressure, density, and velocity of the SF6 gas after wave generation. With a 0.2-mm discharge gap and 0.4-MPa pressure, the discharge generates a spherical shock wave, centred at the contact between the discharge channel and electrodes, that propagates in all directions. The shock wave gradually weakens after 20 mu s, propagating at near-sonic speed, and its Mach number decreases from 2.92 to 1.15; similarly, its post-wave parameters sharply decrease during the first 20 mu s. Additionally, a significant reflection occurs when the shock wave propagates to the metal wall. The authors' findings provide a valuable reference for detecting and diagnosing the internal discharge in GISs. This study focuses on understanding the characteristics of internal discharge shock waves in gas-insulated switchgears (GISs). Using state-of-the-art experimental techniques, such as high-speed shadowgraphy, the authors have investigated the phenomenon of shock waves induced by gas discharge in GISs, and extensively assessed various thermodynamic parameters of interest.image