Alternative test method of internal arcing for replacing SF6 by air in SF6-insulated power equipment

Abstract

To develop an alternative test method of internal arcing for replacing sulfur hexafluoride (SF6) by air in SF6-insulated power equipment, it is important for the public safety to clarify the thermal effect of hot SF6 and air from the equipment on the surroundings. In this study, an analytical model for evaluating the incident heat energy on a metal plate by exhausted hot gas was developed and validated. SF6-air mixtures with a range of gas thermodynamic and transport properties up to 30,000 K were modelled using computational fluid dynamics (CFD) to simulate the increase in pressure. The analytical results are investigated using the experimental results on SF6-air mixtures. Subsequently, a method of setting the test conditions for the internal arc testing in SF6-insulated power equipment, is proposed based on the analytical model. Using the mixture model, assuming an alternative arcing test for replacing SF6 by air in the SF6-insulated power equipment, the method of setting a current or the duration of current is demonstrated and verified. The results indicate that the current and duration of current can be set such that the incident heat energy on the metal plate by exhausted hot gas are approximately equalized. This study could establish an alternative test method of internal arc in SF6-insulated power equipment.