INTERNAL ARC ROOT MOVEMENT AND BURNTHROUGH PREDICTION BY SIMULATION USING FIRST PRINCIPLE

Abstract

Safety related to internal arc in a switchgear is a major concern. The switchgear designers have used different methods over the years to calculate important variables (pressure etc.) for internal arc design. In the beginning, considering the outflow of gases due to volumetric heating by arc energy, pressure rise was calculated. Afterwards CFD (computational fluid dynamics) was introduced to model in detail the flow and energy balance. In all of the above models, there are lot of fit parameters to begin the calculation and they only provide approximate pressure rise. All these methods need input in the form of electrical energy (fault current and arc voltage). Fault current is defined by standards, but arc voltage is an unknown input. In addition, these methods don't tell about the arc propagation, which can be useful to avoid the burn-through. In order to overcome the above-mentioned limitation, for the first time, the modelling of free burning arc in large switchgear volume was performed. The advantage of such a method is that the arc voltage and the heat transfer are calculated from first principle and assumptions are not used for the input parameters. The movement of arc also shows the location where designers can introduce extra protection to avoid burnthrough