Internal Arc Fault Simulation in Medium Voltage Panel for Thermal and Structural Withstand

Abstract

During an event of internal arc fault in MV switchgears electrical energy of the order of several MJ is released, major portion of which is utilized in heating the enclosure gases resulting in significant temperature and pressure rise inside the chamber. An internal arc simulation model is developed to investigate various arc parameters such as pressure rise in compartments, exhaust gas temperature, temperature at indicator plane, pressure on panel walls and structural withstand. This simulation model has been developed to improve design efficiency, safety and specially to minimize the need for physical testing. A 3Dimensional CFD simulation of high temperature gases in switchgear panel is carried out taking into account the coupled interactions between flow, temperature, turbulence and radiation fields. Temperature and pressure rise due to internal arc at different locations in breaker, cable and busbar compartments are compared. Temperature rise at different locations on indicator walls are obtained from CFD.Panel enclosure structure should be able to withstand high pressure and temperature caused by arc fault. Overpressure due to arc fault can create significant mechanical stresses on the enclosure structure causing deformation of walls, doors getting blown out, failure at fastener location, etc. Pressure data obtained from CFD is used as an input to carry out stress analysis of the enclosure structure using FEA. Transient structural simulation is performed considering geometric and material non-linearity to obtain deformation and mechanical stresses on all walls. Results from FEA can be used for design qualification as well as for the optimal designing of structure and its components. Simulation model of a typical MV panel arrangement is discussed here.