Paper Title
Modeling of Low Voltage Switchgear and Controlgear Assemblies Using Computational Fluid Dynamics

Abstract
Low voltage switchgears and controlgear assemblies contain multiple conductors and electrical devices ensuring current distribution and protection of an installation. During operation, heat is dissipated by conductors and electrical devices leading to temperature rises in the panel. For different reasons, internal temperature must be limited and controlled. Hence, the target is to determine innovative cooling solutions with quantified efficiency. Designing and testing each variation is a costly and time consuming process. This challenge is tackled by developing a simulation model to predict temperatures and airflow characteristics for different enclosure design variants. Yet before assessing any new designís efficiency, the simulation model must be validated. The present study introduces the methodology used to model the complete assembly system, from 3D simplifications to specific simulation parameter settings, to achieve this validation step. To ensure a reliable validation, two specific types of switchgears are studied: one with a hermetic enclosure and another one with a ventilated enclosure. Three important aspects are considered during the design of the simulation model. The first aspect is the high scale variations within the object considered. Modeling thin walls including scales from the meter (height of the enclosure) down to the millimeter (thickness of the wall) poses severe meshing challenges. The shell conduction method is applied to model thin sections. The second aspect relates to the air density model. An incompressible ideal gas model has been used to model buoyancy and gravity forces driving natural convection. The third important aspect is radiation. The role of radiative heat transfer is studied using a surface-to-surface radiation model. Index Terms- Low voltage switchgear; natural convection; shell conduction; radiation; thermal management