Internal arc fault simulation using CFD to predict thermal behavior in switchgear
During an event of internal arc fault in LV/MV switchgears an electrical energy of the order of several Mega-joules is released which should be dissipated in the span of few milliseconds. Major portion of this energy is utilized in the heating of the enclosure gases resulting in the significant pressure rise inside the chamber. Objective of the simulation model developed is to improve design efficiency, increased safety, and especially to minimise real-world testing. Internal arc parameters such as pressure rise in various compartment, exhaust gas temperature, indicator temperature and pressure on panel walls are investigated with CFD simulation methodology. A 3-D CFD simulation of high temperature gases in LV/MV panel is carried out with coupled interactions between flow, temperature, turbulence and radiation fields taken into account. The internal temperature and pressure rise due to internal arc at different locations in breaker, cable and busbar compartment were compared. The same is used further to analyse structural forces and stresses on the panel members. Temperature rise at different locations on indicator walls which are modelled at a distance of 300 mm from panel were estimated from simulation. Visualization of the temperature, pressure and flow field is possible with CFD model.
Internal Arc Fault Simulation in Medium Voltage Panel for Thermal and Structural Withstand
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.
Experimental Study on Pressure Drop Characteristics of Vents
One of the major impacts on the thermal design of electronic systems over the past decade has been the use of computational fluid dynamics and heat transfer tools. System level thermal simulation has driven the need to understand the performance and the reliability aspects of boundary conditions. In addition to the modeling inaccuracies, computation results also reflect the influence of the accuracy of input parameters. The computational fluid dynamics model of electronic enclosures requires the pressure drop details of vents to predict the system impedance and air flow through the system thereafter. The temperature of electronic components depends on the rate of airflow through the electronic system. Loss coefficient of vents appears to be the major source of error. The modeling of each vent is typically not possible and is represented by its pressure drop. An experimental setup is established to measure the pressure drop characteristics of different patterns of vents commonly used in electronic equipment. Pressure drop of different vent patterns, with hole diameter varying from 1.6 mm to 3.0 mm, the pitch varying from 3.2 mm to 6.5 mm, and the porosity varying from 20% to 45%, are measured using an experimental setup. In this paper, a practical formula for the loss coefficient of vents is presented. This formula takes into account important parameters such as hole diameter, pitch, porosity, and Reynolds number.