Heat transfer mechanisms in MV load break switches
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- Master i teknologi 
This report is part of an ongoing research project between University college of Southeast Norway and ABB Power product division. This report focuses on the heat transfer from two load break switch (LBS), normally used in gas-insulated switchgears. The two LBS designs examined are the knife and puffer switch. How the heat transfer from the conductive paths, in both LBS designs, are affected by the encapsulating structures are investigated. There have been conducted temperature measurements with and without the structures, inside air-filled enclosures. Calculations of the heat transfer from both LBS designs and theoretical calculations of encapsulation have been conducted. For both LBS designs the structures have small effects on the temperatures rise. For the knife switch, there were small changes in distribution of the heat transfer mechanisms. For the puffer switch the effect of radiation increases, when the structures are added, from 7 % to 50 % of the total power loss. The convection decreases, when the structures are added to the LBS, from 76 % to 35 % for the puffer switch. The reason for changes in distribution of heat transfer mechanisms for the puffer switch, is a higher percentage of encapsulation (with higher emissivity coefficient) and changed surface area. The power loss due to conduction was approximately 15 % for both LBS designs with and without encapsulation.