Influence of thermal radiation in MV switchgear
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- Master i teknologi 
When developing MV switchgear units it is important that the finalized product is within IEC maximum temperature rise limit. When a switchgear unit is developed it is continuously tested until it meets the requirements, the process may be time consuming, costly and involve several prototypes. A method who can decrease the number of tests and minimize the cost and time, is to use simulation tools to simulate the temperature rise. One challenges when simulation temperature rise is to find the thermal radiation, as it is difficult to estimate. The purpose of this report is to estimate how much of the power loss goes to thermal radiation in a MV switchgear unit with 630 A, 500 A, 400 A and 200 A current load, with both painted and non-painted current conductors. This will be done experimentally by measuring the temperature, the emissivity and the resistance and use this to estimate the power loss and the thermal radiation. For unpainted conductors the silver coated switch contributes with 10 % thermal radiation of the power loss in the switch. The temperature rise is higher with unpainted conductors and the thermal radiation is lower. For unpainted conductors the switch contributed with 45-50 % of the power loss in the switch. Painting, coating or using other methods to rise the emissivity lowers the temperature rise and increases the contribution of thermal radiation. It is crucial to take the thermal radiation into account for objects with higher emissivity, as the contributes with more thermal radiation.