Estimate the Temperature Rise of Medium Voltage Metal Enclosed Switchgear by Simplified Heat Transfer Calculations

Electrical equipment will experience a rise in temperature during normal operation. During a development process, prototypes and laboratory tests will be required to make sure the temperature rises are within acceptable limits as defined by standards. The aim of having a tool to predict the temperature rise, is to reduce the number of prototypes and test loops needed in the laboratory during a development period. Advanced simulation tools such as CFD can give valuable results, however, they require expertise user and extensive compute and manpower allocation. This paper presents a practical design approach developed for providing a first, quick and rough estimate of the temperature rise of the most critical parts in an air insulated switchgear. The main idea behind the method is to first use the method described in IEC 60890 to estimate the temperature rise of the gas inside the switchgear. Then, simplified heat transfer calculations are used to estimate the over-temperature of critical parts relative to the surrounding gas. The accuracy of the temperature estimates will depend on how well the power input is known, especially the contact resistances. Further, it may be challenging to predict the influence of large metallic construction elements that may function as heat sinks.