THERMAL DESIGN OF FUTURE MEDIUM VOLTAGE SWITCHGEAR.pdf - 23rd International Conference on Electricity Distribution Lyon 15-18 June 2015 Paper 1090

THERMAL DESIGN OF FUTURE MEDIUM VOLTAGE SWITCHGEAR.pdf -...

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23 rd International Conference on Electricity Distribution Lyon, 15-18 June 2015 Paper 1090 CIRED 2015 1/5 THERMAL DESIGN OF FUTURE MEDIUM VOLTAGE SWITCHGEAR Elin FJELD Wilhelm RONDEEL Knut VAAGSAETHER Telemark University College – Norway TUC – Norway TUC - Norway [email protected] [email protected] [email protected] Magne SAXEGAARD Pål SKRYTEN Elham ATTAR ABB – Norway ABB – Norway ABB - Norway [email protected] [email protected] [email protected] ABSTRACT Air is a desirable alternative to SF 6 in medium voltage (MV) switchgear. However, the thermal properties of air is poorer compared with SF 6 , and this paper presents a first step in the process of finding an optimized thermal design. Mapping of the resistances and the thermal condition have been performed on a custom made prototype. Together with CFD-simulations, these methods are found to be useful for gaining insight and improving the thermal design of MV switchgear. The combined contact resistances (bolted and others) was for found to constitute about 35 % of the total resistance of the prototype. Possible contributions from the skin-effect and/or iron losses seem to be of little or no influence to the power input. INTRODUCTION Medium voltage (MV) switchgears are used in the distribution network to ensure a safe and reliable power supply to the customers. For decades, SF 6 gas has been used to ensure the reliability, compactness, and robustness of these switchgears. Unfortunately, SF 6 suffers from a very high global warming potential. MV switchgears are manufactured to be sealed for life and to have SF 6 emissions of < 0.1 % / year. Nevertheless, since SF 6 emission can occur due to incorrect handling during installation and decommissioning, the industry is interested in finding a suitable alternative. For the future generation of MV switchgears, it is desirable to keep the compact switchgear design [1]. Load currents cause ohmic losses and thus heating inside the switchgear. Air is a desirable alternative to SF 6 , however, since the thermal properties of air is poorer compared with SF 6 , this causes some extra care to be taken regarding the thermal design in order to satisfy the requirements of the temperature rise test specified in the standard IEC 62271-1 [2]. Thermal design has traditionally been devoted little attention as SF 6 has relatively good thermal properties. To be able to keep the compact design when changing to a more environmental friendly gas, thermal design needs to be more optimized. This paper presents the results from the first step in this process. Mapping of the resistances and the thermal condition have been performed on an air filled prototype with dimensions comparable to an SF 6 -filled switchgear installation. The temperature and power measurements are used as input data in simplified heat transfer simulations. ANSYS- fluent CFD software is used in addition to calculations according to the empirical guidelines given in IEC TR 60890 [3].
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