| At present, economic development and people’s livelihood is becoming more dependent to energy security. In some way, the energy supply level determines the economic development degree and people’s life quality, so various countries in the world are doing their best to enhance their energy safety and to improve energy crisis supply efficiency. Large current switchgear is the familiar device, it is usually used to protect valuable industry equipment and residents power supply. Since opening to the outside world, our economic has being improved for 30 years, markets demand more efficient switchgear. Now each switchgear capacity is becoming lager and lager; and switchgear is set in corporations, even in high buildings, the smaller and smaller installation space results bad thermal dissipation.The vital parts, fixed contacts of large current switchgear were installed in the resin contact-boxes. Narrow air convection space and abominable lead to overheat, vigorous oxidation and burn melt fault frequently. When residential electric peak meets industrial electric peak, the contacts temperature can reach higher than 100℃ and breaks the industrial national standards, and that made a huge threat to the security and reliability of the power supply system. Limiting current might relieve the situation, but the maintenance costs raises greatly. Heat pipe have perfect conductivity, simple structure, high reliability natures. The subject put heat pipe technology into KYN44A-12 switchgear contacts cooling. Six heat pipe exchangers were designed and installed in contacts boxes to help the contacts and to avoid overheating and explosion faults.The degree thesis main contents as follows. The urgency and necessary of switchgear cooling was demonstrated after analyzing the development situations and related technologies; Switchgear FEM model was established and the air condition inside it was researched; Combining FEM results and heat-pipe theory, heat dissipation and exchangers were finished; At the end, authority agency made temperature raising experiments on switchgear prototype; According to the results, the installation methods of exchangers, contacts boxes and the cabinet structure were optimized. The tests results show that:1.Comparing the exchangers II, the III does not need move copper bar, but additional heat generation makes it unacceptable for cable room; 2. The exchangers I between fixed contacts and copper bar in bus room also has additional heat generation problem, which would disappear when the exchanger is installed in copper bar near the fixed contacts, but the tests results not good enough. Finally its installation method turned into hugging tightly on fixed contacts,and with the help of optimizing cabinet structure and resin contacts boxes with air duct, the key parts temperature raising lower 30K.3. Optimizing cabinet structure, resin contacts boxes with air duct.installing heat pipe exchangers and developing their installation methods all these make large current switchgear can self cool effectively, sole element could not control key parts temperature raising.When current level reaches 4000A, the prototype also can self cool effectively. Compared with installing fans, widening switchgear width and using bigger cross-section copper bar, the method released in this thesis more effective, air inside switchgear is much cleaner, and the dust in the conductive parts is much less. Bottleneck problem limiting current is broken, the switchgear design volume could be made good use, and the heat fault rate is drasticly reduced. Above all, the easy and cheap methods is benefit to market promotion. |
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