569 / 2017-05-14 20:14:32

Thermal analysis of switchgear using FEM considering the heat from the main circuit

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Now the switchgear is very extensive use in the power grid. Overheating of the switch cabinet can affect the normal operation of electrical equipment or even cause accidents and endanger the safety of the power grid. Therefore, the temperature rise of switchgear issues have attracted people’s great attention. The article take into account of the thermal effect of the circuit conductors, the contact interfaces between contacts and the terminals in the main circuit. The heat generated by the main circuit is calculatd by thermo-electricity coupled analysis. The key issue in thermal anslysis of switchgear is the heat due to electric contacct. In this article the circuit breaker in the switchgear is a vacuum circuit breaker where the method of contact is plane-plane contact. This article uses two methods to simulate such contact resistance for this contact. The first method uses the traditional conductive bridge model to simulate. It is assumed that all of the conductive spots are concentrated in the center of the contact plane. The radius of the conductive bridge can be expressed by the Holm formula. The material properties of the conductive bridge are the same as those of the contact material. The height of the conductive bridge is generally 0.1~0.25mm. The second method is the contact area coupling method. On the basis of not changing the model, the area on both sides of the contact surface is coupled together so that the current can only flow from the coupling surface. By controlling the coupling area value can achieve the current shrinkage effect and simulate the appropriate contact resistance value. On the basis of the theory , the author compares the simulation results with the actual values and further studies to prove the effectiveness of the two methods.