三种绝缘气体下开关设备的温度场及流场对比与分析

Analysis of Thermal and Fluid Field of Switchgear in Three Insulating Gases

基于热传导微分方程、流体运动控制方程及辐射换热方程,建立了开关设备的传导、对流和辐射换热相互耦合的数学模型,并采用壁函数法处理对流换热边界条件。利用棱边单元法计算了考虑集肤效应、邻近效应及涡流效应下载流导体和外壳的焦耳热损耗。以某型号开关设备为对象,采用有限容积法和六面体网格,分别计算分析SF6、N2、空气中开关设备的三维温度场与气流场,从温升角度探讨空气、N2作为SF6替代气体的可行性。计算结果表明,三种气体中温度分布基本相同,温升大小表现为SF6气体内的最高,N2内与空气内的差别不大;三种气体中的气流速度大小顺序也表现为相似的规律。从温升角度考虑,在满足绝缘条件的前提下,空气、氮气具有替代SF6的可行性。

Based on the heat conduction equation, fluid flow governing equation and radiation heat transfer equation, a multi-physics coupled mathematical model is established, in which the convection heat transfer problem between solid and fluid is solved by wall function for simulating the temperature in the switchgear. The joule heat losses of current-carrying conductors and shell are calculated respectively including skin, proximity and eddy current effects with the use of 3D edge element method. The three dimensional thermal and fluid field in a type of switchgear filled respectively with SF6, N2, and air are calculated numerically by the finite volume method and the hexahedral grid and analyzed to discuss the feasibility of using air or N2 as the substitution of SF6. The results show that the temperature field and fluid field in three gases are similar in the switchgear. The temperature rise of current-carrying loop is the highest in SF6 and is approximately equal in the N2 and air. The flow velocity in SF6 is the highest and is the lowest in the air. So the conclusion could be made that under the qualified withstand voltage air or N2 could replace SF6 as the insulating gas of switchgear from the perspective of temperature rise.