基于耦合场的通风电缆沟敷设电缆载流量计算及其影响因素分析

Current-carrying capacity calculation based on coupling fields for cable in ventilated trench and its influencing factors

根据电缆沟通风系统内流体流动与传热的特点,建立电缆沟通风系统三维流体流动与传热耦合计算模型,给出求解域相应的边界条件和假设条件,采用有限元法对流体场和温度场方程进行耦合计算,得到电缆沟内流体速度分布和电缆表面温度分布特性,验证了耦合模型的正确性;并在求得电缆表面最高温度的基础上,利用电缆区域的等值热路法和数值迭代法计算了电缆允许载流量。此外,基于该模型通过实例仿真得出了不同影响因素对通风电缆沟敷设电缆允许载流量的影响规律:电缆载流量随着进风速度的增大而增大;进风温度每升高1 K,电缆允许载流量相应下降约5.6 A;随着电缆隧道通风长度的增加,电缆允许载流量随之下降。

For the flow-heat coupling analysis,a 3-D model of cable trench ventilation system is established according to the characteristics of air flow and heat transfer,based on which and with the corresponding boundary conditions and assumptions ,the finite element method is applied to calculate the coupling between fluid field and thermal field and the fluid velocity distribution in cable trench and the temperature distribution on cable surface are obtained. Its accuracy is thus verified. Based on the calculated highest temperature of cable surface,the cable-area equivalent thermal circuit method and the numerical iterative method are applied to calculate the cable current-carrying capacity. The influence of different factors on cable current-carrying capacity is investigated by case simulation and results indicate that,the capacity increases along with the increase of inlet air velocity;the capacity decreases about 5.6 A per 1 K increase of inlet air temperature ;and the capacity decreases along with the increase of cable trench length.