基于电磁-热-流耦合场的非开挖敷设方案的海底电缆载流量计算

海底电缆在登陆处采用非开挖敷设方式时,由于埋深较大、管道内散热较差,该敷设段成为整个海底电缆载流量的瓶颈点,为此搭建基于电磁场、流体场和热场3物理场的耦合模型,计算对比不同敷设方式下海底电缆载流量的受影响情况。首先借助于Comsol软件建立了电磁-热-流耦合物理场的有限元模型,将电磁场、温度场及管道内的空气流速场耦合求解,得到给定负荷电流下的温度分布和管内空气流速分布特性;继而以广东某地2个回路220 kV 3芯交联聚乙烯(polyethlene,PE)绝缘3×500 mm^2海底电缆为例,分析计算海底电缆在水泥顶管和定向钻PE排管2种情况下的载流量。结果表明:采用水泥顶管敷设方案时能满足工程输送容量的要求,而采用PE排管敷设方案的载流量略低于额定值;另外可通过改变管道材质、管道内充水达到提升非开挖敷设方式下海底电缆载流量的效果。

Calculation of Ampacity for Submarine Cables Under Trenchless Laying Method Based on Electromagnetic-thermal-flow Coupled Field

Due to large buried depth and poor heat dissipation in the pipeline under the trenchless laying method, this laying section of the submarine cable becomes the bottleneck point to limit the ampacity of the whole submarine cable. Therefore, this paper proposes a coupling model based on the electromagnetic field, the fluid field and the thermal physical field, calculates and compares different laying methods affecting the ampacity of the submarine cable. It firstly uses the Comsol software to establish the finite element model of the electromagnetic-thermal-current coupling physical field so as to solve the electromagnetic field, temperature field and air velocity field in pipeline and obtain distribution characteristics of temperature distribution under the given load current and air velocity distribution in the pipe. Afterwards, by taking a two-circuit 220 kV three-core XLPE insulated 3×500 mm^2 submarine cable in a certain area of Guangdong province as an example, it analyzes and calculates ampacity of the submarine cable in the case of cement jacking-pipe and directional drilling PE pipes. The results show that the laying method of cement pipe-jacking can meet the requirements of engineering transportation capacity, while the ampacity of the PE pipe laying method is slightly lower than the rated value. In addition, it is able to improve ampacity of the submarine cable under the trenchless laying method by changing the material of the pipeline and filling the water in the pipeline.