高压直流XLPE绝缘电缆载流量的数值算法及特性分析

Numerical algorithm and characteristic analysis on current-carrying capacity of HVDC XLPE insulated cable

载流量是电缆传输能力的重要指标,直接影响高压直流电缆的运行可靠性和经济性。根据直流电缆绝缘层中电场分布的特点,提出了基于等效电导率的绝缘层内外侧电场分布的解析计算方法,并以±535 kV交联聚乙烯绝缘直流电缆为例,同时考虑电缆导体最高运行温度和绝缘层最大允许温差,得到不同运行工况下高压直流电缆的负载控制域。结果表明:电-热场解耦方法能有效分析直流电缆的载流量和应用特性,其中绝缘层最大温差是限制临界环境温度以下直流电缆载流量的核心因素,在此临界环境温度下,提升导体最高运行温度对载流量影响有限,而优化绝缘材料耐电性能和电缆结构才是提升载流量的关键。

Current-carrying capacity is an important indicator of cable transmission capacity, which directly affects the operation reliability and economy of HVDC cables. According to the electric field distribution characteristics in the insulation layer of DC cable, an analytical calculation method of the electric field distribution inside and outside the insulation layer based on the equivalent conductivity was proposed. Taking a ±535 kV XLPE insulated DC cable as example, considering the highest operating temperature of cable conductor and the maximum allowable temperature difference of insulation layer, we obtained the load control domains of the HVDC cable under different operating conditions.The results show that the current-carrying capacity and application characteristics of HVDC cables can be analyzed by the electric thermal field decoupling method effectively, and the maximum temperature difference of insulation layer is the core factor limiting the current-carrying capacity of DC cable below critical ambient temperature. Under the critical ambient temperature, raising the highest operating temperature of conductor has limited influence on the current-carrying capacity,while optimizing the electrical resistance of insulating materials and cable structure is the key to improving the currentcarrying capacity.