提高XLPE高压直流海缆经济性的研究展望

Research Prospect on Improving Economy of XLPE HVDC Submarine Cable

结合我国高压直流海缆工程直流海缆选型、电压等级和输送容量的关系,以单位输送容量所需直流海缆原材料投入作为典型经济性指标,发现随着单回路直流海缆电压等级和载流量升高,直流海缆经济性呈上升趋势。通过对比不同路线提高电压等级和载流量后直流海缆耗材的变化,可知分别通过提高直流海缆绝缘电气水平和导体最高允许运行温度的方式实现电压等级和载流量提升对提高直流海缆经济性更为有效。此外选取导体最高运行温度为70℃的±525 kV直流海缆为典型规格,利用有限元仿真分析外加电压提高至972 kV和导体运行温度提高至90℃后直流海缆绝缘场强分布的变化,结果表明电压等级和导体运行温度的提高均会造成绝缘场强翻转后靠近绝缘屏蔽处的场强进一步升高,且二者存在协同作用,在此基础上,设定绝缘屏蔽与绝缘界面存在向绝缘内尺寸为0.125 mm的半圆形突起,有限元仿真结果表明该点的场强对比无突起情况增大了35.8%。

Combining with the relationships among the DC submarine selection, voltage level, and transmission capacity of HVDC submarine cable projects in China, taking the raw material input of DC submarine cable required per unit transmission capacity as a typical economic index, we find that with the increase of voltage level and current capacity of the single loop DC submarine cable, the economy of DC submarine cable increases. By comparing the materials consumable variation of different routes after improving the voltage level and transmission capacity, we find that it is more effective to improve the economy of DC submarine cable by increasing the electrical level of DC submarine cable insulation and the maximum operating temperature of conductor to improve the voltage level and transmission capacity, respectively. In addition, a ±525 kV DC submarine cable with the highest conductor operating temperature of 70℃ was selected as the typical specification, and its insulation field strength distribution variations were analyzed through finite element simulation when the applied voltage and conductor operating temperature increased to 972 kV and 90℃, respectively. The results show that the increase of voltage level and conductor operating temperature will both cause a further increase of field strength close to insulation shield after the insulation field strength reversal, and there is a synergism effect between them. On this basis, a semicircular protuberance with 0.125 mm of depth was set on the interface of insulation shield into insulation, and the finite element simulation results show that the field strength at the protuberance increased by 35.4% compared with the case without protuberance.