交联电缆集群敷设载流量的数值计算

Numerical Calculation of Ampacity for XLPE Cables in Cluster Laying

在人口稠密的大城市,电力通常通过直埋电力电缆集群来传输。电缆载流量是电缆设计和运行中的一个重要参数。IEC 60287标准给出了单一媒质即均匀土壤中电缆群稳态载流量的计算方法,并给出了有回填土的非单一媒质中电缆群的载流量修正计算方法。为给电缆工程的设计与运行提供科学依据,采用基于场路结合的有限差分法,提出了非单一媒质中电缆群的载流量数值计算方法,深入研究了不均匀土壤中的电缆载流量及其影响因素。计算结果表明,IEC外部热阻修正计算方法的计算精度与回填土热阻系数有关。回填土热阻系数较大时,IEC计算载流量显著偏低。

International Electrotechnical Commission（IEC） methods for calculating cable ampacity assume that buried cables are surrounded by a single,homogeneous material.These ampacity methods have limited application when a thermal backfill is used.IEC correction methods are presented to calculate cables＇ ampacity of non-homogeneous soil.Based on the finite difference method of field-circuit coupling theory,a new numerical calculation method of cable ampacity of non-homogeneous soil is presented.The numerical calculation method which is accomplished through the calculation of cable temperature field distribution can deal with any combination of backfill materials that are placed adjacent to the cable.The calculated results show that IEC thermal resistance correction methods can be effectively used to calculate amapcity when the thermal resistivity of the backfill soil is lower.When the thermal resistivity of the backfill soil is higher,IEC calculating ampacities of correction methods are obviously lower.