以单相电流测试三芯钢带铠装电缆载流量的可行性分析

Analysis on the Ampacity-Testing Feasibility of Steel-Armour Three-Core Cable by Feeding One-phase Curren

配电电缆一般为三芯钢带铠装结构,加载于三相导体的交流电流在磁性材料的钢带铠装层将产生工频磁场,由此产生铠装损耗;若三相导体加载三相对称电流,铠装层的合成磁场较小(甚至为零),其铠装损耗较小;若三相导体加载单相电流,铠装层磁场较大,其损耗较大。在开展三芯电缆载流量试验时,由于电源容量限制,拟加载单相电流,可能会对载流量的试验结果产生影响。为研究三芯钢带铠装电缆通以三相和单相电流的铠装损耗,及其对载流量试验结果的影响,本文研究了三芯电缆钢带铠装损耗的计算方法;在试验场开展了加载单相电流的直埋单根三芯电缆载流量试验,定量计算了加载单相电流时的三芯电缆的铠装损耗;分析了加载单相电流时铠装损耗对载流量试验影响的程度。研究表明,三芯铠装电缆加载单相电流时的铠装损耗不可忽略,但对载流量的影响不大,且偏保守。

Distribution three-core cable is usually with steel armour. When AC current is applied to the cable,there is a magnetic field in its armour and then steel armour loss. If the current is three-phase symmetry,the magnetic field of armour is small and its loss is ignorable; If cable is feed with a single phase current,its magnetic field is big and its armour loss cannot be ignored. For restrict of power capacity,the rating experiments of 10kV cable with cluster laying are intended to apply a single-phase current,which bring in the steel armour loss and may decrease the experiment result. To research the armour loss and its effect on the rating of three-core cable with single-phase current applied,the calculation method of armour loss is research here; the current rating experiment is carried out,its steel armour loss is calculated; and the current ratings applied with single-phase current is compared with that applied with three-phase current in this paper. The research and analysis shows that the armour loss applied with single-phase current is too big to neglect,However,the rating with single-phase current make not much difference with that with three-phase current,and the effect of single-phase current on rating experiment could be accepted.