根据电缆表面温度推算导体温度的热路简化模型暂态误差分析

Analysis on Transient Error of Simplified Thermal Circuit Model for Calculating Conductor Temperature by Cable Surface Temperature

电力电缆运行中导体的温度是确定电缆是否达到载流量的依据,为分析热路简化模型计算电缆导体温度的精度,根据110 kV交联聚乙烯电缆各层温度的热路模型及其简化模型,借助Matlab软件推导出了基于电缆表面温度推算电缆导体温度的计算式,理论上演算了电缆热路完整模型与简化模型之间的误差,并给出该误差与所施加电流的函数关系。同时,设计了直埋电缆的暂态温升试验,根据实测表面温度数据利用简化模型计算了导体温度、绝缘层温度,对比分析了简化模型所计算的导体温度、绝缘层温度与实测导体温度、绝缘层温度之间的误差。结果表明,简化模型计算电缆导体温度与实测导体温度之间的误差在允许范围之内,可用于工程上基于电缆表面温度推算电缆导体温度。

The temperature of power cable conductor of being operated cable is the foundation to judge whether the cable reaches its rated current carrying capacity or not. To analyze the accuracy of cable conductor temperature calculated by simplified thermal circuit model, based on the thermal circuit model to calculate the temperatures of different layers of 110 kV XLPE cable and its simplified model, by means of Matlab software the cable surface temperature-based computation expression to calculate cable conductor temperature is derived, and the error between the cable conductor temperature calculated by complete thermal circuit model and that by its simplified model are computed theoretically, then the functional relation between the error and the current applied to the cable is given. Meanwhile, a transient temperature rise test of directly buried cable is designed. According to the measured data of cable surface temperature, the temperatures of conductors and insulating layers are calculated by the simplified model, then the comparative analysis on the errors between the temperatures of conductors and insulating layers calculated by the simplified model and the measured temperatures of conductors and insulating layers is performed. Analysis results show that the errors between the cable conductor temperatures calculated by simplified model and the measured cable conductor temperatures are inside the allowable range, thus in engineering application the simplified thermal circuit model can be used to calculate cable conductor temperature by surface temperature of the cable.