摘要
运行中电力电缆线芯温度随负荷电流和电缆本体及周围媒质热特性参数的变化而变化,准确地确定电缆暂态温度场和线芯温度是提高电缆输送能力的基础。针对有限差分法计算电缆温度场难以处理电缆圆形边界和周围土壤矩形边界的问题,采用阶梯直线代替电缆圆形边界,在直角坐标系中直接求解电缆暂态温度场。基于坐标组合的有限差分法和大电流模拟试验验证该方法的有效性和实用性。计算程序分析了恒定负荷电流下电缆线芯的温升过程和载流量试验误差。计算结果表明:电缆线芯温升速度随土壤热阻系数的增加和电缆根数的增加而减慢,目前载流量试验中采用的热稳定判据可以使载流量试验值显著高于载流量实际值。
The conductor temperatures of power cables change with load current as well as thermal characteris- tic parameters of power cables and surrounding medium. For the safety and the economy of transmission, it is meaningful to accurately predict the transient state thermal field of underground cables. Determining conductor temperatures is the basis of improving the current-carrying capacity. The finite difference method has shown difficulty in dealing with circular boundary of power cables and rectangular boundary of the surrounding soil when calculating temperature field of power cables. In this paper, ladder straight lines are adopted to substitute circular boundary of power cables, and temperature fields as well as ampacity are solved in Cartesian coordinate system. Numerical calculation results of finite difference method, which are based on the combinatorial coordi- nate and the temperature rise tests of the constant as well as variable load current, have proved that the method presented in this paper is effective to calculate the temperature fields of underground cables. The ampacity of power cables is often determined by experimental test. The present experimental ampacity, and the temperature rise of power conductors of constant load current, are studied based on the method presented in this paper. The results show that the temperature rise speed of power conductors slows when the soil thermal resistivity and the power cables increase. The tested ampacity may be much higher than the real ampacity because of the thermal steady criterion used in the test.
出处
《东北电力大学学报》
2016年第5期25-31,共7页
Journal of Northeast Electric Power University
基金
吉林省科技发展计划项目(20130101071JC)
吉林省电力有限公司科技项目(2013-39)
关键词
电力电缆
暂态温度场
有限差分法
载流量试验
热稳定判据
试验误差
Power cables
Transient temperature field
Finite difference method
Ampacity test
Thermalsteady criterion
Test error
