输电线路工频参数影响因素的量化研究

Quantification of Factors Influencing Transmission Line Parameters

输电线路参数的准确性对于系统的正常运行、计算及保护整定等起着至关重要的作用,为此分析了诸多影响线路参数准确性的因素,并将这些因素量化到计算公式中。计算一条220 kV线路修正前后相关参数的结果表明,考虑这些因素影响后的计算结果更接近于实际运行状况或实测值。由此得出以下结论:多回运行线路间的磁场作用会使线路阻抗值变大;不同的土壤类型及湿度、温度等环境因素会影响土壤电阻率值,进而影响零序阻抗值;在长距离线路中,将考虑弧垂的地面平均高度作为导线对地高度来计算零序电容会大大减小与实测值的误差。

Accurate transmission line parameters play an important role in the operation, calculation and maintenance of power systems. Inaccurate parameters may influence the operation of power equipments, lead to the misoperation of protection and cause accident even. The example of a 220 kV transmission line is given in the paper. Considering the influence of inductive magnetic field among operating lines, resistivity of soil and sag of transmission lines on transmission line parameters, the influential elements are quantified as parts of the formulas. Then parameters of transmission lines are recalculated and compared with the results ignoring influential factors above. The interaction of induced magnetic fields among operating transmission lines may cause the alteration of parameters such as impedance; different type of soil, humidity and temperature have a significant impact on the resistivity of soil, then the zero-sequence impedance is influenced as well. Taking the measured value of the resistivity of soil into the calculation, the accuracy would be improved effectively and the calculated error would be decreased correspondingly; for long distance transmission lines, the sag is large. It is not reasonable to take the hanging point altitude for calculating the zero sequence capacitance. Taking the average altitude considering sag as the calculation altitude of transmission lines, the zero-sequence capacitance is recalculated, the error decreases greatly. The analysis results show that the calculated parameters are closer to the actual situation or actual parameters when influential factors are taken into account.