Research on Dynamic Current Carrying Capacity Calculation Model Based on Conductor Sag Correction

Excessive current carrying capacity of transmission lines may lead to increased sag, reduced air insulation distance, and discharge of grounded objects such as trees. If it is too small, it limits the transmission capacity of the transmission system. For example, dynamic capacity expansion technology has always been limited by the accuracy of existing physical calculation models for current carrying capacity. To improve the safety of line-to-ground insulation and enhance the universality of dynamic capacity expansion technology, this paper proposes a dynamic current carrying capacity calculation model for overhead transmission lines based on laser point cloud sag data correction to improve the accuracy of current carrying capacity model calculation. Firstly, by analyzing, screening, and optimizing existing heat sub-models, the calculation accuracy of the current carrying capacity model can be improved. Secondly, by introducing the oblique parabolic model of overhead transmission lines, a nonlinear programming mathematical model is constructed with the calculation error of the second sag measured by the unmanned aerial vehicle laser point cloud as the objective function and the average parameter as the optimization variable. Further correction of parameters with statistical average significance within the model, such as radiative heat dissipation coefficient <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ϵ</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub>, conductor surface heat absorption coefficient <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">α_s</i>, and safety coefficient <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Security</sub>, has been achieved. The final test case analysis shows that the sag calculation error has been reduced to 0.02m, and the maximum current carrying capacity has changed and reduced by 45.46A from original capacity (500.85 to 445.39A) compared to before the correction. The optimized parameters can effectively improve the calculation accuracy of the conductor sag and maximum allowable current carrying capacity calculation model.