In view of the difficulty in obtaining accurate transmission line temperatures due to fluctuation in transmission line resistance estimation

a semi-parametric adjustment model is developed to realize robust estimation of transmission line temperatures. Based on an analysis of the factors influencing the estimation results of transmission line temperatures and the correlation between measuring equations

a two-stage estimation method for precisely estimating the resistance value is proposed. Considering the retardation in resistance changes

a semi-parametric adjustment model is developed

in which the linear equation is adopted with unknown errors as parameters to be estimated. Furthermore

the choice of the smoothing parameter β and regular matrix M is accounted for. Hence

the accuracy and stability of the transmission line temperature estimation is improved

which provides a firm basis for the application of soft dynamic thermal rating (DTR). Finally

based on the measured data of 220 kV Fangshan-Caocheng transmission line in Shandong Province

the semi-parametric model is compared with the traditional least square model. The result shows that the method proposed is valid and practicable. This work is supported by Shandong Provincial Natural Science Foundation of China (No. ZR2013EEL005)

Research Award Foundation for Outstanding Young and Middle-aged Scientists in Shandong Province (No. BS2013DX046) and National Natural Science Foundation of China (No. 51407111

No. 50677036).