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Power transmission line capacity is restricted with the maximum temperature that can withstand without inadmissible of line sag. Regardless of the carried current, the temperature of the transmission line conductors was affected by various weather variables. However, the maximum capacity of the line current known as static thermal rating was determined based on the conservative weather conditions for safe operation, but the restriction of the line capacity may be modified which results in the additional capacity of the line. As a result, real-time thermal rating technique was applied on thermal model of the transmission line. Generally, the information about weather conditions is considered uncertainty, however, the weather variables should be dealt with and studied statistically for determining the accurate rise in the conductor temperature. The real-time thermal rating technique is evaluated using weather variables. The most important parameter is the wind speed, which greatly influence s conductor temperature and implicitly affects power transmission line capacity. Thus, in this study, the real-time thermal rating technique is developed by weather variable model based on the variational mode decomposition technique that applied only on the wind speed for adapting wind speed measurements to produce conservative evaluation of convective cooling on the conductors of power transmission system without violating the maximum operating temperature inside the core of conductors. The developed real-time thermal rating is implemented on sections of the power transmission system of western Saudi Arabia. The developed technique is compared with other techniques to investigate its applicability. [ABSTRACT FROM AUTHOR]

A speed control of sensorless induction motor (IM) drives at zero and very low frequencies is designed in this paper. A new adaptive sliding mode observer (SMO) to estimate the stator current, rotor flux, and rotor speed is proposed. To improve the robustness and accuracy of an adaptive SMO during very low frequency operation, the sliding mode flux observer uses independent gains of the correction terms. The gains of current and rotor flux SMOs are designed using Lyapunov stability theory to guarantee the stability and fast convergence of the estimated variables. A Lyapunov function candidate utilizing the error of rotor fluxes and speed estimation error is synthesized for speed estimation. Detailed simulations and experiments are given showing the operation of the sensorless speed control at very low frequency. The results prove the accuracy and robustness of the proposed adaptive SMO. Also, comparison results with the state-of-the-art methods prove that the proposed method shows excellent transient and steady-state speed estimation, particularly at very low and zero frequency operations. [ABSTRACT FROM PUBLISHER]