Static Voltage Stability Assessment Considering Impacts of Ambient Conditions on Overhead Transmission Lines

The static voltage stability assessment model is effective in analyzing system stability states. However, the electrothermal coupling relationship dependent on practical current-carrying and ambient conditions is generally ignored for models concerning overhead transmission lines, thereby introducing certain analysis errors. Therefore, this article proposes a unified power flow model which allows for the electrothermal coupling effect characterized by the balance of heat absorption and dissipation for overhead conductors. Moreover, the meteorological and geographic information around the transmission lines is involved as variables in the power flow calculation. Then, the Newton iteration formulations are restated and the improved power flow model is solved by continuously adjusting the variables and updating an extended Jacobian matrix. Then, the extended matrix corresponding to the final power flow solutions is used to establish the improved
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sensitivity and modal analysis methods, which allows one to evaluate system static voltage stability considering variations of ambient factors. Consequently, based on an IEEE 14-bus test system, the results obtained by the traditional model and the improved model are contrastively analyzed in different scenarios, which are substantially different from each other. The results illustrate that the consideration of ambient conditions around the transmission line will cause remarkedly impacts on the static voltage stability assessment results.