Contingency Analysis Considering the Transient Thermal Behavior of Overhead Transmission Lines

In conventional contingency analysis (CA), the overloading of transmission lines is identified by the violation of current or power flow rather than the temperature rise. Thus, the transient thermal behavior of transmission lines is usually neglected, which may cause underestimation of power transfer capability and lead to misoperations. In this paper, a new CA method that considers the transient thermal behavior of overhead transmission lines is proposed, where a transient heat balance based power flow (THB-PF) model is established to estimate the temperature dynamics of the lines after contingencies. The THB-PF model is represented by algebraic differential equations, which can be solved as a sequence of extended power flow problems by discretizing the differential equations into difference equations. Moreover, a simplified solution method for the THB-PF is also developed, in which the THB difference equations are linearized and solved separately from the power flow equations. The simplified method can yield an acceptable approximate solution within a considerably shorter time. Numerical simulations verify the effectiveness and efficiency of the proposed methods.