Application of direct collocation method in short-term line ampacity calculation

Commonly for the calculation of line ampacity (rating) the steady-state heat balance equation is used. In this paper a novel method for the calculation of line ampacity is developed. This method is based on the definition of an optimal control problem and its solution represents the line ampacity in the desired time range. The solution of the defined optimal control problem is obtained by applying the direct collocation method. In this manner the short-term line ampacity is obtained by solving a nonlinear programming problem. Nowadays, many algorithms and hardware implementations are available for solving similar nonlinear programming problems. Thus, the usage of this method is suitable for simplifying the calculation of the short-term line ampacity in contemporary dynamical line rating systems. Finally, the developed is compared with existing methods for the short-term line ampacity calculation and the advantages and the disadvantages of each method are discussed. At the end of the paper for a 240/40 mm(2) aluminium steel-reinforced conductor, the methods are tested on several cases and the results compared. The effectiveness of each method is checked by simulating the conductor non-steadystate heat balance equation with the obtained results for the line ampacities. From the obtained results it is proven that the developed method effectively calculates the short-term line ampacity, and at the same time simplifies the calculation process. This paper is recommended for researchers focused in the field of dynamical rating systems. (C) 2017 Elsevier B.V. All rights reserved.