Multi-objective optimization of overhead transmission lines including the phase sequence optimization

Since the human density, technologies, industries and services are in continuous grow, the electrical power consumption increments over the time. To satisfy those power levels the transmission lines should increment their power capacity. However, the increment has to be done taking into account that the line projects should use the lowest possible space to decrease their environmental impact. The present paper proposes the use of optimized multi-circuit transmission lines with several circuits and voltage levels on the same tower. A mixed-integer non-linear programming (MINLP) model with variables in a permutation based space for optimizing the surge impedance loading (SIL), right of way (ROW), costs and height of power transmission lines is presented and solved using evolutionary computation with a multi-objective approach based on the Non-dominated Sorting Genetic Algorithm II (NSGA-II). The optimization is done by choosing the optimal position, type and quantity of conductors as well as the phase sequence in multi-circuit transmission lines. To deal with the different types of decision variables, a custom constraint handling is proposed. As a result of the optimization process, multi-circuit power transmission lines with narrower ROW, lower environmental impact, higher SIL and similar costs to conventional lines are obtained.