Estudo de alternativas para a redução do campo magnético de linhas subterrâneas com o menor comprometimento de sua capacidade de transmissão

Abstract

There is an increasing concern in the world about the problems caused due to the magnetic field generated by underground power cables and so, the restrictions imposed on allowable levels of the field intensity are becoming stricter. Thus, to conform to current legislation, in many times, becomes necessary to use some techniques to mitigate the power frequency magnetic fields generated by underground cables. However, in some situations, in addition to reducing the field, the shielding devices can cause an additional temperature rise of the conductors, thereby leading to a reduction in the current rating of the line. In this context, this work has as main goal, conduct a study on the efficiency of some of the best known settings shielding, featuring not only their effects on the reduction of the field, but also its impact on the current carrying capacity of the system. To this end, a methodology based on the finite element method to calculate the magnetic field and temperature distribution in the vicinity of an underground transmission line, even in the presence of shielding equipment, is presented. For this, a coupling between the models of the thermal and magnetic calculation was performed, also allowing the consideration of the variation of electrical conductivity with temperature for all elements in the system. The principal results were summarized in a table, and can serve as a guide for situations where there is a need for some of the shielding field.