Analysis of transient overvoltages caused by energization of multi-conductor transmission lines

This paper presents a detailed study of the behavior of transient overvoltages in high-voltage transmission systems, using simulations in alternative transients program/electromagnetic transients program (ATP/EMTP) software. Two representative cases were analyzed: the first involves the sequential energization of an initially de-energized 230 kV circuit, while the second corresponds to the reclosing of a 400 kV circuit after opening due to a fault, in the presence of an already energized adjacent circuit. The transmission lines were modeled using the JMARTI model, suitable for representing frequency-dependent phenomena characteristic of switching transients. Non-simultaneous phase-to-phase closure conditions were considered, which allowed the most critical overvoltage scenarios to be identified. In the first case, overvoltages reached values greater than 2 per unit (pu), while in the second, during reclosure, overvoltages of up to 2.33 pu were observed, corresponding to more than 1300 kV. Additionally, induced voltages in adjacent circuits were evaluated through 30 simulations, varying the distance between tower centers from 50 m to 500 m. The results showed a clear decrease in induced overvoltages with increasing distance, although significant values of up to 0.25 pu were recorded even at 200 m. The results obtained were compared with the basic insulation levels (BIL) recommended by international standards such as IEC 60071-1 and IEEE Std C62, demonstrating the need to implement mitigation strategies. This study highlights the importance of considering both the switching sequence and the physical configuration of the system in the design of reliable and safe transmission networks.