Electric Arc Resistance Sizing in Conceptual Design Studies of Transmission Lines

In electromagnetic transients studies for conceptual design projects of transmission lines, electric arcs are commonly represented by a switch in series with a fixed-value resistance. Although valid, this simplification could lead to improper equipment sizing if not properly conducted. Using empirical models and taking into account the structural aspects of the transmission lines, a method was developed to size the resistance that represents electric arcs. With the aim of enhancing result accuracy, current and arc length parameters were considered and calculated using easily accessible or estimable information. A minimum arc length was defined based on the distance occupied by the lines insulator chain, allowing for extrapolation to a maximum length. In the analysis of a single-phase switching study, the observation of the lines structural profile and the application of the sizing method confirmed that a delayed current zero crossing previously encountered with the use of an initial conservative value was not real and the lines own dissipation capacity was sufficient to extinguish the phenomenon. Thus, it was demonstrated that a straightforward and effective representation of the electric arc is possible, by employing a resistance sizing approach that remains true to the actual conditions of the line which it was designed for.