Aprimoramento de técnicas de seleção de reatores de neutro em linhas de transmissão.

Abstract

This paper presents a parametric analysis and suggests a proposal for determining reactan ces for neutral reactors used to mitigate secondary arc current during single-phase faults. The parameters analyzed were the length of the transmission line (TL), the level of reactive com pensation shunt, and the ratio between positive and zero sequence capacitances c1/c0. To this end, a sensitivity analysis was conducted using the program ATPDraw (Alternative Transients Program) on a set of 10 TLs. The effective current and the first peak of the transient restoring voltage (TRT) values were collected during simulations of single-phase faults. The data was used to identify the influence of changing the selected parameters. Increasing the length made the secondary arc currents higher, and this effect was more pronounced for the lower compen sation levels. Reactive compensation had a greater impact on the ratio between the positive and zero sequence reactances considered “optimal”, with this effect being more noticeable in TLs with a higher c1/c0 ratio. A curve-fitting procedure was used to obtain equations that represented the data set. Two scenarios were considered: the neutral reactors with the lowest reactances whose resulting currents were below 50 A (“minimum” reactors) and those whose applications provided the lowest TRT peaks and effective currents, called “optimal” reactors. The analyses for the “optimal” case led to a set of equations that allow neutral reactor values to be obtained for different TLs based on capacitances without depending on the length of the TL. The analyses for the “minimum” case proved to be more complex, and it was not possible to identify behaviors between different TLs that would allow a single set of equations to be formulated. Finally, a methodology was proposed and compared with results in the literature, allowing the normative criteria to be met for a wider range of reactive compensation.