Comprehensive Assessment of Lightning Protection Schemes for 10 kV Overhead Distribution Lines

This paper presents an assessment of lightning protection schemes for overhead lines from two aspects: protection performance and economic cost. Considering the random nature of lightning, the Monte-Carlo method with a heuristic technique is applied in the assessment. The one-dimensional finite-difference time-domain method is adopted to evaluate lightning overvoltages on insulators and lightning currents in surge arresters for failure assessment. The failure rate of an overhead line is addressed under both direct lightning and indirect lightning. A reduced set of design parameters are identified. It is found that the line insulation itself with a critical flashover overvoltage of less than 200 kV is not sufficient for lightning protection, especially against direct strokes. With other protection options, however, increasing the insulation level can greatly improve the protection performance. Installing surge arresters on every pole results in the best protection performance, but could be extremely expensive due to the replacement of failed surge arresters. The shielding wire provides moderate protection performance with a relatively low cost. The combination of the shielding wire and surge arresters provides much better performance under a wide range of soil conductivity with a moderate cost. It is worth mentioning that adopting high insulation strength for overhead lines in the new-line design could lead to significant cost savings for lightning protection. Guidelines for selecting design parameter values and protection schemes are provided, as well as a procedure for performance-cost evaluation.