Analyses and practical measures to reduce lightning-caused outages on a 110 kV overhead line

This paper presents a project, which deals with various analyses and practical measures to increase the reliability of a 110 kV overhead line in an existing overhead distribution network by taking measures addressing lightning. Due to the fault statistic, a specific overhead line was identified as a main reason for lightning-caused outages. Analytical methods as well as evaluation processes for possibilities to reduce the lightning-caused outages are described and the consequential practical measures on this single line are discussed. All considerations took the special grounding issues of this high alpine situation (2300 meter) and the local lightning activities (4 to 5 times higher than in other Austrian regions) into account. Numerical calculations are performed to assess the application of line arrestors regarding the transient voltage stress for the insulation coordination. According to the simulation results, a strategy is laid out to implement surge arrestors in two phases. To obtain a better grounding- and shielding-situation, two phases of the parallel three- phase system are used as additional shield wires. Further, arrest discharge loggers were installed to record and evaluate the effectiveness of these measures.