Improvement of the transmission and sub-transmission overhead lines lightning performance using line arresters – Experience in Brazil
Keywords:Line arresters, Overhead line performance, Lightning performance improvement
Lightning has been reported as the major cause of non-scheduled outages that occur in Brazilian’s power system, being responsible for approximately 50 – 70% of the outages verified in overhead lines with rated voltages up to 230 kV and creating many issues for power supply utilities and consumers. In agreement with the information of the National Institute for Space Researche (INPE) Brazil is the country with the largest incidence of lightning activities in the world, with about 50 - 70 million lightning outages a year somewhere in the country. With this considerable amount of lightning caused distubances, the resulting damages caused to the electric power systems are high such that the costs of losses and repairs exceed an annual value of 350 million dollars. This fact has been taken up by several power supply utilities and industrial consumers and caused them to invest in partnership with universities and research centers in the development of theoretical studies and the promotion of improvements along the critical sections of their overhead lines with poor lightning performance, thereby increasing their reliability. In many cases line arresters have been considered as the most effective method to improve the lightning performance. In Brazil, the first application of line arresters was in the middle of the nineties and from this time on more than 3,000 units of gapless line arresters were installed on overhead lines from 34.5 kV up to 230 kV. The analysis and evaluation of overhead lines lightning performance before and after the line arresters installation have shown a good effectiveness, with average indexes for the improvement higher than 70%. Good field experience and the proven results obtained in the the overhead lines lightning performance after the line arresters installation have been encouraging more and more Brazilian power supply utilities and industrial consumers to develop studies to evaluate the line arresters application along their overhead lines presenting poorer lightning performance. This paper presents information about the experience of the Brazilian power supply utilities as well as industrial consumers in the application of line arresters to improve the overhead lines lightning performance. Procedures used to optimize the characteristics of the line arresters, quantity and location along the critical sections of the lines; field experience as well as the lightning performance of the lines before and after the line arresters application are presented and discussed.