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The study of improving the lightning performance of the double circuit 220 kV line Plomin-Pehlin

This paper presents the results of the study conducted in order to improve the lightning performance of the double circuit 220 kV transmission line Plomin-Pehlin connecting the power plant on the power system. There were used the data of the lightning location system (LLS) collected during the period of the last seven years considering the lightings striking the routes of transmission lines. The computational simulations were conducted with the use of EMTP and SIGMA SLP software. The appropriate parameters of the line surge arresters (LSA) with polymeric housing for installation on double circuit transmission line were selected. The conducted simulations showed that 8.85% of all lightning striking the transmission line could hit directly the phase conductor. The largest number of strokes hits the conductors of the upper phase of the tower of double circuit line. Whether the flashover will happen during the direct lightning striking the phase conductor depends primarily of the amplitude of lightning current and the instantaneous values of phase voltages at the time of impact. The reduced number of back-flashover on the existing transmission lines can be achieved by: 1. Improving grounding resistance of the towers ; this measure is applicable depending on local soil characteristics. 2. Increasing the insulation level – a measure that can be implemented if the line construction is a suitable (space limitations, safety heights and distances). This measure could be implemented on the only one circuit of the double circuit transmission line. 3. Installation of LSAs ; this measure can be implemented as a stand-alone or in combination with the measures 1 and 2. The possible locations for installation of LSAs were determined according to the results of the simulations conducted with the EMTP and SIGMA SLP programs and by using the data of the LLS for the transmission line route. The installation of LSAs should be carried out in several stages ; first installations should be carried out on the part of the line route on which the ground-flash density is the largest. The planned timetable of the line arresters installation should be coordinated with the overhaul in the power plant. In implementing the LSAs to protect double circuit transmission line 220 kV Plomin-Pehlin against atmospheric surge will use the experience in previous application of LSAs to 110 kV transmission lines in the Croatian transmission network.

Line surge arresters, lightning location system, 220 kV double-circuit line, modeling, EMTP, flashover, lightning performance

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