Improvement Of Lightning Performance Research Articles

Investigation of line surge arresters application to the 150 kV system of Rhodes

• The application of line surge arresters to 150 kV overhead lines is investigated. • The required energy absorption capability of line surge arresters is determined. • Non-gapped line arresters and externally gapped line arresters are compared. • Surge arrester installation configurations are evaluated for critical lines. • Lightning performance improvement of a critical 150 kV overhead line is quantified. This paper investigates the application of Line Surge Arresters (LSAs) to 150 kV double-circuit overhead lines through ATP-EMTP simulations. The 150 kV lines under study are the backbone of the autonomous electrical system of Rhodes island in southeastern Aegean Sea, Greece. Hence, lightning-related insulation flashovers causing outages of these lines may lead to a blackout of this isolated system. In this work, both Non-Gapped Line Arresters (NGLAs) and Externally Gapped Line Arresters (EGLAs) are evaluated. Two installation configurations with 3 and 6 LSAs per tower are considered protecting one circuit and both circuits of the line, respectively. Simulations were performed for both lightning strikes to phase conductors and tower; these may cause shielding failure flashover and backflashover, respectively. The conducted current through the LSAs and the voltage at their terminals are computed, enabling the estimation of the energy stressing the LSAs. The effects of the lightning current time to half value, the phase angle of the operating voltage, and the power frequency ground resistance of towers are assessed. The required LSA energy absorption capability is determined. The lightning performance of a critical overhead line of the Rhodes 150 kV system is estimated and its improvement due to LSA installation is quantified.

Lightning Performance Improvement Of 123 kV Line Ston – Komolac By Use Of Line Surge Arresters

This paper presents HEP - Transmission System Operator Ltd. Line surge arrester (LSA) application pilot project on the Ston – Komolac 123 kV line. This 44 km long single circuit shielded transmission line operates in the region with a high lightning activity (keraunic level about 70 thunder days). In addition, it was very difficult to obtain good footing resistance. For these reasons, considered line used to have very bad lightning performance. It was decided to install Line surge arresters for line lightning performance improvement. In order to optimize arrester installation configuration sigma slp software simulations were performed. LSA are installed according to the results of the software simulations. LSA are installed in summer 2007 (110 gapless, IEC-class II Line arresters). Sixty one LSA are equipped with Excount - II monitoring sensors (monitoring arrester leakage current and peak of the impulse current). Based on the 8-month experience, LSA installation has improved line lightning performance. New line performance is close to the targeted once (improvement by 50 to 60 %). Surge arrester monitors collect very interesting information. Collected info will be compared with the software simulations.

Optimal placement of surge arresters for transmission lines lightning performance improvement

Installation of transmission line surge arresters (TLSA) is one of the solutions found to improve the lightning performance of overhead transmission lines (OHTL). This work proposes a new multi-criteria methodology for the optimal placement of surge arresters on OHTL based on a multi-objective optimization algorithm coupled with ATP (Alternative Transient Program) software. Lightning performance calculation is performed considering the transfer effect of the lightning surge due to arresters operation. This transfer mechanism that can lead the adjacent towers to flashover is rarely mentioned in the literature. A case study considering a 230 kV transmission line with 231 towers and 105 km long operating in Brazil is presented. Compared to the real performance data, the solution found with the best cost-benefit ratio allows a reduction of 68% in the line outages with the use of 90 surge arresters (i.e., 0.86 TLSAs/km of line). This is practically 50% of the number of arresters calculated using the classical placement method based on the tower-footing impedance value. Regarding the transfer effect of the lightning surge, the results show that the performance levels and, consequently, the number of TLSAs to protect the line may be underestimated if this effect is not considered in the modelling.

Techniques for the improvement of the lightning back-flashover performance of double circuit HVDC lines

This paper addresses different issues regarding the lightning back-flashover performance of HVDC lines, especially regarding double-circuit configurations. In such configurations, two poles may present very similar flashover risks due to a lightning strike, leading to a double flashover. Therefore, it is of particular interest to investigate solutions to protect at least one circuit from flashovers and avoid the temporary loss of the transmitted power and the associated consequences to the system. In this work, electromagnetic transient models are implemented to investigate two solutions for the improvement of the lightning performance: the installation of surge arresters and the use of unbalanced insulation. The results are analysed thoroughly and the mechanisms and theoretical bases behind them are explained. In addition to the grounding resistance of the tower, the coupling between the conductors and the DC pole configuration within the tower also play a major role in determining the lightning back-flashover performance of a double circuit HVDC line. The installation of a single arrester can achieve a very significant improvement of the overall lightning performance of a tower. A proper implementation of an unbalanced insulation solution is very effective in limiting the incidence of double flashovers while maintaining an optimal overall performance.

Importance of Lightning Activity Monitoring Systems for Transmission Line Lightning Performance Improvement Studies

Abstract Line surge arresters are mainly used for transmission line lightning performance improvement. Calculation of energy stresses of lines surge arrester is of extreme importance for the selection of the arrester class. Energy stresses of transmission line surge arresters due to multicomponent lightning flashes are analysed in this paper. To obtain lightning data two approaches were used: direct measurements using instrumented towers and lightning location systems. Both lightning monitoring systems are described. Data obtained from lightning monitoring systems are compared and used in simulations. Detailed modelling procedure for a transient analysis of the transmission lines is also described. Multicomponent lightning flash and 110 kV transmission line were modelled using Electromagnetic Transient Program -Restructured Version (EMTP – RV). The arrester current shapes and arrester energy duties are presented in order to clearly show influence of lightning current parameters to arrester energy duty.

Lightning Performance Analysis of an Overhead Transmission Line Protected by Surge Arresters

In general, the main causes of unacceptable lightning flashover rates of overhead transmission lines are a bad shield design or too high footing impedances. The first reason will cause unacceptable shielding failure flashover rates (SFOR); the second one can cause high backflashover rates (BFOR). The lightning flashover rate of a shielded transmission line can be reduced by installing surge arresters. In fact, the rate can be reduced to zero by installing arresters at all phases and all towers of the line, but even if arresters are not installed at all phases, a significant improvement of the lightning performance can be achieved. However, arresters have to be selected to withstand the energy stresses caused by lightning strokes; otherwise, failures could be caused by an excess of energy absorption. This paper is aimed at analyzing the lightning performance improvement of a shielded transmission line that can be achieved after installing metal oxide surge arresters as a function of the number of phases at which they are installed and at estimating the energy absorption capability of the selected arresters.

Transmission line arrester energy, cost, and risk of failure analysis for partially shielded transmission lines

Application of metal oxide surge arresters in power systems has been traditionally linked to electrical equipment protection. The industry has noted a very significant increase in the application of metal oxide arresters on transmission lines in an effort to reduce lightning initiated flashovers. This paper describes a cost-effective installation of surge arresters on a partially shielded transmission line. It compares several options with respect to cost and gains in terms of lightning performance improvement. This paper also presents a new approach to calculate risk of failure of transmission line surge arresters (TLSAs) due to lightning strokes to towers, shield/phase conductors, and illustrates the method with an example for a partially shielded line. Results show that the risk of failure is very small. The installation of TLSAs completed in 1997 demonstrated that it is possible to afford adequate lightning protection levels by selectively applying surge arresters only to the towers most sensitive to backflashover and shielding failures.