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• Analysis of the lines shielding failure and back flashover performance. • Investigating the impact of each flashover parameter by multivariate analysis. • Simulated fault waveforms exhibit similar pattern with recorded field waveforms. • The average peak voltage difference between the simulated and actual data is 6 %. • Obtained waveforms are useful for designing lightning fault classification system. Lightning overvoltage causes outages of transmission lines (TLs) in tropical countries. Identifying and analyzing the key factors responsible for tripping the lines can improve the performance of the lines. In this work, the flashover patterns due to direct lightning strikes on 275 kV double circuit TLs and towers in Malaysia was evaluated with Electromagnetic Transient Program (EMTP-RV). Three parameters that include lightning current magnitude, power frequency angle and tower footing resistance were analyzed on the line performance during direct lightning strikes. The simulated results found that two key parameters, lightning current at 270 kA and footing resistance at 50 Ω, reveal the highest impact on the insulator flashover. This finding was also verified from multivariate analysis results which is rarely found in the previous works in this field. As a key contribution in this work and in validation to the model, the simulated fault waveform patterns and voltage magnitudes were compared with the actual site data obtained from six different locations in Peninsular Malaysia. The analyzed results show a similar waveform pattern with an overall average voltage magnitude difference of 6.0 % before and after fault. The model is useful to electric utilities for analyzing transient performance of TLs. [Display omitted] [ABSTRACT FROM AUTHOR]

• Analysis of NGLA, EGLA, and MCIA performance on mitigating double circuit tripping. • Installing four arresters per tower is the most optimal and universal solution. • All arresters are operating below manufacturers' maximum discharge energy level. • MCIA discharges 54% and 44% less energy than NGLA and EGLA respectively. • The most suitable arrester was selected based on the proposed protocol. Direct lightning strikes on overhead lines and towers causes power system outages. Optimal surge arrester placement is a practical and economical protection technique. From research trends, three types of transmission line arresters are in practice: Non-Gapped Line Arrester (NGLA), Externally Gapped Line Arrester (EGLA) and Multi Chamber Insulator Arrester (MCIA). This study proposed a simplified guide for selecting the most suitable line arrester considering the placement configurations, double circuit outage prevention and energy capabilities. Electromagnetic Transient Program was implemented to analyze back flashover performance of a typical 275 kV double circuit transmission line in Malaysia. Critical flashover parameters considered are lightning current magnitude, tower footing resistance, and power frequency angle. Analyzed results from the three arresters found that installing four arresters, two per circuit, at the lower and upper phases respectively, is the most optimal and universal double outage mitigation technique. Energy comparison reveals that MCIA discharges 54% and 44% less energy than NGLA and EGLA respectively. Also, from 132 kV system results, MCIA discharges 74% and 22% lesser energy respectively. From further validation of the simulation model, NGLA discharged 23.8% more energy than EGLA from experimental results. The proposed guide is applicable to double circuit lines below 275 kV. [ABSTRACT FROM AUTHOR]

Measurement of lightning and switching transient overvoltage in power system is significant to the research that guides the protection of power system. A new type of sensor for non-contact measurement of lightning and switching transient overvoltage in power system is designed in this study. This sensor is composed of two parts, namely, voltage induction and optoelectronic conversion units. Given the existing stray coupling capacitor C 1 between the transmission line or bus bar and a metal plate placed under it, a voltage induction unit is designed by utilizing the C 1 and a capacitor with fixed value C 2 connected in series, then the high-voltage non-contact induction on a transmission line or bus bar is achieved. The optoelectronic conversion unit is designed based on the Pockels effect of the LiNbO 3 crystal. The voltage signal induced by the voltage induction unit can be converted to an optical signal by the optoelectronic conversion unit for long-distance transmission through optical fibers without power supply at the monitoring site. Laboratory and field tests revealed that the new developed sensor possesses good linear region, high precision, and wide frequency band of the response to lightning and switching transient overvoltage in power system. The sensor can also be applied to the non-contact measurement of lightning and switching transient overvoltage in power system with different voltage levels by conveniently adjusting the distance between the sensor and the line. [ABSTRACT FROM AUTHOR]

The application of metal-oxide surge arresters to protect distribution lines from lightning is of great interest to electric utilities seeking to improve reliability and quality of the energy supplied to consumers. However, due to the high cost of purchase and installation, technically and economically viable solutions must be found to protect these systems from lightning overvoltages. Thus, this paper describes aspects of modeling and simulating the performance of a protection system using metal-oxide surge arresters, when exposed to direct lightning. A practical methodology is developed for the specification, simulation and definition of the best sizing, location and number of surge arresters for the protection of an overhead distribution line located in a rural area. Moreover, the energy absorption for selection of surge arresters is also analyzed and the performance of different configurations of the protection system against lightning is evaluated. [ABSTRACT FROM AUTHOR]

Abstract: Lightning overvoltage is the major cause of the transmission line interruption in Malaysia. It is the main reason that endangers the safety and reliability of transmission line system. The phenomenon is a dominant factor considered in designing substations and transmission-line insulation, therefore its investigation is important. This work modelled a 132kV overhead transmission line for shielding failure pattern recognition by using ATP-EMTP software, as they are vital to the evaluation of lightning performance. The modelled transmission-line is divided into few parts: wires (shield wires and phase conductors), towers, cross-arms, insulator strings, tower-surge impedance and tower-footing resistance. The developed model is simulated with four different magnitudes of lightning-strike current on each phase conductor in order to investigate the shielding failure voltage pattern across the line insulation in the transmission line system. When the lightning- strike current is injected from upper phase to lower phase conductor, the magnitude of the maximum induced voltage across the insulator string at those phases has been decreased. On the other hand, as the magnitude of the lightning- strike current has been increased, the magnitude of the maximum induced voltage across the insulator string at each phase will be increased. Flashover occurs when the voltage induced across the insulator string at each phase is equal or exceeds the CFO voltage. These analyses have been done based on the waveforms obtained from the simulations on developed model. [Copyright &y& Elsevier]

Abstract: Lightning overvoltage protection is of great importance to the safety of devices in UHV GIS. In practice, insulation failure of UHV transformer due to lightning strike is often reported. The widely used UHV metal-oxide arresters can suppress the magnitude of lightning overvoltage but lack effectiveness on alleviating the steepness. A new protection method is proposed in this paper using ferromagnetic ring as supplement to the arresters in suppressing lightning overvoltage within UHV GIS. Moreover, equivalent model based on the characteristic of ferromagnetic material and factual dimensions of the ring is established. Simulation of an actual 1000kV GIS is carried out to thoroughly evaluate the lightning overvoltage suppressing effect of ferromagnetic rings with different materials and structure parameters. [Copyright &y& Elsevier]

Abstract: Lightning overvoltages threaten the safe operation of the photovoltaic (PV) power system. This document uses the generalized modified mesh current method and establishes a time-domain multiport model of thin-wire system to simulate the lightning transient process of the solar arrays in a rooftop PV power system with and without the external lightning protection system. Different factors of the PV power system are simulated in order to study the effects of these factors on the induced lightning overvoltages. The simulation results show that the induced lightning overvoltage of the solar arrays in a rooftop PV power system is highly dependent on the lightning striking position, the lightning current amplitude, the building''s height, the soil resistivity, and the distance to the external protection system. Therefore, when choosing the SPD configuration for a PV power system, the factors mentioned above should be considered comprehensively. [Copyright &y& Elsevier]

Abstract: This paper analyzes the maximum lightning overvoltage due to shielding failure along a cable inserted in an overhead line. The cable is protected by surge arresters at both ends and the maximum voltage appears normally somewhere along the cable. The maximum voltage can for severe cases of lightning overvoltages be found by calculating the voltage at a limited number (e.g. 10) of equidistant positions along the cable. [Copyright &y& Elsevier]