Line Surge Arresters Research Articles

The principles of a new line surge arrester's transient current measurement system

Power systems are exposed to different types of electromagnetic transients, which involve a large spectrum of signals whose duration can range from several nanoseconds to several milliseconds, and whose peak values can also cover a wide range of values. Therefore, measuring electromagnetic transients in power systems is a challenging task. Fast front transients caused by lightning events are especially dangerous, and improved knowledge about them is essential for better protection design. The development of measuring systems for such phenomenon is important. This paper is dedicated to the development of a measuring system for lightning and line surge arrester currents. Modern electronic tools and equipment, as well as cutting-edge communication and information technologies, constitute the foundation of the proposed system. This includes the most recent models of acquisition units and GPS devices that are now available on the market, as well as communication networks including 4 G, 5 G, and WiFi. Software and hardware components of the system are described. The paper presents laboratory tests conceived to prove that the system operates correctly and provides accurate results. The measurements are compared to EMTP and MATLAB simulations. Both are in agreement.

Numerical Analysis of Electromagnetic Field, Heat and Thermal Stress of a Transmission Line Surge Arrester for Lightning Currents

The voltage across a 77‐kV‐class transmission line surge arrester (TLSA) and the heat in the TLSA have been computed using the finite‐difference time‐domain (FDTD) method for a lightning current having a magnitude of 50 kA, a risetime of 1 μs, and a half‐peak width of about 100 μs. The TLSA is represented with series‐connected‐nine ZnO elements, each of which has a length of 36 mm and a diameter of 32 mm. The ZnO element is represented with many 2 × 2 × 2 mm cubic cells, each of which has a nonlinear resistivity in each of the x‐, y‐, and z‐directions dependent on the electric field in each direction and the temperature in each cell. From the spatial and temporal distributions of FDTD‐computed heat in the TLSA, the spatial and temporal distributions of thermal stress in the TLSA have been computed using the finite‐element method. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

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.

APPLICATION OF LINE SURGE ARRESTERS IN THE PROTECTION OF THE 110 kV STON – KOMOLAC TRANSMISSION LINE FROM ATMOSPHERIC DISCHARGES

The reliability of the operation of a transmission network largely infl uences the reliability of the power system and the security of the electricity supply to consumers. During the past 10 years, there have been a large number of outages of the 110 kV Ston – Komolac Transmission Line due to its specifi c location in a zone where the intensity of atmospheric discharge is high, which has thereby signifi cantly reduced the reliability and security of the operation of that section of the transmission network. As the most technically and economically desirable solution for improving the protection of the transmission line from atmospheric discharges, it was decided to equip the transmission line with line surge arresters. Their installation signifi cantly reduced the number and duration of forced outages and increased the reliability of the transmission network in the greater Dubrovnik region. Equipping the transmission line with line surge arresters was the basis for a pilot project of monitoring the operation of the transmission line during atmospheric discharges. The experiences and results regarding the effi ciency of the protection of the 110 kV Ston – Komolac Transmission Line from atmospheric discharges will provide the basis for further applications on transmission lines of higher voltage levels.

First Experience in Monitoring of Line Surge Arresters Installed on 110 kV Transmission Line Ston – Komolac in Croatia

In paper are presented some first results and experience in real time monitoring of line surge arresters installed on 110 kV transmission line Ston – Komolac in southern part of Croatia. Mentioned line is the first line in Croatian transmission network equipped with line surge arresters (LSA). The line with its length of 43,95 km is situated in region with high soil resistance, exposed to one of the highest level of lightning activity in Croatia. At the same time it is the most important line in connecting HPP Dubrovnik (240 MVA) to the main part of 110 kV transmission network. Due to all mentioned reasons and great number of annual outages, it was decided to equip the line with LSA for improving the lightning performance and the availability of line. As result of performed numerical simulations on simulation line model it was decided to install 110 kV gapless, IEC Class II line arresters. Also, to improve analysis of expected results the 61 line arresters were equipped with Excount-II type of monitoring sensors. The main goal was to determine the behaviour of line arresters arrangement across the line during overvoltage events on towers. This installed “realtime” monitoring system enables remote control and wireless exchange the collected data from local data logger installed on LSA. Line arresters activity is monitoring through numbers, date and time and level of surges and the condition state of LSA, through the measuring of leakage current. First results in application of LSA are showing significant reduction of line outages with registered relatively strong activity of monitored line arresters. Also, as it was expected some particular part of line is espied to be exposed to higher frequency and higher level of registered arresters surge current. During collecting the data of LSA activity, some practical problems were encountered with time synchronization between monitoring devices and it is mentioned and discussed in paper, too. Although the analysed time period of eight months with LSA application is too short to allow strong final conclusions, obtained first experience will be very helpful in assessment of further LSA application in Croatian transmission network.

Line Surge Arresters Applications On The Multi Circuit Overhead Lines

This paper presents application of line surge arresters (LSA) on the different voltage level multi circuit overhead lines. Double circuit shielded compact line with and without distribution circuit on the same tower is analyzed. Distribution circuit has lower insulation level, meaning that almost all flashovers will happen on that circuit. Flashovers on the distribution circuit help to improve lightning performance of the transmission circuits. Flashovers on the distribution circuit diverts fraction of the lightning current along its phase conductors, improving at the same time coupling between distribution and transmission circuits. All software simulations are performed using sigma slp software package. A short description of the modeling for multi circuit flashover rate determination is given. In order to prevent flashovers on the distribution circuit LSA are installed on this circuit only. The improvement in the transmission circuit lightning performance is similar to that obtained without LSA. LSA installed on the distribution circuit are much cheaper than transmission LSA.

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.

The Possibility of Insulation Level Reduction on 110 kV Overhead Line with Built-in Post Insulators Using Line Surge Arresters

Installation of line surge arresters (LSA) on overhead lines is normally accomplished with aim of line performance improvement. Co-ordination insulation procedure carried out during the line design in most cases doesn't take into account a suppression of overvoltages by using any overvoltage limiting devices. The decision supported by poor line performance to install LSA is usually made later. The reduction of overvoltage level depends mainly on the number of LSA installed, but in any case it is considerable. It means that insulation regarding dielectric strength might this way be over dimensioned. This fact could be considered for reduction of phase-to-ground and phase-to-phase distances, which lead to greater level of line compaction. This is of the most importance for lines with post insulators, since shorter insulators could be used and consequently narrower right of way achieved. Our target was to investigate the possibility of reducing lightning overvoltages by using LSA’s attached parallel to the insulators. For the analyses purpose we implemented a mathematical model of a single-system 110 kV compact overhead line. The Sigma Slp software was used for computer simulations. The line was investigated from the perspective of lightning over-voltages as they are the factors the most severely stressing the insulation. We focused to lightning strikes at a tower top for the case of single-phase (C) LSA installation configuration. The main influencing parameters were varied such as lightning current, surge shape and tower earthing resistance according to their most probable values to obtain overvoltage properties. We concluded, that adoption of LSA’s does not only reduce the overvoltage amplitude in that phase but also changes its shape, which has to be taken into account for test impulses generation. The physical model of wooden pole with composite line post insulators was built for testing in high-voltage laboratory. Power frequency and impulse tests were performed on insulators (phase-to-ground) and between phase conductors (phase-to-phase) in dry and wet conditions when necessary. Besides standard also non-standard impulse shape tests were accomplished to obtain withstand voltages for different arching distances. Based on our comparison with the simulation results we concluded that - speaking in terms of lightning overvoltages - it is possible to use insulators for the insulation level Um = 72,5 kV (140/325 kV), if LSA’s in phases A, B and C would be installed. To verify the conclusion in all other respects, further analyses are needed.

Line Surge Arresters Applications On The Compact Transmission Lines

This paper presents application of line surge arresters on the compact transmission lines. Single and double circuit compact transmission lines are considered. Line lightning performance is computed using sigma slp simulation software. Different line surge arrester installation configurations are considered. Line lightning performance is computed for different tower footing resistance. Line performance before and after line surge arrester installation are compared. Line lightning performance of the unshielded line with line surge arresters is compared with the performance of the shielded line without line surge arresters. For double circuit shielded compact lines, double circuit outage rate is computed. Influence of the tower footing resistance on the double circuit outage rate is presented.

EVALUATION OF ENERGY STRESS ON LINE ARRESTERS

Line Surge Arresters (LSAs) are efficient means for the improvement of the lightning performance of transmission lines. Determination of optimal LSA number, location and rating is important for the improvement of the reliability and availability of a transmission system. In selection of the LSA special attention should be paid to their energy stress which depends on complex interactions between the arrester locations, grounding, shielding and the local lightning environment. LSAs experience higher energy stress compared to station arresters, because the incoming surge to a station is limited by insulator flashover on the transmission line and impulse corona. In this paper calculations of energy stresses were carried out for a double-circuit 220 kV line with a single shielding wire. Parametric studies were conducted in which arrester discharge energy was a function of: time to half value of stroke current, number of towers with arresters, footing resistance, span length and angle of power frequency voltage. Arrester energy stress is analyzed in case of stroke to tower and shielding failure. From conducted analysis it can be concluded that energy stress on LSAs is lower for shorter span lengths. Tower footing resistance has only minor effect on the discharge energy. Arrester discharge energy strongly depends on time to half of the stroke current, number of towers with installed arresters and angle of power frequency voltage.

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.

MODELLING AND ANALYSES OF OVER-VOLTAGE IN 400 KV OVERHEAD TRANSMISSION LINE CAUSED BY LIGHTNING STRIKE

In power system, lightning stroke is one of the main causes of overvoltage. At the point of contact, a current with several KA is injected into transmission lines. A flashover take place and could cause serious damage in insulators of transmission lines. In this paper PSCAD/ EMTDC software is using to perform this study. PSCAD (Power System Computer Aided Design) is one of the powerful programs used for various specialized studies including fast front surge study (lightning surge study). A modelling of seven towers with its transmission lines, insulators, tower footing resistance and lightning stroke will be simulated. The surge voltages induced by lightning strikes are evaluated at various sites along transmission lines. The study also will include a comparison between shielded wire and transmission line surge arrester (TLSAs) for the protection purpose.

Application of Line Surge Arresters for Switching Over-voltages in UHV Transmission Systems

Application of Line Surge Arresters for Switching Over-voltages in UHV Transmission Systems

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.

Application of a Gapless Arrester to Protect 77/66 kV Temporary Overhead Cables

Lightning protection is an issue for temporary overhead cables installed on overhead transmission lines. Existing line surge arresters for overhead transmission line are not expected to provide sufficient lightning protection performance due to the air‐gap discharge delay. Accordingly, a gapless arrester has been developed to protect temporary overhead cables. This paper reports on the results of development tests and experimental constructions. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Determination of Cumulative Distribution Function of the Crest Value of the Lightning Current Circulating Through Line Surge Arresters

For the selection and design of line surge arresters (LSA), it is essential to know the characteristics of the lightning current circulating through LSA. When lightning strikes a transmission line, only a part of the lightning current circulates through LSA.This part mostly depends on the point of impact, and the characteristic of the lightning stroke current. The determination of the cumulative distribution function of the lightning current circulating through arresters is presented in first part of the paper. It can be applied on transmission lines where LSAs will be installed to protect the line against the effect of atmospheric discharges.Second part of paper presents the calculation results of the cumulative distribution function of the lightning current circulating through arresters for particular 110 kV transmission line located in an area with high lightning activity.

Constraints on the use of surge arresters for improving the backflashover rate of transmission lines

The effectiveness of using transmission line surge arresters (TLSA) under different conditions for improving the lightning performance of lines is assessed by means of computational simulation. These conditions comprise using TLSA only in critical towers and/or using devices only in certain phases, leaving one or two-phases unprotected. In addition to assess the effect on stricken towers, the transfer of overvoltage to unprotected adjacent towers is also addressed, considering different values of tower-footing impedance. In the analyses, lightning overvoltages across insulator of typical single-circuit 138-kV and double-circuit 230-kV transmission lines were calculated by using the Hybrid Electromagnetic Model (HEM) and flashover occurrence was assessed by using the Disruptive Effect method (DE), in each simulated condition. The results indicate that the operation of TLSA protects the own insulator and diminishes the backflashover risk at unprotected insulators. However, this risk remains high, depending on tower-footing impedance. Also, the risk of flashover at the unprotected adjacent towers due to the operation of surge arresters at the stricken tower was found to be significant in the case of all phases of the stricken tower protected, notably when the tower-footing impedance of the protected tower is high and that of the adjacent tower is low.

Temporary overvoltage suppression in half-wavelength transmission lines during asymmetric faults

This paper approaches the principal electric characteristics of half-wavelength transmission lines and possible voltage transients resulted from asymmetric faults. Although this non-conventional AC transmission technique presents some attractive advances for electric power transmission through long distances, when compared to the well-established HVDC systems, some important issues should be investigated on eventual overvoltage levels along half-wavelength transmission lines during temporary asymmetric operation conditions, e.g. phase-to-ground fault and single-phase reclosing. In this research, an iterative computational routine locates the overvoltage points by varying the asymmetric fault location from the sending to the receiving end of the transmission line. This procedure provides a full mapping of the most critical overvoltages as a function of the fault point through the line length. Since the most critical fault occurrences and overvoltage locations are known, an alternative method for overvoltage suppression is proposed by using line surge arresters directly at the phases in parallel with the tower insulators. This technique represents an original method to contain overvoltages at middle sections of half-wavelength transmission lines.

Evaluating the overvoltage performance of an overhead line taking into account the frequency-dependence of its tower’s grounding electrodes with high soil resistivity

The paper demonstrates the importance of taking the frequency-dependence of the tower grounding impedance into account when studying the lightning performance of an overhead line located in an area with high soil resistivity. Towers’ impulse grounding impedance measurements and their rational approximations are used to construct a wideband model of the towers’ grounding electrodes in an EMTP-type software program.In order to examine the impact of tower grounding impedances, simulations of lightning strokes to the overhead line tower were performed using an EMTP-type tool in the following three different cases: constant grounding impedance of the tower hit by a lightning stroke, frequency-dependent tower grounding impedance and frequency-dependent tower grounding impedance for the tower equipped with a Line Surge Arrester (LSA) installed at the lowest phase.The simulations have shown the influence of the frequency-dependence of the tower grounding impedance on the level of the build-up voltage across the tower’s insulator string and consequently on the flashover occurrence in the observed configuration with a high soil resistivity.

Estimation of Energy Stress of Surge Arresters Considering the High-Frequency Behavior of Grounding Systems

This paper presents a probabilistic evaluation of energy absorption capability of transmission line surge arresters (SAs), based on Monte-Carlo method. In the presented approach, a wideband model of tower-footing grounding system is adopted taking to account both constant and frequency-dependent soil electrical parameters. Furthermore, the effect of multistroke lightning flashes on the energy stress experienced by SAs is taken into account. To this aim, simulation is performed for a typical 400-kV transmission line which is modeled in EMTP-RV. From the simulation results, it is found that the absorbed energy is significantly affected by the modeling type of grounding system, i.e., static or wideband model. This effect seems to be more pronounced for the soil characterized by frequency-dependence electrical parameters. The presented results show that wideband modeling of grounding system can affect the estimated lifetime and the energy absorption capability of SAs. Hence, the wideband model of grounding system is suggested to be taken into account for the proper selection and sizing of SAs.