Transmission Line Surge Arresters Research Articles

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.

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.

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.

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.

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.

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.

FDTD-Based Lightning Surge Simulation of an HV Air-Insulated Substation With Back-Flashover Phenomena

The operating voltages of low-voltage control circuits in power plants and substations have decreased with the installation of digital control equipment. This increases the susceptibility of control equipment to abnormal surges, which arise mainly from lightning. To protect control equipment from lightning, it is necessary to predict lightning surges invading power plants and substations and design effective lightning protection methodologies. Compared with conventional simulation techniques based on circuit theory, full-wave numerical approaches are advantageous in handling three-dimensional structures such as transmission line towers, grounding structures, nonhorizontal wires, such as incoming power lines to power plants and substations, and lightning-induced effects. In this study, to apply the finite-difference time-domain (FDTD) method to the lightning surge analysis of an air-insulated substation, we first propose techniques for simulating the nonlinear breakdown characteristics of short-air-gap arcing horns and transmission line surge arresters installed in 77 kV transmission lines for FDTD-based surge simulations, and compare the breakdown characteristics calculated using the proposed techniques with measured results for validation. Second, as an example of the application of the proposed techniques to practical surge analysis, it is confirmed that we can reproduce the measured results of lightning surges invading a 77 kV air-insulated substation in the case of a direct lightning strike to its nearby transmission line tower by taking into account lightning-induced voltages arising from the lightning current flowing through the lightning channel and transmission line tower, which are commonly ignored in conventional circuit-theory-based simulations, multiphase back-flashover phenomena, and the effect of applied AC voltages.

Determination of surge arrester discharge energy using finite element analysis method

Surge arrester is widely used as a protective device to reduce possibility of flashover during transient overvoltage event. The device needs to withstand high energy discharged by the overvoltage which may increase the degradation rate of its characteristics. In this study, a set of transmission line surge arresters with different dimensions and ratings was simulated to investigate their discharge energy capabilities during fast-front surge events using the finite element analysis method. To validate the accuracy of the method, the arrester models were also simulated by the use of PSCAD/EMTDC and EMTP-RV software and compared with the specifications provided by the manufacturer. In spite of distinctive representations of the arrester models in COMSOL Multiphysics, EMTP-RV and PSCAD, the comparison made between the simulation results indicates a satisfactory agreement. The manufacturers’ data were used to validate that the proposed simulation model is acceptable. It was found that the simulation results were comparable with the manufacturer's test data of the discharge voltages and energy withstand capability, thus proving that all studied cases were adequately modelled. Parametric analyses were also conducted using finite element method to study the effects of varying the design geometry of the ZnO blocks and the arrester's housing on the energy absorption, which cannot be evaluated using PSCAD and EMTP-RV software.

Probabilistic evaluation of failure risk of transmission line surge arresters caused by lightning flash

Transmission line surge arresters (TLAs) are vital elements for protection of power networks against the lightning surges. The proper selection of TLAs leads to a reduction of the lightning-related outages as well as the costs imposed to the power utility, because of the undelivered energy and damage to the equipment. The selection of the optimal arrester depends on how well its stresses can be estimated. Although a ground flash very frequently consists of multiple strokes, it is usual to consider only a single lightning stroke to calculate the lightning-related failures. A probabilistic method is presented for risk calculation that considers multiple strokes of each lightning flash to estimate the annual outage rate of TLAs. In the presented method, once the equivalent wave of the flash is computed, the probability of arrester failure is estimated by means of two indices, including total charge and maximum energy stress by the flash, separately. The energy stress caused by the flash is calculated using a few electromagnetic transient program (EMTP) simulations. Then, the obtained results from EMTP simulation are utilised to estimate the probability of failure. The accurate evaluation of failure probability of arresters permits the power utility to select the optimal arresters, considering a desirable average life.

Assessment of surge arrester failure rate and application studies in Hellenic high voltage transmission lines

Abstract The use of transmission line surge arresters to improve the lightning performance of transmission lines is becoming more common. Especially in areas with high soil resistivity and ground flash density, surge arresters constitute the most effective protection mean. In this paper a methodology for assessing the surge arrester failure rate based on the electrogeometrical model is presented. Critical currents that exceed arresters rated energy stress were estimated by the use of a simulation tool. The methodology is applied on operating Hellenic transmission lines of 150 kV. Several case studies are analyzed by installing surge arresters on different intervals, in relation to the region's tower footing resistance and the ground flash density. The obtained results are compared with real records of outage rate showing the effectiveness of the surge arresters in the reduction of the recorded failure rate. The presented methodology can be proved valuable to the studies of electric power systems designers intending in a more effective lightning protection, reducing the operational costs and providing continuity of service.

Evaluation of line surge arrester failure rate for multipulse lightning stresses

This paper develops a method to analyze energy stresses on transmission line surge arresters. The approach computes the failure rate of arresters due to energy stresses, convolving the density probabilities of first and subsequent pulses. Multipulse stroke effects are considered in a 138 kV line case study, typical of single circuit lines, located in regions with high densities of ground flashes, in SE Brazil. The proposed method provides an improved insight into energy stress evaluation for selection of line surge arresters.

Application of 800-kV SF6 dead tank circuit breaker with transmission line surge arrester to control switching transient overvoltages

An 800-kV metal oxide transmission line surge arrester (TLA) has been developed, installed and tested on the AEP 765-kV Marysville-Kammer transmission line. The purpose of this TLA is to pave the way for the development, construction and application of an 800-kV SF/sub 6/ dead tank circuit breaker without closing resistors and free standing current transformers at American Electric Power's (AEP) 800-kV Orange station. Eight hundred kilovolts is the maximum design operating voltage, and 765 kV is the nominal operating voltage. Successful field test results of the TLAs ability to limit switching overvoltages emanating from circuit breaker operation to below the transmission line switching withstand are given. In addition, successful test results of the 800-kV dead tank circuit breaker design dielectric test are given in this paper.

Application of 800 kV SF6 Dead Tank Circuit Breaker with Transmission Line Surge Arrester to Control Switching Transient

An 800 kV metal oxide transmission line surge arrester (TLA) has been developed, installed, and tested on the AEP 765 kV Marysville to Kammer transmission line. The purpose of this transmission line surge arrester (TLA) is to pave the way for the development, construction, and application of an 800 kV SF6 dead tank circuit breaker without closing resistors and free standing current transformers at AEP's 800 kV Orange station. The maximum design operating voltage is 800 kV, and 765 kV is the nominal operating voltage. Successful field test results of the TLA's ability to limit switching overvoltage emanating from circuit breaker operation to below the transmission line switching withstand are given. Successful test results of the 800 kV dead tank circuit breaker design dielectric test are given.

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.

Use of line surge arresters for the improvement of the lightning performance of 63 kV and 90 kV shielded and unshielded transmission lines

The lightning performance of 63 kV and 90 kV shielded and unshielded power transmission lines, protected by surge arresters are considered. A specialized software package is used for the computation of the line's fast front transients. A Monte Carlo statistical method, together with a three-dimensional electrogeometric model is used to determine the lightning stroke locations. Different arrester installation configurations are analyzed and compared. The energy duties of the transmission line surge arresters are computed statistically.

Controlled closing on shunt reactor compensated transmission lines. II. Application of closing control device for high-speed autoreclosing on BC Hydro 500 kV transmission line

In the past, BC Hydro used circuit breaker closing resistors to limit switching surges on its 500 kV transmission system. This approach was considered undesirable for new transmission lines and an innovative scheme incorporating special transmission line surge arresters and controlled high-speed autoreclosing of the circuit breaker was developed. The scheme and its basis as applied on a new 330 km long 500 kV transmission line are described. Actual line switching tests, also described, confirmed the validity of the studies performed and applied design concepts, and the value of the scheme.