Installation Of Surge Arresters Research Articles

Surge arrester allocation for lightning protection of VSC based HVDC prototype

High-voltage direct current (HVDC) systems, based on voltage source converters (VSC), enable asynchronous interconnection of grids with different frequencies and contribute to grid stability by controlling power quickly and precisely. Effective protection of these expensive systems, which must be in continuous operation, increases their lifetime. An overvoltage protection study is needed to ensure the proper protection of HVDC systems that contain multiple devices with varying insulation levels. In this study, lightning protection studies on a prototype VSC-based HVDC (VSC-HVDC) system are explained. In line with this, lightning impulses were modeled and applied to various points in the PSCAD model of the prototype VSC-HVDC, and the response of the system combined with the protection equipment was examined. All stages of protective equipment selection were explained step by step. The suitability of the selected protective equipment was verified based on the simulation results. After running dozens of scenarios, the protection coordination was optimized, and the critical points were determined instead of installing surge arresters at each connection point. In this way, a significant cost benefit was obtained for the investment in protective equipment. Finally, the results of the lightning impulse tests performed to verify the insulation of the VSC-HVDC prototype are reported.

Performance Against Direct Lightning on 10-kV Overhead Distribution Lines With Counterpoise Wires

This article investigates the lightning performance of a 10-kV overhead distribution line equipped with grounding counterpoise wires under extremely low soil conductivity conditions. A partial element equivalent circuit model with the lossy ground being considered is adopted for lightning surge investigation. The Monte Carlo method considering natural lightning randomness is used for the flashover rate evaluation. It is found that under extremely low soil conductivity conditions, the simple vertical grounding rod is not effective in lightning protection, while the performance is significantly improved with extended counterpoise wires. The single-row counterpoise wire with a length of line span performs best. The single-row counterpoise wire with a half-length of line span is a competitive one, due to a half-cost reduction and a competitive performance. If a higher performance of lightning protection is expected, further extending the length of counterpoise wires would be ineffective. Increasing the CFO level or installing surge arresters on all poles would be the possible solution.

Influence of a shield wire flashover on the indirect lightning performance assessment of distribution lines

This paper presents a new aspect of shield wire (SW) modeling for assessing the indirect lightning performance of overhead medium-voltage distribution lines: a flashover (FO) between an SW and the reinforcing bars of a distribution pole or a crossarm (SWFO). In general, an SW is periodically grounded approximately every four to ten poles and not grounded at the other poles. However, owing to lightning-induced overvoltages, the voltage difference between the SW and the distribution pole may even exceed 100 kV, and the SWFO can occur. In this paper, we evaluate the effect of the SWFO on the number of FO occurrences of phase-conductor insulators by the Monte Carlo method using a 2D finite-difference time-domain-based indirect lightning surge analysis program. The effect of the SWFO is more significant in lines with high soil resistivity (a soil resistivity of 1000 Ωm was assumed) regardless of the installation of surge arresters: the total number of FO occurrences markedly differs by up to 50% between cases in which the SWFO is considered and not considered. The analysis presented in this paper will assist the formulation of lightning protection measures particularly, in regions with high-resistivity soils.

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.

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.

Comprehensive Assessment of Lightning Protection Schemes for 10 kV Overhead Distribution Lines

This paper presents an assessment of lightning protection schemes for overhead lines from two aspects: protection performance and economic cost. Considering the random nature of lightning, the Monte-Carlo method with a heuristic technique is applied in the assessment. The one-dimensional finite-difference time-domain method is adopted to evaluate lightning overvoltages on insulators and lightning currents in surge arresters for failure assessment. The failure rate of an overhead line is addressed under both direct lightning and indirect lightning. A reduced set of design parameters are identified. It is found that the line insulation itself with a critical flashover overvoltage of less than 200 kV is not sufficient for lightning protection, especially against direct strokes. With other protection options, however, increasing the insulation level can greatly improve the protection performance. Installing surge arresters on every pole results in the best protection performance, but could be extremely expensive due to the replacement of failed surge arresters. The shielding wire provides moderate protection performance with a relatively low cost. The combination of the shielding wire and surge arresters provides much better performance under a wide range of soil conductivity with a moderate cost. It is worth mentioning that adopting high insulation strength for overhead lines in the new-line design could lead to significant cost savings for lightning protection. Guidelines for selecting design parameter values and protection schemes are provided, as well as a procedure for performance-cost evaluation.

Evaluation of the Lightning Performance of Transmission Lines Partially Protected by Surge Arresters Considering the Frequency-Dependent Behavior of Grounding

This work evaluates the efficiency of installing surge arresters in only one or two phases concerning the lightning performance of transmission lines. The simulations were performed in the ATP software, taking as reference a Brazilian 138 kV transmission line, and considering the rigorous representation of the frequency-dependent behavior of the tower footing impedance. The electrical parameters of the soil were considered as either constants or frequency-dependent, in order to analyze the influence of this effect in partially protected lines. The results obtained have shown that the partial protection technique is highly efficient. Although it does not guarantee the protection of the unprotected phase(s), the probability of insulation breakdown is strongly decreased. It was also verified that the inclusion of the frequency-dependent effect in the soil parameters significantly reduces the backflashover rate estimates of the studied line when compared to the constant values situation.

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.

Comparison of Backflashover performance between a novel composite pylon and metallic towers

A design of a fully composite pylon with external grounding down-leads has been proposed for new-generation 400 kV transmission towers, able to save lines corridors and to reduce visual impact. This paper investigates and compares the backflashover performance of a composite pylon and two conventional metallic towers, which have been widely installed in Denmark. The transient models of overhead lines and all three towers were established respectively and the transient analysis was carried out in PSCAD. Monte Carlo method was used to estimate backflashover rate. The backflashover rate of composite pylon is 0.4526 cases per 100 km per year, which is in the same range, but slightly higher than that of metallic towers. The separated grounding down-leads of double circuits on composite pylon eliminates the danger of simultaneous backflashover of double circuits, which exists in transmission lines supported by metallic towers. After comparing the overvoltages to three phases of the three towers from backflashover, it is worthy considering that the installation of surge arresters at all three phases of composite pylon has a strong impact on the backflashover rather, but for the two metallic towers only the surge arresters at the upper phase has an impact.

Lightning Overvoltage Protection of Step-Up Transformer Inside a Nacelle of Onshore New-Generation Wind Turbines

This paper presents an electromagnetic transient analysis of lightning-initiated overvoltage stresses of the step-up transformers installed inside a nacelle of onshore, multi-megawatt, new-generation wind turbines. The increase in the wind turbine (WT) nominal power output, necessitated introducing the step-up transformer into the nacelle. A transformer installed inside a nacelle is subjected to completely different overvoltage stresses from those present if it were installed at the base of the WT tower. This has serious repercussions on its overvoltage protection (i.e., selection and installation of surge arresters) and insulation coordination. Furthermore, the overvoltage protection of medium-voltage cables (inside the tower) is also problematic when considering their length, proximity to the tower wall, and their screen grounding practices, and needs to be tackled in conjunction with that of the step-up transformer. This paper presents detailed models for the various components of the latest-generation WTs, intended for fast-front transient analysis and assembled within the EMTP software package. We further present the comprehensive results of the lightning-transient numerical simulations, covering both upward and downward (first and subsequent) strikes, their analysis, and recommendations for the optimal selection of medium-voltage surge arresters for the step-up transformers installed inside a nacelle.

Optimized Surge Arrester Allocation Based on Genetic Algorithm and ATP Simulation in Electric Distribution Systems

The efficient protection of electric power distribution networks against lightning discharges is a crucial problem for distribution electric utilities. To solve this problem, the great challenge is to find a solution for the installation of surge arresters at specific points in the electrical grid and in a sufficient quantity that can ensure an adequate level of equipment protection and be within the utility’s budget. As a solution to this problem of using ATP (Alternative Transient Program), this paper presents a methodology for optimized surge arrester allocation based on genetic algorithm (GA), with a fitness function that maximizes the number of protected equipment according to the financial availability for investment in surge arresters. As ATP may demand too much processing time when running large distribution grids, an innovative procedure is implemented to obtain an overvoltage severity description of the grid and select only the most critical electric nodes for the incidence of lightning discharges, in the GA allocation procedure. The results obtained for the IEEE-123 bus electric feeder indicate a great reduction of flashover occurrence, thus increasing the equipment protection level.

Reduction of the number of faults caused by lightning for transmission line

In this paper, author proposed an algorithm to determine method which is used to reduce the fault number caused by lightning on a transmission line. The algorithm is developed based on three methods including increase in the insulator string length, surge arrester installation, and surge arrester installation in combination with increase in the insulator string length. The output of algorithm is the proposed method which makes the number of faults caused by lightning satisfy the requirement and its investment is the cheapest in them. Based on this algorithm, the reasonable method (the number of tower positions needing to improve) to reduce the number of lightning caused faults of the transmission line can determine if we know the ratio of the required number lightning caused faults to the current value. This algorithm is applied to a transmission line to propose an improving method so that the fault number satisfies the requirement. This algorithm is implemented to a 220kV transmission line. The calculation results show the reasonable method and it also indicates in detail which towers should install surge arrester, which towers should increase the insulator string length.

Optimal Surge Arrester Placement for Extra High Voltage Substation

Lighting Phenomena is one of the important considerations during the design of Extra High Voltage and Ultra High Voltage Transmission Lines. Most of the authors have discussed regarding the benefits of using Surge Arresters as a way to improve the performance. In this paper, simulation analysis is done on 400kV/220kV Gwaka Substation, AP, India for optimal, cost effective placement of surge arresters. The most difficult configuration has been identified. A new method of “Voltage-Distance curve” is proposed to evaluate different Surge Arrester installation configurations. Finally the way to determine the optimal surge arrester configuration for each line section is then introduced in this paper.

Neural Network Model to Estimate Resistivity of Ground Enhancers Reinforced with Graphene Nano Particles for Transmission Lines

For many high voltage transmission lines, lightning is the first cause of outages. Different alternatives have been used to diminish these outages, like the use of counterpoise wires, installation of surge arresters, and the improvement of the grounding system using ground enhancers or chemical enhancers. In this paper, graphene nanoparticles were used to reformulate commercial ground enhancers. The results of this research end up in an improvement factor of up to 100 times the reduction in resistivity, when graphene nanoparticles are used. After lightning current impulse tests done on both types of samples, the performance of the un-reformulated ground enhancer samples shows a faster deterioration than the graphene reinforced ground enhancer samples. In order to establish a criterion to quantitatively rank the chemical ground enhancers ́ performance after the lightning impulse current tests, a neural network model was developed.

Analysis of discharge energy on surge arrester configurations in 132 kV double circuit transmission lines

Surge arrester has been proven to be the most effective application to provide optimum lightning protection for the transmission line. Thus, many works on optimizing lightning protection for transmission line have been conducted since the past. However, works on minimizing double circuit outages and surge arrester physical properties during transient overvoltages are less likely to be found. Therefore, in this work, several surge arrester configurations installed on a 132 kV double circuit transmission line were modelled using EMTP-RV to investigate their capability to withstand current and energy discharged by lightning strokes during back flashover phenomena. These configurations were then compared to determine the most effective protection design based on the actual tripping pattern recorded by the lightning detection system (LDS) in Malaysia. The selection was made by considering arresters’ discharge energy due to variation in tower footing resistance, current magnitude, power frequency voltage, lightning tail time and front time, number of towers and span length. It was found that double circuit transmission line tripping can be completely eliminated by installing surge arresters at each phase conductor of one circuit. The selected arresters configuration provides sufficient lightning protection to the transmission line and complies with the discharge energy capability requirement specified by the utility company in Malaysia, of 5.1 kJ/kV for maximum continuous operating voltage (MCOV).

Performance of Surge Arrester Installation to Enhance Protection

Performance of Surge Arrester Installation to Enhance Protection

Response of distribution networks to direct and indirect lightning: Influence of surge arresters location, flashover occurrence and environmental shielding

The paper deals with the response of distribution networks to direct and indirect lightning. The response of the network is analyzed with the aim of inferring the mean time between failures of the connected transformers. This is accomplished taking into account the voltage at the utility frequency, the flashovers occurrence in the line insulators, the location of surge arresters, and the shielding provided by nearby buildings. Two different transformer failure criteria are assumed: a critical value and a disruptive effect model.The results make reference to multi-conductor overhead systems with two different topologies: simple straight line and a real feeder with laterals. It is shown that such a detailed lightning performance analysis is useful in order to select the most appropriate strategy for the installation of surge arresters, which may allow the achievement of the desired mean time between failures at affordable costs.

On the role of transformer grounding and surge arresters on protecting loads from lightning-induced voltages in complex distribution networks

This paper presents a study of overvoltages caused by cloud-to-ground lightning strikes on loads connected to a complex low-voltage distribution network. The importance of the transformer grounding in the resulting load overvoltages is discussed for two different lightning events. These events emphasize either the induced-voltage component or the surge transference through the distribution transformer as the main source of overvoltages on the connected loads. A brief discussion is also presented on the efficiency of low-voltage surge arresters in protecting loads connected to complex low-voltage networks. The obtained results indicate that the effectiveness of improving the transformer grounding and of installing surge arresters at specific points of the low-voltage network is limited in terms of load protection if a complex network topology is considered. In some cases, especially for a lightning strike close to the low-voltage line, improving the transformer grounding can even increase load overvoltages.

Proposals for protection of return cables on SwePol Link

The return cable on the SwePol Link has been introduced as an alternative forced by environmentalists due to lack of social acceptance of other solutions. This is why in the proposed solution water and earth have been replaced by two return cables, although from a technical point of view such a solution is less effective. The last, eleventh fault of the return cable took place on 15 October 2012. In eight earlier cases the faults were caused by electrical failures in the cable in the sea and were located between ten and twenty kilometers from the Polish shore and triggered by disturbances in the northern part of the Polish power grid. In this situation it has been suggested to analyze and introduce one or two solutions shown below which may significantly limit the effects and lower the costs caused by return cable faults: a) assembly of additional surge arresters b) return to electrodes – lack of return cables c) ”partial” electrodes working with one return cable d) operation of the link only with earthings on converter stations. To sum up it needs to be stated that: • a relatively cheap way of protecting return cables against electrical failures is installing surge arresters in the cabinet located next to the cable container on the Polish shore • from the suggested preventive measures it seems reasonable to introduce the above mentioned solutions a) and d) simultaneously, as both of them are simple solutions which require neither considerable financial expenditure nor authorizations and may quickly show the expected results. DOI: 10.12736/issn.2300-3022.2013113 1. Reasons for introducing return cables The return cable on the Sweden-Poland link appeared as an alternative forced by ecologists. The decision on laying the return cables was made only at the stage of laying the main cable. In the original projects the construction of an anode and cathode was assumed, and the electrical circuit was supposed to be closed through the earth. In the proposed solution water and earth were replaced by the return cable; however, from a technical point of view, this solution is worse as the efficiency of the whole connection is lower (it is sufficient to build electrodes of proper low resistance values when closing the circuit through the ground, and the ground resistance practically equals zero). At the time of making the decision to lay the return cable there was no cable with a cross section of at least 1100 mm2 and insulation strength of 20 kV on the market that would be suitable for laying at the bottom of the Baltic Sea. It was decided to lay two cables at the marine section with a cross section of 630 mm2 each, and to lay one cable at the Polish land section with a cross section of 1100 mm2, all with an insulation strength of 20 kV. The first failure of the return cable showed the relevance of the decision to lay two return cables; in a failure scenario the damaged cable is disconnected and the other operates with the load of 473 MW [1, 2, 3, 4]. 2. Damage to return cables The damage to the return cable connecting Sweden and Poland that happened on 15.10.2012 was the eleventh in the history of cable operation (almost ten years had passed since the earlier tenth damage). Previous instances of damage occurred in 2001–2003 (that is, during the guarantee period). The cause of the last damage has not been clearly established yet; however, the final insulation breakdown was certainly of an electrical nature. The damage repair procedure for the return cable of the SwedenPoland link is always pretty much the same. First, it must be established which of the two cables is damaged, then the damaged cable is disconnected from the terminals and using mobile Murray bridges the approximate damage spot is located, which T. Szczepanski | Acta Energetica 1/14 (2013) | 147–152

The use of shield wires for reducing induced voltages from lightning electromagnetic fields

The mechanisms from which lightning overvoltages can be produced on a power line depend on the system voltage. In medium voltage (MV) overhead distribution systems, lightning transients can be originated from either direct or indirect strokes. The main methods that can be adopted to improve the line lightning performance concern the increase of the critical impulse flashover voltage (CFO) of the line structures, the installation of surge arresters, and the use of one or more shield wires. This paper deals with the evaluation of the effectiveness of shield wires in reducing the magnitudes of the surges induced by nearby strokes on MV distribution lines. Such effectiveness depends on the combination of several parameters such as the relative position of the shield wire with respect to the phase conductors, the grounding interval, the ground resistance, the stroke current steepness, and the relative position of the stroke channel with respect to the grounding points. Realistic situations corresponding to typical configurations of a rural distribution line with either an overhead ground wire or a neutral conductor are considered. The analysis is carried out based on both computer simulations and test results obtained from scale model experiments, under controlled conditions.