Lightning-induced Overvoltages Research Articles

A Novel Solar-Cell String Wiring of Photovoltaic Module for Reducing Lightning-Induced Overvoltage

A Novel Solar-Cell String Wiring of Photovoltaic Module for Reducing Lightning-Induced Overvoltage

A Correction to Rusck Expression for the Evaluation of Lightning-Induced Overvoltages for High-Resistivity Ground

A Correction to Rusck Expression for the Evaluation of Lightning-Induced Overvoltages for High-Resistivity Ground

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.

Development of a Lightning-Induced Overvoltage Suppression Device for the 10 kV Distribution Network

The critical point of lightning protection of the 10 kV distribution network is lightning-induced overvoltage protection. The traditional lightning protection measures cannot solve the problem for the 10 kV Distribution Network. This paper developed a distribution network lightning-induced overvoltage suppression device. The device comprises core inductance, nonlinear resistance, and a parallel adjustable gap. The device operates in three states according to the lightning overvoltage amplitude. The lightning energy is discharged through the device to the earth. The lightning-induced overvoltage amplitude is reduced to below 75 kV. The device’s effectiveness is verified by theoretical analysis and simulation in MATLAB/SIMULINK. The device has significant advantages, such as good lightning protection affection, minor disturbance to the distribution network, and light installation work volume. The device has a good application prospect.

Effect of Eddy Current for Photovoltaic Module on Lightning-Induced Overvoltage Caused by Electromagnetic Coupling

Lightning electromagnetic field will induce a high voltage on the photovoltaic (PV) farm and also generate the eddy current. To study the effect of eddy current inside a PV module, the mechanism of the eddy current is elucidated. The density of eddy current is derived and it is solved by the method of moments. The eddy current produces a magnetic field to weaken the original field, which can reduce the lightning-induced voltage. The eddy current is mainly distributed on the outside surface of both aluminum-back surface field solar cells and aluminum foil. Moreover, the lightning transient of a PV array is computed. It is concluded that the PV backsheet cored with aluminum foil can greatly reduce the differential-mode-induced voltage of PV module. Several crucial factors, including foil material, foil thickness, and the distance to solar cells, are discussed. In order to minimize the induced voltages of PV modules, the PV module with aluminum foil on backsheet is proposed and the suitable range of the foil thickness is determined.

A Novel Crossover Wiring of DC Cable for Photovoltaic System Against Lightning-Induced Overvoltage

Photovoltaic (PV) arrays are installed in wide-open areas, and they are vulnerable to indirect lightning strikes. The electronic devices in proximity may be damaged by the induced voltage caused by the impulse magnetic field across the dc cable loop for PV system. By compensating the magnetic flux, a novel crossover cable wiring is proposed in this article against lightning-induced overvoltage. Considering the electromagnetic coupling of PV bracket and metal frames, the magnetic field near PV array is computed, and the differential-mode-induced voltages in cables under different wirings are then compared. The influences of lightning striking points, mounting system structure, PV oblique angle and soil, etc., are discussed. The results indicate that the use of the proposed cable wiring scheme can reduce the induced voltage remarkably without any additional protective devices. The proposed crossover wiring scheme is easy to implement and cost-effective, which can provide guidance for cable wiring design of PV systems.

On the Role of Shield Wires in Mitigating Lightning-Induced Overvoltages in Overhead Lines - Part II: Simulation Results for Practical Configurations

In the companion Part I, the theory relevant to the role of shield wires in mitigating lightning-induced overvoltages in overhead lines has been analyzed and clarified. A more consistent meaning has been assigned to the concept of Shielding Factor by introducing two innovations compared to the current literature: the first one concerning the distinction between <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">internal</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">external</i> parameters, and the other one concerning the point along the line where to assess the mitigation effect. Thanks to this new approach, uncertainties seen in the literature have been sorted out, and the Shielding Factor has been shown to be a parameter which can be precisely quantified. However, our new contribution was applied to a schematic (unrealistic) configuration: a line with a shield wire grounded at only one point. This Part II is precisely devoted to confirming the results obtained in Part I, by applying the proposed approach to more realistic and practical line configurations, namely a line with multi-grounded shield wire, and a line equipped with laterals too.

On the Role of Shield Wires in Mitigating Lightning-Induced Overvoltages in Overhead Lines - Part I: A Critical Review and a New Analysis

The ability of shield wires installed in overhead lines to mitigate lightning-induced overvoltages has been extensively investigated. Unfortunately, these studies came to different results, sometimes contradicting each other: some authors found that shield wires produce a significant overvoltage reduction, while others found the reduction negligible; conflicting results also pertain to the role played by the various parameters involved, such as the relative height of the shield wire(s) compared to the phase conductors. This paper aims to clarify this topic. The paper is organized in two parts: Part I, which starts from the analysis of the theory behind the mitigation effect, is devoted to establishing a more solid base to the topic. Two fundamental improvements are proposed. The first one is the distinction between <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">internal</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">external</i> of the parameters involved: current literature makes an indiscriminate grouping of all of them; the second one is concerned with the point along the line where the mitigation effect needs to be assessed. Thanks to this new approach, we show that this effect can be precisely quantified. The analysis in this Part I is limited to the basic case of a single grounding point of the shield wire, which represents an unrealistic case. Part II is devoted to completing the study, by applying the proposed approach to more realistic and practical cases.

Frequency of Damage of Low Voltage Apparatus Due to Lightning Flashes to Ground Nearby HV Overhead Lines

The paper deals with a simplified approach to evaluate the frequency of damage of low voltage apparatus powered by a in housing HV/LV transformer against overvoltages due to nearby lightning flashes (source of damage S4 according to IEC 62,305 standard). The approach is based on computer simulations with validated models according to the current state of the art. The paper evaluates: the overvoltages stressing the HV/LV transformer due to lightning-induced over-voltages on the supplying HV overhead line; the voltage transferred to low voltage circuit through the power transformer and the influence of the transformer characteristics and of the LV circuits feeding the apparatus; the influence of the characteristics and the number of LV circuits on the frequency of damage of the apparatus. The different contributions to the voltage at the apparatus terminals, namely, the voltage transferred by the HV/LV transformer and the voltage induced by lightning current in the circuit downstream the transformer, are recognized. The voltage drop along the earthing system between the points where the transformer and the apparatus are earthed is, in the case considered, not effective because the apparatus and the transformer are bonded at the same point to the earthing system of the electrical installation. Even if these voltage components exhibit different shape and time at peak, for safety, they are added. When the resulting voltage is higher than the rated impulse voltage of apparatus insulation, damage of apparatus occurs. The evaluation allows to conclude that the frequency of damage of the LV apparatus supplied by circuits in a multipolar cable is about a thousand times lower than the one relevant to circuits in plastic conduit. If the tolerable frequency of damage of the LV apparatus is kept in the range of 0.01 damage/year, the adoption of protection measures against overvoltages caused by the source S4 is practically not necessary, except for the case of long circuits in conduit, powered by long HV overhead lines in areas with high values of lightning flash density. As this matter has not yet been considered in the IEC 62305 standard series, the results presented in this paper will be useful in the light of the revision of requirements of this standard.

An Efficient Method for the Computation of Electromagnetic Fields Associated With Tortuous Lightning Channels

Lightning electromagnetic (EM) fields are typically computed by assuming the current propagation within a straight vertical channel of negligible cross section. However, it is well known that the lightning path is tortuous and this can significantly affect the radiated fields and the lightning-induced voltages on power lines. Lupò <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">et al.</i> (2000) proposed an analytical method evaluating the EM fields radiated by a tortuous channel assuming a step current source; to consider an arbitrary (realistic) current source, a slow-converging convolution integral was applied. The aim of this article is to reduce the computation time of such procedure by extending to the tortuous channel case the approach proposed by Brignone <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">et al.</i> (2021) for the evaluation of the lightning EM fields with arbitrary current source, originally developed for a straight vertical channel. The performances of the present method are evaluated by means of comparison with the solution proposed by Lupò <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">et al.</i> (2000), showing an excellent agreement with a significant reduction of the CPU effort. This in principle will allow the computation of lightning-induced overvoltages at both individual and statistical level without a prohibitive computational effort.

A New Method to Distinguish between Nearby and Direct Lightning Strikes for Long Operational Medium Voltage Lines

Lightning strikes near Medium Voltage (MV) electricity distribution lines cause voltage transients to be induced onto the conductors of the power lines. The resultant Lightning Induced Overvoltage (LIOV) on the phase conductors may be estimated using computer models or measurements. Models and measurements are mostly limited to short floating lines to simplify calculations and to ensure accurate results that can be easily compared between different models. Existing measurement methods cannot be used to distinguish between nearby lightning and direct lightning strikes to an operational MV network by using only one instrument on a line that is more than 100 km long. The instrument needs to be less than a hundred meters from where the LIOV amplitude on the line is the highest. The new method described in this paper allows one to distinguish between nearby and direct lightning strikes to the line; by comparing the polarity of the current transient recorded at the substation to the lightning return-stroke polarity obtained from a lightning detection network. The new method also allows one to determine whether the LIOV of a particular lightning transient exceeded the Basic Insulation Level (BIL) of the line, by observing the power frequency fault current. The new method was applied to an operational 714 km network operating at 22 kV, and the results were compared with predictions in IEEE Std 1410-2010. Significantly fewer line faults due to nearby lightning were observed than predicted; the reason for this is explained.

A Prediction Model For Lightning-Induced Overvoltages Over Lossy Ground Using Gaussian Process Regression

The accurate assessment of lightning-induced over-voltages is essential for proper insulation coordination studies. In this paper, a novel machine learning based Gaussian process regression model is developed for the prediction of lightning-induced over-voltages considering wide range of ground resistivity and permittivity. The lightning-induced over-voltages have been computed using two-dimensional finite-difference time-domain technique associated with Agrawal field to line coupling model. To account for the input space variability, seven predictor variables namely: resistivity, permittivity, return stroke velocity, distance from flashpoint, return stroke peak current, front-time, and height of an overhead line are considered to determine the response variable, that is, lightning-induced over-voltages. Accordingly, the training of the Gaussian process regression model is carried out using lightning-induced over-voltages obtained from two-dimensional finite-difference time-domain technique for both first and the subsequent strokes. The estimation accuracy of model is appraised using root mean squared error indicating that the exponential kernel function has the least error than other kernel types for describing the covariance. The predictive performance is evaluated by corroborating the predictions from the model against the random test cases generated from two-dimensional finite-difference time-domain technique. The predicted results showed a good agreement with those obtained from finite-difference time-domain technique.

Impact of Lightning Channel Base Current (CBC) Function Modeling on Computed Lightning Induced Overvoltage Waveshapes

Adverse effects of lightning strike are studied through the modeling of the lightning-induced over-voltage (LIOV) using the channel-base current (CBC) functions. A lightning current is characterized by the parameters like current peak value (Im), time-taken by the current to reach Im (tm), maximum rise-rate of the current (di/dt)max (steepness), and charge transferred at the contact point of the strike (Q). Using the CBC functions, the lightning electromagnetic fields (LEMFs) are calculated to compute the LIOV using a coupling model. Since the choice of CBC function plays an important role in LIOV computation, the present work studies its effect on the computed LIOV for matching and zero load impedance. As a case study, two functions: Heidlers and NCBC functions were examined. It was shown that a-sort-of delay characteristic from the NCBC function is reflected in the computed LIOV and also the tripolar nature of the LIOV for the case of imperfect ground. The difference between the LIOV computed using NCBC and Heidler?s function shows space-time reflections of the order of <formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex>$10^4$</tex></formula> magnitude.

Research on Protective Measures of Lightning Induced Overvoltage in Urban Distribution Lines

Research on Protective Measures of Lightning Induced Overvoltage in Urban Distribution Lines

Arc-extinguishing characteristics of semi-enclosed structures based on theory of positive shock wave reflection

Lightning current in the process of discharge can cause the potential differences between insulators to rise, hindering the normal operation of the equipment. To reduce the potential difference between insulators during a lightning strike, this study proposes a semi-enclosed structure to limit the rise of potential between insulators. Lightning-induced overvoltage causes the semi-enclosed structure to discharge, forming an arc channel. Because the arc is compressed by the structure, an overpressure-induced shock wave is generated. Positive reflection occurs when the shock wave hits the wall that damages the development of the arc through superposition. By using the theory of positive reflection of shock waves, the overpressure due to a positively reflected wave, generated by an impulse current of 8/20 µs with a peak value of 10 kA, was as high as 4.8 MPa, 48 times the initial pressure. Moreover, a 3D high-current impulse discharge model was established in COMSOL to simulate the process of shock discharge of the structure in the case of a large current. Finally, current-induced shock tests were carried out in the semi-enclosed structure. The results show that the maximum pressure in the semi-enclosed structure was 4.38 MPa at 10 µs and conductivity dropped to zero at 80 µs. In experiments, the amplitude of the impulse current decreased from 9.54 to 5.72 kA, and the current dropped to zero at about 65 µs. The results show that the semi-enclosed structure can extinguish the arc and limit the rise of potential between insulators.

Design Consideration of the Shielding Wire in 10 kV Overhead Distribution Lines Against Lightning-Induced Overvoltage

This paper presents a systematic investigation into the performance of a shielding wire on 10 kV overhead lines (OHLs) against indirect lightning, from the design point of view. The design parameters addressed include the grounding interval, grounding resistance, and position of the shielding wire. As a system outage is usually caused by insulator flashover at OHL poles under indirect lightning, the induced voltages there are investigated with the code developed from the Agrawal model. In the evaluation, the location of a lightning return stroke relative to a grounded or ungrounded pole is considered. It is found that the lightning channel positioned in the front of an ungrounded pole could completely wipe out the effect of the shielding wire. This occurs if the wave from the grounding point arrives later than the time to the peak of the voltage directly arising from the lightning return stroke. It is suggested providing the wire grounding at every pole even if the grounding resistance at some poles is much higher than the design value. Grounding spacing does not affect the induced voltages at the pole generally if the pole has been grounded. One critical parameter is identified, i.e., the distance between the shielding and outer phase wires. Minimizing the distance can effectively reduce the lightning-induced voltages.

Impacts of Lightning-Induced Overvoltage on a Hybrid Solar PV–Battery Energy Storage System

With increased electrical energy demands projected in the future, the development of a hybrid solar photovoltaic (PV)–battery energy storage system is considered a good option. However, since such systems are normally installed outdoors and in open areas, they are vulnerable to lightning strikes and may suffer from malfunctions or significant damage to sensitive components, which may result in a major breakdown and loss of revenue due to equipment replacement costs and inefficient operation. Thus, the objective of this paper is to investigate the effect of lightning-induced overvoltage on a hybrid solar PV–battery energy storage system, considering indirect lightning strikes nearby the system. The presented hybrid solar PV–battery energy storage system and lightning-induced overvoltage are modeled in Electro-Magnetic Transient Program-Restructured Version (EMTP-RV) software. The lightning-induced overvoltage is simulated based on a lightning waveshape of 10/350 µs using the Heidler expression, whilst the Rusck model is used to simulate the lightning-induced overvoltage. Different lightning current amplitudes (3, 19, and 169 kA), lightning strike locations (20, 50, and 100 m), and cable lengths (5, 10, and 20 m) are used to investigate the induced effects on the system and on the impulse withstand voltage of 6kV, as stated in MS IEC 60664-1 for solar PV–battery systems and inverters at the DC side. The results indicate that as the lightning strike distance increases from 20 to 100 m, the percentage of strikes exceeding the impulse withstand voltage reduces from 67% to 54% at 19 kA. At 169 kA, the impulse withstand voltage is exceeded by more than 100%, regardless of the strike distance (from 20 to 100 m). Furthermore, differences in cable length do not have much impact on the lightning-induced overvoltage due to the small voltage drop across the short cable length. This study provides useful information for PV systems owners and will be useful in assigning appropriate lightning protection schemes for PV farms.

Computation of Energy Absorption and Residual Voltage in a Fourth Rail LRT Station Arresters in EMTP-RV: A Comparative Study

This paper presents a study on the performance of a fourth rail direct current (DC) urban transit affected by an indirect lightning strike. The indirect lightning strike was replicated and represented by a lightning-induced overvoltage by means of the Rusck model, with the sum of two Heidler functions as its lightning channel base current input, on a perfect conducting ground. This study aims to determine whether an indirect lightning strike has any influence with regard to the performance of the LRT Kelana Jaya line, a fourth rail DC urban transit station arrester. The simulations were carried out using the Electromagnetic Transients Program–Restructured Version (EMTP–RV), which includes the comparison performance results between the 3EB4-010 arrester and PDTA09 arrester when induced by a 90 kA (9/200 µs). The results demonstrated that the PDTA09 arrester showed better coordination with the insulated rail bracket of the fourth rail. It allowed a lower residual voltage and a more dynamic response, eventually resulting in better voltage gradient in the pre-breakdown region and decreased residual voltage ratio in the high current region.

Electrical Performance of Polymer-Insulated Rail Brackets of DC Transit Subjected to Lightning Induced Overvoltage.

The fourth rail transit is an interesting topic to be shared and accessed by the community within that area of expertise. Several ongoing works are currently being conducted especially in the aspects of system technical performances including the rail bracket component and the sensitivity analyses on the various rail designs. Furthermore, the lightning surge study on railway electrification is significant due to the fact that only a handful of publications are available in this regard, especially on the fourth rail transit. For this reason, this paper presents a study on the electrical performance of a fourth rail Direct Current (DC) urban transit affected by an indirect lightning strike. The indirect lightning strike was modelled by means of the Rusck model and the sum of two Heidler functions. The simulations were carried out using the EMTP-RV software which included the performance comparison of polymer-insulated rail brackets, namely the Cast Epoxy (CE), the Cycloaliphatic Epoxy A (CEA), and the Glass Reinforced Plastic (GRP) together with the station arresters when subjected by 30 kA (5/80 µs) and 90 kA (9/200 µs) lightning currents. The results obtained demonstrated that the GRP material has been able to slightly lower its induced overvoltage as compared to other materials, especially for the case of 90 kA (9/200 µs), and thus serves better coordination with the station arresters. This improvement has also reflected on the recorded residual voltage and energy absorption capacity of the arrester, respectively.

Quantification of the Indirect Lightning Using FIT Analysis Under Soil Nonuniformity

One of the phenomena affecting the insulation coordination of power distribution systems is indirect lightning. This article aims to investigate the impacts of stratification of the soil along with the characteristics of the lightning current, i.e., peak, current time-derivative, striking distance to overhead lines on quantification of the lightning indirect overvoltage (LIOV). Accordingly, comprehensive analyses have been established based on the finite integration technique. The flexibility of the method and the simulation results have been compared with the other finite element method and well-known formula, i.e., Rusck and Darveniza. It is also demonstrated that the Darveniza's formula cannot be relied upon as a precise approach in nonuniform grounds. It is revealed that more resistivity of the lower layer results in the increase of LIOV peak in a two-layer soil. It is comprehended that the increase in the number of layers could highly affect LIOVs. Furthermore, the results indicate that the nonuniformity of the ground increases the sensitivity of LIOV to the characteristics of lightning strokes. Finally, an intelligent package is introduced to assess the characteristics of the indirect lightning-induced overvoltage in the complex situation within acceptable accuracy and computation time based on an equivalent resistivity of the soil.