Lightning Overvoltage Research Articles

Analisis Arrester Sebagai Sistem Proteksi Pada Transformator di Gardu Induk Keramasan

Lightning overvoltage is a periodic overvoltage caused by external causes. An arrester is equipment that protects installations from overvoltage disturbances due to lightning strikes or electrical surges. The transformer functions to distribute electrical power by increasing or decreasing the voltage at the substation. This research focuses on substation equipment, namely the type 3EP 2150-2PL3 arrester connected to a 100 MVA IBT Transformer. Good protection is obtained if the arrester is placed as close to the transformer as possible. Therefore, this distance is determined so that protection can take place properly. The distance between the arrester and the transformer used at the Keramasan 150 KV substation is 5 m. while from the calculation results it is 22.5 m. based on SPLN 7: 1978 that for a 150 kV system the distance between the lightning catcher and the transformer does not exceed 80 m. This means that the distance between the arrester and the 100 MVA IBT Power Transformer is still within the limits set by PT PLN. The continuity of the spark that occurs in the arrester is still within safe limits and in accordance with mathematical analysis.

Lightning Overvoltage Simulation and Design of a Novel Surge Protective Device for High-Power Offshore Wind Farms

Lightning Overvoltage Simulation and Design of a Novel Surge Protective Device for High-Power Offshore Wind Farms

Methodology to accelerate the statistical assessment process of evaluating the transmission line lightning performance

The lightning performance of transmission lines is a criterion of utmost importance to be evaluated in transmission system reliability. In order to accurately estimate the expected number of shutdowns, it is imperative to account for the stochastic nature of the lightning phenomenon. In this sense, the most widely used technique to estimate these shutdowns is the Monte Carlo method (MCM). Although the MCM is a trustful method, it has a huge drawback in terms of computational burden. Therefore, this paper proposes the use of an alternative statistical technique, the Unscented Transform method (UTM). This method achieves an approximate non-linear mapping by employing a set of points (associated with input statistical data), which are deterministically selected and weighted. The set of these points and weights is then used to estimate the lightning overvoltage across insulator strings, which represents a significant reduction in the number of samples evaluated in the process in relation to the application from MCM. In this paper, the MCM and UTM methods are applied and compared in the lightning overvoltage evaluation, which is carried out with the help of the Alternative Transient Program (ATP). From the studies conducted, it was found that the application of UTM in place of MCM allowed for significant computational gains while maintaining satisfactory levels of accuracy in the estimation of indicators.

Surge arrester optimal placement in distribution networks: A decision theory-based approach

The study introduces a novel method for optimizing surge arrester placement in the distribution line to mitigate lightning-induced overvoltages, employing a single-objective optimization algorithm. The study assesses the effectiveness of two types of surge arresters concerning discharge energy in reducing lightning overvoltage. Moreover, the comparative analysis takes into account the transfer of overvoltage performance from protected to unprotected towers, highlighting its significance in estimating flashover rates under different protection alternatives. Decision theory analysis is employed in the present study to identify optimal arrester locations. The study aims to minimize the expected flashover rate and identify the most effective protection strategy by considering futures/scenarios associated with different values of peak current and lightning locations. The results of numerical applications also showed the substantial impact of lightning surge transfer within the network, emphasizing the imperative to incorporate this phenomenon into lightning protection modelling.

Исследование влияния импульсной короны на проводах ВЛ 110 кВ, грозозащитном тросе на энергетические характеристики линейных ОПН во время грозовых перенапряжений

The corona effect has a significant impact on calculations of lightning protection of the high-voltage overhead transmission line. The corona effect in the calculation of the transient process during a lightning overvoltages is often neglected due to the complexity of modeling the corona effect. The issue of the corona effect influence on the operation of non-linear surge suppressors installed on overhead lines hasn’t been sufficiently studied. The aim of the research is to evaluate the energy characteristics of linear surge arresters considering the corona effect on the overhead line. Simulation of the transient process on the overhead line during lightning overvoltages is carried out in the EMTP-ATP software. There is no corona model among the basic models in EMTP-ATP software. Thus, the corona model on overhead line wires using dynamic capacitances is under consideration. A model of corona on overhead line wires in EMTP-ATP is developed. Calculations of energy characteristics of linear surge arresters on an overhead line model considering the corona and without corona effect are carried out. The comparison of the obtained energy characteristics is carried out. The corona has a significant effect on the energy absorbed by the linear surge arresters during lightning strikes to the ground-wire if the front time of the lightning current impulse has a value near 1 s. When lightning strikes to the phase wire, the energy absorbed by the linear surge arresters is so great that the influence of the corona effect is insignificant. The corona model used in calculations in EMTP-ATP software has several limitations. Therefore, in future research it’s advisable to improve the model and simplify it, when calculating lightning protection of overhead lines.

Flashover pattern analysis for 275 kV double circuit transmission lines during direct lightning strikes

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

Response Characteristics of a ZnO Arrester Under Nanosecond Electromagnetic Pulse

Zinc oxide arresters, a major type of overvoltage protection equipment in power systems, can suppress transient lightning overvoltage, operation overvoltage, and other types of power surges. However, the response characteristics and protection effects under nanosecond pulses, such as those in a high-altitude electromagnetic pulse conduction region, remain unclear. Therefore, the surge protection performance of arresters should be properly understood, and high-performance arresters should be developed. In this study, critical parameters, including overshoot peak voltage, residual voltage, response time, and voltammetry characteristics of a representative 10 kV ZnO arrester under nanosecond pulses, were obtained using a double exponential pulse current injection source. The overshoot peak voltage of this arrester under a nanosecond pulse is 2.19 times of lightning impulse residual voltage, and the residual voltage ratio under a nanosecond pulse is 4.31. The average response time is approximately 45 ns, and the response time is independent of the nanosecond pulse amplitude. Furthermore, an electromagnetic transient model of this type of lightning arrester is established based on the CIGRE guidelines, as well as a method to determine the key parameters. The model can simultaneously account for the response characteristics of the small current region and the conduction region of the arrester, which properly agrees with the experimental results.

Research on Lightning Overvoltage Protection of Line-Adjacent Pipelines Based on Solid-State Decoupling

Existing transmission lines and pipelines are frequently crossed and erected in parallel, meaning that if lightning strikes a wire and causes insulator flashovers, the resulting lightning current will spread through the grounding of the tower where the flashover insulator is located. This dispersion of current can lead to overvoltage effects on nearby pipelines. This study performs simulation calculations to analyze the overvoltage experienced by pipelines due to the dispersion of grounding current from the tower. Furthermore, this paper proposes a method for protecting the pipeline from such an overvoltage. Firstly, the lightning transient calculation model of a transmission line tower is constructed using the electromagnetic transient software ATP-EMTP 5.5. The model calculates the effects of lightning peak currents and soil resistivity on the distribution characteristics of lightning current in the tower, specifically in the area where the flashover insulator is located. Subsequently, a calculation model of the tower grounding grid–natural gas pipeline is developed, taking into account the distribution characteristics of lightning current in the tower. This model analyzes the impact of lightning peak currents, soil resistivity, and pipeline spacing on pipeline overvoltage. Finally, the effectiveness of the solid-state decoupler in mitigating lightning overvoltage in the pipeline is verified. The results demonstrate a positive correlation between the lightning current entering the tower grounding grid through the flashover insulator and the lightning current distribution characteristics. The solid-state decoupling device proves to be effective in reducing the voltage of the pipeline insulation layer, and the simulation results provide the optimal laying length of the bare copper wire.

Lightning Flashover Characteristics of a Full-Scale AC 500 kV Transmission Tower with Composite Cross Arms

Overhead transmission lines (OTLs) have always been the major means of power delivery. With the significant increase of transmission voltage and transmission capacity, the dimensions of transmission towers are increasing accordingly, resulting in extensive occupation of land resources. Towers with composite cross arms are a promising solution to this problem, considering the remarkable performance of composite line insulators. In this research, a full-scale alternating current (AC) 500 kV model of a transmission tower with composite cross arms is manufactured and applied under a lightning overvoltage of different polarities. The developing process of streamer-leader discharge is recorded with a high-speed camera, and the major path of the flashover is identified. The flashover voltages are measured and corrected to standard conditions while considering the air humidity and air density, and clearly confirm the polarity effect. The tower’s lightning-withstand level is calculated based on the tower structure and the flashover characteristics. Based on the results obtained from full-scale experiments, the feasibility of composite cross arms is confirmed, and a structural optimization is proposed.

CALCULATION OF FAST FRONT OVERVOLTAGES IN VICINITY OF A POWER TRANSFORMER

During their lifespan all the primary equipment installed in power system is subjected to transients. Therefore, it is necessary to adequately dimension and protect the equipment. However, in the networks with high share of renewables, power electronics, cables or near GIS, the failure can occur even though good practice of insulation coordination are fulfilled.
 In this paper high frequency power transformer model is presented. Such model is based on measurements of admittance matrix and is adequate for simulation of fast front transient in EMTP like software. Additionally, simulations of lightning and switching overvoltages are given for the observed power transformer unit.

Evaluation of Lightning Overvoltages for Overhead Transmission Lines Using Unscented Transform

The Monte Carlo method (MCM) is the most widely used statistical approach to evaluate the lightning performance (LP) of overhead transmission lines (OTLs). However, the MCM has a very high computational burden, making LP studies time consuming. To overcome this difficulty, this letter proposes a new alternative approach for calculating the the lightning overvoltages (LOs) using the unscented transform method (UTM). This letter compares the UTM and MCM for calculating LO in insulator strings of OTLs through extensive tests carried out using the Alternative Transients Program (ATP). Such LO evaluation is an essential requirement for LP evaluation of a transmission line. The results indicate that the UTM significantly reduces the processing time to generate LOs while its accuracy is similar to that of the MCM.

The Impact of Transmission Line Modeling on Lightning Overvoltage

In most of the work that investigates the backflashover phenomenon due to direct lightning strikes, using EMT-type simulators, transmission lines are represented by the J. Marti model and the ground effect is computed employing J. R. Carson’s formulations. Thus, the ground displacement current is neglected, the line voltage definition corresponds to the wire potential formulation, and soil resistivity is considered frequency-independent. These considerations can lead to erroneous measurements of the occurrences of the backflashover phenomenon in the insulator strings of transmission line. In this sense, this paper presents a systematic sensitivity analysis study of lightning overvoltage in insulator strings considering more physically consistent models of the transmission line, which consider the displacement current, ground admittance correction, rigorous voltage definition, and frequency-dependent soil parameters. According to the results, for the case study, transmission line parameters modeling can present a maximum percentual difference of around 71.54%, considering the frequency range of first strokes. This difference leads to a percent difference of around 5.25% in the maximum overvoltage across the insulator strings. These differences confirm that the occurrence or not of backflashover in the insulator strings, including the disruption time, are sensitive to the line model considered.

LEMP and ground conductivity impact on the direct lightning performance of a medium-voltage line

• Assessment of the LEMP influence on direct lightning overvoltages of medium-voltage distribution lines of the type equipped with a shield wire and surge arresters. • Comparison between the results obtained by a 3D-FDTD method and the LIOV-EMTP code. • The LEMP contribution on the overvoltages across insulators increases with increasing values of the soil conductivity. • The appropriate modeling of the LEMP effects is important for the lightning performance assessment of the type of lines considered in this paper. In medium-voltage distribution lines equipped with a multi-grounded shield wire and with surge arresters installed along the line at relatively short intervals, lightning outages associated with indirect lightning are less frequent than those associated with direct ones. The protection for this type of distribution lines is therefore dependent on the response to direct strikes. This paper presents and analyses the response to direct lightning overvoltages of lines of such a type located over a lossy soil considering the influence of the lightning electromagnetic pulse (LEMP), which is typically disregarded in the calculation of overvoltages due to direct strikes. The calculation results, performed by means of a three-dimensional finite-difference time domain (3D-FDTD) method and of the LIOV-EMTP code, indicate that the voltage across the insulator is enhanced by LEMP effects. In addition, it is shown that the enhancement due to the LEMP increases with the increase of the soil conductivity value. The modeling of the LEMP effects is therefore important for the accurate assessment of the lightning performance of medium-voltage distribution lines of the type considered in this paper, even when direct strikes are considered.

Influence of configuration of power distribution lines on failure probability of surge arresters

In Japan, many surge arresters have been installed on 6.6 kV overhead distribution lines for reducing lightning overvoltages. The increase of surge arresters has resulted in a remarkable decrease of lightning outages of distribution lines caused by insulator flashovers. In contrast, several surge arresters have been damaged by direct lightning strikes to distribution lines. Studies of countermeasures for the failure of surge arresters are generally carried out by lightning surge analysis using the Electro Magnetic Transients Program (EMTP). In the previous studies, a simple model of a straight line is used, however, branch lines and termination points also exist in the actual distribution lines. In this paper, we present the influence of configuration of distribution lines on the failure probability of surge arresters obtained by the lightning surge analysis.

Rancang Bangun Pembangkitan Generator Marx 10 Tingkat pada Uji Kapasitor 220 pF dan Lightning Protector

The Marx generator circuit is an impulse voltage multiplier that is used to represent lightning overvoltage and switching overvoltage. In this research, a 10-level Marx Generator impulse generator design was carried out by varying the distance between the spark gaps of 2.5mm, 5.0mm, 7.5mm, and 10.0mm and the test load was a 220pF capacitor and a lightning protector. The results of the design and simulation of the 10-level Marx Generator produce an impulse voltage according to the IEC 60060-1 lightning impulses standard, which is 20.20kV with a wavefront and tail time of 2.29 µs and 52.3 µs. The test results for the 220pF capacitor load at a distance of 2.5 mm, the resulting voltage is 23.5 kV with a wavefront and tail time of 1.7 µs and 25 µs, while the lightning protector test load produces a voltage of 24 kV, with a wavefront and tail time of 2.1 µs and 43 µs

Research on Lightning Overvoltage Characteristics of High-Voltage Diode Rectifier

Failure of the high-voltage diode rectifier caused by lightning will cause huge losses. The traditional analysis of overvoltage induced by the high-voltage diode rectifier shell under lightning stroke cannot adapt to the overvoltage process caused by lightning stroke-induced conduction invading the inside of the high-voltage diode rectifier. Therefore, this paper proposes to establish a high-frequency equivalent model of the core components of the high-voltage diode rectifier, including diodes, reactors, transformers, and overhead lines. On this basis, a lightning overvoltage model of lightning-induced conduction into the high-voltage diode rectifier is built, and the transient process of diode lightning overvoltage under the constraint of reverse recovery charge is analyzed. Then, we describe the transient distribution of overvoltage in high-voltage diode rectifiers caused by lightning stroke. The transient distribution of overvoltage induced by lightning in series diodes under different diode equivalent models is analyzed by simulation. The simulation results show that the inconsistent parameters of series diodes can easily lead to diode damage due to uneven voltage distribution when lightning strikes. Therefore, this paper puts forward a scheme to reduce lightning damage, including selecting diodes with the same parameters and adding fast-melting fuses at the transformer’s secondary side and in front of the series diode bridge arm. The simulation shows that the scheme proposed in this paper can effectively prevent the high-voltage diode rectifier from being damaged by lightning strikes.

Identification of Lightning Overvoltage in Unmanned Aerial Vehicles

This paper presents research on the model developed in the Matlab environment for simulating effects of overvoltage in an unmanned aerial vehicle (UAV) upon lightning discharge. They are based on transmittance obtained from voltage surge impulse measured in drone circuits. Overvoltage waveforms were measured at the input and output of different parts of the machine. It was then possible to calculate the transmittance of those (chosen) circuits. The motors, supply system, communication lines, and sensors were primarily tested. Both positive and negative polarization of the surge pulse were used and compared. The shape of pulse, is standardized by international norms for avionics tests (RTCA DO-160). The special surge generators were used to prepare the same repetition of each pulse (for all measurements). The simplified model of surge pulses propagation in drone circuits was prepared in Matlab. The differential between direct and step-by-step paths of pulse propagation in some connected circuits were also compared.

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.

Analysis and Mitigation of The Lightning Overvoltage in Capacitively Coupling Grid Connected Offshore Wind Turbine

Analysis and Mitigation of The Lightning Overvoltage in Capacitively Coupling Grid Connected Offshore Wind Turbine

Lightning caused overvoltages on power transformers recorded by on-line transient overvoltage monitoring system

Transient overvoltages generated by lightning strikes or switching operations represent a significant risk to bushings and windings of power transformers. They cause stress on the insulation system and can, over time, cause dielectric failure and damage to power transformers. Many transformer failures are reported as dielectric failures and they are not necessarily linked to any particular event when they occur but may be the result of prior damage from transient overvoltage events. Lightning and switching overvoltage waveforms appearing at transformer terminals in real operating conditions may significantly differ from standard impulse voltage waveforms used during laboratory testing. The number and amplitudes of overvoltages which stress the insulation depend on various parameters such as the lightning strike density in the considered area, since it determines how often the transformer is stressed by lightning overvoltages. Since the overvoltage amplitudes at transformer terminals are usually unknown, an on-line overvoltage transient recorder can be used with the ability to sample, analyse and store transients in real-time. In this paper, an on-line transient overvoltage monitoring system (TOMS) for power transformers is presented that is capable to continuously record in real-time various kinds of transient overvoltages such as lightning or switching overvoltages. Special attention is paid to lightning caused transient overvoltages recorded at the terminals of 150 MVA power transformer. Recorded waveforms originating from lightning strikes to overhead lines are correlated with data from the lightning location system (LLS) and supervisory control and data acquisition (SCADA) system. Collected data about overvoltage stresses can be used as the basis for the assessment of the transformer insulation condition, estimation of health index and for analysis of various kinds of events such as faults or equipment failures.