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The coupling capacitance between the line and the transducer cannot be ignored when making non‐contact voltage measurements on low‐voltage three‐phase power lines. This leads to an increase in the number of unknown capacitances, and the number of correlatable response voltage equations is less than the number of unknown coupling capacitances. In this paper, a simplified decoupling method is proposed based on the characteristics of triangular three‐phase lines erected in distribution areas. Firstly, the equivalent circuit measured by the voltage sensing mechanism during three‐phase operation is established, and the three‐phase line response voltage equation is derived. Secondly, this paper proposes a three‐phase line response voltage decoupling algorithm after designing the decoupling matrix. Then, this paper uses the least squares method to solve the coefficients in the equations. Finally, the three‐phase voltage fluctuations of the actual low‐voltage stations are simulated by simulation. The measured sensor voltage values are substituted into the algorithm to invert and calculate the three‐phase line voltage. The three‐phase phase error is less than 2°. The amplitude error is less than 1.77%. The experiment verifies the stability and accuracy of the proposed decoupling method. [ABSTRACT FROM AUTHOR]

This paper proposes a new multistage AC model for transmission expansion planning that finds an optimal combination of transmission lines, fault current‐limiting high‐temperature superconducting cables, and multiple distributed generations (DGs). On this basis, the proposed model, from a new perspective, allows for simultaneous improvement of the short‐circuit level and grid‐scale flexibility (GFLX) under both normal and fault conditions. The objective function to be minimized includes not only the net present worth of the total investment and operation costs but also the congestion‐induced GFLX degradation measure. This model also takes the AC power balance and flow relationships, equipment capacity limits, nodal voltage bounds, DG penetration level limit, as well as discrete logical and financial restrictions together into account with the short‐circuit level constraint. To overcome the complexity of solving the resultant non‐convex mixed‐integer non‐linear optimization problem, a multi‐objective integer‐coded melody search algorithm is employed, followed by a fuzzy satisfying decision‐making mechanism to obtain the final optimal solution. The exhaustive case studies conducted on the IEEE 24‐ and 118‐bus test systems verify the efficacy of the newly developed model in terms of cost‐effectiveness, flexibility, and short‐circuit level suppression when facing different normal and fault conditions. [ABSTRACT FROM AUTHOR]

A machine learning‐based optimized droop method is suggested here to simultaneously reduce the production cost (PC) and power line losses (PLL) for a class of direct current (DC) microgrids (MGs). Traditionally, a communication‐less technique known as the hybrid droop method has been employed to decrease PC and PLL in DC MGs. However, achieving the desired reduction in either PC or PLL requires arbitrary adjustments of weighting coefficients for each distributed generator in the conventional hybrid droop method. To address this challenge, this paper introduces a systematic approach that capitalizes on the benefits of artificial intelligence to accurately predict both the PC and PLL in a DC MG. Furthermore, an optimization technique relying on the gradient descendent method is employed to independently optimize both PC and PLL for each scenario. The effectiveness of the proposed method is confirmed through a comparative study with classical and hybrid droop coordination schemes under various scenarios such as rapid load changes. [ABSTRACT FROM AUTHOR]

The paper presents a ground fault location algorithm (GFLA) in double‐circuit transmission lines (DCTL) with a T‐off connection to an industrial microgrid (IMG) containing electric arc furnaces (EAF), renewable distributed generations (RDG), and static VAR compensator (SVC). The design presented utilizes the information on the current and voltage phasors of one side of the transmission lines (TL) during the fault period, and there is no need for the availability of information on the type of faulty phase(s) and even the faulty section. To find the exact location of the fault in this design, the voltage phasor equations governing the fault point in positive, negative, and zero‐sequence (PNZS) domains, the zero‐sequence current (ZSC) equation of the fault point, and the boundary condition equation of the fault point have been used. The simulation system is implemented in Simulink/MATLAB using accurate modelling of all network components. The algorithm has been tested and evaluated in different fault conditions, including various locations, phase types, phase‐to‐ground connection resistance, occurrence time, and microgrid (MG) operation modes. The successful results of various tests of the proposed design as well as the analysis of various sensitivities confirm the satisfying performance of the suggested algorithm. [ABSTRACT FROM AUTHOR]

Affected by inverter station commutation failure and fast control, line fault characteristics are obviously different from traditional AC transmission line fault characteristics. The existing protection methods for AC line connected to line commutated converter based high voltage DC (LCC‐HVDC) inverter station (ACLs) have the problems of complex setting, weak anti‐noise and high demand for data synchronization. This paper proposes a pilot protection scheme based on high‐frequency transient current waveform similarity. Firstly, with analyzing the fault traveling wave propagation process, the obvious differences are found in the transient current waveforms at both ends of the line when internal and external faults occur. Then the similarity of transient current waveforms is measured with the improved longest common similar subsequence (LCSS) method. And the weak high‐frequency current is extracted with the improved synchronous squeezed S‐transform (SST) method. Finally, a large number of power systems computer aided design (PSCAD) simulation results show that the proposed protection method does not require strict data synchronization, has strong anti‐noise performance, and is tolerant to the influence of abnormal point fluctuations. [ABSTRACT FROM AUTHOR]

The increasing interactivity between energy carrier networks such as electrical, natural gas (NG), and heating can be appropriately used for improving the operation optimality along with overcoming some challenges of those systems. With such a view, this paper studies the practical issue of power transmission lines congestion management in integrated multicarrier energy systems (MCESs) and makes a comparison with the only electrical operation mode. The MCES consisting of electrical and NG network infrastructures with exchanged energy between them is modelled by considering the several local energy hubs and their electrical and heat loads. Rescheduling of energy sources (power plants and gas wells) and demand side management in both electrical and NG networks have been utilized as the two important tools in the developed congestion alleviation framework. The proposed method confirms that the provided flexibility in the integrated operation of the MCESs can lead to a remarkable reduction in the congestion management cost index. Implementing the proposed congestion management framework on an assumed test MCES with a combined 39‐bus New England power system and 20‐node Belgium NG system demonstrates its effectiveness and applicability for the system operators. The issue of power transmission lines congestion management in integrated multi‐carrier energy systems (MCESs) has been studied. The proposed method confirms that the provided flexibility in the integrated operation of the MCESs can lead to reduction in the congestion management cost. [ABSTRACT FROM AUTHOR]

The distribution of transmission lines is complex, influenced by terrain and topography, making their maintenance and management challenging. With the advancement of global mechanization, various types of construction machinery and large‐scale mechanical equipment are continually increasing. Accidental contact of construction machinery near transmission lines poses a serious threat to the stability of the power system. Traditional drones and inspection robots face difficulties in achieving real‐time monitoring of construction machinery and equipment around transmission lines, quickly identifying potential risks. Conventional image processing techniques and convolutional neural networks struggle with effective handling of small targets and densely packed detection tasks involving multiple targets. To address these challenges, this paper proposes an intelligent detection algorithm Swin Transformer attention efficient algorithm‐you only look once (YOLO) (STAE‐YOLO). It is based on the Swin Transformer global self‐attention mechanism, cross‐channel fusion attention mechanism, enhanced small object detection framework, and a focused and efficient regression loss function. The experimental results show that the STAE‐YOLO algorithm model improved by 6.3% in mean average precision, 3.7% in precision, and 3.1% in recall compared to the baseline model. Meanwhile, deploying the window multi‐head self‐attention global self‐attention mechanism in the model can strengthen the global multi‐scale semantic information in detection. [ABSTRACT FROM AUTHOR]

A power line carrier (PLC) communication characteristics‐based method is proposed for single‐phase‐to‐ground fault location in neutral isolated medium voltage meshed distribution networks in this paper. The carrier signals with a time‐varying frequency and constant amplitude are processed by a set of PLC transmitters and receivers, whose placement is optimized by regarding the power network as an undirected graph. Two signal encoding and decoding algorithms for the PLC terminals are proposed to avoid using expensive timing systems between the terminals. The fault location technique is implemented by comparing the cosine similarity of amplitude attenuation and phase offset between the fault and a feature library. The node corresponding to the maximum cosine similarity of the characteristics between the present fault and the library is selected as the location of the current fault. Only one set of low‐cost PLC communication terminals and the widely available power lines are needed in the fault location system, making this approach highly practical. Numerical simulations using MATLAB/Simulink have been performed to verify the technique's feasibility. The results show that the method can accurately locate faults in neutral isolated medium voltage meshed distribution networks. Besides, the presented approach achieves a high level of accuracy in estimating transition resistance values. [ABSTRACT FROM AUTHOR]

In this paper, a collaborative stochastic expansion planning model of cyber‐physical system (CPS) with resilience constraints is proposed. The model can reduce the coupling risk and enhance the resilience under extreme scenarios, from the perspective of the structural/functional coupling between the physical and cyber systems. The model is to collaboratively optimize expansion transmission line siting, expansion communication fibre siting, and service routing distribution to minimize total investment cost. Constraints are divided into conventional constraints and resilience constraints. In the resilience constraints, the impact of cyber failures on the dispatch strategy is analyzed, and the load shedding in stochastic scenarios is limited to guarantee the resilience of the planning scheme. Particularly, to reach a stable solution for the stochastic planning, a mixed scenario set is proposed based on the probabilistic typhoon model and the complex network theory. Finally, the model is solved by the progressive hedging (PH) algorithm. The case studies of the IEEE RTS‐79 test system demonstrate that, compared with the traditional independent planning model, the model proposed in this paper performs better in limiting load loss and enhancing resilience under extreme scenarios. [ABSTRACT FROM AUTHOR]

The secular increase of load causes the evolving power system to operate near the critical margins. In such attitudes, the probability of cascading line outages, as the major reason for recent blackouts, is much more than expected. As a result, an innovative approach for optimal AC transmission expansion planning (TEP) to minimize the risk of cascading blackouts is presented in this paper. The proposed multi‐objective AC‐TEP problem minimizes the expected energy not supplied due to the total load shedding imposed on the system to mitigate the risk of cascading line outages along with the total investment and operational costs of the new transmission lines planned to be optimally added to the system. This probabilistic procedure is based on self‐organized criticality and considers the actual aspects of the power system such as reactive power and voltage concerns in the planning stage. The obtained Pareto front set provides the opportunity for the planners to choose the most preferred solution. The proposed method is implemented and verified in the IEEE 118‐bus test system and compared with two types of TEP approaches. The first one is a previously reported version of this work which was a simplified DC model of the problem and the second one is the conventional AC‐TEP model. The obtained results show the benefits of the proposed AC model on the mitigation of cascading line outages in a more realistic framework, considering the impact of reactive power and voltage stability concerns. An innovative approach for optimal AC transmission expansion planning (AC‐TEP) to minimize the risk of cascading blackouts is presented in this paper. The proposed multi‐objective AC‐TEP problem minimizes the expected energy not supplied due to the total load shedding imposed on the system to mitigate the risk of cascading line outages along with the total investment and operational costs of the new transmission lines planned to be optimally added to the system. This probabilistic procedure is based on self‐organized criticality and considers the actual aspects of the power system such as reactive power and voltage concerns in the planning stage. [ABSTRACT FROM AUTHOR]

The existing relay protections for line‐commutated converter (LCC)‐ultra high voltage DC (UHVDC) transmission lines are insufficient in protection sensitivity and operation speed. The travelling wavefront fault distance information can be used to improve protection performance, which has been used in protection of voltage source converter ‐high voltage DC (HVDC) transmission lines. The adaptability of travelling wavefront protection in LCC‐UHVDC transmission line is analyzed in this paper. First, the conditions that need to be met for the travelling wavefront protections to be able to effectively recognize faults are analyzed. Eight applicability conditions of wavefront protection are revealed from the perspective of travelling wavefront generation and practical application requirements. Then the degree of match between the applicability conditions and the conditions of LCC‐UHVDC system is analyzed as a basis for assessing the adaptability of travelling wavefront protection in the LCC‐UHVDC system. It is pointed out that the index coefficient‐based wavefront protections are not available for LCC‐UHVDC transmission lines since the hardware sampling rate of protection device is insufficient, while first peak time of transient voltage (FPTV)‐based wavefront protection is available for LCC‐UHVDC transmission lines if it has enough anti‐noise ability. Finally, an enhanced anti‐noise algorithm is proposed for the FPTV‐based travelling wavefront protection. The adaptability of the travelling wavefront protection is verified by hardware‐in‐the‐loop test and filed recording experimental data. [ABSTRACT FROM AUTHOR]

Transmission lines may suffer from pin defects, necessitating regular patrols and maintenance. The traditional maintenance approach not only involves a substantial workload and low efficiency but also poses a threat to the safety of maintenance personnel. To address the issue of pin defects in high‐voltage transmission lines, this paper introduces the design of an intelligent pin‐eliminating robot. The research focuses on two main aspects: firstly, analyzing the transmission line environment and employing Solidworks software to design the mechanical structure of the robot. Subsequently, a static stress analysis of the robot's structure is conducted to ensure the rationality of the design. The second aspect addresses the impact of the robot on the electric field distribution of the transmission line in high electric field intensity areas and whether the robot itself experiences discharge phenomena. COMSOL simulation software is utilized to globally calculate and analyze the electric field of the robot. Research results indicate that the threshold for the curvature radius of the pin‐eliminating robot's tip is 2.5mm, and values below this threshold may lead to the occurrence of discharge phenomena. The optimized pin‐eliminating robot, under normal operation, does not exhibit discharge phenomena in a 500kV strong electric field. [ABSTRACT FROM AUTHOR]

This paper proposes a nonlinear analysis of the parameter estimation problem in overhead and submarine power cable applications. The proposed methodology is able to estimate both positive and zero sequence parameters. Also, the measurement model incorporates random uncertainty in a rigorous manner, addressing the issue of noise propagation after applying symmetrical components. Three nonlinear estimation methods were studied to address the nonlinear least squares problems. Several noise levels and sample sizes were considered to demonstrate the robustness of the proposed approach. Finally, the methods were validated using both a simplified 2‐bus system and the IEEE 14‐bus system. The results obtained demonstrated significantly better performance compared to similar results found in the technical literature. [ABSTRACT FROM AUTHOR]

This paper conducts the frequency‐dependent grounding system impact on externally gapped line arresters (EGLAs) operation and their placement effects on the lightning performance of a transmission line (TL). The study involves placing EGLAs at different phases of a 400‐kV double‐circuit TL with two downstream shield wires and selecting the optimal state with fewer back‐flashover incidents. The results show that using a non‐linear grounding system leads to a higher back return current from insulators or EGLAs, resulting in a higher flashover rate compared to the frequency grounding system (FGS). Installing four EGLAs in the middle and upper phases of the TL provides satisfactory lightning protection, and the flashover probability is zero and 4.2% for the FGS and the non‐linear grounding system, respectively. A sensitivity analysis including soil resistor variation, economic analysis, and grounding electrode configuration has been performed that confirms installing downstream shield wires and EGLAs is an effective and economical technique for lightning protection. [ABSTRACT FROM AUTHOR]

Bird's nest defect is an important cause of transmission line faults. To achieve accurate detection of bird nest defects in complex scenarios, a bird nest defect detection model for transmission lines was proposed that combines domain knowledge and occlusion reasoning networks. On the one hand, the model utilized the domain knowledge of the location of the bird's nest, using edge detection to obtain tower area information to constrain the location of candidate frames. This helps to reduce the false detection caused by complex backgrounds. On the other hand, on the basis of analyzing the occlusion characteristics of bird nests, the model employed occlusion reasoning networks that randomly erase features at the feature level to simulate the occlusion of bird nests in real scenes and improve the model's detection capability for occluded targets. Additionally, a multi‐scale feature fusion algorithm was designed in this paper to adapt the model to the scale variations of bird nests in aerial images. Experimental results demonstrate that the model outperforms advanced target detection models and other bird nest defect detection methods, with an AP50 of 78.8% and an AR10 of 72.4% for defect detection. [ABSTRACT FROM AUTHOR]

Overhead transmission line detection based on deep learning of aerial images taken by UAVs has been widely investigated. Despite its success, it is limited by several factors, including inappropriate evaluation criteria and dramatic scaling of components in the images. To mitigate these issues, a relative mean Average Precision evaluation index is proposed to accurately measure the model's detection performance for smaller objects. A data enhancement strategy including multi‐scale transformation is adopted to alleviate the problem of drastic scaling. The existing Cascade RCNN target detection technology is enhanced by incorporating Swin‐v2 and a balanced feature pyramid to improve feature characterization capabilities, while side‐aware boundary localization is utilized to improve the positioning accuracy of the model. Experimental results demonstrate that the proposed method outperforms state‐of‐the‐art methods on CPLID and achieves 7.8%, 11.8%, and 5.5% higher detection accuracy than the baseline for mAP50, relative small and medium mAP, respectively. Additionally, the paper discusses the influence of adopted data enhancement on the robustness of the model. [ABSTRACT FROM AUTHOR]

With the improvement of smart grid, utilizing unmanned aerial vehicles (UAV) to detect the operation status of insulators has attracted widespread attention. The insulator defects can lead to serious power loss, damage the service life of power lines, and even result in power outages in serious cases. The small‐scale object, complex background, and limited‐number collected data make insulator defect still a challenging problem. Benefitted by the advances in deep learning, deep learning‐based insulator defects have achieved great progress in recent years. In the paper, the authors present a novel systematic survey of these advances, where further analysis about different processing stages methods is introduced: (i) insulator processing stage methods exploit the specific image pre‐processing algorithm for data augmentation and low‐level vision information extraction; (ii) defect detection stage model can locate and classify diagnosis fault with different task targets, like sequential task strategy and multi‐task strategy. In addition, the authors also review publicly available benchmark and datasets. The future research direction and open problem are discussed to promote the development of the community. [ABSTRACT FROM AUTHOR]

Tower impulse grounding resistance is important for judging the lightning protection performance of transmission lines. Therefore, it is significant to accurately measure the tower impulse grounding resistance. Existing measurement methods mainly contain the real‐type test method and the impulse coefficient method. However, the real‐type test method requires heavy and complex excitation and measuring equipment, which is difficult to be used in a practical environment. The impulse coefficient method adopts the empirical equations, which could have large measurement errors in different environments. To solve the above problems, this paper studies a novel impulse grounding resistance measurement method (IGRMM) based on multiple frequency impedance. Spectrum characteristics of typical lightning currents and the calculation method of impulse grounding resistance of grounding electrodes are studied, the IGRMM is proposed. Finally, a case study and on‐site tests are carried out. The results show that the proposed IGRMM can accurately obtain the impulse grounding resistance by measuring grounding impedance at a few frequency points, which helps accurate and convenient evaluation of impulse grounding performance in practical environments and lightning protection performance of the power transmission systems. [ABSTRACT FROM AUTHOR]

Conventional phase‐shifting transformers (PST) have been utilized for power flow control in transmission networks for many years. Compared to the slow reacting PSTs, recently trending unified power flow controllers (UPFC) enable much faster power flow control. This paper introduces a decentralized power flow control scheme for power flow controllers (PFCs) without the need for communication between the PFCs. For each PFC, an influence area is defined. The line loading of the transmission lines in this influence area is monitored in real‐time operation and if there is an overloading of a line, a feedback control scheme is used to mitigate the overloading of the line. As the power flow control of UPFC is dependent of the network topology and the UPFC converter limit, additional control measures are introduced to circumvent potential critical scenarios. Supplementary control measures are also developed to increase the robustness of control scheme for the simultaneous operation of UPFC with slow reacting PST. Using RMS simulation in DIgSILENT PowerFactory, the developed control method is validated in the IEEE 68‐Bus NETS/NYPS test bench network. The method is also validated for UPFCs with overlapping influence areas and the combination of fast acting UPFCs and slow acting PST devices. [ABSTRACT FROM AUTHOR]

The UK net‐zero target requires the integration of significant renewable energy resources into the electrical grid. This, together with the projected growth in electricity demand imposes practical challenges on the power transfer capability of existing transmission feeders. For environmental and planning reasons, construction of new overhead lines is problematic, and where possible upgrading of existing substations and lines is preferred. This paper investigates the feasibility of transforming an existing three‐phase (3Φ) double‐circuit 400 kV line into a six‐phase (6Φ) feeder for a simulated future GB scenario. Results indicate a 6Φ feeder, operating at a 'phase‐adjacent phase' voltage of 400 kV can effectively solve the constraints of boundaries in transmission networks. When considering the various operating contingencies, associated with an important UK network boundary and its expected near‐future winter‐peak power transfer requirements, the thermal overload issues are mitigated by transforming a feeder from 3Φ to 6Φ. The paper demonstrates upgrading to 6Φ technology is a potential solution to certain future boundary constraints and in these cases avoids the need to build new underground or overhead AC/DC lines. [ABSTRACT FROM AUTHOR]

This paper presents a two‐stage resilient framework for generation and transmission expansion planning that profits static and dynamic models. The first stage problem finds the generation and transmission expansion results without considering extreme events. Given the planned power system, in the second stage, a simulation‐based method is employed to accurately model the effects of the severe events and measure the expected demand not served. The proposed framework updates the formulation of the planning problem to efficiently search for a new expansion plan resulting in higher resilience levels. This paper uses the maximizing social welfare in the planning model to find the optimal result. Also, the effect of maximizing social welfare in updating the formulation of the planning problem is investigated. In this case, the planning problem is a bi‐level problem that using the primal‐dual formulation leads to a single‐level problem called a mathematical program with equilibrium constraints. After the linearization, the planning problem becomes a mixed‐integer linear programming problem. The planning model profits from reinforced transmission lines to improve power system resilience. The proposed framework is evaluated on 4‐bus, 6‐bus, and 118‐bus systems. According to the results, the proposed method with a low additional cost boosts power system resilience. [ABSTRACT FROM AUTHOR]

The phenomenon of wind abandoned caused by fault of transmission lines has occurred frequently. Since fault current output by wind turbine after fault may induce the frequency variation of the fundamental frequency, fault location based on the fundamental resistance is easily invalid. In order to locate fault accurately and rapidly after wind farm transmission line faults, a time‐domain‐based novel fault location method for transmission line of wind farm is introduced in this paper. The main idea of the proposed scheme is to discretise the distributed‐parameter model of transmission line that is given in the form of partial differential equations by using the finite‐difference time‐domain. In addition, the phase current and voltage at both ends of lines are regarded as boundary conditions. Then, the variational iteration method is utilised to calculate transmission line equations to obtain line length function. At last, fault location function is constructed by a minimised objective function. This paper builds wind power transmission line system simulation model and carries out simulation experiments on PSCAD/EMTDC. To verify the performance of the algorithm, several factors are taken into account for simulation including different fault distances, different fault types, different fault resistances, and different fault inception angles. Simulation results reveal the performance of the proposed method to locate fault for transmission lines connected to wind farm with high accuracy. [ABSTRACT FROM AUTHOR]

Exponentially decaying direct current (EDDC) components in the faulted current of a power system can result in an imprecise estimation of the fundamental frequency component. Because of sources such as the faulted transmission line, the current transformer (CT), and the relay's internal CT, current signals tend to include multiple EDDC components. This paper presents an accurate model of the faulted current, including a new term of EDDC components that belongs to the relay's internal CT along with the transmission line and the CT response. Moreover, this paper proposes an innovative algorithm to eliminate multiple EDDC components. The feasibility and performance of the proposed algorithm were validated using several static, dynamic, and experimental tests. The static test was carried out using MathWorks' MATLAB® software. For dynamic validation, the transient data of a power system (simulated in the commercial PSCAD© software) were employed to test the performance of the propounded method. The experimental test was performed on a distance protective relay manufactured by VEBKO AMIRKABIR Co. The main advantages of this method include the practical feasibility resulting from its simple structure, the ability to effectively suppress the adverse influence of multiple EDDC components (including the response of the transmission line, the CT, and the relay's internal CT), and the accuracy in estimating the fundamental frequency component. [ABSTRACT FROM AUTHOR]

Multi‐year generation and transmission expansion planning (MY‐G&TEP) is a critical issue in power systems. The present paper considers the optimal placement of Fixed Series Compensation (FSC) and Phase Shifting Transformer (PST) proposes a pool‐market‐based mathematical model (MY‐G&TEP) for maximizing social welfare (SW) and reducing investment costs of transmission lines and new power plants. Following the determination of optimal strategy, the present paper compares the usefulness of PSTs and FSCs in the MY‐G&TEP problem in three scenarios. Since MY‐G&TEP is a complex hybrid, mixed‐integer linear programming (MILP), and nonlinear optimization problem, the YALMIP toolbox and CPLEX solver have been applied to find the optimal solution, a globally optimized solution is obtained. For evaluation, the proposed model has been tested on the IEEE 24‐bus and IEEE 57‐bus systems, and the simulation results indicate that the installation of PST and FSC not only improves market conditions but also increases the flexibility of MY‐G&TEP, and adding these FACTS devices to the studied system leads to an increase in the network's performance and enhancement of objectives of the proposed model. [ABSTRACT FROM AUTHOR]

The effective design of controlling parameters in AC–DC conversion in power cables has played an important role in transmission security. The state‐of‐the‐art studies determining the voltage level and ampacity of cables are mostly based on the core temperature at 70 ℃. Accordingly, this paper proposed a technique to determine the cable DC voltage level and ampacity of AC–DC conversion by taking operational temperature, the steady and the transient state electric field intensity constraints and the critical reversal temperature difference (CRTD) into account. The results of the research indicated that the voltages of 66 kV AC cable can be transformed to ±55 kV, ±50 kV and below, the voltages of 35 kV AC cable can be transformed to ±50 kV, ±30 kV and below, the voltages of 10 kV AC cable can be transformed to ±20 kV, ±10 kV and below. Although one of three phases is idle, the capacity of transmission line has improved effectively, and the idle phase could be an alternate to enhance the reliability. Compared with AC operation, the maximum transmission capacity of DC operation increased on different levels. The design results and the approaches of AC‐DC conversion in this paper can contribute a valuable recommendation to the electrical engineering field. [ABSTRACT FROM AUTHOR]

Structural damage identification technology based on modal parameters is an extremely effective monitoring method. Because of the structural characteristics of the conductor, with its small diameter and long span, it is not easy to obtain the modal parameters by manual excitation. Here, a method for structural health monitoring of the conductor under wind load excitation is proposed. Firstly, the natural frequency change law of the conductor after broken strand damage is obtained by analyzing the conductor modal parameters calculation formula and IEEE standards. Then, the vibration characteristics are calculated by vibration experiments and finite element methods. Finally, through the broken strand experiment, this paper demonstrates how to determine the damage degree of the conductor using the modal parameters. And it is applied to online monitoring in the field. The results show that this method is convenient, fast, and accurate. [ABSTRACT FROM AUTHOR]

With an increased focus on renewable power generation, dynamic thermal ratings of various power equipment are being investigated to connect the new intermittent generation to the grid without needing to replace existing infrastructure. Previous research is mainly focused on a dynamic thermal rating for overhead lines. End‐of‐line equipment are also restricted by a thermal limit. This paper combines the thermal model for overhead lines with the transformer thermal model, to investigate the impact of environmental conditions on both. A wind farm case study is used to determine the potential increase in capacity using a combined thermal model. The impact of a higher thermal limit on the loss of life of the transformer is compared to the amount of curtailed wind and the potential revenue from the added wind farm. This analysis serves to provide a method to analyse the risks of using a higher transformer thermal limit, compared to the benefits of increased wind penetration and additional revenue. [ABSTRACT FROM AUTHOR]

Buildings near direct current transmission lines are sensitive to the electromagnetic environment, and the measurement of the electric field above them is important in engineering design and environmental assessment in China. The models of buildings and probes in the ion flow field were established to explore the accurate measurement method of the electric field above the building. Based on the upstream finite element method and the predictor–corrector method, the influence of whether the probe was grounded or not above the building was studied. On this basis, simulation experiments and real‐type experiments were carried out. The results show that when the electrical conductivity of the building was greater than 10−10 S/m, being grounded or not would not change the results. When the building conductivity was between 10−11 and 10−12 S/m, the electric field measurement results would be increased by 30% to 120% after grounding. In the real‐type experiments on the platform with a plywood roof, the relative error in the electric field when grounded or not was only 2.6%. This proved the reliability of the calculated results. In this paper, the measuring method of the DC space charge‐modified electric field above buildings was analyzed first, and the conclusion that ground wire can be cancelled above buildings with general materials was presented. The research results can provide a technical basis for the accurate measurement of the electric field above the buildings near DC transmission lines. [ABSTRACT FROM AUTHOR]

With the fast development of cyber‐physical power systems, coordinated cyber‐physical attacks have become one of the main threats to the security of modern power grid. Considering that it is difficult for attackers to obtain full information of the entire power grid, the coordinated cyber‐physical attack problem for partitioned power grid is studied in this paper, and a tri‐level defender‐attacker‐dispatcher optimization model with consideration of wind power uncertainty in a specific coordinated cyber‐physical attack mode is proposed. The Karush‐Kuhn‐Tucker (KKT) condition and an improved implicit enumeration algorithm are applied to obtain the solution of the complicated optimization problem effectively. In addition, two risk assessment indices pertinent to the physical lines and load measurements are proposed according to the obtained total amount of optimized load shedding and coordinated attack‐defense strategy under valid attack‐defense scenarios. Taking a partitioned IEEE 39‐bus test system as example, the risks of physical transmission lines and load measurements in different areas under attacks are elaborately studied, and the impact of wind power uncertainty on attack‐defense strategies is discussed as well. Numerical simulation results illustrate the effectiveness of the proposed optimization model and risk assessment indices, and some significant conclusions are drawn. [ABSTRACT FROM AUTHOR]

Monitoring and alarm play an important role in preventing trip‐out caused by wildfires for high‐voltage transmission lines. This paper proposes a multi‐Doppler weather radar‐based method for monitoring and alerting of wildfires near transmission lines. Firstly, characteristic parameters are mathematically proposed to distinguish wildfire's radar echoes. Then, the four‐site neighbourhood algorithm and the multithreading method are used to extract all possible wildfire echo units detected by various Doppler weather radars, and a cumulative probability is calculated to identify the wildfire. Finally, a regional block search method is used to quickly locate wildfire‐affected transmission towers. The membership function of spread time in the fuzzy set is proposed to determine the alarm level, which takes into account the influences of environment, topography, and vegetation on wildfire spread rate. The application to a provincial power grid demonstrates that the proposed method has an accuracy of 82.4%, a missing alarm rate of 27.4%, and a delay of fewer than 15 min. In addition, the joint observation of wildfires by multi‐Doppler weather radars and satellites indicates a promising application prospect for transmission line wildfire fighting. [ABSTRACT FROM AUTHOR]

Frequency domain methods had been commonly used in power transmission line fault location. To improve the accuracy of frequency domain fault location methods, this paper studies a robust and accurate discrete Fourier transform (DFT)‐based phasor estimation method. First, this paper analyses the deviation characteristics of DFT output phasors caused by decaying DC components with data window sliding. Based on these characteristics, this paper employs rotation factor computation to construct linear equations for the purpose of estimating the accurate fundamental frequency phasor during fault transient process. In this way, the accurate fundamental frequency phasor can be calculated by a two‐step linear operation. Furthermore, to eliminate the effect of off‐nominal frequency, the proposed method adjusts frequency deviation by using interpolation method. To further enhance the robustness for frequency domain fault location, the PauTa criterion is used to exclude the anomalous equations in the phasor estimation process. Finally, electro‐magnetic fault simulation is used to evaluate the proposed method. The test results demonstrate that the proposed method improve the accuracy of fault location during the fault transient process. [ABSTRACT FROM AUTHOR]

Even though shunt compensation of transmission lines (TLs) is a common practice to limit the overvoltages stemming from the Ferranti effect, it may cause transient and steady‐state resonant overvoltages when one phase is left open due to the single‐pole‐open condition following the temporary phase‐to‐ground (Ph‐g) fault. Furthermore, the existing shunt reactors potentially increase the duration of the secondary arc current at the fault point and hence prevent offering fast single‐pole reclosing. To exploit the mentioned issues, in recent studies, a neutral reactor is introduced, which is installed in the neutral point of the shunt reactors; nonetheless, obtaining the appropriate amount of it is remarkably challenging. In this paper, an optimal neutral reactor (ONR) is determined based on an optimization problem, which minimizes the neutral reactor cost subject to limiting both resonant overvoltages and the duration of the secondary arc current. In modelling, the Laplace domain is employed rather than the phasor domain to consider both transient and steady‐state conditions since this technique allows having better control over transient overvoltages as well as transient secondary arc. [ABSTRACT FROM AUTHOR]

The application potential of aluminium conductor composite core (ACCC) conductors in the 1000‐kV power transmission line project deserves to be investigated. Its economic evaluation is a contentious issue. This paper proposes a method for selecting the type of conductors based on the life cycle cost (LCC) of a transmission line, which includes the initial investments, operation costs, maintenance costs, failure costs, and discard costs. The mathematical model of electromagnetic loss differs due to the various operational circumstances surrounding a transmission line; therefore, a novel three‐dimensional electromagnetic–fluid–thermal coupling model based on the finite element method (FEM) was proposed. The simulation error of ACCC and aluminium conductor steel reinforced (ACSR) conductors is 2.56% and 0.5%, respectively, compared to the experimental value. Subsequently, the LCC model is applied in the economic analysis of a 1000‐kV transmission line, and the costs of ACCC conductors and ACSR conductors under different annual power load utilization hours are calculated. The results indicate that the overhead power transmission line with ACCC conductors saves at least 2 × 106 ¥/km compared with ACSR when annual utilization hours reach 3500 h; meanwhile, energy saving benefits are achieved. [ABSTRACT FROM AUTHOR]

Nowadays, due to the simplicity of operation and proper coordination characteristics, distance relays are being extensively used in the protection of power transmission lines. Despite many advantages, the distance relay is exposed to a maloperation when a power swing phenomenon occurs. Power swings may occur due to major disturbances, such as switching lines, generator interruptions, and connecting or disconnecting a large part of the loads, causing outages in healthy lines. Detecting power swing and preventing distance relay maloperation has always been a challenge. In addition, different parameters can have a great impact on the performance of power swing detection methods. In this paper, these parameters and their effects are examined along with various methods for detecting power swings. Accordingly, this comprehensive review covers all aspects of power swing phenomenon and its detection, including causes of power swings, power swing detection methods, determining threshold values in power swing methods, effecting of compensated lines and wind farms in power swing detection methods, and testing power swing function in the distance relays. It is hoped that this study will be helpful for researchers in power system protection to find relevant references and develop new methods for power swing function. [ABSTRACT FROM AUTHOR]

The unnecessary prolonged operating time of conventional current differential protection under high‐impedance DC line faults is an important issue affecting the continuity of power supply. This issue originates from the extreme differential current fluctuation under fault conditions. This paper presents a reinforced pilot protection algorithm for bipolar CSC‐HVDC transmission lines to achieve a selective and sensitive performance without sacrificing the protection speed. In this regard, the characteristics of low‐frequency transient modal currents are investigated along with the impact of discharging capacitive current under various fault conditions. Based on the features arising from line‐mode compensated currents, it is shown that their opposite changing directions induces a positive high‐value differential current during DC line faults, whereas the compensated line‐mode currents follow the same changing trend under external faults. After detecting internal faults, the faulted pole is detected by utilizing the polarity of ground‐mode components. Compared to other pilot protections, the proposed protection provides more reliability, selectivity, and sensitivity with high operating speed. Moreover, it has robust performance against discharging capacitive current, asynchronous measurement, line parameters uncertainty, and noise. Various simulation tests are performed on a ±500 kV HVDC test system in PSCAD to verify effectiveness of the proposed protection. [ABSTRACT FROM AUTHOR]

The energy exchange between series and shunt converters is the basis for the powerful functioning of the unified distributed power flow controller, which can be realized through the 3rd harmonic current. In this paper, based on the established 3rd harmonic equivalent network of unified distributed power flow controller power system, the influence of the additional loss caused by the 3rd harmonic current on the line transmission capacity is analysed. The mathematical relationship between the neutral point voltage of the transformer and the 3rd harmonic current is constructed, and it is simplified according to the different 3rd harmonic currents. By analysing the power relationship of the 3rd harmonic equivalent network, it is found that there is a contradiction between improving the 3rd harmonic output efficiency of the shunt single‐phase converter and reducing the neutral point insulation voltage of the transformer. The constraint conditions of the 3rd harmonic current are simulated by the advanced digital power system simulator. Finally, the method of obtaining the economical and safe 3rd harmonic current value range is summarized, which provides a theoretical basis and reference for the device parameter design. [ABSTRACT FROM AUTHOR]

Anticipating and relieving congestions is an ongoing challenge for transmission system operators. Distributed grid‐scale battery energy storage systems enable operators to shift power flows and remedy congestion through virtual power lines and grid boosters. This paper includes battery energy storage systems in a combined preventive and curative congestion management optimization. First, it analyzes the impact of the two operational strategies in a case study of the German transmission grid. Furthermore, it outlines curative ad‐hoc measures to overcome uncertainties during operational planning and real‐time operation. The simulation results indicate that battery energy storage systems further increase the use of curative measures and reduce congestion management costs. [ABSTRACT FROM AUTHOR]

This paper presents a novel protection method for transmission lines that estimates the superimposed component phasor using phaselet transform. The phaselet transform computes the phasors over variable‐lenfgth data window at the instant of a fault, so it can estimate the phasor less than one full cycle. The presented method phaselets are used to extract the superimposed component instead of the samples and the initial phase angle difference (IPAD) of the superimposed currents between terminals is used to detect internal and external faults. The main contribution of this method is an accurate, fast and robust superimposed component‐based algorithm that uses the phaselet transform to estimate the phasor of the superimposed component for distinguishing internal faults from external faults; this method is also reliable against transients such as current transformer (CT) saturation and capacitor bank switching. To evaluate the performance of the proposed method, a three‐terminal transmission line is modelled in the alternative transients program/electromagnetic transients program (ATP/EMTP) software and several cases including fault and transients are simulated; finally, the data has been analyzed in MATLAB software. The simulation results show that the proposed method is able to quickly and accurately distinguish internal faults from external faults and is not affected by transients. [ABSTRACT FROM AUTHOR]

The impulse grounding impedance of tower grounding device is one of the important factors in the lightning protection evaluation of transmission line. The impulse characteristic test of the actual tower grounding device under lightning was rarely carried out due to the limitation of the test conditions. With the help of Guangzhou Field Experiment Site for Lightning Research and Testing, the artificial lightning characteristic test of the true tower grounding device was carried out. This paper presented partial observation experimental results and related analysis of the impulse grounding impedance of tower grounding device subjected to artificial lightning M‐component. A calculation model of the tower grounding device subjected to lightning M‐component was established. The changes of the surface soil resistivity under the action of rainwater were taken into account in the calculation. The test data and calculation results of the tower grounding device under the impact of the artificial lightning M‐component had achieved good agreement. The non‐linear ionization of the soil around the tower grounding device can be ignored, and the real impulse grounding impedance was very close to the DC grounding resistance or power frequency grounding impedance, when the tower grounding device in the experiment was subjected to lightning current M‐component. [ABSTRACT FROM AUTHOR]

The parameter estimation for transmission systems is important to power flow analysis, planning the expansion of electric power systems, stability, dispatch and economic analysis. This type of task is developed through systems identification methods, being the least squares method and its variations the most common techniques to obtain the transmission line parameters. However, these techniques have some disadvantages, such as non‐recursive parameter estimation or the availability of an ideally transposed line, in order to address a problem with symmetric matrices, which simplifies the estimation process. In this paper, a non‐linear method (Extended Kalman Filter) is presented to obtain the states of the transmission line terminals jointly with the vectorized matrix of parameters; such approach is strongly affected by the initial conditions; these conditions are usually obtained manually, which requires a lot of time and effort. Therefore, an optimization method (Particle Swarm Optimization) is applied in order to improve the convergence of the EKF, which reduces the time for adjusting the hyper‐parameters and improves the estimated results. The proposed method showed accurate results for non‐transposed systems, and also in comparison with results obtained from the same EKF‐based method without the proposed optimization technique. [ABSTRACT FROM AUTHOR]

At present, the MVDC distribution grid is developing rapidly and relay protection is the key technology to ensure stable operation. Therefore, this paper focuses on the fault line selection method. Firstly, the fault characteristics are analysed when a fault occurs in the line, and a novel single‐pole fault line selection method is proposed based on 0‐mode power. The polarity of current fault component measured at the terminal of each line is used to identify the internal and external faults. And the 0‐mode power is used to select the faulty line. Finally, to verify the correctness of the proposed method, a radial MVDC distribution grid is built in PSCAD to output fault data in different fault conditions, and the fault line selection algorithm is implemented in MATLAB. The simulation results show that the proposed method is fast, effective, reliable and it has a certain degree of tolerance to transition resistance with a strong anti‐data delay and anti‐interference ability. Moreover, the fault line selection method proposed in this paper can still correctly select the fault line in the case of serious faults such as multiple line faults, sudden removal of lines, and sudden changes in photovoltaic output power. [ABSTRACT FROM AUTHOR]

Phasor measurement units (PMUs) are important data source for parameter identification of the transmission line (TL). However, the "seesaw" phenomenon exists in the identified susceptance and reactance (B&X) based on real‐world PMU data, that is, the accuracy of X increases with the increase of the active power transmitted in the TL (APT), while the accuracy of B decreases. Recognizing the above, with the approximations of the opposite influence characteristics of relative errors of the identified B&X with respect to the APT, this paper proposes a method of selecting the steady‐state PMU data to improve the accuracy of the identified B&X. In detail, firstly, the "seesaw" phenomenon of the identified B&X is demonstrated based on the real‐world and the simulated PMU data. Secondly, the approximate relationship between the relative errors of B&X and the APT is derived and summarized, which can explain the "seesaw" phenomenon theoretically. Thirdly, combining the above relationships and the principle that B/X identified with the low/high APT respectively, the practical thresholds of APT for B&X identification are determined, and then, the method for selecting the steady‐state PMU data is proposed. Finally, results using both the simulated and the real‐world data demonstrate the effectiveness and practicality of the proposed method. [ABSTRACT FROM AUTHOR]

The power outage caused by decay-like fracture of composite insulators significantly impacts the power grid. In this paper, a decay-like fractured insulator of 500 kV transmission line is taken as a research object. The detailed observation of core rod and silicone rubber housings, discharge results, temperature rises, and electric field distribution are obtained. (a) The fractured insulator has abnormal heating on the exposed core rod and sheath surface, and the ambient temperature and humidity significantly influence the temperature rise. (b) It is proposed that one of the most obvious characteristics of decay-like insulator is abnormal temperature and temperature rise (such as T > 50°C, ΔT > 30 K). (c) Under the same conditions, temperature rises, electrical discharge, and electrical field strength of decay-like insulator are higher than those of other insulators, and the discharge at the bare core rod is intense. (d) The electric field strength distribution and discharge distribution of decay-like insulator are different from other aging and new insulators. However, the measurement results are significantly affected by test conditions. Therefore, it is difficult to determine whether the composite insulators are decay-like using electric field distribution and UV measurement on site. [ABSTRACT FROM AUTHOR]

Line loss accounts for most of the energy loss in low-voltage distribution network. Accurate prediction of line loss rate (LLR) is of great significance to eliminate abnormal transmission line faults in time and ensure power supply safety. The existing prediction methods for LLR seldom consider the seasonal trend data that affect it, and there is a hysteresis effect in predicting non-stationary line loss sequences. To solve the above problems, this paper proposes a prediction method based on multi-dimensional information matrix and dimensional attention mechanism-long-and short-term time-series network (DAM-LSTNet). Firstly, the maximum information coefficient (MIC) method is used to screen the distribution network characteristics and seasonal trend parameters. Secondly, the variational mode decomposition (VMD) method optimized by the genetic algorithm is used to decompose the historical line loss data and form a multi-dimensional information matrix with the screened characteristic parameters of the network. Finally, the multi-dimensional information matrix is put into the LSTNet network with dimensional attention mechanism to predict the LLR. The example analysis shows that compared with the existing methods, it has the advantages of sufficient consideration of prediction parameters, adaptive changes of prediction weights, weak hysteresis effect and high prediction accuracy. [ABSTRACT FROM AUTHOR]

Icing threatens the safe and stable operation of transmission lines. Accurate prediction of the icing process of conductor can help the work of anti-icing and disaster reduction of transmission lines. Generally, the icing of conductor is accompanied by the torsion process of conductor. Because of the interaction of conductor torsion and icing, there is a big difference of the icing shape and rate between different positions on a transmission line. In order to improve the accuracy of numerical calculation of conductor icing, a dynamic numerical calculation model of conductor icing torsion is established based on hydrodynamics and basic mechanics in this paper. Comprehensively, the model takes the effects of torsion angle and torsion icing shape on the icing process into consideration, including the effects on airflow filed and trajectories of water droplets in the air. Through the simulation, the change law of the torsion angle at different positions of the conductor, the influence characteristics of the conductor torsion on the icing process, and the differences of the icing torsion of conductor under different environmental parameters are analysed. The results show that, compared with the condition without torsion, the collision range of water droplets on the conductor is larger under the torsion condition, the average value of collision efficiency β1 is higher, and the icing rate is faster. The larger the wind velocity and the median volume diameter of water droplets in the air, the faster the conductor icing torsion development. [ABSTRACT FROM AUTHOR]

High voltage direct current (HVDC) transmission technology has incomparable advantages in long‐distance and large‐capacity transmission. With the development of HVDC transmission technology, transmission lines inevitably pass through some densely populated and economically developed areas. Due to environmental considerations, the space electric field around the buildings that are adjacent to HVDC transmission lines has aroused increasing attention. However, it is hard to be predicted by simulation because of the calculation complexity. This paper proposed a new calculated method to obtain the composite electric field around HVDC transmission lines with adjacent residential buildings, and the validity and correctness of the method are verified by the experimental results. Then, the distortion of the electric field around the building and its impact on the design of the safe corridor width of the HVDC transmission line is analyzed. The proposed method, unlike existing methods, can be used to predict the space composite electric field distribution around HVDC transmission lines and their adjacent residences, which are of arbitrary material, shape, and size. It can provide guide for the optimal design of transmission line corridors. [ABSTRACT FROM AUTHOR]

Successive failure propagating through a power system, typically caused by extreme weather such as storm and lightning, can cause blackouts by means of a variety of processes. To address this issue, this paper proposes preventive control for successive failures of power system to mitigate the consequences of successive failures in extreme weather. First, based on the Poisson process theory, the authors model the successive failure propagation, and present the confidence interval estimation for the time interval between successive failures. Then, a failure pre‐control methodology that quantifies the grid regulating ability and actions is developed to make decisions for system operators on mitigating overloads of transmission lines. Furthermore, a systematic pre‐control framework for successive failures is first proposed to detect latent risks, eliminate predictable consequential outages, and secure power system stability. Results from IEEE‐9 bus and IEEE‐39 bus standard systems as well as a real‐world system show the feasibility and effectiveness of the proposed method. The proposed preventive control framework can provide a systematic pre‐control action scheme for system operators, and realize enhancement of stability and resilience to power system failures. [ABSTRACT FROM AUTHOR]

Real-time pricing is an attractive tariff for demand response programs, in which consumers could provide load flexibility by adjusting their electricity consumption in response to timevarying electricity prices. This paper reveals a new threat called real-time pricing response attack (RPRA), which manipulates consumers' electricity consumption by tampering with electricity price signals. Simulations are performed in IEEE 24-bus, 39-bus, and 118-bus systems, and the results show that 8%to 28% of the transmission lines could be overloaded by the attack, which could cause serious security problems. Results of sensitivity analysis indicate that the attack effects are influenced by various factors, such as DR models, price elasticity, line capacities etc. To defend against the RPRA attack, we have proposed various detection and mitigation strategies. [ABSTRACT FROM AUTHOR]

Fast clearing of a short‐circuit fault is vital to increase the transmission capacity of power grid transmission lines and improve the transient stability of a power system. A fast vacuum circuit breaker (FVCB) is a good candidate to realize quick elimination of a short‐circuit fault. The original contribution of this paper is to present the design of a 72.5 kV single‐break FVCB and its verification of short‐circuit breaking performance. A specially designed 72.5 kV vacuum interrupter, with floating shields and reduced mass of moving components, was developed. An electromagnetic repulsion actuator was used to provide a high initial opening speed, V1, of 5 m/s over half of the full‐contact gap and a relatively low average opening speed, V2, of 1.59 m/s in the full contact gap of 30 mm. The high‐designed V1 and low‐designed V2 were achieved with the aid of a deliberately designed oil buffer. The opening and closing time of the designed 72.5 kV FVCB was 1.2 ± 0.04 ms and 18 ± 0.20 ms respectively. The terminal fault test duty of T100s(b), carried out on the 72.5 kV FVCB, demonstrated both the 40 kArms and 80 kArms short‐circuit current breaking performance. The short‐circuit current breaking arcing time windows of FVCB, including the minimum arcing time, the maximum arcing time, and the middle arcing time, was verified to fulfill the requirement of the international standard, IEC 62271‐100 2017, and the Chinese standard, GB/T 1984–2014, both for the 40 kArms and 80 kArms switching cases, respectively. Further development of the 72.5 kV single‐break FVCB would benefit the development of ultra‐ or extra‐high voltage FVCBs by reducing essential numbers of series‐connected breaking units. [ABSTRACT FROM AUTHOR]

This paper reports the observation results of three‐phase overvoltage at the lightning strike point of a 1.5 km, 10 kV power distribution line that was struck directly by rocket triggered lightning to its phase wire C. The arrester of the direct struck phase at the lightning strike point operated in all return strokes corresponding to return stroke current from −3.3 kA to −32.9 kA. The waveform of direct struck phase includes an initial spike before negative peak, operation area of metal oxide varistor, and the final attenuation with oscillation. The overvoltage waveforms of the indirect struck phase at the lightning strike point show a small initial negative peak, rapid transition to a large positive peak, and the final negative attenuation with oscillation. The negative peak value of the indirect struck phase at lightning strike point ranged from −4.1 kV to −25.2 kV and that of the direct struck phase was between −78.1 kV and −167.8 kV. The positive peak value of indirect struck phase was between 0.2 kV and 49.8 kV. The negative peak value, zero‐crossing time and the peak‐to‐peak value of voltage all have a good linear relation with the peak value of lightning return stroke current. [ABSTRACT FROM AUTHOR]