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This paper introduces a fault location method based on time analysis, utilizing synchronized data collected from both ends of the faulted line. The data is obtained either from Common Format for Transient Data Exchange (COMTRADE) files or Sampled Measured Value (SMV) of the IEC-61850 protocol. The method proposed in this study employs the implicit finite difference solution to the Telegrapher's equations. In certain fault scenarios, such as when one or both transformers experience saturation, a narrow time window of data can be utilized to accurately pinpoint the fault location. The implicit solution method is unconditionally stable and therefore decouples the choice of the line discretization step from the sampling time interval, which is commonly required to maintain numerical stability of the explicit strategies for fault location. Furthermore, the numerical stability of the implicit process allows for devising a systematic search procedure that improves the accuracy of the calculated fault location, regardless of the transmission line length. By conducting numerical comparisons with an explicit time-domain fault locator and recent frequency-domain algorithms, the superiority of the proposed approach becomes evident. The results highlight the significant improvements achieved through the utilization of this method. Specifically, the results demonstrate that Telegrapher's Equations implicit finite difference solution maintains accuracy under current transformer saturation, as it can locate the fault using data from a brief interval where the current transformer is not saturated. • In this paper, an implicit PDE solver for two-ended fault locations is proposed. • The proposed strategy improves the solution process's numerical stability. • It maintains the best numerical conditioning by using integration steps that produce the least amount of calculation error. • The method outperforms the previous published method. • The method can be applied in cases where CTs are saturated, and when there is only a limited window of "healthy" data available. [ABSTRACT FROM AUTHOR]

• Calculation of reactor and grid coefficients for magnetically coupled series reactor design. • Considering calculated coefficient to design series reactor out of saturation region. • Presenting saturation issue as a main challenge of the series reactors. The rapid increase of integrated distributed generators results in higher fault currents in the future modern grids. A remedy for the concern is employing series reactors as fault current limiters. This paper elaborates on a ferromagnetic core series reactor, which, when saturated, adversely affects the operation of the series reactor during faults. The main goal of the paper is to calculate grid and series reactor coefficients by applying a simplified power line model during a fault condition. These coefficients are the primary considerations of a series reactor design to avoid its saturation. Moreover, the study of the relationship between the reactor inductance and obtained coefficients will be carried out. The obtained results are validated by simulations performed in MATLAB Simulink. [ABSTRACT FROM AUTHOR]

• This paper proposes a fault location method based on directional traveling wave principle for wind power transmission line. • The similarity of forward current traveling wave and reverse current traveling wave at both ends of line is higher after external fault, while similarity of forward current traveling wave and reverse current traveling wave at both ends of line is lower after internal fault. • Discrete Frechet distance is utilized to calculate similarity coefficient of forward traveling wave and reverse traveling wave at both ends of transmission line. The short-circuit current from the new energy power generator presents special characteristics such as frequency shift, restricted amplitude, unequal positive and negative sequence impedance, high percentage of harmonic content, etc., resulting in the risk of misoperation or rejection of conventional protection. By analyzing the propagation characteristics of traveling wave in the transmission line after the fault, this paper reveals difference between traveling wave waveforms at both ends of the line under internal fault and external fault. The similarity between forward traveling wave and reverse traveling wave at both ends of line is higher when an external fault occurs, while the similarity between the forward traveling wave and reverse traveling wave is lower after internal fault. According to this difference, a pilot protection algorithm based on discrete Frechet distance is proposed, which can calculate similarity coefficient of forward traveling wave and reverse traveling wave at both ends of line to construct protection criteria, and then identify internal and external fault. Through the analysis of PSCAD/EMTDC and experiment platform of hardware-in-the-loop test verify that the proposed protection algorithm can accurately and reliably distinguish internal and external fault. [ABSTRACT FROM AUTHOR]

• This paper proposes a fault location method based on composite traveling wave, which can easily eliminate the traveling wave from adjacent lines. • The traveling wave from other adjacent lines, which is never detailed discussed in previous research, hinders the accurate identification of wavefront. • The refraction coefficient of busbar with multiple transmission lines is negative for current traveling wave, but positive for reflection coefficient. • The time–frequency matrix is able to present the energy of traveling wave in wideband. As the speedy expansion of power gird, the traveling wave fault locator in substation may not always connect to newly added transmission lines in time, which reduces the effectiveness of fault locator. In this paper, an adjacent fault-free line based fault location scheme for newly additional line is proposed. Since the traveling wave from adjacent fault-free line results in severe difficulty for identification of traveling waves from faulty line, the time–frequency matrix is performed to screen traveling waves. Firstly, in order to remove the influence of waves from remote terminals of adjacent fault-free line, the current refraction coefficient is theoretically analyzed. Due to the negative refraction coefficient, traveling waves from remote terminals of adjacent fault-free line can be reduced by the proposed composite traveling wave. Secondly, the time–frequency matrices of composite traveling wave and original traveling wave is obtained by S-transform. Then, these matrices are applied to form ratio matrix which thoroughly eliminated waves from remote terminals of fault-free lines. Moreover, the robustness of the proposed fault location scheme is thoroughly validated by the simulation of PSCAD/EMTDC. Finally, the proposed fault location method has the great accuracy in simulation tests and field data test. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of how corona losses on transmission lines depend on weather conditions in their vicinity. Two years of synchronized phasor measurement data has been collected to monitor corona losses over a longer period of time. From the same time period, both hourly and 10 min weather monitoring data has been obtained for comparison. The dependence between various weather parameters and corona losses is presented with graphical data analysis. In addition, feature importance methods have been applied to rank the weather parameters and determine which of them have the largest influence on the occurrence of significant corona losses. The results presented in this paper are directly applicable for transmission systems operators for adequate planning of system operation. • Transmission network corona loss monitoring using Phasor Measurement Units. • Analysis of corona loss dependency on various weather parameters. • Ranking of weather parameters based on importance. • Dependency of data availability on corona loss estimation results. [ABSTRACT FROM AUTHOR]

• We conducted a thorough review on Transmission Expansion Planning (TEP) models for electricity networks. • The paper survey reviews literature and practice over the years. • A classification of more than 70 recent articles are conducted in this work. • Literature insights and identified gaps are presented. • It provides a detailed analysis of the TEP over the years and the prospects for this challenging task. Transmission Expansion Planning (TEP) problem aims at identifying when and where new equipment as transmission lines, cables and transformers should be inserted on the grid. The transmission upgrade capacity is motivated by several factors as meeting the increasing electricity demand, increasing the reliability of the system and providing non-discriminatory access to cheap generation for consumers. However, TEP problems have been changing over the years as the electrical system evolves. In this way, this paper provides a detailed historical analysis of the evolution of the TEP over the years and the prospects for this challenging task. Furthermore, this study presents an outline review of more than 140 recent articles about TEP problems, literature insights and identified gaps as a critical thinking in how new tools and approaches on TEP can contribute for the new era of renewable and distributed electricity markets. [ABSTRACT FROM AUTHOR]

This paper introduces a pilot protection method for two-terminal transmission lines based on the measurement residual of an extended Kalman filter designed to track alternate current signals. Transmission lines that interconnect generation plants to consumers are the primary equipment most susceptible to faults, and failing to isolate them correctly and promptly may lead to system collapse. In this context, the measurement residual allows for rapid fault identification and tripping. In addition, the proposed solution requires computing and communication resources typically available for pilot protection since it uses conventional sampling rates and has a low computational burden. This paper details the theory and application of the extended Kalman filter and the results of the proposed method when tested against different simulation scenarios. These scenarios were built on an extra-high voltage transmission system implemented in ATP/EMTP, varying fault impedance, inception angle, distance, phases involved, and fault type. It also presents a statistical analysis of these scenarios, including channel asymmetry, errors in the current transformers' conversion rate, and noise. Besides, it describes an analysis of the proposed method regarding current transformer saturation, high impedance faults, zero-crossing faults, external breaker opening, and power-swing. Finally, it compares the solution with other algorithms in the literature. The results indicate that the proposed solution is fast, accurate, secure, and dependable. • Transmission lines are susceptible to faults that need fast isolation. • Fast isolation preserves stability, avoids equipment damage, and reduces life risk. • The method is based on the extended Kalman filter; estimates the signals' behavior. • Method tested against simulations from an existing 500 kV system. • Faster than conventional protection algorithms, secure, dependable, and accurate. [ABSTRACT FROM AUTHOR]

• Matrix aggregation algorithm considering the direction of power flow. • A new comprehensive index with line outage distribution factor & line load rate. • A new quantification index of the power flow transfer impact ratio is proposed. • Accuracy of the obtained key lines of key transmission sections increases by 19.6 % With the increasing complexity of high-proportion new energy connected to power systems, the volatility and uncertainty of the power system increase, resulting in the changing operation status of the system. The original general sections may become key transmission sections. According to the power flow characteristics of power systems, this paper proposes an improved matrix aggregation algorithm to determine the initial transmission sections. On this basis, this paper defines an improved comprehensive index based on line outage distribution factor and line load rate. According to the principle of emphasis on detection in the actual power system operation, weight coefficients are considered for the two parameters to determine the key transmission sections. Finally, the correlation between multiple transmission sections is analyzed by quantifying the impact of the trip off line on the power flow transfer of other lines, and the strong correlation section is obtained. Case studies of the IEEE 39 bus system show the validity and effectiveness of the proposed method in this paper. [ABSTRACT FROM AUTHOR]

• The proposed single-ended method uses the extra information brought by the time interval between the operations of the circuit breakers at two line ends; the proposed method also considers distributed line parameters. Therefore, the proposed method has higher fault location accuracy than the existing method. • The proposed formulation of the fault location problem with distributed parameters is subtly simplified by Taylor expansion, and a non-iterative fault location method is proposed. The risk of unconvergence is systematically avoided and the fault location accuracy is ensured at the same time. • The proposed method does not rely on the assumptions of legacy methods (e.g., the fault current and the terminal current are in the same phase, the system is homogeneous, etc.). The proposed method does not require the parameters of the remote power system. Fast and accurate fault location methods can save costs and ensure power supply reliability. This paper proposes a novel noniterative single-ended phasor domain fault location method with distributed parameter model for AC transmission lines. Due to the limitation of information, the legacy impedance-based single-ended fault location methods usually are based on assumptions on the line or system to obtain more information. The method proposed in this paper takes advantage of the additional information brought by the operation mode of circuit breakers. The proposed method only needs the local measurements and does not need the measurements and the equivalent source parameters of the remote system. The proposed method only uses single-ended data and is not affected by communication and synchronization. The proposed method is noniterative and there is no risk of non-convergence. In addition, the method proposed in this paper does not rely on the assumptions of legacy methods and considers the distributed parameters, avoiding the disadvantages of the legacy methods. The effectiveness of the proposed method is verified through a lot of case studies in PSCAD/EMTDC, with different fault types, fault locations and resistances. © 2017 Elsevier Inc. All rights reserved. [ABSTRACT FROM AUTHOR]

• The flexibility of power planning on external tie lines is greatly enhanced. • The novel flexible load aggregation model improves the accuracy response curve. • Strategies focus on the PFS in NZCPGs rather than the distribution and microgrids. • Offset the actual ETLPF to the largest extent and reduce NZCPGs operating pressure. In a net-zero carbon power grid (NZCPG) with a relatively high proportion of renewable energy sources, significant power fluctuations occur, severely constraining the development of both the NZCPG and the New Urban Power Grid (NUPG). In the NZCPG, the proportion of traditional hydro and thermal power units used to mitigate power fluctuations has decreased. It is necessary to explore the load resources in the NUPG to stabilize the power fluctuation between the NUPG and the NZCPG, and to reduce the operating pressure of the NZCPG. Firstly, this paper proposes a method for developing external tie line schedules based on the load operation band (LOB) to relax the constraints on the schedule for the NZCPG. Secondly, A revised load response aggregation model is proposed to improve the aggregation accuracy under uncertainty factors by online correcting their impact on the load response characteristics. Thirdly, considering the flexible loads in NUPG can only compensate for a part of the power fluctuation, this paper proposes a method to judge the power fluctuation that these loads can offset. Two PFS optimal strategies are proposed among NUPG partitions considering deviation penalty and within each NUPG partition reducing the number of participated load-users. This paper focuses on the PFS in bulk NZCPGs other than in the distribution grids and microgrids. Our work can effectively smooth the power fluctuation within NUPG regulation capability meanwhile reducing the number of participated load-users. Fourthly, a method is proposed to judge the power fluctuation beyond NUPG regulation capacity in NUPG. Using the actual load response capacity, the over-amplitude/time layered smoothing strategy with optimal load is proposed, which can offset the power fluctuation of the bulk NZCPG to the largest extent. Finally, the IEEE-39 system is used to verify the effectiveness of the proposed methods. © 2017 Elsevier Inc. All rights reserved. [ABSTRACT FROM AUTHOR]

• The proposed ACLC fully utilizing the electrical quantities of the line to identify the fault area has achieved the selectivity of ACLC, preventing ACLC from expanding the scope of fault impact. • The proposed ACLC start-up threshold and control parameters are independent of the simulation. • The proposed ACLC presents a phased approach that satisfies both speed and selectivity. • The proposed ACLC can effectively limit the fault current and has certain adaptability to the fault type, fault resistance, and noise. The modular multilevel converters (MMC) based high-voltage direct-current (HVDC) grids have a fast rise rate and higher peak value of fault current. The active current limiting control (ACLC) of MMC can effectively reduce the breaking current of DC circuit breakers (DCCB) and reduce the requirement for rapid fault identification in the line protection. However, the current ACLC based on changing the MMC control strategy cannot meet the selectivity requirements. The lack of selectivity may lead to power transmission on non-faulty lines in a multi-terminal DC power grid, thus expanding the range of fault influence. Therefore, this paper proposed a selective and staged ACLC. Firstly, the starting range of ACLC is determined according to the selective requirement and purpose of ACLC in the flexible DC power grid. Secondly, a staged ACLC approach was proposed to balance the speed and selectivity of ACLC. In this approach, the single end and both terminals electrical quantities of the line are fully utilized as the starting criteria for staged ACLC, and corresponding ACLC principles are proposed. Finally, the AC side current and MMC bridge arm current under ACLC were analyzed, and an ACLC scheme was proposed in coordination with DC circuit breakers (DCCB) and fault identification. The simulation results show that the proposed ACLC guarantees the current limiting ability and the MMC does not block during the whole fault period, and has a certain adaptability to the fault type, fault resistance, and noise. [ABSTRACT FROM AUTHOR]

• For the time-domain distance protection, its location error caused by the fault resistance is derived. • An improved time-domain distance relay is proposed to solve the calculation non-convergence and improve the location accuracy. • A threshold selection method is proposed to avoid the possible overreach problem under external resistive faults. • A prototype protection device is developed, and its feasibility and superiority are verified by hardware-in-the-loop tests. Time-domain distance protection has a good transient performance and operation speed when applied to wind power transmission lines. In this paper, the error analysis and improved method of phase-to-phase time-domain distance protection are investigated. Firstly, based on the time-domain mathematical model, the location error caused by fault resistance is analyzed, and then the algorithmic convergence and accuracy of conventional phase-to-phase distance relay are evaluated. To solve the computational non-convergence problem, an improved phase-to-phase distance relay is proposed, in which the instantaneous negative-sequence current is used to improve the location accuracy, especially during the fault transient stage of wind farms. In order to avoid the protection overreach problem, the threshold selection method is designed based on the maximum allowable error of the calculated distance. According to the proposed method, the corresponding protection device is developed. And the hardware-in-the-loop (HIL) test system is built based on the real-time digital simulation (RTDS) platform. Extensive experimental tests are carried out, to verify the feasibility and superiority of the proposed time-domain distance protection. [ABSTRACT FROM AUTHOR]

The decreasing cost of energy storage technologies and the increasing utilization of renewable energy sources have made distributed transmission-scale energy storage economically viable. Merchant energy storage investors can collect significant profits through spatiotemporal energy arbitrage from congested transmission lines. This paper formulates a three-stage, four-level min–min–max–min problem from the viewpoint of power system operators and planners such that they will build new transmission lines and identify potential locations for profitable merchant energy storage investments. The first level determines transmission expansion decisions from the system operator's perspective. The second level plans potential investments in merchant energy storage to ensure profitability at a desired rate of return. The third level realizes the worst-case situations of long-term uncertainties related to the expansion of wind farms and peak load growth in each regional zone, while the fourth level simulates market clearing for representative days, modeling short-term uncertainties. A novel iterative nested column and constraint generation (C&CG) technique is adopted to cope with numerical issues caused by binary variables of transmission lines and storage blocks and the enormous size of the problem. The case study of a modified IEEE 24-bus test system was used to assess the effectiveness of the proposed algorithm. • Proposing a new robust co-planning of transmission expansion and profit-driven merchant energy storage. • Considering short-term variability and long-term uncertainty of wind farm expansion and future load growth. • Adopting a novel iterative nested column and constraint generation (C&CG) technique to solve the four-level problem. • Validating the effectiveness of the proposed method and sensitivity analysis in 24-bus IEEE test system. [ABSTRACT FROM AUTHOR]

• The impact of distributed capacitance is eliminated due to the capacitance current can be ignored at the low frequency. • The low-frequency components only exist between the BES and the fault point, and will not flow to the opposite grid. • The least square algorithm is employed to solve the overdetermined equations, improving the accuracy of calculation. The fault current of the photovoltaic (PV)/battery energy storage (BES) hybrid power generation system contains harmonic components, which might cause the maloperation of the distance relay. The time-domain distance protection has attracted more attention recently. However, the distributed capacitance of long transmission lines negatively affects the performance of time-domain distance protection, which hinders its application. To solve this problem, this paper proposes an improved time-domain distance protection based on fault active control. By leveraging the fault active control capability of the BES inverter, a specific low-frequency characteristic voltage is modulated through the phase-locked loop (PLL). By injecting the low-frequency characteristic voltage, the influence of line distributed capacitance can be ignored. Thus, the accuracy of time-domain distance protection based on the equivalent R-L model of transmission lines is guaranteed, which is the first advantage of injecting the low-frequency characteristic voltage. The other advantage is the low-frequency components only exist between the BES and the fault point, and will not flow to the grid on the opposite side of the line. The accuracy of time-domain distance protection has been further improved. In Addition, the faulty line's derivative equations for different fault types are deduced based on fault active control. Finally, the least square algorithm is used to calculate fault distance. The proposed scheme's feasibility and effectiveness are verified through simulations in PSCAD/EMTDC. [ABSTRACT FROM AUTHOR]

• Dynamic line rating (DLR) allows the full capacity of the lines to be utilized. • We study the effect of emissivity on the DLR rating of transmission line conductors. • We also propose model-based method for measuring the emissivity value. • Experimental results show that aged conductors perform better than new ones. Emissivity and absorptivity are important parameters in overhead power line conductors that depend on the conductor surface condition, so their values change as the conductors age. They have an important effect on their thermal behavior, so it is important to know their value when designing dynamic line rating (DLR) strategies. DLR methods are becoming increasingly important, especially in areas with congested power lines, as they allow the full capacity of the lines to be utilized by dynamically determining their maximum allowable currents without exceeding the safe temperature limits of the conductors, thus ensuring that they operate within safe limits. However, measuring emissivity and absorptivity is non-trivial and requires complex tests that cannot be performed in the field. Using simulations based on a realistic thermoelectric model and experimental tests performed on three types of transmission line conductors in a high-current laboratory, this paper shows the importance and effect of emissivity on conductor temperature. It also presents a method for measuring the emissivity value based on adjusting the emissivity and absorptivity values in the thermoelectric model to match the experimental values. The results presented show that aged conductors allow an increase in the maximum current carrying capacity compared to new conductors in the order of 5–14 %, depending on the conductor type considered and the operating conditions. [ABSTRACT FROM AUTHOR]

• A new single-end fault location method is proposed for double-circuit transmission lines. • It does not require knowing the impedance of the remote end source. • Just one formulation is used for all symmetrical and asymmetrical faults, both transposed and untransposed lines. • It is suitable for fault location of double-circuit with non-identical circuits. • It reduces the negative effect of unknown fault impedance. A new fault location method based on single-end measurements is proposed in this paper. The proposed method decomposes the fault location problem into two sub-problems and uses the voltage and current phasors of one of the line ends to solve the sub-problems. In the first iteration, an initial value is assumed for the fault location and then, based on the network equations, the first sub-problem calculates fault characteristics such as its voltage, current, and impedance which are fed into the second sub-problem as its inputs. Then, the second sub-problem updates the estimated fault location based on the received inputs. This approach is efficient and comprehensive method in the sense that it is not susceptible to the value of fault impedance, it is applicable for symmetrical and asymmetrical faults, transposed and untransposed lines, identical and non-identical circuits, and both short and long double circuit transmission lines. Finally, the method converges quickly in maximum three iterations although it is iterative. Numerous case studies by changing the line length, fault impedance, location of fault, line characteristics and noise level are carried out using distributed line model to verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Highlights • Direction discrimination ability. • Faulty pole selection ability. • High reliability. • No time synchronization system. Abstract As known, hybrid high-voltage direct current (HVDC) is wide applied in power system. Because two converter stations are line commutated converter based HVDC (LCC-HVDC) type and voltage source converter based HVDC (VSC-HVDC) type respectively, the HVDC transmission line (HVDC-TL) has special travelling wave (TW) propagation characteristic. Especially, due to the capacitance installed at VSC-HVDC station, the relay at VSC-HVDC side cannot detect voltage TW (VTW) signal. Meanwhile, TW protection is widely applied in HVDC transmission system, but it has no fault direction recognition ability. Hence, the paper proposes a novel TW directional pilot protection. Firstly, the paper analyzes the special propagation characteristics of TW along HVDC-TL. Secondly, the paper proposes novel fault direction discrimination criterions based on the integration of instantaneous power and current at LCC-HVDC side and VSC-HVDC side, respectively. Meanwhile, faulty pole selection criterion is also proposed based on the ratio of positive pole current to negative pole current. Thirdly, based on PSCAD/EMTDC, a simulation model of ± 400 kV LCC-VSC-HVDC transmission system is established. And the simulation results prove that the proposed protection method is immune to fault location, fault resistance and fault type. [ABSTRACT FROM AUTHOR]

Highlights • A method to compute transient profiles along transmission lines is presented. • Time-varying and non-linear elements are included in the transmission line model. • The solutions are computed using a line model defined in the q-s domain. • It is possible to observe the voltage and current behavior along transmission lines. Abstract In this paper, a combination of a transmission line model defined in the q-s domain (spatial frequency-temporal frequency), the two-dimensional Laplace transform and the principle of superposition is applied to compute transient voltage and current profiles along transmission systems including time-dependent and non-linear elements. The detailed internal information provided by these profiles can be very useful in applications such as insulation coordination design, fault detection and location. The method presented in this paper has significant advantages over the computation of transient profiles using EMTP-type software, given that the latter requires the subdivision of the line, which is time consuming and prone to numerical error accumulation. Additionally, since the line model is defined in the frequency domain, it is possible to include the frequency dependence of the electrical parameters in a very straightforward manner. In order to evidence the accuracy and versatility of the proposed method, several applications examples are presented, and the computed results are compared with those obtained using ATP. [ABSTRACT FROM AUTHOR]

To maintain the reliability, availability, and sustainability of electricity supply, electricity companies regularly perform visual inspections on their transmission and distribution networks. These inspections have been typically carried out using foot patrol and/or helicopter-assisted methods to plan for necessary repair or replacement works before any major damage, which may cause power outage. This solution is quite slow, expensive, and potentially dangerous. In recent years, numerous researches have been conducted to automate the visual inspections by using automated helicopters, flying robots, and/or climbing robots. However, due to the high accuracy requirements of the task and its unique challenges, automatic vision-based inspection has not been widely adopted. In this paper, with the aim of providing a good starting point for researchers who are interested in developing a fully automatic autonomous vision-based power line inspection system, we conduct an extensive literature review. First, we examine existing power line inspection methods with special attention paid to highlight their advantages and disadvantages. Next, we summarize well-suited tasks and review potential data sources for automatic vision-based inspection. Then, we survey existing automatic vision-based power line inspection systems. Based on that, we propose a new automatic autonomous vision-based power line inspection concept that uses Unmanned Aerial Vehicle (UAV) inspection as the main inspection method, optical images as the primary data source, and deep learning as the backbone of data analysis and inspection. Then, we present an overview of possibilities and challenges of deep vision (deep learning for computer vision) approaches for both UAV navigation and UAV inspection and discuss possible solutions to the challenges. Finally, we conclude the paper with an outlook for the future of this field and propose potential next steps for implementing the concept. [ABSTRACT FROM AUTHOR]

Integration of renewable energy sources (RESs) at transmission level is getting popular in the recent years. RESs have advantages of generating clean and environmentally friendly electricity. However, due to the uncertainty and less inertia characteristic of the RESs based power plant, it can bring negative impacts on small signal stability which is also known as low-frequency oscillatory stability. Hence, utilizing an additional device, such as battery energy storage (BES) in power system with high penetration of RESs is inevitable. BES system could provide additional active power to the grid to overcome the shortfall energy from RESs. Conversely, BES installation may also introduce negative impact on system dynamic in terms of possible interaction with other elements of the power system. Therefore, proper gain control setting of BES is required to avoid undesirable interaction and make sure system stability. This paper investigates the impact of gain variation in BES controller to oscillatory stability and modal interaction on the power system. Eigenvalue trajectories, participation factor and time domain simulation of the critical modes are thoroughly investigated. Influence of the capacity of BES and its location on damping ratio of weak modes is also examined in the paper. Moreover, the mitigation of modal interaction occurrence through BES gain tuning using metaheuristic algorithms is proposed in this paper. From the simulation results, it was found that increasing BES’s gain controller could lead to the interaction events. It was also reported that the proposed tuning method is feasible to mitigate the occurrence of modal interaction. [ABSTRACT FROM AUTHOR]

The rotor structure varies with different types of wind power induction generator (WPIG), which leads to their different dynamic behaviors during power system disturbances. This paper proposes a generic implementation framework of explicit damping torque analysis to investigate the damping mechanisms of power system integrated with induction generator based wind power generation, so that the essential difference and inner connection between two main types of WPIG (i.e., DFIG and FSIG) in damping power system oscillation can be revealed. The linearized models which can represent DFIG and FSIG as well as three transitional wound rotor generators are established to facilitate the analytical comparison analysis. Phillips-Heffron system linearized model is employed to derive an explicit expression of damping torque contribution from main dynamic components of WPIGs. In the paper, 16-machine 5-area NYPS-NETS example system is used for the demonstration of proposed framework and comparison analysis. Both damping effectiveness and robustness of different WPIGs are extensively examined under multiple operating status, in order to provide useful guidance to system planner for the real-time operation of induction generator based wind generation. [ABSTRACT FROM AUTHOR]

• A flexibility enhancement pre-selection strategy based on network flexibility balance degree and line outage distribution factor is proposed. • The available flexibility index (AFI) is proposed to quantify the supply of system flexibility. • An optimization model of power system flexibility enhancement method based on pre-selection of structure adjustment strategy is proposed. The flexibility enhancement method of power system usually focuses on node flexible resource, without considering the transmission process. It may result in some flexible resources not being transferred, thus affecting the accuracy and effectiveness of the flexibility enhancement. In this paper, a flexibility enhancement optimization model based on pre-selection method of structure adjustment strategy is proposed, which can improve system flexibility with guaranteed availability of flexible resources. Firstly, the flexibility enhancement pre-selection method based on power system topology adjustment mathematical formulation is proposed to select the lines suitable for topology adjustment. Secondly, a flexibility enhancement optimization model considering economy and available flexibility is developed, which takes the maximum available flexibility index as the objective function and ensures the system flexible and economical by cost-floating constraint. The available flexibility deviation constraint corrects the system flexibility supply to guarantee the accuracy of available flexibility. Finally, the effectiveness of the proposed method is investigated through the case study on modified IEEE 24-bus and IEEE 118-bus system. [ABSTRACT FROM AUTHOR]

The priority to reactive power contribution from the Voltage Source Converter (VSC) based High Voltage Direct Current (HVDC) connection to support the grid during faults as suggested by the modern Network Code (NC) for HVDC affects the distance protection of transmission lines. Moreover, suppressing the negative sequence current during an unbalanced condition also interferes with the proper operation of the distance relays. This is because the current contribution from the converter is limited in magnitude and modified in the waveform in order to protect the power electronic devices during the fault in comparison to the synchronous generator fault current characteristics. This paper discusses the cause as well as the severity of the problems faced by the distance protection of transmission lines connected to the VSC based HVDC system by analyzing the apparent impedance analytically and in the simulation. The response of the relay to balanced and unbalanced faults lying on transmission lines is investigated. It is shown that the VSC limited reactive support and suppressed negative sequence current affect fault detection, forcing the relay to malfunction. The results of this paper can be used as a reference for understanding the effects of VSC-HVDC system on the operation of the distance protection during faults. [ABSTRACT FROM AUTHOR]

• This paper proposes a Novel Multi-Functional Capacitive Bridge-Type Fault Current Limiter (MCBFCL). • It acts as a variable capacitor to control active power flow under normal operating conditions. • It improves the low-voltage ride-through (LVRT) performance of wind farm (WFs) under fault operating conditions. This paper proposes a new concept of the fault current limiter (FCL) named multi-functional capacitive bridge-type fault current limiter (MCBFCL). It acts as a variable capacitor to manage active power flow under normal operating condition and enhances the low-voltage ride-through (LVRT) performance of wind farms (WFs) under fault operating conditions. The MCBFCL have been presented based on the capacitive bridge-type fault current limiter (BFCL) and is modified to compensate the transmission line impedance in order to manage power flow, while it is not bypassed under normal operating conditions unlike the conventional FCLs. In this paper, first, the power circuit and principle performance of the MCBFCL are discussed. Then time domain simulations are conducted in PSCAD/EMTDC environment to check the MCBFCL performance under both normal and fault operating conditions. Also, the MCBFCL performance is compared to the resistive and inductive BFCLs in transmission lines with series capacitive compensation. In this work doubly fed induction generator (DFIG)-based wind turbines have been utilized. Simulation results showed that the MCBFCL can manage the power flow under normal operating condition and enhances the LVRT performance of the WF under both symmetrical and asymmetrical fault operating conditions. Also, it has a superior performance in terms of LVRT indices values compared to the resistive and inductive BFCLs. [ABSTRACT FROM AUTHOR]

This paper focuses on the protection of transmission lines connected to doubly-fed induction generator (DFIG)-based wind power plants (WPPs). DFIG-based wind turbines (WTs), which are connected to the AC grid via reduced-size converters, impose additional challenges on the reliable operation of distance relays due to their distinctive fault current characteristics, converter protective actions, and voltage or reactive control strategy of the converter. In this paper, a modified distance protection scheme is proposed which is able to reliably estimate the fault distance under the aforementioned challenges. The proposed scheme consists of two main components: phasor correction and fault resistance elimination. The phasor correction component eliminates the impedance error due to the fault-induced rotor frequency component of the DFIG short-circuit current. The fault resistance elimination component eliminates the impedance error due to the fault resistance during non-solid faults, which cannot be eliminated by conventional methods as a result of the variable nature of the equivalent impedance of the DFIG-based WTs during faults. Various simulation results are exhibited to validate the effectiveness of the proposed scheme in detecting and identifying all different types of faults on transmission lines emanating from DFIG-based WPPs. • Impact of rotor frequency component of WPP fault current on distance relay. • Proposed averaging filter can eliminate the off-nominal frequency component. • Measured impedance error due to non-solid faults. • Simulation results ensure accurate fault location estimated by the proposed algorithm. [ABSTRACT FROM AUTHOR]

Transmission lines are heavy assets of power systems. Therefore, the rapid and accurate identification of fault locations is important for power grids' safe and stable operation. Traditional methods based on impedances or traveling waves are facing increasing challenges like uncertain power generation and unknown power electronic device characteristics when modern power systems are transitioning to deeply renewable energy source (RES) penetrated grids. In order to solve the above problems, this paper proposes a high-dimensional time–frequency feature extraction method that does not require expert knowledge of physical features. This paper proposes a fault location framework for learning picturized and time-series data (FltLoc-FPTD) with renewables. The developed loss function is suitable for the classification of faulty lines, considering the challenges of distinguishing faults in adjacent lines. Furthermore, we design an enhanced convolutional neural networks (CNN) subsampling layer with blur kernels to replace the traditional subsampling layer to eliminate the influence of high-frequency noise and improve the robustness against noise. The effectiveness of the method is verified by simulation under two benchmark systems. The average fault location errors with and without environment noises are 0.0189 and 0.0124. • A novel deep learning framework for extracting high-dimensional fault signals. • Designing a loss function more suitable for power system fault line identification. • Antialiasing high frequency noise to prevent overfitting of the model. [ABSTRACT FROM AUTHOR]

• The equivalent impedance of the wind farm integrated VSC-HVDC is deduced, where effect of the cable line is considered. • The occurrence mechanism of high frequency oscillation is analyzed, which indicates that the control delay of HVDC and the capacitive characteristic of the cable line both contribute to the instability. • A vector modified resonator control (VMRC) is proposed, the design thought, procedure and superiority are detailly presented. Its validity is certified by experimental tests. When a wind farm connects to the grid via a high voltage direct current transmission based on voltage source converter (VSC-HVDC), high frequency oscillation (HFO) is a critical issue that threatens the system stability, this issue has been reported in many HDVC projects all over the world. The current research proved the negative resistance brought by the effect of control delay in VSC-HVDC is a primary cause of instability. This paper ulteriorly analyzes the influence on system stability caused by the long ac cable between the wind farm and the VSC-HVDC, and indicates that the effect of the cable transmission line can contribute to the system instability as well, while the existing damping methods did not consider this effect. Then the control failure of the exiting damming methods when considering the cable transmission line is analyzed and verified by the impedance analysis theory. Thereby, this paper proposed a vector modified resonant controller (VMRC) which can independently and flexibly regulate the magnitude and phase of HVDC impedance, to solve the HFO issue caused by the combined effect of the control delay and the cable transmission line. Also, the design procedure of the proposed control strategy is detailly presented. Finally, experimental results are provided to verify the correctness of the mechanism analysis and the validity of the proposed control strategy. [ABSTRACT FROM AUTHOR]

• Volt-ampere characteristics of direct current long arc on ice-surface are obtained. • The effect of volt-ampere characteristic parameters of arc length is analyzed. • Differences between long and short arc on ice surface are compared. • The dynamic and static volt-ampere characteristics are redefined and studied. With the continuous construction of ultra-high voltage transmission lines, the problem of long insulator string ice flashover in the icing area is becoming more and more prominent. At present, only the volt-ampere characteristics of short arc on the ice-surface have been studied in the previous research. However, the volt-ampere characteristics of the long arc on ice-surface are significantly different from the short arc, so the flashover characteristics obtained from the short insulator string aren't suitable for the long string under icing conditions. Therefore, in this paper, the volt-ampere characteristics of direct current long arc on the ice-surface are measured by using ice column in a multi-functional artificial climate chamber. The results show that the arc length has an effect on the volt-ampere characteristic constant A , exponent n and expression. In addition, the dynamic volt-ampere characteristics and the static volt-ampere characteristics are redefined and studied, which lays a foundation for the flashover voltage prediction of long iced insulator string. The research of this paper has important theoretical guiding significance for the external insulation design of ultra-high voltage direct current transmission lines in icing areas. [ABSTRACT FROM AUTHOR]

• Analytical approaches to evaluate the effects of series compensation are proposed. • Line loadability curves are computed as a function of the compensating reactance. • A fast analytical method based on the compensation theorem is presented. • The method gives the compensation required to achieve a desired power flow increase. • Comparison with an Optimal Power Flow algorithm shows the method effectiveness. The paper proposes an analytical approach to evaluate the effects of series compensation of an overhead transmission line (OHL) concerning the increase of (1) loadability and (2) practical loading of the line. The first part of the paper focuses only on the line characteristics, and proposes an analytical approach to determine the loadability curves of the line as a function of the compensating capacitive reactance. In the second part of the paper, the perspective shifts to examine the power loading of the selected OHL in a meshed electrical network. The target is to evaluate the compensation degree required to achieve a desired power flow increase in the line. To this purpose a fast analytical method, based on the compensation theorem, is presented. Preserving the linearity of the network model, the proposed method allows computation of the needed compensation degree by means of a closed form equation. Numerical applications performed on two simple test networks allow to compare the method with an ad hoc implemented classical optimal power flow. The results validate the method and highlight its effectiveness as a simple and useful tool to support power system planners and designers. [ABSTRACT FROM AUTHOR]

The objective of this paper is to propose a simple transmission congestion pricing scheme based on tracing principle by considering generator fixed cost, cost for incurring loss and transmission congestion cost. Restructuring has brought about considerable changes by the virtue of which electricity is now a commodity and has converted into deregulated type. Such a competitive market has paved way for innumerable participants. This concept of restructuring has led to overloading of transmission lines. In this paper, power flow tracing has been employed by using suitable optimization algorithm, where the real power generation has been maximized. Congestion in the transmission line has been produced in a new fashion by maximizing the real power demand. The power flow under normal operating condition and congestion is determined and hence the difference in power flow is estimated. Based on the estimated power flow difference, the transmission line congestion cost is computed. Pool model and bilateral model has been considered in simulation study to introduce the concept of deregulation. The proposed method is tested and validated on Modified IEEE 30 bus test system and Indian utility 69 bus test system. [ABSTRACT FROM AUTHOR]

Recent reports indicate that electric vehicle charging stations (EVCSs) are susceptible to remote exploitation through their vulnerable software/cyber components. More importantly, compromised EVCS can be leveraged to perform coordinated oscillatory load attacks against the interconnected power grid, leading to power grid instability, increased operational costs, and power line tripping. In this paper, an edge-based approach for the detection and localization of coordinated oscillatory load attacks initiated by exploited EV charging stations against the power grid is investigated. The edge-based detection relies on the behavioral characteristics of the power grid in the presence of interconnected EVCS while combining cyber and physical layer features to implement deep learning algorithms for the effective detection of oscillatory load attacks at the EVCS. The proposed detection approach was evaluated by building a real-time test bed to synthesize benign and malicious data, which was generated by analyzing real-life EV charging data collected during recent years. The results demonstrate the effectiveness of the implemented approach with the Convolutional Long-Short Term Memory model producing optimal classification accuracy (99.4%). Moreover, this analysis results shed light on the impact of such detection mechanisms towards building resiliency into different levels of the EV charging ecosystem while allowing power grid operators to localize attacks and take further mitigation measures. Specifically, the detection mechanism of oscillatory load attacks is decentralized and created an effective alternative for operator-centric mechanisms to mitigate multi-operator and Man-in-the-Middle (MitM) oscillatory load attacks against the power grid. Additionally, the created test bed is leveraged to evaluate a distributed mitigation technique, which can be deployed on public/private charging stations to average out the impact of oscillatory load attacks while allowing the power system to recover smoothly within 1 second with minimal overhead. Finally, a security metric is createdto evaluate the resiliency of the ecosystem based on its design and architecture. • Creating an edge-based detection mechanism of oscillatory load attacks hosted on Electric Vehicle Charging Stations (EVCSs). • We introduce a distributed mitigation mechanism that is hosted on EVCS that deprives the adversary the ability to synchronize attacks. This was also demonstrated on a co-simulation platform. • Create a security metric that helps evaluate the resiliency of the ecosystem by taking into consideration various components. [ABSTRACT FROM AUTHOR]

Superconducting fault current limiters (SFCLs) offer an efficient means of limiting fault currents and supporting system reliability. However, they weaken the fault characteristics and reduce the sensitivity of traditional relay protection. The seamless integration of SFCLs with protective relays remains a complex and under-explored area, impeding their widespread industrial adoption. In parallel, current differential protective (CDP) relays are almost the primary protection for all high-voltage electrical equipment and are the cornerstone of global power system security. This paper fills a critical knowledge gap by researching the intricate interaction between resistive superconducting fault current limiters (R-SFCLs) and current differential protective relays. Our investigation commences with a comprehensive mathematical analysis, while researching the influence of R-SFCLs on CDP operation. Subsequently, we conduct a series of comparative experiments using the Matlab Simulink software platform. These tests evaluate the sensitivity, dependability, and security of CDPs in scenarios with and without R-SFCLs. The simulation results not only confirm the accuracy of our analytical framework but also shed light on the multifaceted relationship between R-SFCLs and CDPs. This research contributes to a deeper understanding of how R-SFCLs can be effectively integrated into power systems, offering a roadmap for enhancing grid protection. • Innovative Integration and Mathematical Analysis: This study presents a comprehensive exploration and rigorous mathematical analysis of the challenges in integrating Resistive Superconducting Fault Current Limiters (R-SFCLs) with current differential protective relays (CDPs) in power systems. It revealed the relationship between these components, providing a theoretical foundation for their integration. • Simulink Experiments and Validation of Framework: Extensive comparative experiments conducted using Matlab Simulink offer practical insights into the behavior of R-SFCLs and CDPs under various fault scenarios. The simulation results validate the accuracy of the analytical framework, confirming its effectiveness in addressing key challenges such as fault current limitation and relay sensitivity improvement. • Practical Implications and Contribution to Grid Protection: The study offers practical recommendations for effectively incorporating R-SFCLs into power systems, enhancing grid protection without compromising the reliability and sensitivity of protective relays. It contributes to the field of electrical power and energy systems, providing insights with the potential to influence industrial practices and enhance grid resilience. [ABSTRACT FROM AUTHOR]

Traditionally, the problem of congestion arising in power system networks due to various contingencies and varying renewable generation is addressed by optimal power flow-based methods, once in every 5–30 min. As these techniques are performed for a block period of time using forecasted data, they are not effective in real-time congestion mitigation through corrective actions. This paper proposes a controller-based approach for real-time congestion management through line power flow regulation. We consider a robust H ∞ power flow tracking control strategy to regulate the line power flows to the specified limit, while attenuating the effect of disturbances on the system. Using synchrophasor measurements from the lines, the proposed controller can detect line overloading and automatically re-dispatch the selected generators and battery energy storage systems to maintain power flow within the desired limit. The robust line power flow tracking problem with disturbance rejection is formulated as a dynamic game between the controller and disturbance entities, and robust static output feedback H ∞ controller gains are obtained via an iterative algorithm. The efficacy of the proposed controller in regulating line power flow and mitigating congestion is verified by extensive simulations on a 16-machine 68-bus test system and Kundur's 4-machine 2-area test system. It is shown that the designed controller can regulate line power flows within 40–60 s, which is fast enough to avoid overheating of transmission lines. Furthermore, the proposed strategy is simple from the perspective of design and implementation, and outperforms the existing congestion management techniques. • Line power flows can be regulated to specified operating limits with the controller. • Congestion in the network can be cleared automatically in short period of time. • Effect of disturbances are attenuated to a prescribed level to provide robustness. • Requires only power flow measurements from lines to implement robust control action. [ABSTRACT FROM AUTHOR]

• The universal technique is applied in any protective zone surrounded by a particular PMUs. • The technique detects faults independent of fault kind or location matching threshold level of unity. • This algorithm detects faults regardless the fault resistance. • The algorithm has accurate simultaneous faults detection. The transmission system is one of the three major parts besides the generation and distribution systems. Transmission system protection requires a vital especially development it involves in modern wide-area systems. This paper suggests a generalized robust fault detection and location algorithm established on the optimally allocated phasor measurement units (PMUs). The optimum allocation of PMUs ensures the entire observability of all transmission lines, that are included within the zones of protection. The generalized fault detection and location algorithm is based on the roots deduced from the basic transmission line model under normal operation. The algorithm enables to detection of faults closed to buses equipped with PMUs and high impedance single line to ground faults. The algorithm is characterized by generality and independent variable system dynamics. The proposed algorithm can detect simultaneous faults of any type with a high degree of accuracy. To validate the developed algorithm, it is utilized in the IEEE 14-bus system. The simulation study is conducted using Matlab/Simulink® software package. Different fault types are modeled under various fault resistances. The modeled fault cases prove the security of the developed algorithm against external faults with a high degree of dependability in the case of internal faults. [ABSTRACT FROM AUTHOR]

• Modeling of electromechanical waves using Euler – Lagrange equation. • Power wave attenuation by means of UPFC. • Power wave transmission coefficient reduction. • Modulation of power line series impedance. In this paper modeling and attenuation of electromechanical power waves in large – scale power systems are discussed. Mathematical model of power wave is derived using Euler – Lagrange equation. The proposed modeling procedure is based on kinetic and potential energies of the system, as well as system's dissipation power. A novel method for incorporation of spatially dependent power losses into Euler – Lagrange equation is defined as well. The obtained mathematical model is simple for derivation, straightforward and practical for use, so it can easily be applied to derive wave equation of other technical systems or natural phenomena as well, which is an additional advantage compared to the existing models. Based on the developed model, an appropriate control system is proposed. The main idea for control system synthesis is to reduce transmitted waves inside the system. It is shown that the series power line impedance and voltage amplitude have the greatest impact on the wave transmission coefficient. Since unified power flow controller (UPFC) is capable of simultaneously modulating both these parameters, this device is chosen to perform control tasks in proposed operation mode. The effectiveness of the proposed solution has been verified by thorough computer simulations on artificial generator array and IEEE benchmark simplified Australian system. The results show significant power wave reduction. Some future works such as derivation of the mathematical model of inverter array or incorporation of artificial intelligence algorithms in UPFC control system based on transmission coefficient reduction might rely on this work. [ABSTRACT FROM AUTHOR]

Travelling wave fault location approach for overhead transmission line is widely applied in actual power grid, which has better fault location accuracy comparing with conventional power frequency data based method. However, travelling wave fault location approach is highly related to the frequency distortion phenomenon of travelling wave propagation velocity, which includes two parts: (i) the distortion caused by reflection and refraction phenomena of transformer substation and (ii) the attenuation caused by distributed resistance of transmission line. Therefore, aiming to improve the fault location accuracy, the paper contributes to two aspects: (i) the complete theoretical analysis of the distortion phenomenon of travelling wave signal and (ii) the improved travelling wave fault location approach considering distortion phenomenon. Eventually, based on PSCAD/EMTDC simulation tool, a typical 500 kV case study model is established to verify the fault location accuracy of proposed travelling wave fault location approach under the influences of fault type issue, fault location issue and grounding resistance issue. • Frequency modification. • Higher fault location accuracy. • Lighter data transmission burden. [ABSTRACT FROM AUTHOR]

This paper deals with nonlinear control and optimal management of wind energy conversion systems connected to HVDC transmission lines. Specifically, the energy system under study consists of a wind turbine driving a permanent magnet synchronous generator, the latter supplies energy to a power grid through a Vienna rectifier and a DC link. To compensate for intermittent nature of wind power and load demand variations, we design a voltage controller as well as a novel energy management strategy that accounts for the available wind power and DC load demands. In the considered management, distinction is made between two operation modes: i) the maximum power point tracking mode using an intelligent adaptive optimizer, where only electrical parameter measurements are used to ensure maximum power extraction; ii) the adaptive power point tracking mode employing demand-driven production. In both modes, the power factor requirement is ensured, regardless the weather conditions and load demand variations, enhancing thus the aerogenerator's efficiency. One more novelty of the proposed control and management system is the online estimation of the DC voltage, avoiding thus the use of a physical sensor. The performances of the control and management system are highlighted by several simulations, showing the achievement all control objectives. • SVPWM applied to the Vienna rectifier. • WECS recursive backstepping nonlinear control design. • ANFIS algorithm-based speed optimizer. • Adaptive high gain observer for HVDC transmission lines. [ABSTRACT FROM AUTHOR]

• Tellegen's theorem is introduced into the LCC-HVDC receiving-end AC power grid, and the instantaneous quasi-power characteristics are derived. • The quasi-power difference differential is defined to characterize differences between the internal and external faults and solve the problem caused by the distributed capacitance and reactive currents crossing through the transmission line. • The proposed pilot protection is immune to the control strategy of the inverter, commutation failure, receiving system strength and other factors. • The proposed protection can detect the fault within 5 ms. Affected by the control strategy and nonlinear characteristics of the inverter station, the traditional pilot protection relays employed in AC transmission lines do not perform well or even fail at the receiving end of the line commutated converter-based high-voltage direct-current system, thereby posing concealed threats to the security of the system. Leveraging the universality of Tellegen's theorem, this paper introduces the theorem to the realm of the AC-DC hybrid system. The characteristics of quasi-power difference under various conditions are analyzed, and a pilot protection criterion is proposed based on the quasi-power difference differential value. The AC grid model of the receiving end of the Tian-Zhong HVDC project in China is established in PSCAD/EMTDC to carry out simulation and performance analysis for the proposed protection under different fault cases. Furthermore, the proposed protection criterion undergoes validation using on-site fault recording data. The test results show that the proposed method is immune to the inverter control strategies, commutation failure, receiving system strength, and other factors. The new method is more adaptive to the AC system connected to the inverter station. [ABSTRACT FROM AUTHOR]

• In response to the inability of traditional consistency algorithms to solve the DC optimal power flow problem constrained by transmission lines, based on the DC power flow model, nodes are treated as intelligent agents, and a decentralized method for solving the DC power flow on transmission lines is proposed, which can obtain overloaded lines. • Aiming at the problem that traditional centralized DC optimal power flow cannot solve the decentralized management of information and the privacy of transactions of a large number of decentralized and different types of renewable energy into the power grid, the Lagrange optimization model and its extreme conditions are established for the traditional DC optimal power flow model, and the decentralized DC optimal power flow models of overload lines and non-overload lines are obtained. • For the proposed model, the relationship between node phase and marginal cost is established, and an iterative solution method based on node phase is proposed. Based on Kaczmarz algorithm, this paper proposes a solution method that takes the Lagrange multipliers of the corresponding nodes of overload lines and non-overload lines as a sub iteration. Tests on a practical system and the IEEE14 bus system demonstrate that the proposed method has good convergence and accuracy. Renewable energy sources such as wind power and photovoltaic are integrated into the power system in a high proportion and a decentralized manner. Driven by factors such as the privacy of the interests of various power sources, the efficiency of communication and computing and the reliability of transaction security, various forms of power sources are managed and controlled in a decentralized manner. It makes the traditional centralized DC optimal power flow difficult to realize. So, based on Lagrangian algorithm and improving traditional consistency algorithms, a decentralized DC optimal power flow model is proposed. Firstly, the decentralized calculation methods of active power, phase and line active power flow at nodes based on the consensus are presented. Secondly, based on Lagrangian algorithm, an improved DC optimal power flow model considering line constraints is derived. Thirdly, the calculation principle of decentralized DC optimal power flow model is proposed. It consists of two parts: the main iteration and the sub iteration. The main iteration is an iterative process with phase angle as a variable. Sub iteration is a process with Lagrange multipliers as iteration variables and using the Kaczmarz algorithm to prevent non convergence of iterations. Finally, a real system and IEEE14 bus system are taken as an example to demonstrate the accuracy of the proposed method compared to the Matpower and Injection Shift Factors(ISF) method. [ABSTRACT FROM AUTHOR]

• Considering the asymmetry of the practically transposed lines and adopting the fully distributed parameters model. • The estimations of unsynchronized angle and location of the fault are obtained with closed-form solutions. • Presenting higher accuracy of fault location than the existing methods under different fault conditions. This paper proposes an unsynchronized two-terminal fault location method on three phase practically transposed transmission lines. Compared to the existing fault location methods, the proposed method considers the asymmetry of the practically transposed transmission lines during the fault in practice. First, the proposed method constructs the practically transposed transmission lines by connecting three untransposed transmission line sections. For each section, the fully distributed parameters line model is adopted to ensure the modeling accuracy. According to the physical laws that the line should obey, the unsynchronized angle is estimated with analytical formulation before the fault. Next, the closed-form solutions of fault location are derived for different fault events, to avoid the risks of unconvergence using the iterative algorithms. In the numerical experiments, the proposed method shows higher accuracy of fault location than the existing fault location methods, regardless of fault types, locations and impedances. The proposed method also demonstrates robustness against various unsynchronized angles, loading conditions, measurement noises and line lengths. [ABSTRACT FROM AUTHOR]

• The concept of a generalized fault chain is first defined. • A construction method of multi-factor dynamic interaction graph based on generalized fault chain is proposed. • New signatures of vulnerable lines are discovered and classified. • The function of online monitoring of vulnerable lines is realized. The use of interaction graph to evaluate and obtain vulnerable transmission lines is an effective means of preventing cascading failure. However, the continuous changes of the key parameters that affect the cascading failure during the operation of the power system will affect the actual vulnerability of the lines. Especially with the increase in the penetration rate of renewable energy, the impact of frequent uncertainty and randomness brought by it can no longer be ignored. Therefore, the assessment results obtained from the static interaction graph cannot meet the accuracy requirements in the engineering, and also limit the scope of its application. How to realize the dynamization of the static interaction graph is the key to solving the above problems, which is also the difficulty that the current research has been facing. This paper proposes a construction method of multi-factor dynamic interaction graph based on generalized fault chains. With data-driven as the core, it realizes true dynamic and more accurate vulnerability assessment with the help of parallel distributed computing, uninterrupted data stream and sliding window. On this basis, according to the characteristics of generalized fault chains and the dynamic interaction graph, we propose and realize online monitoring for the classification of vulnerability lines for the first time. This function provides strong support for the implementation of measures with real-time characteristics, and can also more effectively reduce the risk and harm of cascading failure. Finally, this paper combines the IEEE 118 node system and deliberate attacks to prove the significance and effectiveness of the research. [ABSTRACT FROM AUTHOR]

• The electro-thermo-mechanical coupling power flow model is formulated. • The calculation framework of the probabilistic power flow considering electro-thermo-mechanical dynamics (PPF-ETMD) is presented. • The uncertainties of the meteorological conditions are considered in the calculation of PPF-ETMD. • Two fast calculation methods are presented to improve the computation efficiency of PPF-ETMD. • The distributions of the conductor temperature, stress and sag can be obtained by performing PPF-ETMD. Conductor temperature and tension are important physical states that determine the security of the overhead line. The states are sensitive to the line power flow and the meteorological conditions around the conductor that have strong uncertainty. In this paper, the electro-thermo-mechanical coupling dynamics of the power system are modeled. Then, focusing on the calculation of the distributions of the electro-thermo-mechanical dynamics (ETMDs) of critical spans under the uncertain operational environment of the power system, the implementation framework and the fast calculation methods for the probabilistic power flow considering electro-thermo-mechanical dynamics (PPF-ETMD) are proposed. The work presented in this paper provides an effective method for operators to capture distributions of the ETMDs of critical spans under the uncertain environment and detect the underlying system security risk based on the thermal and mechanical essence of the security of the overhead line. Numerical simulations based on a regional power system in China and the IEEE 300-node system are carried out to verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

• The decaying DC deviation phasor of the DFT output becomes a useful phasor to improve the accuracy of fault location. • By sliding the DFT time window, the phasor-time space curve characteristics of the two-terminal voltage difference function is proposed to describe the feature difference between fault point and non-fault points. • Based on the feature difference, space curve fitting degree is utilized as the evaluation index of fault point characteristic to construct a new fault location criterion of frequency-domain method. To improve the accuracy of frequency-domain fault location methods, finding new fault features in a limited fault data window is the most effective means. Different from the existing methods by eliminating decaying DC (DDC), this paper makes use of the DDC deviation phasor in the DFT output phasors. With the sliding of the DFT time window, the output phasor of two-terminal voltage difference function at different calculated points of the line has the following features: the actual fault point presents the characteristic of phase-time space curve with exponential attenuation in the same plane, but the farther the non-fault point is from the actual fault point, the more it deviates from this characteristic. Based on the feature difference, this paper uses the space curve fitting degree as the evaluation index of fault point characteristic, and constructs a new fault location criterion of frequency-domain method. Finally, electromagnetic transient fault simulation is used to test the proposed method and its comparison test, and the high performance of the proposed method is validated by simulations. [ABSTRACT FROM AUTHOR]

The prediction of typhoon-induced transmission line outages is essential to improve the resilience of urban power systems. This paper proposes a novel data-driven prediction model to promote the accuracy by quantifying the cumulative influence of dynamic data and mitigating the data imbalance. In the model, the static data and the dynamic data compose the disaster-causing feature vector as model input. Then, the denoising adaptive synthetic (ADASYN) sampling algorithm is proposed to select target samples purposely and generate minority samples adaptively to balance the dataset. Also, the discriminative model guarantees the consistency of the data distribution. Thereby, the dual path model is proposed to quantify the stable impact of static data and cumulative impact of dynamic data based on the feedforward neural network and gated recurrent unit (GRU), respectively, and fuse the extracted features with the multi-head attention mechanism to predict the category of the number of line outages. Based on the real dataset, this paper compares the performance of the denoising ADASYN algorithm and dual path model with benchmarking algorithms. The experiment results indicate that the proposed method witnesses a better accuracy in predicting typhoon-induced transmission line outages. • Considered the cumulative impact of dynamic data on the prediction of typhoon-induced transmission line outages. • Proposed the denoising ADASYN algorithm to mitigate the data imbalance. • Built the discriminative model to guarantee the consistency of the data distribution. • Proposed the dual path model driven by static and dynamic data to predict typhoon-induced transmission line outages. [ABSTRACT FROM AUTHOR]

• The paper has derived the correlations between the current of the neutral point reactor and the phase current of shunt reactors. After opening of the transmission line, due to the occurrence of permanent SPG or DPG faults, the current of the neutral point reactor is negatively correlated with the faulted-phase current of shunt-reactors. While these correlations would become invalid after the transient faults are cleared. • The paper proposed an adaptive three-phase reclosure method, which used Pearson correlation coefficient (PCC) to evaluate correlations between the currents of compensation reactors and construct a criterion for detecting when faults were cleared. • The proposed ATPAR scheme is easy implemented with low computational complexity and a fixed threshold. Simulation results showed that the ATPAR scheme proposed could reliably identify the fault nature and was unaffected by fault conditions and measurement errors. This study proposes a novel adaptive three-phase auto-reclosing (ATPAR) scheme for shunt-compensated transmission lines when a single- or double-phase-to-ground fault occurred, which is conducted on the correlations between the currents of shunt-reactors after the line opened. In this paper, the currents characteristics of compensation reactors are analyzed firstly through fault boundary condition theoretical, then, Pearson correlation coefficient (PCC) is used to construct criterions for identifying fault nature and fault cleared time. The proposed ATPAR scheme is implemented on a 230 kV-60 Hz IEEE 9-BUS power simulation system by using ATPDraw, and various faults which considered different fault conditions are simulated. The extensive simulation results verify the efficiency and reliability of the proposed ATPAR scheme. [ABSTRACT FROM AUTHOR]

• Phase-shifting transformers affect both nearby and remote distance relays. • The combined effect of hexagonal PST and fault resistance has been compensated for. • Compensation methods are developed for ground- and phase-faults. • The proposed scheme relies on local measurements and PST tap position transferred. This paper studies the performance of the distance relays for transmission lines equipped with hexagonal phase-shifting transformers (PSTs). PSTs can effectively control the power flow in the transmission lines. However, they alter the operation of the distance protection elements. The influence becomes significant when the fault occurs through a resistance. In this paper, the combined effect of the PST and the fault resistance on the operation of the ground and phase distance relays is considered. The analysis accounts for the effect of the PST not only on near distance relays but also on relays protecting an adjacent line. System analysis is carried out and a compensation technique is derived based on the location of the fault concerning the installation location of the PST. An operation logic is proposed to coordinate the operation of different proposed compensated protection elements. This operation logic helps to select the proper method ensuring the reliability of the protection system. The proposed protection scheme uses the voltage and/or current measurements at the relay point in addition to the transferred PST tap position. Therefore, synchronized voltage and current measurements from different locations are not required. The simulation study conducted with MATLAB/Simulink shows the success of the proposed ground and phase distance elements to account for the combined effect of the PST and the fault resistance. [ABSTRACT FROM AUTHOR]

The aim of this paper is to minimize the total cost of the system by incorporating wind power and plug-in-electric vehicles (PEVs) along with demand response (DR) program. The methodologies have proposed in contrast with the conventional algorithm in which the transmission line investment cost has been minimized without considering the dynamism of the deregulated environment. Moreover, the transmission network planning enhances the competitiveness of the power market, where more market players can participate. In this situation, the network planner has an important role in assessing the needs for transmission investments. Now-a-days practice of the network planner is to utilize more renewable power resources, PEVs and implementation of different electricity price tariffs. To achieve more benefits of PEVs and wind energy, their optimal utilization is a major concern. This paper proposes a mathematical model for solving the combined effect of PEVs and wind power integration with incentive-based DR program on static transmission network expansion planning (STNEP) problem. To solve this non-linear and non-convex problem, a nature-inspired optimization algorithm named gbest-guided artificial bee colony algorithm (GABC) is applied due to its robustness. The algorithm’s performance is evaluated through modified IEEE 24-bus, Brazilian 46-bus and Colombian 93-bus system. The test results indicate that the combined effect of DR, PEVs and wind has reduced the total system cost significantly. [ABSTRACT FROM AUTHOR]

• Proposed an original concept called spatial load migration (SLM), which is supposed to fully utilize the space connection between power loads, and provide a new load dispatch approach to address power transmission limitation. • Analyzed the feasibility and constraints of the typical power loads applied on SLM base on a holistic literature review and a utilized assessment architecture, including data center, base station, electric vehicle, mobile storage, and multi-energy equipment. • Provided a brief case study describing the potential of SLM on effective power distribution. • Concluded the power level and accessible appliance of each load type, and discussed the future research direction of SLM. As the transmission capabilities of power systems face challenges from renewable generation and massive electricity usage, power load resources have an increasingly important role in power dispatch. Traditional load dispatch methods are mainly based on the dispatch of load behavior in the time dimension, disregarding the potential of heterogeneous space connections existing in loads, such as communication connections and transportation connections. Although some studies, such as energy hubs or data networks, have utilized some part of space connections, no unified framework has been proposed to distinguish the problems caused by applying space connections or a horizontal review of spatial resources. In this paper, a framework named spatial load migration (SLM), which provides solutions to solving spatial network constraint problems with the enhancement of space connections, is proposed. With respect to SLM, this paper analyzes the mechanisms of typical power load types participating in SLM and qualitative appliance potential. A multi-system-coupled case study is designed with the occasion of power line disconnection. The results show that applying space connections to load dispatch can both expand the controllable objects and increase system performance. [ABSTRACT FROM AUTHOR]

• Thermo-fluid numerical model of conductor thermal rating due to natural convection. • Laboratory setup for evaluation of cooling of conductors due to natural convection. • Comparison of measurements with simulation shows good agreement. • Forced cooling at 0.6 m/s wind is larger than natural convection cooling. The development of Dynamic Thermal Rating (DTR) systems for transmission lines in recent years has led to a better and safer utilization of the existing transmission network, as it, for most cases, enables transmission capacity of lines to be increased above the traditionally used static thermal rating value, when weather conditions are favourable. Yet, on-site measurements in the Slovenian system have also shown that many sites are regularly subject to conditions of very limited or even no winds, causing the line rating to fall well below the static value. In those conditions, the natural convective cooling can surpass forced convective cooling and correctly assessing natural convective cooling becomes crucial for the Transmission System Operators (TSO). Different mathematical models deal with natural convective cooling in different ways. Moreover, references have emerged that claim that cooling due to the natural convection gives the same results as with forced convection at 0.6 m/s crossing wind. To clarify the thermal behaviour of power lines when no external wind is present, this paper employs thermo-fluid simulation of natural convection and compares it with laboratory measurements for two different conductors. The results are also compared with CIGRE, IEEE and IEC guidelines. [ABSTRACT FROM AUTHOR]

• Robust Complex-Valued Levenberg-Marquardt algorithm. • Bi-quadratic convergence property. • Rectangular coordinates and quadratic mismatch functions. • Easier computer implementation. This paper deals with a robust complex-valued Levenberg-Marquardt algorithm specially developed for solving ill-conditioned power flow problems. Moreover, it can also be a useful tool for voltage instability and voltage collapse studies. Because power flow models are nonlinear, the Wirtinger calculus is applied to develop iterative algorithms based on Taylor series expansions of nonlinear functions of complex variables and their complex conjugates. Our proposal in complex plane is straightforward derived in rectangular coordinates. Consequently, its performance is compared to the well-known optimized multiplier based load flow method. Aiming this purpose, we show that few changes in the codes are required to transform the complex-valued Newton-Raphson power flow algorithm into the complex-valued Levenberg-Marquardt power flow one. Furthermore, we show that the latter lends itself well to modeling new smart grid technologies while exhibiting a bi-quadratic convergence rate and superior performance as compared to the former procedure. The performance of our proposal is demonstrated and analyzed on well-conditioned IEEE-14, −30, −57 and −118 bus systems and the Brazilian Southern-equivalent system termed SIN-1916 bus. Furthermore, its performance is also demonstrated on the ill-conditioned IEEE-11, −43 bus systems besides the SIN-1916 under stressed operating conditions or higher R / X ratios of transmission lines. [ABSTRACT FROM AUTHOR]