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This paper presents a new method for fault location in transmission lines with series compensation, using data from voltage and current measurements at both terminals, applied to artificial neural networks. To determine the fault location, we present the proposal of using current phasors, obtained from the oscillography recorded during the short circuit, as the input to the neural network for training. However, the method does not rely on the internal voltage values of the sources or their respective equivalent Thevenin impedances to generate training files for the neural network in a transient simulator. The source data are not known exactly at the time of the short circuit in the transmission line, leading to greater errors when neural networks are applied to real electrical systems of utility companies, which reduces the dependency on electrical network parameters. To present the new method, a conventional fault location algorithm based on neural networks is initially described, highlighting how the dependency on source parameters can hinder the application of the artificial neural network in real cases encountered in utility electrical systems. Subsequently, the new algorithm is described and applied to simulated and real fault cases. Low errors are obtained in both situations, demonstrating its effectiveness and practical applicability. It is noted that the neural networks used for real cases are trained using simulated faults but without any data from the terminal sources. Although we expect the findings of this paper to have relevance in transmission lines with series compensation, the new method can also be applied to conventional transmission lines, i.e., without series compensation, as evidenced by the results presented. [ABSTRACT FROM AUTHOR]

Protection of critical components in the power sector especially the transmission line system is very important to minimize loss of revenue, resources, and productivity. Improvement of power transfer capacity and voltage profile in smart the power grid is achieved by Series Compensation (SC). However, it poses many serious issues in the protection of compensated transmission lines. The majority of faults occurring in transmission lines are transient in nature for which service continuity can be regained by an auto-reclosing scheme. An efficient auto-reclosing scheme that can provide adaptive protection with reliable operation is required to prevent transient and permanent faults in the series compensated transmission line (SCTL). This work highlights the emulation of an Internet of Things (IoT) aided adaptive auto-reclosing scheme in association with an ESP32 controller that provides adaptive dead time control. The reclosing instance has been identified by means of a synchro-check relay. A real-time IoT-aided auto-reclosing scheme has been realized using the ESP32 controller that can generate a trip/reclosing signal instantaneously using the concepts of edge computing. The projected system has been also corroborated by simulating the modeled smart power grid network with wide variations in fault context in PSCAD. The validation of the set of rules is done in MATLAB software for the proposed auto-reclosing scheme. The extracted test outcomes of the simulation and its laboratory hardware implementation indicate an appreciable reduction in dead time which reflects the efficacy of the developed protection scheme. [ABSTRACT FROM AUTHOR]

This paper presents a magnetically controlled series compensation-fault current limiter (MCSC-FCL) which is composed of a magnetically controlled reactor (MCR) and a compensation capacitor. The device is improved from the traditional thyristor-controlled series compensation (TCSC), which has the characteristics of small output harmonics and simple control. The traditional saturated iron-core reactor is improved to increase the adjustable range of output reactance. During the fault, the MCR is connected to the grid alone to limit fault current; when the grid is normal, MCR and capacitor are used in series compensation mode. It effectively improves the utilization rate of the traditional current limiter MCR. In order to verify the effectiveness of the proposed MCSC-FCL, this paper analyzes the control characteristics of reactor models with different air gap structures by JMAG finite element analysis software, and verifies the voltage regulation characteristics and fault current limitation capabilities on MATLAB/Simulink platform. [ABSTRACT FROM AUTHOR]

Wind power has rapidly emerged as a leading renewable energy source, with doubly-fed induction generators gaining attention for their independent power control capability. Integrating doubly-fed induction generator-based wind farms into the grid requires significant upgrades to transmission and distribution infrastructure to fully harness wind energy's potential and address challenges like sub-synchronous control interaction. This phenomenon poses risks such as equipment damage and power supply interruptions. To mitigate these risks, a novel adaptive control strategy incorporating uncertainty and disturbance estimators, alongside H∞ and μ-synthesis controllers, is proposed. By introducing a time delay into the control system, oscillations can be detected and stabilized, ensuring system stability across various operational conditions. The controller parameters are optimized using a dynamic opposite learning-based enhanced mountain gazelle optimization algorithm. This algorithm is utilized to determine the optimal controller parameters that ensure system stability across different operational conditions. Simulation results conducted in MATLAB validate the effectiveness of the proposed controller in damping oscillations under different compensations and wind speeds. Specifically, it demonstrates superior damping capabilities at various wind speeds and compensations, enhancing power system stability and reliability. Results confirm the better damping capability of proposed controller under different compensations such as 75% and 45% and wind speeds such as 13 m/s, 7 m/s, and 11 m/s. This research provides better stability and reliability of power systems by dampening oscillations at 1.5 s, ensuring the sustainable integration of wind energy. [ABSTRACT FROM AUTHOR]

This paper presents an investigation into the performance of radial distribution systems (DS) with the installation of series capacitors in feeder sections. While the use of shunt capacitors to enhance voltage profile in DS has been acknowledged, the benefits of series capacitors have only been explored to a limited extent. Load flow analysis, while commonly used for offline evaluation of DS, can at times yield inconclusive results due to convergence issues. To mitigate this, an alternative approach is proposed using Artificial Neural Networks (ANN) to directly determine system performance. The viability of the proposed technique is evaluated for IEEE 12 and IEEE 33 bus DS's having series capacitor in feeder section for voltage improvement and line loss minimization. Therefore, this paper serves to contributes to the two main novelties namely, (1) Development of efficient ANN model to directly determine the maximum voltage regulation and line losses and (2) improvement of voltage and line losses reduction through series capacitor installation in feeder section of the DS. The results show that the utilization of an ANN model enhances accuracy and speeds up predictions, while the installation of series capacitors in feeder sections improves voltage regulation and reduces line losses. [ABSTRACT FROM AUTHOR]

During power supply swings, current and voltage waveforms are modulated with additional frequency elements which lead to maloperation of relays. This maloperation may cause cascade tripping of transmission lines, which results in the failure of electrical grid networks. Power Swing Blockers (PSBs) are employed to block and prevent maloperation of distance relays during power swing. Along with power swing, the presence of TCSC compensation in transmission line deteriorates the input signals to relays which make fault classification a complex task. During the PSB blocking period, modulated signals distorted with non-linearities of MOV operation complicate the fault diagnosis functioning. This challenge motivates to develop an algorithm for fault classification during power swings. To address aforementioned challenges, a Wigner Ville energy-based fault classification technique is proposed in this work. A modified 9 bus WSCC system with TCSC compensation is used for testing and validation of the proposed scheme. The scheme is tested for different cases like symmetrical, close-in fault, asymmetrical high resistance fault, and CT saturation, etc. The scheme is also validated against transient conditions like load and capacitor switching. The performance of proposed scheme is compared with existing schemes in literature. The above scheme is also implemented and validated on an Intel Cyclone V SOC FPGA. The results show that the proposed scheme classifies faults accurately during the simulation as well as on hardware platform. [ABSTRACT FROM AUTHOR]

This paper introduces a novel approach to fault localization in transmission lines with series compensation using nonlinear optimization. The objective function minimization provides information on the fault distance and the current at which the protective varistor starts conducting. Terminal source data, the maximum current capacity of the capacitor, and the operating curve of the metal oxide varistor protection element are not required. The proposed method successfully met the predefined objectives, with a maximum error of 1.13% in simulated scenarios. In validating the method using real cases from a Brazilian energy concessionaire, the errors were below 0.5%. [ABSTRACT FROM AUTHOR]

As the load on distribution networks grows, system operators and planners are constantly challenged with the issue of voltage regulation or enhancing the quality of supply to customers at the load end of lengthy distribution lines. This paper presents the optimum determination of series capacitor units in a distribution system to maximize energy‐saving and enhance voltage levels. Interestingly, series capacitors can enhance the capability of transmission lines, reduce line losses, enhance the performance of buses with large induction motor loads and reduce voltage flicker. At the same time, the limitations of series compensation are taken into consideration while calculating its optimum values. To achieve the planning objective and optimal load flow objective, two strategies: The Improved Grey Wolf Optimization method (I‐GWO) and Tabu Search (TS), are hybridized to get the benefit of their advantages. The I‐GWO has a movement strategy called dimension learning‐based hunting for enhancing the balance between global and local search and maintaining diversity. The proposed (I‐GWO‐TS) algorithm can solve mixed‐integer programming to achieve the planning and the optimal load flow objectives. The proposed method can be applied to a real Egyptian distribution system that is heavily loaded, with poor voltage regulation, and also has high‐power losses. The obtained results demonstrate the capability of the proposed approach to determine optimal series capacitors' location and sizing for maximization of energy saving. Further, the proposed method improves the network performance regarding the voltage profile and power losses, although the limitations of including series compensation were considered in the distribution system. [ABSTRACT FROM AUTHOR]

Protection engineers and academicians are continuously working towards better relaying for modern transmission structures. This has become a requirement because transmission structure, nowadays, is being updated with new technologies, e.g. flexible AC transmission system devices. In this paper, it has been observed that the differential DC plays an important role in distinguishing the internal and external faults. A criterion is then developed based on this unique feature of the differential DC for the identification of faults in modern transmission lines. The performance of the proposed criterion has been tested with the help of simulation study carried out using EMTDC/PSCAD software for a variety of fault types with variations in fault location, fault resistance, fault inception angle, and compensation level. Furthermore, the performance of the proposed algorithm is also investigated for several rare conditions such as evolving faults, cross-country faults, noise in measurement, and measurement error. The results prove that the scheme is selective, accurate, and robust for uncompensated and series-compensated lines while it is accurate for low resistance faults in the case of a shunt-compensated line. [ABSTRACT FROM AUTHOR]

Series compensations have been widely used in modern power systems to extend the power transfer capacity. Since more and more renewable power generation systems are installed in power systems, the grid-connected inverters (GCIs) used by the renewable power generations may interfere with series-compensated power lines, which introduce subsynchronous resonance (SSR) causing power system failure that has been observed in real cases. The phase-locked loop (PLL) of the GCI's control system is the main factor that can cause the SSR in the series-compensated power grid. To mitigate the impact of the PLL and obtain the stable operation of the power system, a q-axis voltage feedback method has been proposed in literature to damp the harmonic oscillations in the weak power grid where, however, the series compensation is not considered. Because the real q-axis voltage cannot be obtained, the q-axis voltage output from the PLL is used as the feedback variable in literature. However, due to the dynamic response of the PLL, the q-axis voltage output from the PLL is different from the real q-axis voltage, and the direct use of it for the damping of the SSR in the power grid with series compensations is invalid, which is investigated in this article. Besides, an observed q-axis voltage feedback method is proposed in this article to damp the SSR in the series-compensated power grid with GCIs being connected. By putting an observer in the q-axis voltage feedback path, the real q-axis voltage can be estimated and applied to damp the SSR. Simulation and experimental results have been provided to verify the effectiveness of the proposed observed q-axis voltage feedback method in the damping of the SSR. [ABSTRACT FROM AUTHOR]

• SSR phenomenon due to interaction of series capacitors with droop-controlled grid forming inverters is reported. • Sub-synchronous interactions are dependent on the series capacitor and the power control response of droop control • A transfer function-based approach is presented to analyze the mechanism of instability alongside small signal analysis. • Mitigation approaches such as virtual resistance, split droop, oscillation damping control are presented and validated with EMT simulations. Grid forming inverter controls are becoming increasingly popular due to their advantages in electric power systems with high penetration of inverter-based resources (IBRs). Power system operators across the world are pushing for more grid forming IBRs to be interconnected to stabilize the system. However, there is limited research on the interactions between grid forming inverters and series compensation capacitors when radially connected. Series compensation is commonly used in long transmission networks to reduce the impedance of the line and improve its power transfer capability. Interactions of inverter-based power plants with series capacitors have been observed in the industry and have also been noted in literature. In this work, the performance of droop-controlled grid forming inverters with single loop voltage control interconnected radially through series capacitors is studied. Sub-synchronous interactions are observed which are dependent on the magnitude of compensation and the power control response of droop control. A transfer function-based approach is presented to analyze the mechanism of instability. The transfer function approach is validated by small signal analysis and EMT studies. Approaches to mitigate and damp such interactions are identified. EMT simulation results are presented alongside to validate the proposed approaches. [ABSTRACT FROM AUTHOR]

Deep decarbonization is the goal of modern power systems, so it is inevitable that large-scale wind farms will be integrated into systems. This also gives rise to many problems, which have been studied in detail in the literature. However, these studies basically have two deficiencies. One is to assume that traditional generator units are fully loaded, and the other is not to compare the differences in the impact of different types of wind farm. This paper discusses these two points in detail. Taking a series-compensated transmission system as the research object, and assuming that the wind farm only replaces part of the power of the traditional generator unit in the transition period of energy conversion, the difference between the torsional vibration behaviors of the traditional unit caused by adopting different types of wind farm is discussed. The results of the study show that the impact of integration of the type 3 wind farm is dominated by the induction generator effect of doubly fed induction generator units. The penetration rate as low as 19% could cause instability. However, the paralleled metal-oxide varistor can effectively improve the stability. For the type 4 wind farm, the dominant factor turns out to be the de-rating operations of the steam turbine generator unit. The allowable penetration rate depends on the turbine damping. When the turbine damping is sufficient, the penetration rate can be as high as 87.5%. In conclusion, in order to integrate wind farms into a series compensated transmission system, one should not only focus on the compensation factor to avoid the sub-synchronous torsional vibrations, but also pay attention to the types of wind farm as well as the penetration rate. The findings can be used as the decision-making basis for the integration of wind farms during the energy transition period. [ABSTRACT FROM AUTHOR]

SaLurated core fault currenl limiler will cause higher harmonic pollulion when used in series compensaLion. In order Lo ensure Lhe safe and sLable operalion of the power system, Lhe saturaled core fault currenL limiter with improved air gap structure is designed based on the principle of segment saturated core. The simulation models of saturated core fault current limiter with different air gap structures are established by JMAC. The relationship between current and flux of the current limiter is imported into MATLAB/ Simulink and the corresponding simulation system model is established to further analyze and compare the control characteristics, harmonic content and fault current limiting abiliLy of Lhe Lwo currenl limiLer models. The resulLs show thaL Lhe saLurated core faulL currenl limiter with improved air gap structure has aboul 1. 5 Limes of reactance regulation range and lower harmonic dislortion rale when compared with the full air gap structure without losing the current limiting capacity. [ABSTRACT FROM AUTHOR]

This article presents a new grid connected induction generator (IG) system having open-end stator windings with a series reactive power compensator. The proposed scheme consists of a two-level capacitor fed voltage source inverter (VSI) connected to one side of the stator windings of the IG while the other ends of the windings are directly connected to the grid. A current phasor oriented rotating reference frame based control scheme is developed to control the operation of the VSI to ensure that it compensates the reactive power required by the IG. Thus, the IG system can supply active power to the grid without drawing reactive power from it for excitation. Unlike the shunt compensated IG systems, the proposed scheme does not require an interfacing inductor for connecting to the grid thereby reducing the hardware footprint. The proposed scheme is validated by simulation using PLECS software and the simulation results are presented in the article. A prototype of the system was developed in the laboratory to experimentally verify the proposed scheme and the experimental results are also presented in this article. [ABSTRACT FROM AUTHOR]

This paper presents a control strategy to mitigate subsynchronous oscillations (SSOs) in doubly-fed induction generator (DFIG)-based wind farms integrated into series-compensated transmission systems. The strategy has two parts: in the first one, a compensation filter based on the motion-induction amplification concept is proposed to increase the damping of the DFIG machine in the subsynchronous frequency range; in the second one, a proportional-integral (PI)-like controller is designed using an optimal quadratic technique to minimize the control effort and the additional rotor voltage required by the SSO damping action. The SSO mitigation strategy acts locally on the DFIG control system reducing the negative resistance the rotating machine presents to the grid at subsynchronous frequencies; this approach reduces the control dependence on the topology and resonance frequencies of the network. The control strategy is validated with a case study based on the Argentinian power system and evaluated in a wide range of operating conditions, showing that the DFIG control system can be enhanced to mitigate poorly damped SSOs and increase the penetration level of wind power in the system. [ABSTRACT FROM AUTHOR]

The paper proposes mathematical models and algorithms to calculate processes and characteristics of induction motors in a series compensation of the reactive power. The developed algorithms are based on a mathematical model of the induction motor in phase coordinates. A complete system of differential equations of the electromechanical equilibrium of the stator and rotor circuits is used for a transient analysis. The algorithm to calculate the static characteristics is based on the projection method for solving the boundary value problem for a system of equations of the electrical equilibrium. [ABSTRACT FROM AUTHOR]

This paper introduces a fault detection and faulty phase selection technique for a double-circuit transmission line with thyristor-controlled series capacitor (TCSC). In a transmission system, the nonlinear operation of TCSC during switching modes distorted the voltage and current signals. The effect is more if the fault occurred at zero fault inception angle. An advanced protection approach to overcome these issues based on dynamic phasor estimation of current from local measurements is proposed in this work. The maximum transient component obtained from three phases is used as an index to accomplish the detection task. However, due to the nonlinear operation of different accessories connected to the controller unit such as metal oxide varistor (MOV) and thyristor circuit, identification of the exact faulty phase is still a challenge. To mitigate this issue, fuzzy decision-based rules are framed so that identification of exact faulty phases is possible. For validation, the method is tested on a 400-kV, 50-Hz power system model developed using EMTDC/PSCAD. Results obtained from simulation indicate that the method is reliable and a secure unit protection can be effectively provided to a double-circuit transmission system equipped with TCSC. [ABSTRACT FROM AUTHOR]

Summary: Integration of a series capacitor in a transmission line not only has advantages such as system stability and power factor improvements, voltage profile regulation, and power flow maximization but also shows some unwanted effects such as current and voltage inversion, change in line impedance, and subharmonic frequency that leads to mal‐operation of the conventional protection scheme. This paper introduces a fault detection method for a series‐compensated line. An algorithm is proposed that uses the extracted DC component of currents at both sending and receiving ends to detect the fault and generate a trip signal. The proposed protection criterion is successfully examined for diversified (adverse) conditions using PSCAD/EMTDC simulations. [ABSTRACT FROM AUTHOR]

Summary: Objectives: This paper explores the performance of the Single Machine Infinite Bus (SMIB) power system integrating a Photovoltaic (PV) generator when compensated by the Thyristor Controlled Series Capacitor (TCSC) and the Static Synchronous Series Compensation (SSSC) Flexible Alternating Current Transmission System (FACTS) devices. Method: The analysis is performed after the introduction of a step change in the mechanical input and excitation voltage of the synchronous generator connected in parallel with the PV generator at different levels of solar intensity. Time domain simulations based on a non‐linear dynamic mathematical model are used for numerical simulations. Results: The simulation results demonstrated the effectiveness of the addition of TCSC and SSSC FACTS devices to improve the power transfer capacity of the SMIB power system with a PV generator. Conclusion: The response of TCSC and SSSC is almost similar. Nevertheless, the introduction of the two FACTS devices does not achieve a system stable operation at 50% of the total level of solar irradiance. TCSC is more effective than SSSC in maintaining the stability of the system. [ABSTRACT FROM AUTHOR]

Summary: This paper demonstrates the functionality and control of the gate‐controlled series capacitor (GCSC), a new FACTS device composing a pair of antiparallel GTOs in parallel with a fixed capacitor, to mitigate subsynchronous resonance (SSR) in a thermal generation plant connected to a series compensated transmission line. Firstly, by the use of both small‐signal stability analysis and time‐domain simulation, it is revealed that the studied system compensated by the series fixed capacitor is potentially unstable due to the first torsional mode. Then, in order to take benefits of series compensation without the risk of SSR, the fixed capacitor is replaced by GCSC. The capability and effectiveness of the GCSC to damp SSR are validated using modal analysis and time‐domain simulation. Furthermore, GCSC is used in conjunction with a fixed series capacitor to minimize the overall cost of compensation. For this purpose, unlike previous studies, a linear controller is used to stabilize the system. In this study, the IEEE First Benchmark Model is considered as a case study, and MATLAB/Simulink is used as a tool for modeling and design of the control system. Also, time‐domain simulations are done using PSCAD/EMTDC. [ABSTRACT FROM AUTHOR]

The protection of mutually coupled series capacitor-compensated (SCC) parallel transmission lines is a more complicated task than uncompensated lines due to the effect of mutual coupling, inter-circuit faults, and non-linearity of effective impedance of SCC line. A method that can overcome these issues and still work efficiently is a supervised learning-based method which is an adaptive technique. Hence, in this work, various supervised learning-based intelligent schemes like artificial neural network (ANN), support vector machines (SVM), and decision tree (DT) are employed to find a suitable method for the protection of series capacitor-compensated lines. Discrete wavelet transform has been used to process the three-phase current signals of the parallel lines measured at one terminal only. A moving window of 20 samples is selected, and approximate wavelet coefficient is calculated up to level 1 using DB-4 mother wavelet. The resultant is then given as input to the intelligent schemes (ANN, SVM, and DT). The proposed intelligent schemes have been tested with variety of fault conditions such as inter-circuit faults, cross-country faults, transforming faults, single-circuit operation, and high resistance faults. A large number of fault simulation studies corroborate that DT-based fault classification method is better than ANN and SVM. The accuracy of faulty phase and ground identification scheme is 100% for all the tested fault cases. Hence, the proposed supervised learning-based intelligent method can be implemented in real power system network effectively. [ABSTRACT FROM AUTHOR]

To avoid the under/over-reaching problems of distance protection of extra high voltage/ultra high voltage transmission lines (TLs) in the presence of series compensation, pilot relaying scheme can be preferred. In this article, a pilot relaying scheme is proposed which is unaffected by source-to-line impedance ratio variations and is based on the estimated phase error (EPE) of shunt charging component of the TL. For external fault, EPE is very small or close to pre-fault EPE while for internal fault, EPE is more than 10 times of pre-fault EPE. This scheme can be used to protect the series-compensated line as well as an uncompensated line with the same threshold value. The prerequisites for this scheme are the parameters of the TL which is to be protected. The scheme has been tested using power system computer aided design/electromagnetic transient and DC simulations for three different types of test power systems. The proposal is found to be accurate for different test systems, fault types, variations in compensation level, source impedance, fault location and fault resistance. [ABSTRACT FROM AUTHOR]

This study introduces a fault location technique for three-terminal series-compensated untransposed parallel transmission lines utilizing the three terminals' synchronized data. The proposed technique is applicable for short or long lines as distributed parameter line model is employed and the potential couplings are considered. The fault location for both uncompensated line sections is obtained adopting previously introduced fault location technique. The faulty phases are required initially to be recognized for series-compensated transmission line. The adopted fault location technique for series-compensated line section is derived based on the resistive nature of the fault impedance. The obtained fault locations for each line section are compared with each other to distinguish the faulty branch and obtain the fault location. DIgSILENT Power Factory and MATLAB programs are utilized for simulation studies and required calculations. The obtained results prove the efficacy of the introduced technique. [ABSTRACT FROM AUTHOR]

The paper presents a novel approach for classification of faults in Extra High Voltage (EHV) transmission line with series compensation. The proposed algorithm utilizes single end currents extracted from three phases of a transmission line given to a fault detection and classification system. A detailed model is constructed to analyze fault patterns occurring on a dual feed system with multiple series compensation provided on EHV transmission line. The algorithm uses a full cycle of post-fault currents. A Multiresolution Analysis Wavelet-based decomposition technique is used to provide a joint time frequency analysis. Extensive study is done by designing different fault classifiers using Support Vector Machine (SVM) with different feature vector groups. The SVMs with different parameters are compared to show performance of SVMs in given feature space of faults. A new algorithm is proposed with Ensemble method having group of different classifiers, namely, Artificial Neural Network (ANN), K-Nearest Neighborhood (KNN) and SVM. A combination of feature selection with Ensemble Classifiers is trained and tested on a wide range of fault patterns. A significant improvement in performance is obtained with different combination of features in Ensemble Classifier using subspace partition method.The proposed Ensemble Classifier provides an accuracy of 99.5%. [ABSTRACT FROM AUTHOR]

This paper details a nonlinear Sliding Mode Control (SMC) based Sub-Synchronous Resonance (SSR) mitigation method for Doubly Fed Induction Generator (DFIG) based wind turbines interconnected to series compensated transmission systems. The proposed method is used to control the rotor side converter to mitigate SSR while ensuring decoupled torque and reactive power control ability of the DFIG is maintained. The proposed method is implemented on the detailed DFIG wind turbine model provided in the RTDS platform for validation via simulations. Results obtained indicate the controller is successful at damping SSR when tested under varying compensation levels and wind speeds. [ABSTRACT FROM AUTHOR]

Type-4 wind is claimed to be immune from subsynchronous resonances (SSRs) that have been experienced by Type-3 wind with radial connection to series compensated lines. In this paper, we examine this claim through simplified analytical model building, analysis based on linearized models, and validation against electromagnetic transient (EMT) testbeds with full details. Two analytical models of Type-4 wind farm with radial connection to a series compensated line are built in $dq$ -frames. The main difference of the two models is in grid-side converter (GSC)'s control mode, with one model assuming real power control and the other assuming dc-link voltage control. Relying on the analytical models, an efficient approach is demonstrated to obtain frequency-domain impedance models. Small-signal analysis is carried out using eigenvalue analysis and frequency-domain impedance model-based analysis. Potential stability risk is demonstrated, which is due to interaction of a mode associated to voltage source converter (VSC) in weak grid (termed as “weak grid mode”) and a mode associated to network LC resonance. The weak grid mode is influenced by grid strength and VSC control parameters, including phase-locked-loop (PLL) parameters. The small-signal analysis results are validated against two EMT testbeds with full details in MATLAB/SimPowerSystems and PSCAD/EMTDC, respectively. [ABSTRACT FROM AUTHOR]

Summary: The interconnection between the grid and nonconventional energy sources has become more essential due to the huge rise in energy demand. In the case of wind energy, the grid integration undergoes lots of stability issues. The long‐distance transmission lines are preferred since the wind farms are positioned far from the grid. However, this lowers the bulk power transfer ability of the line. The simple solution to enhance the power transfer capacity is the insertion of series capacitor in the line. However, the frightening factor in inserting the series capacitor is subsynchronous resonance (SSR) oscillations which can lead to shaft fatigue between turbine and generator set. This paper focuses on the analysis of SSR in series‐compensated doubly fed induction generator (DFIG)–based wind energy conversion systems (WECSs). The detailed mathematical modelling of DFIG‐based wind turbine generator (WTG) in state space form which is essential for SSR analysis is explained. The proposed model is found to be more accurate as it includes the dynamics of the rotor‐side converter (RSC) and grid‐side converter (GSC). The influence of series capacitive compensation in a WECs is dealt by employing eigenvalue approach. The developed model is embedded with RSC and GSC controllers for analyzing SSR effect for different operating conditions such as wind speed variations and varying compensation levels using MATLAB/SIMULINK. Also, the scaled‐down model of a 2‐MW wind turbine is deployed in laboratory using a grid‐integrated, series‐compensated 1.1‐kW DFIG machine to realize the influence of series capacitive compensation. It is found that the stability of SSR is affected by different wind velocities and capacitive compensation levels. [ABSTRACT FROM AUTHOR]

Series compensation is used to improve power system transmission capacity. Subsynchronous resonance (SSR) associated with such a system is a challenging issue. Today, with increasing integration of wind farm (WF) to power network, the stability of the system gets deteriorated due to variation in wind speed at the WFs. The reaction between the SSR modes and the doubly fed induction generator converters is known as subsynchronous control interaction (SSCI), due to which, it becomes more challenging to achieve power system stability. To overcome these issues, in this paper, a synchrophasor data-based control (SDC) technique is proposed. The proposed controller diminishes induction generator effect, torsional interaction, and the SSCI effect on the series compensated network, integrating multiple WFs. The SDC provides an auxiliary SSR damping control (SSRDC) with thyristor controlled series compensation (TCSC). This SSRDC uses synchrophasor data from WF connected point of common couplings (PCCs) inside the grid to improve the SSR oscillation damping. The proposed method maintains reference voltage angle of the PCCs by controlling equivalent impedance of the grid. The impedance provides significant damping for SSR along with the TCSC control. The proposed SDC is tested for modified 39-bus New England system with WFs and is found to be effective. Comparison of this method with conventional local control demonstrates its superior performance. [ABSTRACT FROM AUTHOR]

A new controlled switching method for purely series compensated transmission lines is proposed here. The main idea is based on the estimation of trapped charges using a recursive digital filter for correction of the secondary voltage of the capacitive voltage transformer. Several operating conditions of series capacitor banks are taken into account to define the controlled switching strategy for transmission line reclosing. It is also shown that one can take advantage of the existing techniques for uncompensated and shunt compensated lines. The challenges and potentialities of the proposed method are highlighted through alternative transient program (ATP) of a 500-kV power system where switching transient overvoltages are limited to 1.85 p.u. [ABSTRACT FROM AUTHOR]

Transmission network reinforcements are being undertaken to meet renewable energy targets toward a low carbon transition. High-voltage direct-current (HVDC) links and series-compensated ac lines are frontrunners in these developments. Although series capacitor installations can lead to subsynchronous resonance (SSR), HVDC links based on voltage source converters (VSCs) can be used to effectively damp SSR upon occurrence. An active damping technique to mitigate torsional interactions (TIs), a form of SSR, is presented. The damping scheme considers an active wideband filter to ensure positive damping in a wide range of subsynchronous frequencies. A state-space representation of the system has been formulated and eigenanalyses have been performed to assess the impact of the HVDC link on the TIs. A damping torque study for SSR screening is carried out, with results complemented with time-domain simulations to assess the accuracy of the small-signal models. The test system is implemented in a real-time digital simulator and connected to a VSC-HVDC scaled-down test rig to validate the damping scheme through hardware-in-the-loop experiments. The presented damping method exhibits a satisfactory performance, with time-domain simulations and laboratory experiments showing a good correlation. [ABSTRACT FROM AUTHOR]

• A faulty-side identification method for the series-compensated transmission lines is proposed. • The method is characterized by easy and fast operation to apply and embed in the distance relay. • The method relies on the basic theories of the fault analysis and the phasors diagrams of the equivalent apparent impedances. • The method's performance is satisfactory till high fault resistance value. This paper introduces an integrated distance protection technique for series-compensated transmission lines (SCTLs) based on a new scheme to identify the faulty side with respect to the compensator. Conventional distance algorithms suffer from mal-operation under faults behind the Series Compensator (SC). Therefore, the modified mathematical algorithm of the distance relay treats with these faults via compensating the voltage drop through the SC to integrate the relay performance along the line. Consequently, the faulty side either upstream or downstream the SC must be identified. This identification is accomplished via a new function inserted in the mathematical algorithm. The presented function is a voting system based on both of the angles of the obtained conventional and modified apparent impedances. The presented voting scheme is based on basics theories of the fault analysis and the phasors diagrams of the equivalent apparent impedances seen by the conventional and modified algorithms whether the fault is upstream or downstream the SC. The presented scheme is suitable for all fault types even with high fault resistances. MATLAB package is used to simulate 400 kV compensated transmission lines and also to implement the presented algorithm. Diverse fault cases are investigated to test the response of the presented voting system under different fault conditions including the fault type, location, and impedance. The results confirm the efficacy of the presented scheme. [ABSTRACT FROM AUTHOR]

—Subsynchronous resonance (SSR) is an undesirable phenomenon in series compensated power system which tries to menace the stability of both electrical and mechanical system. This paper researches the effect of static synchronous compensator (STATCOM) for mitigation of SSR in a single machine infinite bus system. The mathematical modeling is presented in the form of linearized equations, which can be used for eigenvalue analysis of SSR. A novel control technique based on unit template algorithm is incorporated in STATCOM for alleviation of SSR and it proves to be ingenious in damping out all the oscillations. Furthermore, frequency scan and fast Fourier transform (FFT) analysis are presented, that provide resonant frequencies at different levels of compensation and dominant modes of oscillations respectively. To examine and authenticate the efficacy of the proposed controller, the IEEE second benchmark model on SSR is simulated in MATLAB/Simulink environment and the results are analyzed to illustrate the potency of the proposed control strategy. [ABSTRACT FROM AUTHOR]

This paper presents a new series capacitor based frequency scan method to assess the subsynchronous resonance risk including induction generator effect (IGE) and subsynchronous control interaction (SSCI). Most existing frequency scan methods are generator based and calculate the impedance as viewed from the neural bus of the study generator. In this paper, the generator-based frequency scan method is discovered to be inadequate or inapplicable to deal with a cluster of inverter-based generation resources under some circumstances. The proposed method scans the impedance as viewed from the series capacitor to assess the IGE/SSCI risk. With nearby inverter-based generation resources modeled by their frequency-dependent impedances, the proposed method is capable of assessing the IGE/SSCI risk for a cluster of inverter-based generation resources. The electromagnetic transient simulation was conducted to validate the proposed method. The proposed method also successfully demonstrates the nonlinear impact of the number of in-service units on the SSCI performance for a cluster of inverter-based generators. [ABSTRACT FROM AUTHOR]

Subsynchronous resonance (SSR) is a phenomenon in which electrical energy is exchanged between the generator and the transmission system below power frequency. SSR occurs due to the interaction of a series-compensated transmission line with a generator. It results in shaft oscillation and out-of-step (OOS) condition. During SSR, the magnitude of voltage and current is increased. It also increases probable occurrence of ferroresonance. It is obviously clear that protective relays are affected in such conditions. In this article, Manitoba Hydro electrical network is examined with series capacitors by PSCAD/EMTDC to investigate the impact of SSR on the operation of different types of protective relays. SSR is mostly concerned with transmission lines. In addition, swing characteristic of impedance during SSR causes activation of the OOS blocking (OSB) element of distance relay and OOS protection of generator. Hence, an adaptive algorithm based on subharmonic measurement and ferroresonance analysis in the time domain is proposed for OOS characteristic of generator protective relay to recognize SSR condition and make a decision on behavior of the function. Finally, the algorithm is examined in SSR condition to certify the correct operation. [ABSTRACT FROM AUTHOR]

The interaction between controllers of doubly fed induction generators (DFIGs) and fixed series compensations may cause a new type of subsynchronous resonance (SSR), namely subsynchronous control interaction. To mitigate this emerging issue, a novel suppression method, embedding subsynchronous notch filters (SNFs) into DFIG converter controllers, is proposed in this study. By using the impedance‐model‐based analysis and a quantitative location‐dependent performance index, the best location is identified to insert SNFs into the controllers of both rotor‐side and grid‐side converters. Two specific SNF schemes are recommended for practical use, and a design procedure is developed to tune their parameters. As a case study, they are then applied to a practical series‐compensated wind‐farm system that suffered from SSR. Both impedance analysis and time‐domain simulations have been conducted to investigate their performance. The results verified that they can defuse the interaction between DFIG controllers and series compensation; therefore, successfully eliminating the risk of unstable SSR under all possible operating conditions. The proposed SNF schemes are easy to design and implement, robust to changeable operating conditions and would not affect the normal dynamics of DFIGs. So, they are of great potential in addressing practical SSR issues. [ABSTRACT FROM AUTHOR]

Power swing phenomenon occurred during single-pole auto-reclosing (SPAR) period is called asymmetrical power swing. During symmetrical power swing, power swing blocking is used to block distance relay to avoid the selectivity property. Therefore, fault detection is more challenging during asymmetrical power swing since open-pole condition introduces large amount of negative and zero sequence components in voltage and current signals. Further, fault detection during power swing and SPAR prevailed in a series compensated line is more challenging as the metal oxide varistor protecting series capacitor imposes other frequency components. In this paper, a new superimposed negative sequence (NS) current-based technique is proposed to detect the fault incepted in a series compensated line during asymmetrical power swing. The superimposed NS current is calculated using phasor difference between the fault and prefault NS currents. The proposed technique exploits the presence of substantial amount of superimposed NS current during asymmetrical power swing period to detect fault accurately. A summation index is used to declare the fault when it crosses the threshold value. Transient data, obtained from two systems simulated using PSCAD/EMTDC software, are used to test the performance of approach. [ABSTRACT FROM AUTHOR]

Highlights • Line uprating options are a relevant alternative for integrating renewable energies. • No current models for TNEP are able to consider these options simultaneously. • This proposal enables to include line uprating options in the TNEP in a natural way. • Including line uprating in the TNEP enables to achieve more economic expansion plans. • Reducing the number of new lines to be built is another benefit that can be achieved. Abstract The fast construction times of projects based on variable generation technologies (VGTs) such as photovoltaic and wind generation, together with growing difficulties for building new transmission lines due to socio-environmental requirements, have opened new challenges in the development of sustainable power systems. Due to the complexity of the Transmission Network Expansion Planning (TNEP) problem, current models are usually oversimplified and do not always meet the requirements needed for the practical application. Examples of these simplifications are the use of reduced network equivalents, limiting the planning horizon to one or a few years and limiting the expansion options to adding new lines in given corridors. To meet the new challenges and achieve a time-effective increase of the transmission capacity for the integration of VGTs, improved models and algorithms capable of taking into account a higher degree of detail in the TNEP problem are needed. In this article, a novel meta-heuristic multi-year TNEP model based on Ant Colony Optimization (ACO) is presented. One of the main characteristics of the model is that it enables us to consider simultaneously further expansion options such as line reconductoring, voltage uprating, and adding series compensation to lines. We tested the proposed ACO model with the Garver's 6-bus test system and a modified version of the IEEE 118-bus test system, assuming a significant incorporation of VGTs. The results obtained for a 15-year planning task show (i) an excellent performance of the model in terms of quality of the obtained solution and computational times, compared to the traditional MILP approach, and (ii) including line uprating options within the multi-year TNEP brings significant benefits such as reducing the total investment and congestion costs of the system as well as the number of lines to be built. [ABSTRACT FROM AUTHOR]

Abstract Emerging subsynchronous oscillation (SSO) issues in grid-connected wind farms have gained serious attention after several incidents occurred in the US and China. The temporal and spatial variation of wind speed, the diversified converter control structures, and the continuously varying number of in-service wind turbine generators (WTGs) greatly affect the equivalent impedance reflected by the wind farms. Such frequency-dependent equivalent impedance, as indicated by both theoretical analyses and practical experiences, has a huge impact on the mechanism and characteristics of SSO. In this regard, WTGs contribute to a more complicated type of SSO than those in conventional turbo-generators (CTGs). For instance, SSO in practical wind power systems can be triggered without the participation of series compensation in the transmission network. The emerging SSO phenomena observed in practical WTGs are relatively new, and cannot be properly interpreted by existing literature. This work will first review the historical development of SSO definitions and classification by IEEE, followed by discussions on recent incidents in practical wind farms due to the emerging SSO. Subsequently, new terminologies and classification of SSO are proposed with the aim to better understand SSO in large-scale wind integrated power systems. This paper offers a practical insight and a future perspective for the reader to properly deal with SSO associated with wind power systems. Highlights • WTGs associated SSO is different from that of conventional CTGs. • The frequency of WTG-associated SSO is greatly influenced by wind speed, series compensation, WTC controls and parameters. • The SSO mechanism in wind farms is difficult to explain with existing IEEE classification. • New classification of SSO is proposed in which it's classified into torsional, L-C and converter-grid oscillation. [ABSTRACT FROM AUTHOR]

Power Capacitors plays a vital role in reactive power compensation. When the capacitors are connected to the transmission line, it improves the reactive power. Although the reactive power is improved, there is a possibility for sub synchronous resonance created by this capacitors in the transmission line can travel to the generator side. The sub synchronous resonance causes electro-mechanical stress in the generator shaft which ultimately leads to malfunction of the entire system. It is necessary to find out operating modes of the generator and turbine when the line is compensated with capacitors. Once the operating modes are clear, torsion analysis will give the weak points in the turbine generator shaft which is encountered immediately when sub synchronous resonance arises. It is possible to damp the sub synchronous resonance when the weak points are monitored continuously. In this paper, three phase generator is coupled with a prime mover and the line is compensated with the series capacitors. The stress on the turbine is analyzed based on the torque of two rotating machines. Finite element method gives the weak points in the turbine generator shaft system. [ABSTRACT FROM AUTHOR]

Infrastructure reinforcement using high-voltage direct-current (HVDC) links and series compensation has been proposed to boost the power transmission capacity of existing ac grids. However, deployment of series capacitors may lead to subsynchronous resonance (SSR). Besides providing bulk power transfer, voltage source converter (VSC)-based HVDC links can be effectively used to damp SSR. To this end, this paper presents a method for the real-time estimation of the subsynchronous frequency component present in series-compensated transmission lines—key information required for the optimal design of damping controllers. A state-space representation has been formulated and an eigenvalue analysis has been performed to evaluate the impact of a VSC-HVDC link on the torsional modes of nearby connected thermal generation plants. Furthermore, the series-compensated system has been implemented in a real-time digital simulator and connected to a VSC-HVDC scaled-down test-rig to perform hardware-in-the-loop tests. The efficacy and operational performance of the ac/dc network while providing SSR damping is tested through a series of experiments. The proposed estimation and damping method shows a good performance both in time-domain simulations and laboratory experiments. [ABSTRACT FROM AUTHOR]

A dynamic voltage restorer (DVR) can be installed in a middle-voltage (MV) power grid, to concurrently protect a cluster of sensitive loads from voltage sags. To further improve its efficiency and reduce the difficulty in its implementation, a novel control strategy for operating such a DVR as a virtual impedance in series with sensitive loads is proposed in this paper. In addition to its usual function of compensating for voltage sags, such a DVR can also operate as a virtual inductance, to function as a fault current limiter (FCL) during a downstream fault, or a virtual capacitance, to function as a series compensator (SC) to compensate the voltage loss along the feeder line during heavy load. Based on a dual-loop control design, strategies for operating a DVR as a series virtual inductance and a virtual capacitance are proposed, and methods for tuning the parameter values and a stability analysis of the whole system are presented. The feasibility and effectiveness of the proposed method are verified by simulations using the PSCAD software, and experimental results obtained using a prototype DVR are presented. [ABSTRACT FROM AUTHOR]

This paper investigates the modal repulsion happened in the sub-synchronous resonance between a synchronous generator and series-compensated transmission line. The investigation is based on the closed-loop model of the series-compensated power system consisted of the torsional and electrical open-loop subsystems. Analytical explanation is presented to show how the SSO modal repulsion is formed as the result of moving close and apart between two open-loop SSO modes. Analysis is carried out to indicate that the peak of the SSO modal repulsion occurs when the two open-loop SSO modes from the torsional and electrical subsystem are closest to each other on the complex plane, which is referred to as the open-loop modal coupling. Estimation on the peak, i.e., the maximum damping degradation of the SSO modes, is derived in the paper. Subsequently, a method of open-loop modal analysis is proposed. Applications of the proposed method of open-loop modal analysis to study the SSOs caused by the DFIGs under the condition of the modal repulsion in the power system are demonstrated and evaluated by example power systems. The concept of modal repulsion explains why the grid connection of the DFIGs may bring about the SSO instability risk in the power system. [ABSTRACT FROM AUTHOR]

This paper proposes an H ∞ damping controller for the doubly-fed induction generator (DFIG) based wind farm (WF) to mitigate sub-synchronous control interactions (SSCI) with series capacitor compensated lines. A multi-input multi-output (MIMO) uncertain state-space model is developed to reflect the main SSCI characteristics considering the uncertainties of wind speed, series compensation (SC) levels and system parameters. The SSCI is analyzed using the eigenvalue analysis of the uncertain system model. In order to damp the SSCI between the WF and series capacitor compensated lines under uncertainties, an H ∞ damping controller is designed for the rotor side converter (RSC). The weighting functions are designed to meet the mitigation requirements of sub-synchronous oscillation currents and output power. The robust stability (RS) and robust performance (RP) of the system are validated by the µ analysis. The performance of the H ∞ damping controller is demonstrated by time domain simulations of a 90 MW wind farm model with different wind speed, and SC levels. The case study with 6 m/s wind speed and 70% SC level shows superior performance of the H ∞ damping controller. [ABSTRACT FROM AUTHOR]

Subsynchronous resonance (SSR) is a phenomenon in which electrical energy is exchanged between generators and transmission systems below power frequency. It happens due to interaction of a series compensated transmission line with a generator. It results in oscillation in the shaft and power swing. In addition, SSR causes increased magnitudes of voltage and current consequently occurrence of ferroresonance. It is obviously clear that protective relays are affected in such conditions. SSR can be damped by several methods; however, protective relays must be adaptive to prevent mal operation independently. In this paper, Manitoba Hydro electrical network with series capacitor is simulated by PSCAD/EMTDC. The impact of SSR and ferroresonance on operation of overcurrent relay is analyzed. An adaptive algorithm based on subharmonic measurement and ferroresonance analysis in time domain is proposed for overcurrent relay. The algorithm detects SSR and ferroresonance, and changes setting values of the relay to prevent mal operation. Furthermore, it distinguishes protection of the hydro generator against subharmonics, which interact with natural frequencies of the rotor. Finally, the algorithm is examined in SSR condition to certify the correct operation. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel damping controller for subsynchronous resonance (SSR) mitigation using existing 11-kV variable frequency drive interfaced auxiliary power plant loads. The input of the proposed auxiliary damping controller is the turbine output power (Pt) . This is a standard signal that is monitored in power plant control rooms and is available locally without the need for additional measurement and/or communication infrastructure. The auxiliary damping controller (ADC) adds an auxiliary speed signal to the existing speed reference in the closed-loop motor drive control in response to any torsional range oscillations seen in Pt, via a feedback compensator. The ADC extracts damping by exploiting SSR load interactions and is tuned using a residue-based pole placement technique. The ADC performance is evaluated for both torsional interaction and torque amplification types of SSR in the IEEE First Benchmark and IEEE 68-bus networks. The results show that the ADC is effective in providing positive damping to mitigate unstable SSR oscillations under a range of operating conditions. The proposed solution is a simple yet effective means of providing local control of SSR with minimal additional cost. [ABSTRACT FROM PUBLISHER]

Summary: During thunder storms, multilocation faults may occur at different locations in different phases of the 3 phase transmission lines at same or different time. This paper proposes an artificial neural network‐based solution to locate the multilocation faults in double‐circuit series capacitor compensated transmission lines (SCCTLs), unlike previous works that only locate the fault at single location. Although various fault location schemes have been proposed for normal shunt faults occurring at 1 location in SCCTL, nevertheless, finding the locations of multilocation faults in double circuit SCCTL has not been addressed so far. The proposed artificial neural network‐based method determines the location of multilocation faults by using current and voltage signals of 1 end of line only, thus avoiding the need of communication link. The signals are preprocessed by using discrete wavelet transform. A comparative study of various neural networks such as feed‐forward back‐propagation network with Levenberg‐Marquardt algorithm, Elman recurrent neural network with gradient descent algorithm, radial basis function neural network has been carried out. The proposed method is not affected by variation in different parameters viz. fault type, fault location, fault inception angle, fault resistance, degree of series compensation, and location of series capacitor. The key advantage of the method is that it correctly estimates the locations of multilocation faults as well as single‐location fault, thus making it more reliable and accurate as compared to conventional fault location schemes. [ABSTRACT FROM AUTHOR]

• A PV farm installed close to a wind farm is shown to effectively damp SSO. • Reactance crossover and the Nyquist criterion are used to analyze the risk of SSO. • Instabilities predicted by the two methods are validated with EMT simulations. • Both methods are able to predict SSO. • The Nyquist criterion performs better regarding estimating oscillation frequencies. As more power electronics are introduced into the power system, its stability is impacted, e.g., through undesired interactions. One such interaction is called sub-synchronous control interaction (SSCI), an example being an interaction between a DFIG wind farm and a series compensated line. In this paper, two methods are used to assess the risk of SSCI: the reactance crossover method, and the Nyquist criterion. The analysis is performed on three case studies: one system based on the IEEE First Benchmark System, and the other system is modelled as a typical Swedish transmission system with two different degrees of series compensation. Both methods predict SSCI in all three case studies, with the Nyquist criterion being able to predict the oscillation frequency more accurately. To mitigate the sub-synchronous oscillations, a PV farm is implemented and placed in parallel to the wind farm. The performed simulations show that it is able to damp the oscillations successfully in all case studies. [ABSTRACT FROM AUTHOR]

Locating a fault in a series-capacitor-compensated transmission line (SCCTL) is a challenging task due to the action of a metal-oxide varistor a nonlinear element present as a part of the protection system of the series capacitor. In this paper, an accurate fault-location algorithm that uses synchronized measurements from both ends of the SCCTL is presented which provides fault-location results without using the model of MOV or natural fault loop for single-phase-to-ground, and double-phase-to-ground faults. Another salient feature of the proposed technique is that the subroutines for locating faults in different sections transmission line yield almost identical fault-location results regardless of which section the transmission line is faulted. The proposed technique could also be extended to the double-circuit transmission lines. First, the proposed technique is introduced and its features are elaborated through detailed mathematical analysis. Thereafter, a 500-\textkV system with an SCCTL is designed in PSCAD, while the fault-location algorithm is modeled in MATLAB. The proposed algorithm is tested through simulations covering various fault scenarios in an SCCTL. For performance evaluation, the comparative analysis of the proposed technique with a well-known existing technique is performed in this paper. [ABSTRACT FROM PUBLISHER]

A new two-terminal fault-location algorithm for series-compensated double-circuit transmission lines based on the distributed parameter line model is proposed. The system is considered as fully transposed, and a six-sequence component network is introduced to decouple the mutual electromagnetic effects between circuits. Two subroutines designated for the fault that occurs on the left or right side of the series compensator are developed. In each subroutine, the voltage of the series-compensated device is eliminated based on the fact that the sequence voltages calculated from two sides are equal at the fault point. The fault-location function is constructed by utilizing the feature in which the transition resistance is purely resistant at the fault point. The proposed algorithm does not rely on the equivalent model of a series-compensated device. Moreover, it does not require the fault type to be known, and there are no fault-location identification and pseudoroot elimination problems. PSCAD is employed to generate numerous fault cases in diverse conditions and the high accuracy of the proposed fault-location algorithm is validated in MATLAB. [ABSTRACT FROM AUTHOR]