Search

This paper presents a Monte Carlo method to solve the Optimal Coordination of Directional Over-Current Protections (OC-DOCP) considering transient configurations and all the possible Fault Locations (FLs). Previous methods cannot guarantee complete selectivity because they do not consider all the possible FLs. In the proposed method, near-end, and far-end faults are complemented by additional FLs, which are chosen from many randomly generated candidates (Monte Carlo method). Each FL candidate is included in the set of constraints at once to solve an OC-DOCP, whose results are the inputs for a simulator that assesses speed and selectivity indexes considering all the possible FLs. Thus, the FL with the maximum selectivity index is chosen to remain in the set of constraints for the next steps in an iterative procedure that finishes when the specified level of selectivity is reached. From the first iteration, the selectivity index obtained with the proposed method is substantially better than those obtained with the optimal solution of previous methods. The selectivity index is increased successively until it reaches practically 100%, without the need of including all the FLs in the set of constraints. Furthermore, an important improvement in the selectivity index is obtained without a significant worsening of the protection speed. The fact of solving many small optimization problems is an attractive feature of this method because facilitates the possibility of applying parallel computing to this problem. • Previous coordination methods consider few fault locations in the optimization model. • Optimal coordination with few locations does not guarantee complete selectivity. • The consideration of all fault locations in the model is computationally burdensome. • Monte Carlo is used to select a reduced set of locations that assure maximum selectivity. • A comparison with two existing solutions over the same case study is carried out. [ABSTRACT FROM AUTHOR]

In bulk power systems, the majority of interaction between cyber and physical components takes place in substations. However, in most of the cyber–physical power system models the physical layer is typically done using the bus-branch (BB) model, where each substation is considered as a single node. This approach will not capture the details of the cyber layer. This paper proposes a framework to model the substations using node-breaker (NB) models for physical system representation so that the detailed station configurations, the current and the voltage transformer positions, arrangements of protective relays, bay control units and associated communication infrastructure within the substations and its dependencies on the physical elements can be captured effectively using a single cyber–physical graph. Keeping a transmission system operator in view, who does not use power flow and security assessment tools for station operations and maintenance, a vulnerability assessment approach is proposed to assess the risk using some representative attack scenarios. The proposed approach is demonstrated using WECC 3-machine system for breaker and half station configuration. The attack scenarios are developed based on the real substation configuration and the adversary's ability to understand the substation protection and BI/BO operations. • A framework to model detailed substation configurations as a cyber–physical graph. • Impact factors are proposed for assessing the consequence of cyber attack for TSOs. • Two attack models are discussed considering adversary's knowledge on the protection. • Proposed framework is implemented on WECC 3-machine system and results are presented. • Importance of securing IED placement info and of programmable BI/BO are highlighted. [ABSTRACT FROM AUTHOR]

Modeling protection devices in the Transient Stability Assessment (TSA) of power systems results in an accurate estimation of system stability and behavior. Miscoordination/misoperations of the relays and circuit breakers (CBs) result in higher order contingencies, > N − 1. Substation (SS) configurations and associated CB operations are usually ignored in TSA, even though the relays are modeled in detail. Replicating such scenarios needs manual fabrications in Bus-Branch (BB) models used in commercial TSA tools, which can be eliminated using Node-Breaker (NB) models. Also, incorporating relay algorithms, including the realistic CB operations and coordinating their timings, increases the complexity of the TSA code for large systems. The development of TSA tools to simulate the practical operation of CBs due to protective relay decisions similar to the physical substation operation is essential. This paper attempts in this direction. This paper uses a systematic approach to convert BB models to NB models. The Sparse Tableau Approach (STA) is used to represent the system in the NB model. It provides an algorithmic approach for automatically placing differential, distance and under/over frequency relays. It also gives programming logic to coordinate the timings between relays and the associated CBs. The program complexity increases with the size of the system as the number of CBs and the associated timers significantly increase based on the station configuration. The simulation results demonstrate the scalability and effectiveness of the proposed framework for the WECC 9 bus, New England 39 bus, and Polish 2383 bus systems. The WECC 9 bus system results are compared and validated with the commercial software PSS®E. • Transient Stability Analysis using Node-Breaker models, including relays and CB operations. • Automatic population of relays, associate CBs, and timers in substation configurations. • Time coordination between the simulation time step, relay trip time, and the CB operating time. • A comparison of the proposed framework for the WECC 9 bus system with PSS®E. • Case studies demonstrating the flexibility and scalability of the proposed framework. [ABSTRACT FROM AUTHOR]

• A new protection methodology based on current-voltage characteristics. • Optimal OCR coordination under smart inverter control strategies. • Comparative analysis through the influence of diverse control techniques. The integration of distributed generation (DG) based on inverters into power systems has increased significantly, necessitating a thorough understanding of its impact on fault analysis and the performance of distribution networks' protection mechanisms. This study addresses this issue by examining how various inverter management modes influence protective relay systems within IEEE 9-bus redial and mesh networks, CIGRE and IEEE 33-bus networks featuring Photovoltaic (PV) farms and Battery Energy Storage Systems (BESS), by IEEE1547–2018 and German grid code standards. By analyzing grid-connected scenarios with five distinct PV control modes, the research introduces a novel protection methodology termed the Photovoltaic Overcurrent Relay (PVOCR). This method introduces a current-voltage characteristic to optimally coordinate Overcurrent Relays (OCRs), aiming to reduce their operational time and eliminate mis-coordination events. The proposed PVOCR is evaluated against standard inverse time, SOCR, and modern adaptive voltage, VOCR, relay schemes across various fault scenarios differing in type and location. Furthermore, the PVOCR scheme effectively operates across all PV inverter modes without experiencing miscoordination events, whereas the SOCR and VOCR schemes encountered such issues during the operation of Control 4. These results underscore the potential utility of the PVOCR methodology in enhancing the reliability and efficiency of protection systems in inverter-based DG networks. [ABSTRACT FROM AUTHOR]

• Protection for inverter-based resources (IBRs) based systems has many challenges. • Developed superimposed quantity-based protection elements for a system with IBRs. • Protection elements are tested in a modified IEEE 9-bus system. • Evaluated system resilience with various maximum current limits in PV controllers. The increasing penetration of inverter-based resources (IBRs) to the power grid brings challenges to protection systems. IBRs may not provide sufficient fault current to trip protective relays, leading to delays in fault isolation and increased risk of equipment damage. To overcome the challenges, superimposed quantity-based elements are developed in this paper for transmission line protection in a power grid with IBRs. The characteristics of the designed protection system are tested under fault conditions in a modified IEEE 9-bus system that includes solar photovoltaic (PV) generation, and evaluated with different maximum current limits in solar PV controllers. The applied method in this paper makes contribution to the protection application for IBR-penetrated transmission systems. Simulation results show that the modeled protection system works effectively with different penetration of solar PV, and the system resilience is enhanced under fault conditions considering the tripping response and reclosing of circuit breakers. [ABSTRACT FROM AUTHOR]

• The complex magnitude-phase plane (MPP) of the fault detection index (FDI), is verified as a key indicator for fault detection in microgrid. • The magnitude and angle of the FDI is used to develope the proposed protective relaying logic. • The relaying scheme is extensively evaluated for variations in fault types, fault locations, fault resistances and distributed generation (DG) penetrations in grid-connected (GC) and non-grid-connected (NGC) modes of operation. • The algorithm is initially tested on MATLAB/Simulink platform and validated on Typhoon HIL platform to assess the real-time performance. • The test results and response time show promising performance in detecting faults. The paper introduces a novel protective relaying method using symmetrical components of current to detect asymmetrical faults in microgrid. This approach is focused on utilizing the complex magnitude-phase plane (MPP) of the fault detection index (FDI), which is computed using the positive and negative sequence components of the current signal retrieved at one end of the faulty line. The MPP obtained from the settling values of the FDI's magnitude (MFDI) and FDI's angle (AFDI) after the fault inception, is considered as the key indicator for fault detection. The scheme is comprehensively evaluated for a wide range of fault situations including variations in fault types, fault locations, fault resistances and DG penetrations in grid-connected (GC) and non-grid-connected (NGC) modes of operation. Several critical no fault cases are also tested to show the efficacy of the proposed logic for false operation. The fault study is conducted extensively on a modified low voltage standard Consortium for Electric Reliability Technology Solutions (CERTS) microgrid and a standard IEEE-34 bus distribution system including DGs. Furthermore, the proposed FDI-based scheme is tested on MATLAB/Simulink platform and validated on Typhoon HIL platform to assess the real-time performance. The test results show that this FDI-based scheme using the MPP concept can be a potent solution for the protection of microgrid. [ABSTRACT FROM AUTHOR]

• Detailed modeling of CIGRE-14 bus standard test system along with inverter control scheme (with and without grid code) and protection system is done in PSCAD environment. • The performance of directional relaying schemes (32Q and 67pos,67neg,67zero) are evaluated in the presence of inverter-interfaced renewable energy resources. A comparative study on the performance of the relays is done in the presence of inverter-interfaced renewable energy resources for different fault types and fault resistances. • The interdependencies between the inverter control scheme used and performance of relaying schemes have been analyzed through mathematical analysis and circuit realization of the inverter-interfaced renewable energy resources. • Based on the mathematical analysis and circuit realization, the probable causes of relay failures in the presence of inverter-interfaced renewable energy resources are detailed. • The impact analysis of the dynamic response of the controller on the protective relay settings from the perspective of protection operation time-frame has been attempted. The potential impacts of the inverter-interfaced renewable energy resources (IIRERs) on the performance of sequence-based directional relaying schemes (SBDRS) have been investigated in this paper. The directional overcurrent relays such as 67 POS , 67 NEG , 67 ZERO and 32Q have been considered for the investigation. CIGRE-14 bus system with IIRERs along with detailed modeling of inverter control scheme (with and without grid codes) and SBDRS have been done in the PSCAD environment. The mathematical analysis and circuit realization of the IIRERs have been attempted in the paper. The exclusive fault characteristics exhibited by IIRERs cause the conventional SBDRS to mal-operate. Significant change in levels of sequence currents and angular relationships between sequence voltages and currents during faults contributes to relay's unpredictable behavior. The comparative study based on different fault types, fault resistances and interconnecting transformer connections have also been done. The study reveals the impact of non-generalized angular differences between positive sequence voltage and current at the inverter terminal on performance of 67 POS. It is found that 67 NEG and 32Q mal-operated for all types of unbalanced faults while the 67 ZERO can be utilized for grounded fault with delta-star grounded connection of interconnecting transformer. [ABSTRACT FROM AUTHOR]

• An innovative optimal dual-setting protection scheme is established to handle modern protection system challenges. • Reducing the number of healthy line outages (energy not supplied). • Reducing the total trip time is achieved without any miscoordination. Nowadays, the capacity of Distributed Generation (DG) in the power network is increasing, which increases the challenges and complexity of having a fast and reliable power protection system. Several studies on microgrid protection have been conducted, including advances in overcurrent relays (OCRs) and dual-setting protection schemes. However, there is a gap in the literature on developing an innovative protection scheme with dual-setting for directional or non-directional overcurrent relays, taking into account the limitations of the standard tripping characteristics, OCRs coordination problem due to the stochastic behaviour of DG, and the high energy not supplied because of the setting of primary and backup protective relays. This work aims to fill this gap by developing a novel optimal dual-setting protection scheme based on the nonstandard tripping characteristics of overcurrent relays for highly sensitive and reliable microgrid protection. The proposed dual-setting scheme takes advantage of modern communications techniques to provide high reliability and security and reduce unnecessary feeder outages. In addition, the dual-setting OCRs coordination problem is formulated as an optimization problem and solved by the Water Cycle Algorithm (WCA) to find the optimal relay setting to achieve the minimum overall tripping time of OCRs. The proposed innovative optimal dual-setting protection scheme is compared with conventional OCRs and the dual-setting approach. The effectiveness of the proposed scheme is analysed and investigated on the IEEE-9 and 30 Bus systems equipped with photovoltaic (PV) energy and inverter-based DG under different fault scenarios and grid operation modes. The proposed approach successfully achieved 100% power continuity without any cases of energy not being supplied at different fault locations and recorded a 46.2% reduction in the total tripping time compared to conventional approaches, which will help to increase the stability of the power grid. [ABSTRACT FROM AUTHOR]

Digital fault recorders (DFRs) and some conventional relays operate typically with sampling frequencies up to a few kHz. Conversely, traveling wave (TW)-based methods are usually designed to operate at sampling frequencies in the order of MHz. However, this paper demonstrates that two-terminal TW-based protection that considers the effects of the sampling frequency and TW propagation velocity uncertainties can protect transmission lines using sampling frequencies of a few kHz instead of MHz. This demonstration considers a performance validation based on challenging real-world faults recorded in transmission lines equipped with DFRs operating with a sampling frequency of 15,360 Hz. The low-sampling frequency two-terminal TW protection was implemented in hardware as a protective relay to evaluate actual data in real-time analysis, representing a significant step toward the practical application of the TW concept readily available in real protection devices with a low-sampling frequency. • Traveling wave (TW)-based protection has been used in electrical systems. • Two-terminal traveling wave (TW)-based protection functions can also be used with low-sampling rates. • Consideration of the sampling rate effect results in the protection zones. • Performance assessment with actual faults of a Brazilian transmission system. • The results obtained demonstrate the reliability of the proposed method. • The proposed algorithm can be used in existing systems with low sampling rates. [ABSTRACT FROM AUTHOR]

• This paper proposes a non-unit coordinated protection method for MMC HVDC grids, which rapidly response to severe faults and apply a 3-ms decision-making time window to deal with high-resistance faults. • Coordination between the protective relays at different points of the system is evaluated comprehensively. • Equipped with various fault detection criteria, the proposed protection method distinguishes internal faults at any location along the line up to 700 Ω. • The proposed protection method is able to interrupt fault currents under 6 ms and avoid converter blocking phenomenon. Designing a robust protection system to meet the speed, sensitivity and selectivity targets of MMC HVDC transmission lines is a challenging task. To fulfil these requirements, a non-unit protection method based on coordinated operation of the system protective relays is proposed in this paper. The proposed method employs a criterion based on DC power variation to satisfy the required speed and sensitivity in fault detection. To improve the selectivity in high-resistance fault identification, a coordinated protection method based on analysing the severity of faults and using a 3-ms decision-making time window is proposed, which consists of inner-terminal and between-terminal cooperative action of the system's protective relays. The fault severity evaluation is performed based on overcurrent characteristic of the converter discharging current, which is further used to provide a fast response for severe faults or a delayed response for high-resistance faults. Performance of the proposed coordinated protection method is evaluated on a multi-terminal MMC HVDC system, simulated in PSCAD/EMTDC software environment. The simulation results show that the proposed coordinated protection method is capable of fulfilling the speed, sensitivity and selectivity requirements of MMC HVDC transmission lines, while maintaining a robust performance under external faults. [ABSTRACT FROM AUTHOR]

Faults and maneuvers in the system may trigger undesirable voltage and current waveforms of nonfundamental frequency that may affect the performance of protection and control systems. In this context, the proposed method aims to improve the characteristic of filtering out undesirable frequency components of signals. Comparisons are made in relation to time response and frequency response for the proposed method and four classical phasor estimation methods. A distance relay was implemented by using the MODELS language of the ATP (Alternative Transients Program) in order to evaluate the relay performance. As expected, for the proposed method, the relay exhibited good performance in terms of accuracy. In terms of relay speed, the method showed a performance comparable to that of the other methods. Theoretically, the phasor estimation proposed method here has a better frequency response than those of the four used methods. Besides, it has a response time fully compatible with these methods. Another advantage of the proposed method is that it can be easily programmed, allowing users to change design parameters according to their needs. [ABSTRACT FROM AUTHOR]

• The offset mho characteristics (OMC) for forward and reverse faults are different from each other. • An experimental method to obtain both OMC was not available. • The experimental method to obtain both OMC was developed and successfully tested. • All the points of both OMC can be experimentally tested. • The method does not depend on any power system taken as example, which is an excellent advantage. This article presents a novel experimental method to obtain the offset mho characteristic of memory-polarized and cross-polarized distance functions of protective relays. A proper testing method for these characteristics is not obvious because the offset impedance depends on power system conditions. In the developed method, a constant value of offset impedance is selected by the user, and the voltages and currents during the test satisfy the theoretical conditions for that offset impedance. All the points of the offset mho characteristics can be obtained using this method. The offset impedance is typically in the third quadrant for forward faults, and in the first quadrant for reverse faults. Both cases were tested, taking three relays from different manufacturers as examples. The experimental loci of the offset mho characteristic for reverse faults had not been previously obtained in the literature about this topic. Three options for performing the tests are described: with constant test current, with constant fault voltage, or with constant polarizing voltage. A discussion about some details of the relays under test is included, since those details should be known in order to perform properly the tests and/or the analysis of results. In general, the experimentally obtained loci are in concordance with the theoretical loci. The developed method does not depend on any model for the power system since it is directly oriented to the relay itself, and this fact is an excellent advantage of this method. [ABSTRACT FROM AUTHOR]

• Optimal adaptive protection, considering the limits on the number of setting groups. • Using the DS-DOCRs incorporating independent changes in the setting groups. • Optimal relay curve types and breakpoints for the DS-DOCRs. • Fast protection without selectivity constraint violations in various configurations. • Around 41.66% improvement compared to available studies. Several studies, such as adaptive protection schemes, have been done in the area of smart grids' protection. However, there is a research gap in developing an adaptive scheme with dual-setting (DS) directional overcurrent relays (DOCRs), considering the limitations of the number of setting groups of protective relays. This research aims to fill such a research gap. Optimizing the relay curve types of the first and second parts of the DS relay models and breakpoints (BPs) improves the speed of the protection scheme based on independent changes in the setting groups of DOCRs. Also, there is no coordination constraint violation in various configurations by applying the proposed method, while it requires only a limited number of setting groups. Therefore, the proposed method can be practical in actual systems because the suggested solutions and protective settings can be easily implemented using commercial relays. The proposed adaptive protection scheme is applied to two test systems (the distribution networks of the IEEE 14-bus and IEEE 30-bus test systems). The comparative test results infer that significant improvement in the speed of the protection system of smart grids can be achieved compared to available studies by the proposed method. [ABSTRACT FROM AUTHOR]

Major disturbances in power system can take place after power system elements such as generators, loads, or transmission lines are suddenly disconnected. Such disturbances can create so called “electromechanical wave oscillations” waves which propagate through transmission lines at much lower speed than speed of light. They can cause adverse effect on power system protective relays. In this paper, electromechanical wave oscillation propagation is modeled, and its impact on different power system protective relays, such as overcurrent, distance, and out-of-step relays is studied. Modified protection schemes are presented for each protective device to avoid their malfunction under effects of electromechanical wave oscillations. The electromechanical model adopted in this study considers the dynamics of generator mechanical shaft as well as conversion of mechanical power to electrical. Simulations used for testing of the improved protection solutions are carried out in MATLAB considering 64-bus generator ring system and IEEE 118-bus system. [ABSTRACT FROM AUTHOR]

• Occurrence of ferroresonance in utility system. • Impact of ferroresonance in utility system on operation of DFIG and overcurrent relay in smart grid. • Intelligent algorithm based on wavelet transform, neural network and ferroresonance analysis. Smart grid comprises utility system and renewable resources including wind farm and solar system. It causes bidirectional flowing of power especially in distribution level, and establishing communication facility amongst utility system, distributed generations (DG), and loads. In this study, influence of occurrence of ferroresonance in the utility system is investigated on technical quantities of DFIG and operation of directional overcurrent (DOC) relay installed in wind farm is assessed by means of PSCAD/EMTDC simulation software. Smart grid stand in need of a self-healing protection; therefore, an adaptive algorithm on the basis of neural network and signal analysis tools like, wavelet transform, moreover, analysis of ferroresonance in time domain is designated for overcurrent relay. The relay with new algorithm can conform to protection strategy of smart grid. It discriminates ferroresonance from other nonlinear and transient abnormalities, which affect deviation of electrical quantities. Protection strategy established in smart grid decides on behaviour of the relay through the algorithm. It takes an appropriate decision in ferroresonant states to modify setting quantities of the relay and changes direction of operation to enhance reliability and availability of power electricity in smart grid. The relay is capable of predicting ferroresonance in the network to fulfil smart grid requirements. [ABSTRACT FROM AUTHOR]

■ Fault detection, classification and location based on traveling wave. ■ Lightning and fault classification with current traveling wave. ■ Ultra high speed protection of double circuit transmission line using wavelet transform. ■ Very fast algorithm for fault classification of parallel transmission line with single phase tripping. ■ Traveling wave protection of transmission line. The injection or absorption of reactive power by the static synchronous compensator (STATCOM) may lead to the misoperation of protective relays and single-phase-tripping systems that operate based on impedance measurement. Also, high-frequency harmonic components caused by switching the internal circuitry of a STATCOM lead to unintended tripping of relays that work based on traveling waves. This paper proposes a single-terminal approach to detect, locate, and identify the faulty line(s) and phase(s) in parallel transmission lines equipped with STATCOMs using traveling waves. To that end, these processes were designed so that adding a STATCOM or different operating modes does not degrade their efficiency and accuracy. The faults and faulty phases were simultaneously detected using the first set of traveling waves received at the sending end of the parallel lines at a sampling frequency of 200 kHz. Furthermore, a sampling frequency of 1 MHz was used briefly to improve the fault location accuracy. The discrete wavelet transform (with BD4 mother wavelet) was adopted to extract the traveling waves. All simulations and analyses were conducted in the PSCAD environment. The results obtained from numerous simulations at different places and states of the networks verified the high accuracy and validity of the proposed methods. [ABSTRACT FROM AUTHOR]

• The summation of the accumulated difference of residual voltage is used for discriminating HIF from any other no-fault events. • DWT analysis is used to compute the wavelet features. • The wavelet features are fed to the decision tree to classify the fault event and the faulty zone. • The proposed method is also validated for unbalanced loading, varying the DG parameter and distribution line length, and the addition of noise. • The performance indicators such as accuracy, precision, recall, F-measure of the method are compared with other classifiers like SVM, KNN, and ensemble classifiers. Conventional overcurrent protective relay is unable to detect high impedance faults (HIFs) in the micro-grid system owing to the reduced levels of fault magnitude. In this paper, numerous fault detection methods are discussed for developing a technique to identify HIFs, and also three steps approach of summation of accumulated difference of residual voltage, discrete wavelet transform (DWT), and decision tree(DT) approach has been used to detect and classify the fault. It also differentiates the faulty events from the various non-faulty ones such as switching of generators, capacitors, loads, etc. The residual voltage is used for the extraction of wavelet coefficients by DWT and fed to a DT classifier for fault event classification and confusion matrix created to view the accuracy. After classification, the predicted fault and the actual fault are obtained subsequently by training the data is 99.5% true positive rate and 0.5% false-negative rate. Similarly, this approach is also applied for faulty zone and non-faulty zone classification. The accuracy of the technique is analyzed with other classifiers like support vector machine(SVM), k-nearest neighbor(KNN), and ensemble classifiers. The DT classifier yields more accurate results compared to other classifiers. The proposed method performance is further evaluated by taking different performance indicators such as precision, recall, and F-measure. The proposed technique gives an overall accuracy of 99.95%, precision index of 100%, recall index of 99.9%, and F-measure index of 99.94% as compared to other classifiers under normal operation. The proposed method is also validated with unbalanced loading, varying DG parameters, varying distribution line length, and the addition of noise in the signal. To implement and demonstrate this method, a 5 bus micro-grid system integrated with a wind turbine-based system(WTS) generator is simulated using Power System Computer-Aided Design (PSCAD) software. [ABSTRACT FROM AUTHOR]

• Data-driven approach proposed to bridge power system protection gaps. • Deep learning applied to complement traditional protection technologies. • Transfer learning adopted to address the data limitation problem in practice. Protection is a critical function in power systems to avoid equipment damage, maintain personnel safety, and support system reliability. The existing protection technology that mainly relies on protective relays is not capable of providing 100% protection for all system events. Whenever protective relays fail to respond or respond incorrectly, it leads to the protection gap. In this paper, a new data-driven approach is proposed to complement the traditional protection technology so that the faulty conditions can be adequately distinguished from the transients resulted from normal operations. The proposed approach combines convolutional neural network and long short-term memory (CNN-LSTM) to develop a deep neural network that achieves the invariance in data translation and captures the temporal correlation of input data in time series. It can accurately detect the system faults with the variations and noises in the input data. The use of CNN-LSTM eliminates the complicated and often manual feature extraction procedure that is commonly required by conventional data-driven approaches. In order to address the issue of insufficient training data in practice, a transfer learning method is also applied to facilitate the future practical applications. The efficacy of the proposed data-driven approach is tested for the protection gaps with respect to the transmission line high-impedance fault and transformer inter-turn fault, respectively. The extensive study results demonstrate that the proposed approach can effectively bridge the protection gaps in power system operations. [ABSTRACT FROM AUTHOR]

• The proposed TKEO and XGBoost based scheme provides all protective functions of relaying task namely fault detection, fault classification, faulty phase identification and fault location estimation. • The proposed scheme is suitable for detection of both HIF and LIF. • XGBoost classifier and regression modules have been designed for fault detection, classification, and location estimation respectively. • The proposed scheme based on TKEO and XGBoost based scheme has been tested for IEEE 14 bus system. The study presented in the paper aims to reduce the relaying time associated with detection and classification of fault along with accurate fault location estimation with the help of Teager Kaiser energy operator (TKEO) and extreme gradient boost (XGBoost) algorithm. The complete analysis has been conducted on IEEE 14 Bus transmission network. Four XGBoost modules corresponding to each phase have been developed for fault detection, classification, and similarly four regression modules are developed for fault location estimation depending on the type of fault. The proposed methodology is able to precisely determine the fault, locate it and also recognize the faulty phase(s). Special attention has been paid in determining the high impedance fault (HIF) apart from usual low impedance faults (LIF) while varying the fault parameters such as evolving nature of faults, fault inception angle, power flow angle and change in transmission line parameters etc. Voltage and current measurements recorded at the relay location are utilized. Moreover, the proposed XGBoost algorithm-based approach is able to detect and classify faults in around 1–2 ms time. The absolute error in fault location is around 0–2 km in most of the scenarios. A comparative study clearly states the merits of the proposed scheme. [ABSTRACT FROM AUTHOR]

This paper proposes a simple, accurate and non-iterative fault location scheme for series and shunt compensated transmission lines. The proposed algorithm utilizes unsynchronized measurements from the two ends of a transmission line and the monitoring system if a fixed series compensation (FSC) device is installed. Data synchronization is carried out using post-fault data samples to increase the accuracy. The proposed algorithm is independent of the reference bus selection and is extensively tested for all major fault types and fault resistance variations. The results prove that the proposed algorithm yields accurate estimate of fault location. [ABSTRACT FROM AUTHOR]

Highlights: [•] Prony method is proposed as a digital filter to obtain a better estimate of fundamental frequency phasors in distance relays. [•] Prony method is implemented as a filtering technique as a solution of the apparent impedance measurement error. [•] Impact in the fundamental frequency phasor estimates due to non-filtered frequencies in common digital filters is presented. [•] A simplified model of a wind power plant is presented to perform transmission line protection analysis. [•] Simulated and real fault event are presented to confirm that subharmonics/interharmonics are generated by wind power plants. [ABSTRACT FROM AUTHOR]

• Optimal coordination of the DOCRs in DN integrated with DGs by multi-objective optimization technique (WOA). • Restore the DOCRs coordination in the DNs based on minimum impedance FCLs and WOA. • Minimum number and optimal locations of adaptive relays to minimize FCL impedance. • Minimize the adaptive relay replacement cost on the total protection system cost. Integrating DGs in Distribution Networks (DNs) leads to miscoordination problems in Directional Overcurrent Relays (DOCRs). Optimization techniques and Fault Current Limiters (FCLs) are methods applied for restoring the coordination between protective relays. This paper proposes a new approach to solve the miscoordination problem between the DOCRs caused by the DGs into a looped DN. The Whale Optimization Algorithm (WOA) is used to obtain the optimum values of the pickup currents (Ip), and Time Dial Setting (TDS) of the DOCRs. The approach is applied to overcome the DOCRs miscoordination problem in the case of connecting FCL in series with the DG integrated with DN. The approach computes the minimum impedance value of FCL needed to be installed in series with the DGs to restore the DOCRs coordination. In the case of DN implies adaptive relays, the approach is modified to achieve the optimum combination between the FCL impedance values and the number and locations of adaptive relays to restore the coordination of the DOCRs at a minimum cost. The proposed and modified approaches are tested on 9-bus looped DN connected to DGs at different buses to prove their applicability. Moreover, several simulations are implemented to test the proposed methods for different fault locations. [ABSTRACT FROM AUTHOR]

• Non-unit protection of STATCOM-compensated lines irrespective of compensation mode and level. • Taylor series based detection index using current signal to detect faults. • Accurate identification and discrimination of fault and non-fault events. • Adaptive threshold technique immune to power system structure. • The executional burden time is near about 5 ms. In the presence of nonlinear response created by power electronics-based compensators, reliable fault detection and classification by distance protection relays is a major concern. The static synchronous compensator (STATCOM) has dynamic characteristics that causes stability and protection issues. A Taylor Series-based strategy is proposed for addressing this issue. A detection index computed using Taylor Series and adaptive thresholding technique is employed such that unerring fault detection is achieved wherein faulty phases of a shunt compensated transmission line are well pointed out. Various fault and non-fault cases considering critical power system conditions are analysed for power systems with varying configurations modelled using EMTDC/PSCAD. A comparison of the current detection method to recently proposed techniques reveals the benefits and feasibility of the presented detection strategy, which has been proved to be accurate and efficient. [ABSTRACT FROM AUTHOR]

The protection of active distribution networks incorporating microgrids with high penetration of Distributed Energy Resources (DERs) can be challenging if traditional protective relays are used. This is mainly due to the changes in the power flow, fault current level, difficulty in protection coordination, changes in system topology, and system operating conditions. This paper proposes three new protection algorithms for active distribution networks with large penetration level of inverter-based DERs. These protection algorithms comprise of an adaptive differential protection algorithm, incremental transient energy-based directional protection, and a rate-of-change of current protection. The proposed protection algorithms were tested with a distribution network integrated with wind, solar, diesel generator, and battery storage DERs which are capable of operating in islanded mode forming local microgrids. The distribution system and the proposed protection functions modelled and simulated using the Real-Time Digital Simulator (RTDS®). The results obtained from tests validate the proposed algorithms; and their capability to correctly detect and timely isolate faults without resulting in nuisance tripping of the DERs. [ABSTRACT FROM AUTHOR]

• It has been Mathematically proven that, due to the use of the rate of change of fault current signal, the proposed index has very little sensitivity to the decaying DC component. • Unlike previous methods, the proposed index does not suffer from voltage-drop issues for fault near the directional algorithm. • In the proposed index, a half-cycle moving average indicator is employed and as a result, the presence of the proposed index reduces the sensitivity of the algorithm to noise. • Comparing to the state-of-the-art algorithms, the proposed method requires a low sampling rate. Also, low-complexity. The proliferation of Distributed Generations (DGs) in distribution networks has provided power system operation improvement while raising some protection challenges. Turning to bi-directional, the protection schemes of the deregulated distribution networks should be able to deal with an out-of-zone fault. More specifically, DGs impose bi-directional fault current and directional relay should be employed to identify correct fault direction so that the protective relays are prevented from mal-operation of out-of-zone fault. This paper introduces a current-based directional algorithm that utilizes a pre-fault current signal as the reference. This algorithm is designed based on the pre-fault current and rate of change of the fault current. As it can be inferred from the mathematical basis of the proposed method, it has low sensitivity to decaying DC and noise components. Also, the proposed index has a certain and straightforward range of variation between (-1, 1) for backward and forward fault direction, respectively. The performance of the proposed algorithm is evaluated for different scenarios such as variation of fault resistance, sampling frequency, and types of faults in three simulated systems and a laboratory test bench. The simulation and experimental evaluation results show the accuracy and speed of the proposed algorithm in comparison with similar algorithms. [ABSTRACT FROM AUTHOR]

Abstract: In the liberalized energy market scenario protective relays play an important role in assuring continuous service in the power system where a malfunctioning could lead to serious damages to a wide number of operators having access to the power system. Considering that power lines are operated many times below a rated load current, in this paper an adaptive procedure is presented in order to manage power distribution systems according to dependability or security requirements. In particular, a procedure to obtain an inverse time trip curve by means of a microprocessor, connected to a relay, is presented. The procedure adapts the trip characteristic depending on the conductor temperature, wind speed, emissivity and solar absorbity and is implemented on a microprocessor Rabbit 2200 considering a Drake conductor, 795 kcmil 26/7 ACSR. [Copyright &y& Elsevier]

Abstract: Voltage and current signals used in protection devices may contain harmonics and decaying dc offset in transient states. Because of this, protection devices must contain filters to remove the part of the signal which is not of interest and estimate the value of the component or components which are to be used for protection functions. Traditionally, the discrete Fourier transform (DFT) filter has been used in digital protection devices. This filter has the advantage of being easily applied, but the disadvantage that when an exponentially decaying component is present the results obtained are incorrect. Because of this, different algorithms based on the DFT have been developed in order to remove the decaying dc offset and reduce digital processing errors. This paper describes a new method for removing the exponential component associated with electrical signals in transient states. Its ease of application results in a low computational load as compared with other methods. This characteristic, together with the accuracy of results, makes this new method suitable for application in real time on protection devices. [Copyright &y& Elsevier]

This paper presents a new Wavelet-based fault classification technique that utilises the HF components confined to scale-8 (level-3) of Wavelet analysis of the three line currents in transmission line. Data window required for the algorithm is small (less than half power frequency cycle based on 1.0 kHz sampling rate). In the paper firstly the theoretical background is reported and briefly discussed in relation to reference ‘IEEE, T&D Conf. (2001)’. Then, an extended study is conducted, and the proposed method is described in detail. Finally, some case studies are examined using the emtp and matlab softwares in order to highlight the performance of the method. It is proved that the proposed technique is reliable and appropriate for real-time measurement algorithms and fault classification techniques. [Copyright &y& Elsevier]

• Accurately reconstructs the instrumentation channel primary quantity on a sample by sample basis, under different CT saturation levels, different CT raitos and PT ratios. • Derives physically based high-fidelity dynamic device models of both voltage and current instrumentation channel. • Automatically formulates the measurement model and DSE algorithm in a standard objected-oriented manner. This paper proposes an online instrumentation channel error correction method based on weighted least square-dynamic state estimation (WLS-DSE), which can be integrated within Merging Unit (MU). It derives the mathematical dynamic device models of both voltage instrumentation channel and current instrumentation channel, which include physically-based high-fidelity dynamic device models of instrument transformers (potential transformer or current transformer), AC cable and burden resistor. To obtain the best estimate of the instrumentation channel's primary quantities, three major modules are designed in a standard object-oriented manner to create the measurement model and construct the dynamic state estimation algorithm. With the introduction of MU, each instrumentation channel of a MU can be integrated with the proposed error correction method, so that MU is able to directly report corrected primary values, which is applicable in real-time protective relays. The performance of the proposed error correction method is validated through extensive numerical experiments under different current transformer (CT) saturation levels and different instrument transformer ratios. The results demonstrate that the proposed method is capable to accurately reproduce the primary quantity on a sample-by sample-basis. [ABSTRACT FROM AUTHOR]

This study presents an interface method (IM) to interconnect real-time simulators (RTSs) without amplifiers for different intelligent electronic devices (IEDs), such as protective relays, smart meters, and other devices. It is a significant topic for the power systems protection community because there are many protection devices with different requirements. These protection devices have pinouts that measure bus voltages/currents and breaker pole states and generate trip/close pulse signals. Most of the emulation test beds with RTSs and HIL need amplifiers to connect IEDs from different product manufacturers because the low-voltage interface levels are not available in some instruction manuals. Additionally, commercial amplifiers have cutoff frequency limitations and have an excessive cost when several IEDs are wired onto test beds. Then, the validation of protection and control systems with RTSs and IEDs in the loop from different vendors without amplifiers results in an unfeasible alternative. In this paper, the IM was based on using an interface box, power source, and RTS to identify IED inputs/outputs. The sequence to recognize IED pinouts and calculate the current/voltage scaling factors is described. The IM was validated satisfactorily with RTS and a protection device (with unknown pinouts) in the loop. [ABSTRACT FROM AUTHOR]

• Real-time multi-rate RMS-EMT co-simulation of power systems using OPAL-RT and RTDS. • Transmission line interface using built-in models avoids to developing hybrid lines. • Non-buffered curve fitting method allows phasor calculations using few samples. • RMS-EMT co-simulation for testing protective relays allows to simulate large systems. • OPAL-RT and RTDS co-simulation. This work proposes an interfacing technique that uses the built-in three-phase transmission line models available in simulation platforms to perform Root Mean Square (RMS)- Electromagnetic Transient (EMT) real-time, multi-domain and multi-rate co-simulation. The main objective of this paper is to show the application of this kind of simulation in hardware-in-the-loop (HIL) testing of protective relays. Two well-known platforms are considered in this work: OPAL-RT with its ePhasorSim tool is used for RMS simulation, and RTDS is used for EMT simulation. However, the proposed technique is sufficiently general to be applied to other real-time simulation platforms that have similar built-in transmission line models. To convert waveforms to phasors, a non-buffered rapid curve fitting method was implemented to attend to real-time constraints. During the testing phase of this research, tests for the HIL were completed using an actual transmission line protection relay. The presented results of tests highlight the benefits of the proposed interfacing technique. [ABSTRACT FROM AUTHOR]

• Identifying abnormality and determining time of disturbance occurrence. • Discriminating the incipient fault from capacitive switching and sudden load variations. • Discriminating the incipient fault from harmonic loads considering arc fault models. The incipient faults which mainly occur due to the electric arc occurrence in the power cables with insulation defects are hardly detectable by the conventional protective relays, and over time can develop into a permanent fault in the system. Employing Kalman filter, this paper puts forward a method to detect the incipient faults and to discriminate them from other similar incidents in the power system. The proposed method is established on the comparison between the waveform of the measured voltage and fundamental component of the measured voltage, estimated by Kalman filter algorithm in the sending end of the cable during the fault. Employing the difference between the measured and estimated waveforms, the incipient fault detection and discrimination are carried out within two stages. In the first stage, event detection is relegalized by comparing the standard deviation of the obtained error with a certain threshold. The second stage is conducted to find the incipient fault based on the non-attenuating characteristic and quasi-periodic nature of the incipient fault. The feasibility of the proposed method is verified through computer simulation using four different electric arc models and also the acquired experimental data from real incipient faults. [ABSTRACT FROM AUTHOR]

• Robust faulted phase selection for high resistance faults. • Robust faulted phase selection for high impedance faults. • Robust faulted phase selection for week infeed transmission systems • Faulted phase selection for long transmission lines. • Faulted phase selection based on incremental quantities. This work proposes the use of a novel faulted phase-selection phasor-based algorithm to solve the high-resistance and weak-infeed fault condition selection problem in existent long compensated transmission lines. The algorithm was originally developed for future half-wavelength lines (3000 km for 50 Hz system or 2500 km for 60 Hz), and was slightly modified and tested in a real 645 km 1000 kV Ultra High Voltage transmission system. The algorithm was implemented in a programmable protective relay and tested using a real-time simulator. A series of tests under extreme conditions (such as high impedance fault and very week infeed system together) were conducted to evaluate the performance and robustness of the proposed algorithm. [ABSTRACT FROM AUTHOR]

• Logic equations are automatically obtained, therefore, removing the possibility of user error in entering the equations. • Measuring and tripping zones are represented as graphs, which facilitates the implementation of the method and expansion of the busbar arrangement dynamic zone selection logic. • The proposed method also introduces a low-impedance differential protection scheme based on graph theory. • The equations obtained by the method were tested using real-time simulation and a commercially available relay. • Enhanced representation of polarity of CTs by using directed edges This paper presents a detailed description of a dynamic zone selection approach for busbar protection using path analysis and graph theory. The main benefit is that the dynamic zone selection logic equations for busbar protection applications are automatically obtained by an offline software-based tool. The method accounts for normal busbar-switching sequences, in-service transfer, bypassed current transformers, breaker substitution, paralleled busbars, and a check zone. The equations can be set up and executed in existing protective relays. The method was tested in a busbar arrangement for different switching scenarios and fault conditions, and the results have proven its effectiveness. [ABSTRACT FROM AUTHOR]

• Fault location is very important to speed up the restoration of transmission lines after the occurrence of faults. • M-class PMUs present filtering response times larger than those observed in P-class units and protective relays. • Although M-class PMUs are widely available in several power systems, they are often disregarded in fault location schemes due to their intrinsic measurement response times. • Studies evaluating the feasibility of M-class PMU-based fault location procedures in real systems are not available in the literature. • The obtained results reveal that, unlike the preliminary expectations, the evaluated M-class data resulted in acceptable fault location errors. Transmission line fault location is of paramount importance to speed up the power system restoration after outages. Among the existing fault location methods, the most widespread are those based on fundamental phasors, whose estimations must converge to the fault steady-state regime before the line circuit breakers open. Thereby, traditional fault locators usually consider phasor estimations obtained from protective relays or P-class Phasor Measurement Units, which present filtering latency times shorter than those of M-class Phasor Measurement Units. However, although it is commonly assumed that M-class phasor samples are not suitable for fault location applications due to their intrinsic filtering delay, studies on the feasibility of M-class data-based fault location applications are not yet available in the literature. Therefore, this work aims to investigate if M-class Phasor Measurement Units could be used in real fault location schemes, taking advantage of already deployed measurement systems. To do so, actual fault events occurred on the Brazilian power grid are analyzed, and the performance of four different phasor-based fault location algorithms are evaluated when phasor samples obtained from a traditional protective relay algorithm and from M-class Phasor Measurement Units are used as inputs. Unlike the preliminary expectations, the obtained results highlight evidences that M-class phasor measurements can be used in fault location applications, since they resulted in errors within the expected levels for phasor-based fault location methods. [ABSTRACT FROM AUTHOR]

• Electromagnetic transient simulation of two-stage BESS under unbalanced grid fault. • Short-circuit behavior of BESS differs with operating mode and grid codes. • Charging mode is more stringent on grid voltage support and dc-link regulation. • German grid code is more stringent on BESS operation in charging mode. Battery energy storage systems (BESSs) are expected to play a key role in enabling high integration levels of intermittent resources in power systems. Like wind turbine generators (WTG) and solar photovoltaic (PV) systems, BESSs are required to meet grid code requirements during grid disturbances. However, BESSs fundamentally differ from WTG and PV systems because they are not only required to operate as a source (discharging) but also as a load (charging). This paper investigates the system-level behavior of BESSs under grid fault conditions. It presents first a generic electromagnetic transient (EMT)-type model of a two-stage Li-ion BESS that can be configured to comply with grid codes. Compared to previous studies, the proposed model introduces a key step in the characterization of BESSs considering decoupled sequence control (DSC) and the non-linear impact of current limiters under stringent unbalanced faults. The model is used to demonstrate that BESSs behave differently in charging mode, a factor that needs to be accounted in protective relaying practices. The conducted simulations show that the charging mode is more stringent on both dc-link voltage regulation and grid voltage support, and that this is aggravated by the use of DSC scheme compliant with VDE-AR-N 4120 grid code. [ABSTRACT FROM AUTHOR]

Microgrids operate in islanding or utility grid mode. In islanding mode, distributed energy sources with power electronics inverters can generate fault currents over a wide range of frequencies. To gain a better understanding of the nature of these events, it is crucial to measure currents at frequencies of up to 20 kHz at transient states with protective relays. Protective relays at these frequency responses should be tested prior to being installed in microgrids. However, testing at high-frequency currents cannot be done with Relay Test Equipment (RTE) that generate signals up to 50th Harmonic for 60 Hz (3 kHz). In this study, a frequency response method and testbed for high-frequency currents of up to 20.16 kHz was developed and tested. The testbed utilized a RTE and High-Frequency Power Source/ Amplifier. Frequency relay experiments were run at frequencies of up to 1 and 20.16 kHz at a current magnitude of 0.1 and 0.5 A, respectively. The events were collected, and the current magnitude and frequency were plotted at time and frequency domain, respectively. The study of current magnitude and frequencies of up to 20.16 kHz for two overcurrent relays was performed and validated the variable frequency testbed and methodology. [ABSTRACT FROM AUTHOR]

• This paper illustrates an innovative signal processing method based on the concept of the signals conjugate. • The conjugate signals based innovative method protects the generator and the transformer as one unit and identifies the faulted zone based on unique relations. • It uses nine CTs and one relay and saves three CTs and one relay. • It contributes to encouraging results in the cases of the CTs saturation, power swing, generator startup, generator startup with faults, and different fault parameters. • It isn't affected by the type of connection of the transformer. • The tripping signal to only the generator will be sent in case of a fault inside the generator while the tripping signal to only the transformer will be sent in case of the fault inside the transformer. This study presents an innovative protection method for the generator-transformer zone based on the conjugate concept of the positive sequence component. The traditional protection for such zone employs two relays which generally uses twelve CTs. The proposed method uses one protective relay and utilizes nine CTs (a protective relay and three CTs are saved). The conjugate based innovative method protects the generator and the transformer as one unit and identifies the faulted zone. Such conjugate based inventive protection is based on the building of two relations. The 1st relation is between an adaptive conjugate signal of the neutral-generator current and an adaptive conjugate signal of the generator-transformer current. The 2nd relation is between adaptive conjugate signals of both transformer sides. Various types of external and internal faults, CTs saturation conditions, power swing conditions, and generator startup conditions have been generated by simulating part of the IEEE 9 bus system in the ATP program. The results clearly display the worth of the proposed protection in detecting the various types of internal faults. Other than, the new scheme can accomplish sensible differentiation among generator faults, transformer winding faults, and external faults. What's more, it contributes to encouraging results in the cases of the CTs saturation, power swing, generator startup, generator startup with faults, and different fault parameters. It isn't affected by the type of connection of the transformer. The tripping signal to the generator will be sent in case of a fault inside the generator while the tripping signal to the transformer will be sent in case of the fault inside the transformer. [ABSTRACT FROM AUTHOR]

• Investigates the effects of DSE-based instrumentation channel error correction on protective relays. • Discusses possible mis-operations of relays caused by CT saturation for three typical protection schemes: distance protection, current differential protection and setting-less protection. • Compares the relay responses with the estimated measurement samples and with the legacy measurement samples, respectively, for each protection scheme. • Improves the protection relay reliability using the estimated measurement samples. This paper presents the effects of dynamic state estimation (DSE)-based instrumentation channel error correction on protective relays. It discusses the possible mis-operations of relays caused by current transformer (CT) saturation for three typical protection schemes: distance protection, current differential protection and setting-less protection. For each protection scheme, it compares the relay responses with the estimated measurement samples and with the legacy measurement samples, respectively. Extensive cases have demonstrated that when large errors introduced by CT saturation, the legacy measurement samples can lead to slower operations for distance relay in case of internal faults, and unnecessary trip decisions during external faults for current differential relay and setting-less relay. In contrast, with the estimated measurement samples, the relays can correctly identify internal faults and avoid mis-operation in case of external faults. [ABSTRACT FROM AUTHOR]

• Several algorithms to reduce wildfires caused by power systems due to high impedance faults (HIFs) are assessed in this paper. • An actual uni-grounded system in northern nevada is modelled and practical usefulness of the HIF detection algorithms embedded in a new commercial relay is tested in a HIL platform using RTDS. • The limitations of the HIF algorithms and solutions for mitigating the fire and human safety hazards are discussed after testing a large number of HIFs scenarios in different ground surfaces. • The pros and cons of each approach are demonstrated to allow power utilities to choose a wildfire mitigation technique which is more practical for their specific network. This paper assesses methods to reduce wildfires caused by power systems due to high impedance faults (HIFs). HIFs have been challenging researchers and utilities for years since their current magnitudes are below traditional overcurrent relay pickups. Most of HIFs include igniting arc between a conductor and a ground surface that may cause fire and human safety issues. Operating behavior of uni-grounded, ungrounded, multi-grounded, and high impedance grounded distribution systems are described and an actual uni-grounded system in Northern Nevada is considered for HIF study. Two different HIF detection methods based on non-harmonic and odd-harmonic content of fault currents that can be used in a substation-based protective relay are described and tested in a hardware-in-the-loop (HIL) platform using a real-time digital simulator (RTDS). HIFs in different ground surfaces such as wet sand, dry sod, dry grass, wet sod, wet grass, and reinforced concrete are modelled in RSCAD software. Practical merits of the two HIF detection methods embedded in a utility-based relay is evaluated. The limitations of the relay and solutions for mitigating the fire and human safety hazard are discussed. [ABSTRACT FROM AUTHOR]

• Protective relaying scheme for long transmission line. • Fault detection using positive sequence admittance of two-ends of the line. • Segregation of internal and external fault. • Localization of internal fault using positive sequence fault components. In this paper, a novel integrated approach of protective relaying methodology has been adopted for detecting faults and its location estimation in long transmission line. First, the detection algorithm has been formulated using positive sequence admittance. Subsequently, fault location algorithm has been developed using positive sequence voltage and current phasors. The proposed algorithms have been implemented on a 50 Hz, 400 kV single-circuit transmission line in MATLAB environment. A wide range of diversified and challenging cases have been simulated to test the reliability of this scheme. The results confirm the preciseness of the algorithm, as it can produce accurate results under stressed conditions, viz. high impedance fault (HIF), current transformer (CT) saturation/ capacitive voltage transformer (CVT) transient, close-in faults, swing condition, source strength variation, etc. Moreover, this scheme has also been successfully tested in series-compensated and double-circuit transmission line, which brings out the superiority of this scheme. The comparative analysis with recent protective relaying techniques institutes the potentiality and robustness of the scheme. [ABSTRACT FROM AUTHOR]

• Dynamic state and parameter estimation using digital protective relay records. • Use of constrained iterative unscented Kalman filter for estimation. • The Adomian Decomposition Method is used for solving the differential equations. • Improvement in convergence and accuracy is achieved by using scaled sigma points. • The proposed approach is demonstrated using WECC-9 bus system simulation data. This paper proposes an approach for the estimation of dynamic states and parameters of a synchronous generator from digital protective relay (DPR) records. Digital fault recorder data or phasor measurement data based approaches are mostly used for aggregate generator models in the literature. The DPR records are usually available for individual generators in a plant and hence can be used for individual generator model development. Constrained Iterative Unscented Kalman Filter (CIUKF) is used in this paper which combines the benefit of iterations and constraints on variables to improve the accuracy of estimation. Adomian Decomposition Method (ADM) is used for solving the IEEE model 1.1 synchronous machine equations which has a less computational burden and higher accuracy when compared to the widely used Modified-Euler (ME) method. The effectiveness of the proposed approach is demonstrated using the WECC-3 generator 9 bus system. The simulation data is generated from a transient stability program with 1 kHz sampling rate for a duration of 3 s to resemble a DPR record. The CIUKF is tailored to get good convergence and accuracy with short data records. It has been observed that the accuracy obtained with the proposed approach is good enough to preserve the rotor modes of oscillation. [ABSTRACT FROM AUTHOR]

• Faults are located on any line in the transmission system using a limited number of PMU measurements. • Fault location is independent of the fault type, unknown fault resistance. • Post-fault voltages are recovered from limited period of recorded transients after the fault occurs until the relay clears the fault. This paper presents an approach which allows system-wide fault location using only a sparse set of synchronized phasor measurements. The proposed algorithm combines post-fault voltage prediction and sparse estimation. The resulting method enables practical application of the sparse estimation formulation by using Prony analysis to predict post-fault steady-state voltages at those buses equipped with phasor measurement units. The prediction requires only a short transient recording which is typically available before the actuation of protective relays. Following the prediction step, the least angle regression based sparse estimation algorithm is employed to identify the fault location. However, for particular conditions usually associated with small fault currents, the sparse estimation algorithm may not be able to correctly identify the fault location. To mitigate this problem, ordinary least squares is used to increase the robustness of the proposed method. A 3-Phase model of the IEEE 118 bus system is developed on the alternative transients program to simulate realistic fault transients and test the performance and accuracy of the proposed fault location method. [ABSTRACT FROM AUTHOR]

• Locating faults on transmission lines is an important task. • Most existing applications use phasor-based fault locators. • Reduced fault period can affect the performance of phasor-based fault locators. • Fault location issues due to short fault period are demonstrated through ATP and RTDS simulations. • Statistical analyses improve phasor-based fault location performance. This paper presents a study on the performance of phasor-based fault location methods under reduced fault period conditions. Such a scenario can arise in lines equipped with high-speed circuit breakers (CBs) and time-domain protective relays, so that the fault can be eliminated even before it reaches its steady-state. Considering this context, challenging scenarios that may arise during phasor-based fault location procedures are firstly addressed, and then statistical approaches for fault location estimation sample processing are investigated, evaluating their advantages and limitations. Initially, Alternative Transients Program (ATP) fault simulations are carried out to generate realistic fault records, which are played back into actual micro-processed relays equipped with both high-speed time-domain protection functions and phasor-based fault location algorithms. Finally, by means of tests using a Real-Time Digital Simulator (RTDSTM) and an actual Digital Fault Recorder (DFR), different procedures to analyze phasor-based fault location data are assessed. The obtained results show the statistical processing of fault location estimations can improve existing fault location procedures in some cases, but not completely solving the problem if CBs come to be faster than those in the present technology. [ABSTRACT FROM AUTHOR]

• Apparent RMS Current Ratio Index introduced. • Maximum permissible current in a feeder in harmonic polluted networks calculated. • Non-linear load effect on the capacitor bank current evaluated. • Over-current relay malfunction investigated in harmonic polluted networks. • All resonance paths for a capacitor bank in a substation investigated. Overcurrent (OC) protective relays use different methods to calculate the RMS value of the current signal, based on the CT data. One common technique uses the peak-to-peak value, which is called the Apparent RMS Value in this paper. But using this value, when there are noticeable harmonics in feeders current, may lead to OC relay malfunction. The ratio of maximum possible Apparent RMS value to True RMS value is introduced as the Apparent RMS Current Ratio Index (ACRI). Then maximum permissible current in a feeder is determined so that no relay malfunction is guaranteed. This malfunction occurs more often in capacitor banks feeders in MV/LV substations with big nonlinear loads such as big induction furnaces, especially in resonance situation. Results are investigated on a typical 63 kV/20 kV substation including a big nonlinear load compensated by four back-to-back capacitor banks. [ABSTRACT FROM AUTHOR]

• The frequency components of p 3 ϕ (t) can be used as a fault indicator. • p 3 ϕ (t) oscillates at twice fundamental frequency when an asymmetrical fault occurs. • p 3 ϕ (t) oscillates at slip frequency (between 0.3 and 3 Hz) during power swings. • A setting-free fault detector is developed based on the frequency components of p 3 ϕ. • The setting-free feature removes any daunting efforts of parameter tuning. This manuscript describes a setting-free fault detector based on the unique features of electric power. In contrast to the common practice in fault detection, which uses immediate signals, i.e., voltages and currents, the proposed technique has been inspired by raising this question "What if the information of voltages and currents are gathered in one quantity and fault detection is developed on this basis?" An intelligent choice can be the electric power, as it comprises the information of both voltages and currents. With that in mind, multiple unique features of electric power are disclosed to detect asymmetrical faults. The proposed fault detector works with fixed thresholds, i.e., revising is not needed from one system to another system. In other words, the fault detector is setting-free, which is remarkably an interesting feature in protective relaying. An IEEE-approved power system is considered to evaluate the dependability and security of the fault detector by extensive numerical simulations. The results are promising and show improvement to fault detection during power swings. [ABSTRACT FROM AUTHOR]

• Protective relaying scheme of UPFC compensated transmission line. • Fault detection using complex power of two end of the line. • Segregation of internal and external fault. • Localization of internal fault using sequence component of voltage and current signal. This study presents an integrated approach for discrimination of internal and external fault, and to obtain pin-point location of the fault in a transmission line connected to unified power flow controller (UPFC). To detect internal fault, this method uses positive sequence component of voltage and current at the local and remote end bus. Fault location estimation technique requires both positive and negative sequence voltage and current components measured from both ends of the line. The performance of the proposed technique has been evaluated by simulating a 400 kV double circuit UPFC compensated transmission line. This technique can detect internal fault under stressed conditions, viz. high impedance fault (HIF), change in source strength, change in load angle, and power swing. Precise fault location has been achieved under wide variation of system and fault parameters. The comparative assessment has been provided to prove the efficacy of the proposed approach. [ABSTRACT FROM AUTHOR]

• Current transformer saturation interval detection. • Integrated filtering approach. • Empirical mode decomposition and SG filtering. • Secondary burden and remanent flux of CT. • Operation of protective relaying. Any secured operation of smart grid highly depends on the signal transmitted through Intelligent Electronic Device (IED) to/from the external source. For this, the healthy operation of system components is essential. Error in measurement due to transient response of instrument transformers such as current and voltage transformer may degrade the healthy operation of protection devices. To mitigate this issue and to improve the function of protective devices, an integrated filtering approach is applied for the determination of the current transformer (CT) saturation interval. The method helps in detecting the exact saturation period so that signal reconstruction or time delay logic can be applied to avoid the error-in-estimation process. The proposed integrated filtering approach is tested for different critical cases through a developed model in EMTDC/PSCAD platform. Results for noisy signal obtained through real-time digital simulation (RTDS) is also presented. The method is also compared with the existing method and found more reliable to be implemented. [ABSTRACT FROM AUTHOR]