Showing papers on "Power-system protection published in 2022"

An Adaptive Overcurrent Protection Scheme for Dual-Setting Directional Recloser and Fuse Coordination in Unbalanced Distribution Networks With Distributed Generation

Abstract: The recloser–fuse coordination of the distribution networks (DNs) equipped with distributed generators may be jeopardized by using the conventional overcurrent protection strategies thus degrading the network reliability. This article focuses on the design of a protection coordination strategy based on the dual-setting directional recloser (DSDR) for the effective implementation of a fuse-saving scheme in DNs. The proposed DSDR-based protection strategy will assist the network operators by providing a flexible coordination range along with more accurate protection settings to meet the protection coordination requirements. The performance of the proposed protection scheme has been validated through its implementation on IEEE standardized test systems and a comparative analysis has been drawn to demonstrate its effectiveness. Furthermore, this article concentrates on the economical design of the protection strategy for DNs by utilizing fewer numbers of protective devices. The results show that the proposed strategy will considerably reduce the number of temporary and sustained interruptions experienced by the consumers of large DNs thus improving the network reliability indices.

Optimal Protection Coordination for Inverter Dominated Islanded Microgrids Considering N-1 Contingency

Abstract: Optimal protection coordination is usually solved for the original network topology with all lines, loads, and generation intact. However, power grids may experience contingencies due to transient events, e.g., generation or line outages. Low fault currents of inverter-interfaced distributed generators (IIDGs) necessitate a sensitive and reliable protection scheme. This paper proposes a protection scheme for islanded microgrids powered by droop-based IIDGs. The protection scheme utilizes virtual impedance-fault current limiters to limit IIDGs fault currents and achieve protection coordination. A two-stage method for optimal protection coordination (OPC) of directional overcurrent relays (DOCRs) is devised. In Stage I, relays short-circuit currents are calculated. Then, constraints on the operation times of primary and backup DOCRs are formulated for the islanded topology and each possible topology following an N-1 contingency. Lastly, in Stage II, the OPC problem is formulated as a constrained nonlinear programming problem and solved to obtain the optimal DOCRs settings. A radial test microgrid that is part of a Canadian urban distribution system is used to ensure the success of the proposed OPC method.

Artificial Intelligence-Based Protection for Smart Grids

Abstract: Lately, adequate protection strategies need to be developed when Microgrids (MGs) are connected to smart grids to prevent undesirable tripping. Conventional relay settings need to be adapted to changes in Distributed Generator (DG) penetrations or grid reconfigurations, which is a complicated task that can be solved efficiently using Artificial Intelligence (AI)-based protection. This paper compares and validates the difference between conventional protection (overcurrent and differential) strategies and a new strategy based on Artificial Neural Networks (ANNs), which have been shown as adequate protection, especially with reconfigurable smart grids. In addition, the limitations of the conventional protections are discussed. The AI protection is employed through the communication between all Protective Devices (PDs) in the grid, and a backup strategy that employs the communication among the PDs in the same line. This paper goes a step further to validate the protection strategies based on simulations using the MATLABTM platform and experimental results using a scaled grid. The AI-based protection method gave the best solution as it can be adapted for different grids with high accuracy and faster response than conventional protection, and without the need to change the protection settings. The scaled grid was designed for the smart grid to advocate the behavior of the protection strategies experimentally for both conventional and AI-based protections.

LSTM-Based Fault Direction Estimation and Protection Coordination for Networked Distribution System

Abstract: While the world’s power distribution system resembles an intricate web-like structure, the most conventionally implemented distribution mechanism is the radial distribution system (RDS) where connection points for each distribution line are normally kept open. However, disadvantages regarding the traditional system have led to active research on establishing the networked distribution system (NDS), in which multiple circuits are interconnected with electricity as well as high-speed communication systems. The NDS offers multiple advantages including increased facility utilization, increased hosting capacity, and higher terminal voltage. Conversely, an unsolved issue prevails as the existing protection coordination method designed for the RDS is inadequate for fault occurrences in the NDS due to inaccurate fault direction identification. Hence, there is an urgent need for an alternative protection coordination method that allows high precision fault direction identification through communication. Moreover, the application of various existing technologies is hindered as the distance relay protection coordination algorithm malfunctions in situations where distribution lines are of short length, loads are dispersed onto multiple lines, and integration of distributed generation (DG) is frequent. Therefore, this paper presents a fault direction identification method that uses the waveform of the fault current based on long short-term memory (LSTM) neural network and a communication-based protection coordination scheme that can be applied in fault situations within an NDS.

An Enhanced Differential Protection Scheme for LVDC Microgrid

Abstract: The low-voltage dc (LVDC) microgrid possesses numerous benefits and their penetration in the power system has increased rapidly in recent years. However, the detection of faults in the LVDC microgrid is a challenging issue due to the large magnitude of fault currents and fault-level variation in the microgrid. The performance of the recent current and its derivative-based protection scheme is limited in case of faults in the islanding mode of operation, different microgrid topologies, varying distributed generations (DGs) penetration, and against the measurement noise. This article presents an enhanced differential protection scheme for LVDC microgrid integrated with multiple DGs and storage. The differential current and its first derivative are processed through the decision tree (DT) algorithm for fault detection and the K-nearest neighbor (KNN) technique is utilized for fault classification. The robustness of the proposed protection scheme is tested for different fault types and fault conditions with variation in microgrid topology and operating conditions. The impact of the intermittent and volatile nature of the DGs, the presence of measurement noise, and assessment during external faults and critical no-fault cases have been investigated. The proposed scheme is tested on the MATLAB/ SIMULINK and validated on the Typhoon HIL platform for the assessment of real-time performance. The test results show that the proposed scheme can detect and classify faults with high accuracy and faster response time and, thus, can be a potential candidate for providing dependable protection measures for LVDC microgrids.

Assessing the Robustness of Cyber-Physical Power Systems by Considering Wide-Area Protection Functions

Abstract: With the deepening deployment of information and communication technologies (ICT), the cyber network is playing an increasingly important role in determining the performance of a power system. In this paper, we assess the robustness of cyber-physical power systems and examine various impact factors on the system’s robustness. A model that integrates the operating characteristics of the physical network and the wide-area protection functions provided by the cyber network is proposed. Based on the model, cascading failure propagation processes in a cyber-physical power system triggered by initial failures are simulated. Two statistical metrics, the power outage risk and the cumulative power outage size distribution, are then used to quantify the robustness by processing numerous cascading failure simulation results. We conduct case studies on IEEE 57 Bus, IEEE 118 Bus, IEEE 145 Bus, and UIUC 300 Bus with the proposed method. Simulation results demonstrate the necessity to consider cyber coupling, the importance of developing advanced wide-area protection algorithms, and the threat posed by cyberattacks compromising the robustness of cyber-coupled power systems.

Online Sensitive Turn-to-Turn Fault Detection in Power Transformers

Abstract: Power transformers are of the most critical and expensive equipment in the power system industry. Meanwhile, they are exposed to a variety of faulty and abnormal operating conditions. Therefore, to prevent extension of these events they are protected by different protective schemes. Among the various types of the transformer faults, detecting turn-to-turn faults is the most challenging one for the protection systems. Industrial experiences and standard documents reveal that the existing protection systems include severe shortcomings, and still more efforts are required to offer a reliable method for detecting such faults. To this end, this article puts forward the proposal of a novel turn-to-turn fault detection method to satisfy the basic protection requirements of dependability, security, and speed. This method properly detects the low-level turn-to-turn faults while is stable during system transients and external faults. Performance of the proposed method is evaluated through various experimental and simulation studies. The obtained results verify superior operation of the proposed method under different faults and conditions.

Local Derivative-Based Fault Detection for HVDC Grids

Abstract: Local-measurement-based algorithms are relevant as primary protection for high voltage direct current (HVdc) grids due to the restriction in operation speed. The communication time delay significantly affects communication-based algorithms, therefore, they are mostly implemented as backup protection or for high-resistance fault detection. This article proposes a local derivative-based protection scheme for HVdc grids. Primary protection is based on the voltage derivative. Conversely, the backup and busbar protections are based on the current derivative. The proposed system is evaluated against low- and high-resistance fault case scenarios via simulation in PSCAD software. The voltage derivative-based algorithm provides a fast and accurate primary protection. On the other hand, the current derivative-based algorithm is implemented to operate when a failure is produced in the primary protection. The parallel operation of these two algorithms saves time when it comes to backup operation after primary protection's failure. Likewise, the busbar protection operates rapidly and selectively. Influence of the limiting inductor's size, sampling frequency, fault resistance, and noise disturbance on the performance of the proposed protection scheme are also analyzed. The presented protection scheme is capable of rapidly and selectively detecting faults up to 200 Ω while covering primary, backup and busbar protections. Moreover, only common local derivative-based algorithms are employed in addition to typical limiting inductor's sizes and relatively low sampling frequencies.

Topology-Agnostic, Scalable, Self-Healing, and Cost-Aware Protection of Microgrids

Abstract: Most microgrid protection schemes found in published literature suffer from a lack of generality in that they work well for the assumed topology, including type and placement of sources. Other generic protection schemes tend to be too complicated, too expensive, or both. To overcome these drawbacks, a topology-agnostic, scalable, and cost-aware protection based on fundamental principles that work in the presence of high penetration of inverter-based resources (IBRs) is developed and tested in this paper. The protection system also implements stable automatic reconfiguration of the healthy sections of the system after clearance of fault, thus increasing resilience by self-healing. To achieve this ambitious goal, stable inverter models are developed that operate in unbalanced networks in grid-connected and islanded modes, even with 100% IBRs, share power without conflicting controls, and can ride through faults while limiting fault currents. The scheme is tested for primary and backup protection and reconfiguration on the IEEE 123-node feeder in grid-connected and islanded modes with 15 IBRs connected to the system.

A Coordinated Multi-Element Current Differential Protection Scheme for Active Distribution Systems

Abstract: This paper introduces a current differential protection scheme, appropriate for application in medium voltage active distribution systems, where it is desired to keep the greatest possible number of loads and DG units energized during a fault. Conventional two-terminal percentage current differential relays are used to form successive, time-current-coordinated, differential protection zones. Multiple time-delayed differential elements in each protection zone guarantee coordination with the zone's lateral protection devices, as well as between successive differential protection zones. Sensitive time-delayed differential elements protect against relatively high-resistance faults, while instantaneous differential elements minimize protection speed whenever possible. Additional emergency differential elements deal with post-fault topology changes and breaker failure conditions enhancing the overall scheme's performance. The proposed scheme is applied to a model of real medium voltage distribution system with distributed generation, considering a ring topology operation. A detailed simulation-based study proves the applicability and enhanced performance of the proposed scheme.

A Novel Fault Isolation Scheme in Power System With Dynamic Topology Using Wide-Area Information

Abstract: The flexible and dynamic operation condition of the power system requires that the fault isolation scheme has sufficient adaptability. A novel fault isolation scheme based on wide-area information is proposed in this article. Based on graph theory, the adjacency matrices of the electrical components and circuit breakers are constructed. The real-time switch status data is exploited to reflect the dynamic changes of the network topology. Then, the tripping path of the circuit breaker connecting each protected electrical component is searched by the Floyd–Warshall algorithm to formulate the fault isolation set for all protected electrical components. The proposed approach is applied to fault isolation from a wide-area perspective, and it is not affected by system coordination and selectivity compared with the one based on local information. The effectiveness of the proposed scheme is verified on a power system with the typical electrical connection under the cases of a single fault, multiple faults, circuit breaker failure, and substation with the outage of dc power supply, and the case where the circuit breakers cannot trip. Since the tripping sequence of the circuit breakers is determined before the fault occurs, even with dynamic changes of the power system conditions, the proposed scheme can minimize the fault isolation zone with low fault clearance time.

An Investigative Analysis of the Protection Performance of Unbalanced Distribution Networks With Higher Concentration of Distributed Energy Resources

Abstract: Despite the substantial reliability and power quality improvements, the proliferation of distributed energy resources can introduce many protection complexities in distribution networks (DNs). This research article presents a comprehensive investigative analysis of the distributed generation (DG) impacts on the protection performance of the DN. Various protection coordination case studies have been analyzed under different operating conditions by varying the DG penetration level or the fault conditions to highlight the potential risks of the protection networks. The severity of the risks is evaluated by considering the DG locations, protection settings, and fault types/impedance parameters on a standardized IEEE 13 node test feeder in DIgSILENT Power Factory/MATLAB softwares. The subsequent protection hazards are examined for the mutual coordination of the overcurrent relays, auto-reclosers, and series fuses in DNs along with the differential protection issues for dc bus system. Furthermore, the impacts of DGs/PDs types are assessed on the nuisance tripping of the protection networks and results are reported.

Adaptive Distance Protection Based on the Analytical Model of Additional Impedance for Inverter-Interfaced Renewable Power Plants During Asymmetrical Faults

Abstract: Due to limited amplitude and controlled phase of current supplied by inverter-interfaced renewable power plants (IIRPPs), the IIRPP-side distance protection of lines connected to IIRPPs fails to detect the fault location accurately, so it may malfunction. The composite sequence network of a line connected to an IIRPP during asymmetrical faults is analyzed, and an adaptive distance protection based on the analytical model of additional impedance is proposed in this study. Based on open circuit property of negative-sequence network at the IIRPP-side, the equivalent impedance of power grid and current flowing through fault point are calculated in real-time using local measurements, which are substituted into the analytical model of additional impedance to calculate fault location. In the case of negative-sequence reactive current injection from IIRPPs during asymmetrical faults, the error of calculating fault point current from local measurements is analyzed and corrected to ensure reliability of the proposed protection. The proposed protection alleviates the effect of fault resistance in a system with weak sources. In addition, the proposed protection can adapt to different grid codes (GCs), the operation mode change of the power grid, and the capacity change of the IIRPP. PSCAD/EMTDC test results verify the effectiveness of the proposed protection.

Vulnerability assessment of line current differential protection in converter–dominated power systems

Abstract: Line current differential (LCD) protection is traditionally considered to be highly dependable and secure. However, the increasing penetration of converter interfaced sources (CIS) (e.g. wind, PV, HVDC systems, etc.) could significantly reduce the system fault level and change the fault characteristics, thus presenting challenges to the reliable operation of LCD protection. In this paper, the impact of the integration of CIS on LCD performance is investigated comprehensively. Analytical expressions representing LCD relay operation in the presence of converter-driven fault currents and weak infeed conditions have been developed. A test network, comprising of a CIS model equipped with a typical converter fault-ride through strategy that is compliant with the GB Grid Code, has been built in a Real-Time Digital Simulator (RTDS). Simulations of LCD performance for different fault and system conditions are performed and presented. It is demonstrated that the dependability of the LCD relay can be compromised during internal phase-to-phase faults. The results also show that with the synchronous generation being displaced by CIS, the increasing CIS penetration and fault contribution from the CIS can lead to an increased phase angle difference between the fault currents contributed from the two ends of the protected line, which will increase the risk of the compromised protection performance.

Converter Control Impacts on Efficacy of Protection Relays in HVDC-Connected Offshore Wind Farms

Abstract: The high-voltage dc (HVDC)-connected offshore wind farms (OWF) is a power electronic converter dominated power system, where conventional protections, including overcurrent protection, distance protection, and differential protection, may not operable effectively. To reveal the impact of converter control on the efficacy of conventional protection relays, this paper first investigates the highly controlled fault current characteristics of HVDC system and OWF. Then, the basic operation principles of conventional protection relays are presented to elaborate their responses to the fault currents of HVDC system and of OWF, based on which, scenarios that lead to the malfunction of protection relays are identified. Finally, the theoretical analysis is verified by electromagnetic transient (EMT) simulations.

Automatic Recloser Adjustment for Power Distribution Systems

Abstract: In this paper, a self-adaptive protection system is proposed for adjusting the time dial (TD) of reclosers found in electrical power distribution systems (EPDSs). The self-adjustment is carried out in both phase and ground protection. The methodology considers the fuses along the feeder to obtain the fuse-saving philosophy. This feature allows less interference on the protection system already implemented by the electrical power distribution utilities. This methodology also allows using other frameworks, such as the estimation of the fault distance. The software used for computer modeling and simulation was PSCAD™/EMTDC™. The flexibility provided by the method, which allows the incorporation of new logic and changes in decision-making, resulted in an adaptive method with a good performance against different locations, types, and fault impedance. It also resulted in better coordination between the protection devices (PDs). The results compared with well-coordinated conventional protection have shown significant performance gain with the adaptive system.

Advancements in Line Protection for the Future Grid

Abstract: Advancements in line protection provide effective protection in power systems with diverse combinations of renewable and conventional generation. These technological advancements improve grid resiliency when the power system experiences reduced fault current levels and abnormal current waveforms, which are common in networks with inverter-based resources (IBRs) such as photovoltaic, wind, and battery energy sources. The technologies described in this article include advanced line current differential protection, communications channels for protection applications, high-accuracy traveling-wave (TW) fault locating, and digital secondary systems (DSSs), also known as digital substations. This article describes the fundamental principles of these technologies.

Polarized Distribution Protection Coordination Strategy Under the Impact from Various Distributed Energy Resources (DER) Generation Points

Abstract: The present design of protection systems is based on power flowing in a single direction, which allows for unpolarized (non-directional) protection schemes. With the large influx of renewable technologies recently introduced into the electric power system, referred to as distributed energy resources (DER), creates many challenges to adequately maintain existing protection schemes. Protection engineers design protection systems to safely eliminate faults from the electric power system that was exclusively built with rotating machines (which have quite a different behavior under fault than inverter-based sources). As the penetration level of DER increases, the adverse impacts from DER is no longer to be considered minimal. With DER becoming influential in the distribution system, the current utility protection strategy merits a comprehensive investigation. This paper discusses major protection issues caused by DERs and provides utility-verified solutions based on more than 500 DER interconnection project system impact studies. An optimized coordination flow chart is provided in this paper along with software CYMEDIST-verified real US utility radial distribution feeders, which were used for simulations and related validation.

Dynamic state power system fault monitoring and protection with phasor measurements and fuzzy based expert system

Abstract: The main aim of this paper is building of a small micro grid test bed system with a few sources, and few loads with various types of lumped resistive (R), capacitive (C) and inductive (L) elements. Before the advent of electric smart grid every load is facilitated with its own electromagnetic. Slowly with an advancement of protection system numerical relays came into existence. Because in the numerical relays the communication between the relays and communication with central computer is possible, with this a coordinative protection system was evolved. For the monitoring and protection of system in dynamic state many of the numerical relays were now replaced by intelligent electronic devices. The system is to be centrally controlled with an improvement in data communications and the artificial intelligence into power system made it is possible to control the power system centrally. In this paper, it is presented that the fault is monitoring and protection against different types of faults, such as frequency variations, voltage variations and different fault conditions using fuzzy based expert system (FBES). The proposed protection scheme is adaptive for frequency variations, voltage variations and fault levels. The FBES scheme is implemented in the LabVIEW software with MAMDANI structure.

System-Based Protection Testing in Digital Substations

Abstract: Since the introduction of digital relays, it became evident that test procedures adopted by the industry in the early days of relay testing needed to be adapted. The cause of misoperations was no longer related to mechanical failures or drifts in the relay components, but mostly related to logic, settings, or design errors as the last editions of the North American Electric Reliability Corporation misoperations studies consistently shows.

Multi-Layer Smart Fault Protection for Secure Smart Grids

Abstract: The trend toward Smart grid (SG) is increasing significantly by incorporating Distributed Generators (DGs), which leads to new challenges, especially in protection systems. SGs should strengthen robust environments against cybersecurity threats. So, the cybersecurity of future SGs is essential. This paper proposes a multi-layer protection scheme for the Medium Voltage (MV) Distribution System (DS), especially with reconfigurable SGs. The main protection algorithm is based on Artificial Intelligence (AI), utilizing the communication between all protective devices (PDs) in the grid, whereas as backup protection, another AI algorithm employs the communication between the PDs in the same line. Then, as alternative protection to provide the protection system with another level of security in case of communication issues or cyberattacks, a third algorithm based on the local data of each PDs is proposed. Both simulations using MATLABTM SIMULINK and experimental results utilizing a scaled physical grid validated the protection algorithms. The scaled grid has been designed for the smart grid in order to test the behavior of the protection scheme experimentally.

Failure analysis of fuse for external protection of capacitor bank

Abstract: The fuse has the characteristics of easy installation and use, low cost, and low investment. It is widely used at home and abroad as a protection device for internal failures of units (single) shunt capacitors above 1kV. This article specifically analyzes a fuse failure for external protection of capacitor banks. Focusing on improving the reliability of the fuse used for external protection of shunt capacitors, analyze and give reasonable suggestions.

Modeling Distributed Energy Resources for Analyzing Distribution Systems with High Renewable Penetration

Abstract: Increasing levels of inverter-based distributed energy resources (IBDERs) impact the legacy overcurrent distribution protection systems. The fault current injections of IBDERs are limited to between 1.25–2.25 p.u. of the rated current. The combination of the limited fault current and varying system load makes it increasingly difficult to reliably set the overcurrent protection. To address this challenge, researchers are proposing adaptive overcurrent protection mechanisms that can adapt to changing system conditions. Accurate modeling of IBDERs is required to develop reliable protection schemes. This paper presents a photovoltaics-based IBDER model in OpenDSS for adaptive overcurrent protection. The paper presents the validation of the proposed IBDER model against a detailed model in electromagnetic transient programs. Protection analysis of the Electric Power Research Institute J1 feeder with the proposed IBDER model is also presented.

Optimal Protective Coordination of Microgrids Considering N-1 Contingency Using Dual Characteristics Directional Overcurrent Relays

Abstract: Microgrids (MGs) could be operated in grid-connected and islanded modes. Although the ability of MGs to operate under various operation modes improve the system flexibility and reliability, the MGs' protection system might be adversely affected due to this matter. The adaptive protection schemes have been introduced for MGs and their different operation modes and network configurations. However, the adaptive protection schemes require communication and monitoring infrastructures. Hence, the communication-free protection schemes using local measurement considering different operation modes and network configurations have received much attention in the literature. The literature shows a research gap in developing a communication-free protection scheme considering different operation modes and network configurations due to the unavailability of upstream substations, distributed generations, and other MGs' elements like distribution lines. This paper tries to fill this research gap by proposing a new protection scheme using dual characteristic overcurrent relays based on N-1 contingency. The proposed method is applied to the IEEE 8-bus test system. The power flow and short circuit analyses are implemented in DIgSILENT, and the genetic algorithm (GA) solves the proposed optimization problem in the MATLAB environment. Test results illustrate the advantages of the proposed method compared to existing schemes only considering the limited operation modes and network configurations. Test results imply that the coordination constraint violation does not appear for N-1 contingency by applying the proposed method.

Resilient Protection of Medium Voltage DC Microgrids against Cyber Intrusion

Abstract: Differential current protection has been a reliable approach for line protection in DC systems. However, due to its dependence on communication for terminal current information, resiliency of such a protection approach is poor against external cyber intrusions (ECI) of different types, i.e., false data injection (FDI) and time synchronization attacks (TSA). As a result of which, the system is prone to collapse due to line tripping in the presence of coordinated ECIs. The scope of paper is to propose a resilient protection approach for medium voltage DC (MVDC) microgrids differentiating between the real faults and the ECIs in a system. The approach also detects ECIs on an adjacent line occurring simultaneous to a real fault where the system deploys current limiting reactors (CLR). Phase-modal transformation is carried out to obtain the mode voltages (line and zero) across these CLRs. The mode voltages across the faulty mode networks are utilised along with differential current protection to propose a resilient protection approach against ECIs, which is sensitive to high impedance faults (HIFs). Further, a sensitivity function is formulated which gives the variation of decisive variables i.e., mode voltages with respect to change in decisive parameters i.e., fault resistance and fault location.