Overcurrent Protection Scheme Research Articles

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

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.

Innovative Adaptive Protection Approach to Maximize the Security and Performance of Phase/Earth Overcurrent Relay for Microgrid Considering Earth Fault Scenarios.

Microgrids are increasingly paying attention to the emerging of distributed energy resources. However, microgrid protection has challenged engineers because of the varying nature of fault current distribution during grid-connected and islanded operations. This paper suggests a novel approach of coordination between phase and earth fault overcurrent relays to ensure stability and security for the performance of protection schemes in active distribution networks. In this study, a combination of phase and earth overcurrent relays is coordinated to avoid mis-coordination in the overcurrent protection schemes. In the proposed approach, phase overcurrent function was employed as backup protection for earth fault function locally in the same relay instead of the traditional remote backup earth fault protection coordination approach. The suggested coordination approach provides a fast and reliable protection performance in different earth faults scenarios. The coordination was tested on the IEC Microgrid Benchmark network. Also, the objective function was modified to reduce the overall operational time using two recently developed metaheuristic optimization algorithms known as the charged system search (CSS) and Teaching-Learning-Based Optimization Algorithm (TLBO) in the MATLAB package. Finally, the time multipler setting values were adapted and compared to verify the speed and reliability of the proposed coordination approach using ETAP.

Effectiveness of hybrid differential-adaptive overcurrent protection scheme for microgrid

To cope with the significant changes in microgrid short circuit (SC) fault current characteristics caused by switching among grid & islanded operational modes, the said article proposes a new Adaptive Overcurrent Relays Protection (AOCRP) & Differential Relays Protection (DRP) arrangement. To minimize construction upgrade prerequisites and set computational burden, the scheme proposes utilizing AOCRP to protect distributed generators (DGs) as well as individual load points (LPs) and DRP to protect feeders, the backbone of feeders, lines, and buses. This protection scheme is useful to protect the microgrid system in both grid-connected as well as in islanded modes of operation from a large amount of 3 phase SC symmetrical faults like LLL, LLLG, etc.By combining the AOCRP and DRP strategies, this suggested methodology enhances the general reliability, efficiency, power quality, as well as stability of the microgrid. The AOCRP arrangement can be used for faults outside the zone of protection in this article, while the DRP scheme is used for faults within the protected zone. Multiple time-domain simulation models for verification purposes have been performed in the context of this article to determine the effectiveness of the suggested scheme in defending a microgrid infrastructure whereas the operating in grid or islanded modes.

Development of a Communication-Assisted Adaptive Overcurrent Protection Scheme in Smart Distribution Networks in Presence of Wind and Solar Generation

Development of a Communication-Assisted Adaptive Overcurrent Protection Scheme in Smart Distribution Networks in Presence of Wind and Solar Generation

Highly Fast Innovative Overcurrent Protection Scheme for Microgrid Using Metaheuristic Optimization Algorithms and Nonstandard Tripping Characteristics

The incorporation of renewable energy microgrids brings along several new protection coordination challenges due to the new and stochastic behaviour of power flow and fault currents distribution. An optimal coordination scheme is a potential solution to develop an efficient protection system to handle the microgrid protection challenges. In this paper, new optimal Over Current (OC) relays coordination schemes have been developed using nonstandard tripping characteristics for a power network connected to renewable energy resources. The International Electrotechnical Commission (IEC) microgrid and IEEE-9 bus systems have been used as benchmark networks to test and evaluate the coordination schemes. The proposed OC relays coordination approach delivers a fast and more reliable performance under different OC faults scenarios compared to traditional approaches. In addition, to improve and evaluate the performance of the proposed coordination approach, four modern and novel metaheuristic optimization algorithms are developed and employed to solve the OC relay coordination problem, namely: Modified Particle Swarm Optimization (MPSO), Teaching Learning (TL), Grey Wolf Optimizer (GWO) and Moth-Flame Optimization Algorithm (MFO). In this paper, the modern metaheuristic algorithms have been employed to handle the impact of renewable energy on the grid, and enhance the sensitivity and selectivity of the protection system. The test cases, consider the impact of integrating the different levels of renewable energy resources (with a capacity increment of 25% and 50%) in the microgrid on the OC relays protection performance by using nonstandard and standard tripping characteristics. In addition, a comparison analysis for the modern metaheuristic algorithms with Particle Swarm Optimization (PSO) algorithm as a common and standard technique in solving coordination problems under different fault scenarios considering also the higher impedance faults are introduced. The results in all cases showed that the proposed optimal nonstandard approach successfully reduced the overall tripping time and improve the performance of the protection system in terms of sensitivity and selectivity.

An Adaptive Overcurrent Coordination Scheme Withstanding Active Network Operations

This paper aims to present a centralized adaptive protection scheme (APS) for the directional overcurrent relays (DOCRs) considering system dynamics such as load demand variations, topology changes and DGs to mitigate the above-mentioned effects. The scheme is suitable for different types of networks whether its radial or meshed. Afterall, it can determine the actual topology with the micro-PMUs and breaker status, automatically generate relay names accordingly with the topology bus locations, establish protection coordination pairs, coordinate DOCRs for parallel lines, identify transformers to offer backup operation for differential protection, perform load flow and fault studies, execute contingency and sensitivity analysis, and lastly, coordinate the DOCRs using differential evolution algorithm so that they always have the proper settings to operate in appropriate time providing selectivity. The performance of the proposed centralized adaptive overcurrent protection scheme is tested on the highly meshed IEEE 14 bus system. The proposed scheme has shown that it can adequately consider impacts of system dynamics and DG.

Protection schemes for a battery energy storage system based microgrid

This paper evaluates directional and adaptive overcurrent protection schemes in microgrids. A microgrid supported by a centralised Battery Energy Storage System (BESS) is chosen for the study. The stringent PQ controller of BESS will not allow it to dissipate into a fault, during its charging mode, causing the conventional directional schemes to mal-operate. A direction estimation scheme using magnitude and angle of superimposed positive sequence impedance is proposed to address this issue in BESS. Further, two fault detection techniques are proposed for BESS integrated feeders. The Main Protection Unit (MPU) detects an internal fault when there is a mismatch in the direction of relays at either end of a feeder. The second scheme uses adaptive overcurrent relay settings. Since the fault current is limited with PQ control, the pickup current is calculated dynamically with this control. Whereas a fixed pickup current is chosen, when the BESS inverter is voltage controlled. Simulations have been carried out using MATLAB/SIMULINK software. The proposed schemes work well for bidirectional power flows and in grid connected and standalone modes of microgrid operation.

분산전원이 연결된 배전계통에서의 모델 기반 지락고장 위치 검출 방법

In a distribution system with distributed energy resources, power flow is not fixed in a single direction. Therefore, from the protection coordination’s point of view, existing over-current protection scheme is not adequate any more. On the other hand, in future’s distribution systems, it is expected that various kinds of information is available with more accuracy, which is one of the advantageous points in protection. This paper suggests a novel fault location method with these factors considered. In the proposed scheme, an existing protective device like a recloser of fuse is replaced by a smart relay with simple calculation and communication ability. A distribution system is divided into several segments and the fault location is calculated through successive circuit analysis at each segment using concentrated parameters of the lines. In this, synchronized power data are assumed to be available at each loading point before a fault occurs and it is also assumed that each load is not changed abruptly. The suggested method is applied to several distribution system models, through computer simulations, and is verified to be useful with accurate fault location.

Differential Evolution-Based Overcurrent Protection for DC Microgrids

DC microgrids have advantages over AC microgrids in terms of system efficiency, cost, and system size. However, a well-designed overcurrent protection approach for DC microgrids remains a challenge. Recognizing this, this paper presents a novel differential evolution (DE) based protection framework for DC microgrids. First, a simplified DC microgrid model is adopted to provide the analytical basis of the DE algorithm. The simplified model does not sacrifice performance criterion in steady-state simulation, which is verified through extensive simulation studies. A DE-based novel overcurrent protection scheme is then proposed to protect the DC microgrid. This DE method provides an innovative way to calculate the maximum line current, which can be used for the overcurrent protection threshold setting and the relay coordination time setting. The detailed load condition and solar irradiance for each bus can be obtained by proposed DE-based method. Finally, extensive case studies involving faults at different locations are performed to validate the proposed strategy’s effectiveness. The expandability of the proposed DE-based overcurrent protection framework has been confirmed by further case studies in seven bus mesh systems.

OC/OL Protection of Droop-Controlled and Directly Voltage-Controlled Microgrids Using TMF/ANN-Based Fault Detection and Discrimination

In this article, we propose a generalized overcurrent (OC) and overload (OL) protection scheme for the droop-controlled and directly voltage-controlled (DVC) inverter-interfaced distributed energy resources (IIDERs) to be used for the protection studies of the alternating-current (ac)-islanded (autonomous) microgrids, and provide a management strategy during and after short circuit (SC) and consequent OLs. The fault is detected, and its type is discriminated by a new method that takes the advantages of both artificial neural networks (ANNs) and transient monitoring function (TMF). By using the proposed strategy, the output current magnitudes of the distributed energy resource (DER) units are limited, and after fault clearance, the microgrid is restored to its normal operating conditions. The proposed OC/OL protection scheme limits the output power of the DERs. In this regard, a generalized fault model is presented, which considers the effect of the control system of the IIDERs. This model exploits a current-limiting strategy (CLS) that can be implemented in different reference frames to enhance the microgrid fault ride-through (FRT) capability. Finally, to demonstrate effectiveness, accuracy, authenticity, and feasibility of the proposed OC/OL protection scheme along with the TMF/ANN-based fault detection method and their desirable performance, offline digital time-domain simulations are done in MATLAB/Simulink environment, and the results are experimentally verified by using the OPAL-RT real-time digital simulator (RTDS).

Support Vector Machine Based Fault Location Identification in Microgrids Using Interharmonic Injection

This paper proposes an algorithm for detection and identification of the location of short circuit faults in islanded AC microgrids (MGs) with meshed topology. Considering the low level of fault current and dependency of the current angle on the control strategies, the legacy overcurrent protection schemes are not effective in in islanded MGs. To overcome this issue, the proposed algorithm detects faults based on the rms voltages of the distributed energy resources (DERs) by means of support vector machine classifiers. Upon detection of a fault, the DER which is electrically closest to the fault injects three interharmonic currents. The faulty zone is identified by comparing the magnitude of the interharmonic currents flowing through each zone. Then, the second DER connected to the faulty zone injects distinctive interharmonic currents and the resulting interharmonic voltages are measured at the terminal of each of these DERs. Using the interharmonic voltages as its features, a multi-class support vector machine identifies the fault location within the faulty zone. Simulations are conducted on a test MG to obtain a dataset comprising scenarios with different fault locations, varying fault impedances, and changing loads. The test results show that the proposed algorithm reliably detects the faults and the precision of fault location identification is above 90%.

Optimized Overcurrent Relay Coordination in a Microgrid System

Background: Microgrids are a conglomeration of loads and distributed generators at a distribution level network. Since this network is no longer a single source fed network, the typical protection strategies may not be deployed. Reconfiguration is a topology changing feature that is visible in microgrid. This is also another factor that is to be considered while protecting the microgrid setup. Objective: To develop an optimized overcurrent relay coordination scheme for microgrid networks. Methods: Inorder to devise suitable overcurrent protection scheme for microgrids, initially the normal and fault currents are captured for all topologies of the microgrid. For each topology, the optimized time multiplier settings of overcurrent relays are computed using Dual Simplex Algorithm. This aids in clearing the fault as fast as possible from the network. Results: A 21-bus microgrid system is considered and the optimized overcurrent relay coordination scheme is realized for the same. Conclusion: The proposed optimized overcurrent relay coordination was tested successfully on the 21-bus microgrid system. The proposed protection scheme was capable of identifying the optimized Time Multiplier Setting values of the overcurrent relays in the path of fault clearance. It is evident that the proposed scheme can be conveniently extended to larger networks.

Fault Detection in DC Microgrid Based on the Resistance Estimation

Evaluation toward the line parameter-based fault detection technique is an attractive option due to the limitations associated with the conventional differential and overcurrent protection schemes, mostly during a high-resistance fault situation. The fault detection strategy based on the line parameter can be exploited using the resistance instead of directly taking the decision from voltage and current. In this article, the proposed technique is focused on estimating the resistance and detecting the fault even during high-resistance fault case. Resistance is estimated using the local measurements available at the bus. After that, the sign of the estimated resistance is compared at both ends of the line segment to detect the fault and the use of the sign of resistance eliminates the time synchronization issues. The proposed method is capable of detecting the fault in radial as well as ring configuration dc microgrid. A ring main dc microgrid system is simulated using the EMTDC software to validate the proposed technique. The performance of the proposed approach is also validated using a dc microgrid hardware setup and tested for numerous situations. The results obtained from simulation and experiment verify that the proposed method accurately detects the faults (close in fault, high-resistance fault) in the dc microgrid.

A Specialized System-on-Chip Based Distance Protection for Distribution Grids with Inverter Interfaced Distributed Generation

Legacy protection schemes face new challenges as Inverter Interfaced Distribution Generation (IIDG) significantly changes the transient fault response of the distribution grid. The performance of the protection near the IIDG side is adversely affected by Low Voltage Ride Through (LVRT) and the negative sequence current suppression control characteristics of the IIDG. The operational characteristics of the protection are very different from those of the legacy protection schemes used in the distribution grid. Traditional overcurrent protection schemes cannot meet the requirements of selectivity and sensitivity. This paper analyses the influence of the IIDG on the protection schemes used in the distribution grid. Based on the positive sequence voltage polarization impedance criterion this study proposes a polarizing impedance criterion based on the fault component of positive sequence voltage, which can adaptively follow the fault resistance variation to satisfy the requirements of grid operation. The simulation results show that: (a) the proposed criterion is immune to the adverse effects of the transient characteristics of the IIDG; and, (b) it can adaptively follow the change of fault resistance making it suitable for application in short distribution lines. Using specialized System-on-Chip technology, a new distance protection device has been developed and tested on an industrial site. Simulation results and field tests showed that the new distance protection meets the requirements of the distribution grid with IIDGs.

Ensemble empirical mode decomposition‐based differential protection scheme for islanded and grid‐tied AC microgrid

This study presents a differential protection scheme based on ensemble empirical mode decomposition (EEMD) for AC microgrid. The fault current level is significantly lower during the islanded operation of a microgrid, which leads to the malfunction of the traditional over-current protection scheme. The proposed differential protection scheme uses the spectral differential energy of the first intrinsic mode function extracted from the decomposition of the current signal using EEMD for effective fault detection in the AC microgrid. The proposed EEMD-based differential protection scheme is validated on 10 bus and modified IEEE 34-bus AC microgrid test systems during various shunt faults. Moreover, the performance of the proposed EEMD-based differential protection scheme is evaluated under high fault impedance scenarios. The simulation results reveal that the proposed differential protection scheme can effectively detect the faulty line in an AC microgrid during seamless islanded and grid-tied operations.

Isolated Gate Driver for Medium-Voltage SiC Power Devices Using High-Frequency Wireless Power Transfer for a Small Coupling Capacitance

A high-voltage operation and breakneck switching speed of medium-voltage (MV) silicon carbide (SiC) devices demand gate drivers (GDs) with high voltage withstanding capability, high common-mode (CM) transient immunity and a reliable short-circuit protection. An isolated GD to meet these challenging requirements is presented in this article. A novel isolated gate driver power supply using high-frequency wireless power transfer (WPT) with a nonoverlapped winding arrangement for a small coupling capacitance is proposed. Moreover, a grounded shield is added to further reduce the effective coupling capacitance and the CM current. The receiver (Rx) coil of the WPT system along with its power processing circuit have been epoxy encapsulated to achieve a very high breakdown voltage and an extremely small form factor without violating very demanding clearance and creepage distance requirements. The impact of epoxy, winding arrangement, Rx circuits, and the grounded shield on the coupling capacitance is analyzed in details. In addition, a sophisticated overcurrent protection (OCP) scheme with soft-turn-off capability for MV SiC devices is developed. The designed OCP scheme achieves fast protection and simultaneously avoids false tripping due to very high current overshoot associated with the MV SiC devices during turn-on transitions. An experimental prototype is developed and the performance of the proposed GD under various operating conditions is evaluated experimentally.

Adaptive overcurrent protection scheme suitable for station blackout power supply of nuclear power plant operated through an integrated microgrid

Inclusion of distributed energy resources based integrated microgrid (IMG) into emergency station blackout (SBO) (EM-SBO) power system of nuclear power plant (NPP) has complicated its existing protection scheme due to varying system fault level with bidirectional flow of power. During SBO in NPP, it is of topmost priority to safeguard the reactor through EM-SBO supply. However, if any severe fault occurs, it may lead to complete collapse of the safety power supply in the NPP. So, availability of this tiny power system is most important as compared to the tripping of reactor safety of the NPP. In this paper, a 460 MWe NPP station has been considered to implement IMG into its EM-SBO power system and focuses on its overcurrent protection coordination scheme as a case study. The combined fuse and numerical relays inter-linked with digital logic-based adaptive overcurrent protection (AOP) scheme has been proposed after load flow analysis and calculating short circuit fault level through ETAP software. The sensitivity, the selectivity and the speed of the protection scheme have been evaluated in different network configurations like on-grid, semi-islanding and islanding mode of operation of IMG. Finally, it is proposed that the protection schemes vary from case-to-case basis leading to necessity of communication among the relays. So, an advanced AOP scheme with digital logic linked through peer-to-peer Hi-speed communication (IEC 61,850 confirmed GOOSE technology) has been proposed to resolve the protection issue of the modern NPPs operated through IMG.

Integration of wind turbines in distribution systems and development of an adaptive overcurrent relay coordination scheme with considerations for wind speed forecast uncertainty

The integration of renewable energy (RE)-based distributed generation (DG) with electric power distribution systems (DSs) in association with smart grid technology has numerous benefits, however, due to their intermittent nature, the utilisation of RE-based DG may pose threats to the proper operation of conventional overcurrent (OC) protection schemes. The resulting threats, malfunctions, and non-selective actions could occur by relays within the DS, and the development of efficient protection schemes is necessary. The objective of this study is to propose and simulate an adaptive OC protection scheme in DSs in the presence of doubly-fed induction generator (DFIG) wind turbines based on wind speed forecast data with considerations for wind speed forecast uncertainty and a low-voltage ride-through requirement for wind turbines. In each time interval and possible operating mode, the output power of DFIG-based wind turbines and relay setting parameters are determined offline. The results show that the proposed protection scheme prevents malfunctions and non-selective operations of relays, and also provides faster fault isolations, as compared to the conventional OC protection scheme.

Design of Setting Group-Based Overcurrent Protection Scheme for Active Distribution Networks Using MILP

In active distribution networks, system reconfiguration and connection/disconnection of distributed generation (DG) can result in protection coordination failure of overcurrent relays. Determining one set of optimal relay settings that would satisfy all possible network topologies is either infeasible or results in high relay operating times. To address this problem, recently the concept of clustering the various network topologies into a limited set is proposed where an optimal Setting Group (SG) is determined for each network topology cluster. This article proposes a novel problem formulation that simultaneously obtains the optimal relay SG and network topology clusters. Due to the complexity and non-linearity of the SG protection coordination problem, the SG protection coordination problem is reformulated as a mixed-integer linear programming (MILP) problem. The effect of the relay characteristic type on reducing the operating times of relays is also investigated. Comparative analysis is provided that highlight the superior performance of MILP over other heuristic optimization techniques. Data exchange between circuit breakers, DGs, CPU and relays are developed based on the IEC 61850 standard to illustrate the implementation of the proposed adaptive protection scheme on real networks.

Updated PSO optimised fuzzy‐PI controlled buck type multi‐phase inverter‐based PMSM drive with an over‐current protection scheme

This study confers a novel approach towards fuzzy-PI (proportional–integral) controlled pulse width modulation (PWM) controlled permanent magnet synchronous motor (PMSM) drive operated through a conventional voltage source inverter (VSI) supplemented with buck-converter fed current source inverter (CSI). It is observed that in a PWM controlled VSI, output voltage and current obtained contains certain harmonic distortion. A buck-converter fed CSI is capable of minimising the voltage and current ripples prominently even with the application of PWM. Thereby, in this study, an economic, as well as robust design procedure for the buck converter, fed CSI is proposed. Moreover, a particle swarm optimisation (PSO) mechanism is introduced to optimise the performance of the proposed fuzzy logic controller. Additionally, an over-current protection scheme of the PMSM motor is proposed. The performance of a PMSM drive is analysed in MATLAB/SIMULINK platform. Furthermore, the proposed concept is tested and verified in a real-time test-bench developed in the laboratory. Finally, from the performed test conditions, it can be confirmed that the proposed current control strategy of the drive system shows excellent performance in various operating conditions and can be employed in light-weight electric vehicles.