Adaptive Protection Scheme Research Articles

Adaptive differential protection scheme for wind farm integrated power network

In this paper, an adaptive differential protection scheme is proposed for wind farm integrated power network. Any fixed threshold setting based protection scheme is not always suitable for the different operating conditions of power system. Considering the possible modulations in the fault signal, a particle swarm optimization (PSO) based differential relay algorithm is proposed in this paper. The positive sequence current differential principle is used. For different operating conditions, fault conditions and configurations of the system, the threshold value can be calculated online. So, practically the method can be applied to any power system model and the impact of dynamic operation of wind farm on the protection function is negligible. The threshold setting is designed considering the fault location and fault inception angle. Initially, the most effective faults among all the possible faults are identified with a single variable (fault location) objective function. Later, only single-phase-to-ground fault is considered for threshold setting with all possible parameters. The method is tested using a standard power system model integrated with wind farm and simulated using MATLAB R2016a software. Results prove the efficacy of the method.

Swarm intelligence-based differential protection scheme for wind integrated transmission system

Conventional differential protection scheme considers a fixed threshold to detect the fault in a transmission system. In a wind integrated transmission system, any fixed threshold-based protection function is not reliable always due to the dynamic variation of control parameters of the wind turbine. To mitigate this issue, an adaptive differential protection scheme is proposed in this work for the transmission system integrated with wind farm. The method uses a particle swarm optimization (PSO) algorithm to generate an optimum threshold for the system considering the varying system and fault operating conditions. An objective function is designed for PSO considering the fault location, inception angle, and fault resistance. The method is tested by using a standard wind integrated transmission system model, simulated using MATLAB software. Performance of the method is tested for numerous test cases considering the wide variations in fault and system operating conditions.

Real-Time Adaptive Differential Feature-Based Protection Scheme for Isolated Microgrids Using Edge Computing

Inhabited isolated areas require independent power systems called isolated microgrids. Conventional protection schemes are not suitable for isolated microgrids due to their dependence on significant fault current. This article introduces an adaptive differential feature-based protection scheme for fault detection and faulty phase identification for isolated microgrids. Instead of differential currents, it proposes differential features, where edge computing is used to extract the features at point of measurement. The most informative one-dimensional feature is extracted from each phase at both ends of the line. The line differential feature is compared with an adaptive threshold to perform fault detection. The threshold is updated every second and is immune to system noises. Faulty phase identification is performed with a logical comparison. An in-memory circular buffer is proposed to store the local features in case of communication delay. Communication and synchronization are experimentally validated, and the worst-case latency is reported along with individual processing time for data acquisition, feature extraction, communication, and fault detection. Extensive validations are done with IEC-based and IEEE 13-node-based isolated microgrid. The test results are compared with state-of-the-art methods and proved that the proposed scheme is practical to be adopted in real- world isolated microgrids of different sizes and topologies.

Adaptive coordination of overcurrent relays in active distribution networks based on independent change of relays’ setting groups

The capability of network configuration change and high penetration of distributed generations (DGs) are two important characteristics of modern distribution networks. The configuration change and connection/disconnection of DGs result in the variation of fault currents’ magnitude and direction besides changing the role of protective devices as primary or back up protection. This fact can make the protection coordination complicated or even impossible in some cases. One of the solutions to this problem is to use a setting group (SG)-based adaptive protection schemes. SG-based protective schemes protect various network states (different configurations and connection/disconnection of DGs) using a limited number of SGs. Therefore, it is needed to propose an algorithm to specify the settings of each SG and the determination of SG selection in different network states (NSTs). In this paper, previous attempts in the utilization of SG capability of Overcurrent relays (OCRs) are examined and a novel approach is proposed which is capable of protecting the same network with lower delay in relays' operation times although it requires a fewer number of SGs. In this paper, a new method based on integer linear programming (ILP) and particle swarm optimization (PSO) is utilized to specify the proper SG to activate for each relay in each NST, in order to minimize the total operating time of OCRs, considering coordination constraints. The efficiency of the proposed method in comparison to the previous methods is demonstrated by applying on a sample distribution network.

Intelligent Fault Detection System for Microgrids

The dynamic features of microgrid operation, such as on-grid/off-grid operation mode, the intermittency of distributed generators, and its dynamic topology due to its ability to reconfigure itself, cause misfiring of conventional protection schemes. To solve this issue, adaptive protection schemes that use robust communication systems have been proposed for the protection of microgrids. However, the cost of this solution is significantly high. This paper presented an intelligent fault detection (FD) system for microgrids on the basis of local measurements and machine learning (ML) techniques. This proposed FD system provided a smart level to intelligent electronic devices (IED) installed on the microgrid through the integration of ML models. This allowed each IED to autonomously determine if a fault occurred on the microgrid, eliminating the requirement of robust communication infrastructure between IEDs for microgrid protection. Additionally, the proposed system presented a methodology composed of four stages, which allowed its implementation in any microgrid. In addition, each stage provided important recommendations for the proper use of ML techniques on the protection problem. The proposed FD system was validated on the modified IEEE 13-nodes test feeder. This took into consideration typical features of microgrids such as the load imbalance, reconfiguration, and off-grid/on-grid operation modes. The results demonstrated the flexibility and simplicity of the FD system in determining the best accuracy performance among several ML models. The ease of design’s implementation, formulation of parameters, and promising test results indicated the potential for real-life applications.

Adaptive protection scheme for microgrids based on SOM clustering technique

Microgrids are penetrating into the power systems at an unprecedented rate. The reason is the mutual economic and environmental benefits of microgrids, both for power grid utility and the consumers. Some special features of microgrids such as, the two main operational conditions called, islanded and grid-connected modes, and being composed of various types of distributed energy resources along with different uncertainties cause some tough challenges to protection and control systems. From the protection aspect, the coordination of overcurrent relays protection will become a difficulty, due to the extensive changes in the fault current levels sensed by these devices. In this paper, a new adaptive protection coordination scheme based on Self-Organizing Map (SOM) clustering algorithm is proposed for digital overcurrent relays equipped with several setting groups. Considering the similarity of mis-coordinated relay pairs for the clustering purpose, the proposed protection scheme focuses on solving the mis-coordination between main/backup relay pairs. As a case study, a modified IEEE 33-bus test system is used as a microgrid. In the case study, a synchronous distributed generation and two electric vehicle charging stations are installed. The results suggest that not only the proposed method is fully capable and flexible to significantly improve the mis-coordination of overcurrent relay pairs, but it can also ameliorate the operating time of relay.

A novel methodology in optimal setting of directional fault current limiter and protection of the MG

Integration of the Distributed Generators (DGs) in the MicroGrid (MG) provides an additional contribution to the fault current causing change of the short circuit current which could lead to the miscoordination problem (in the forms of maloperation and delayed operation) in the existing Over Current Relay (OCR) based protection system. Moreover, contribution of the MG can cause the overall fault current to exceed the designed capability level of distribution components, like Circuit Breakers (CBs). In this case, CBs are subjected to increased stresses and are thus more prone to failure to operate when desired. As a result of the above issues (miscoordination and CB failure) the system reliability degrades.Utilizing a Directional Fault Current Limiter (DFCL) between the MG and upstream network is an effective way to mitigate the above-mentioned issues. Nonetheless, setting of the DFCL parameters is a challenging task and should be done with the aim of restoring coordination among OCRs and also enhancing system reliability. In this paper, a novel methodology for optimal setting of DFCL parameters (R and X) is proposed therein the effect of DFCL on OCRs coordination and system reliability is considered simultaneously. For this purpose, a new objective function in terms of DFCL installation and reliability cost is introduced to minimize the total cost of DFCL utilization. Based on the proposed strategy, which will be evaluated through various scenarios, the optimal coordination between existing relays are restored and the whole MG would be protected without the need to use adaptive protection schemes or new relays.

Hybrid Signal Processing and Machine Learning Algorithm for Adaptive Fault Classification of Wind Farm Integrated Transmission Line Protection

The technological advancement in integration of Renewable Green Energy Sources (RGES) like Wind Farm Generators (WFG), and Photovoltaic (PV) system into conventional power system as a future solution to meet the increase in global energy demands in order to reduce the cost of power generation, and improve on the climate change impact. This innovation also introduces challenges in the power system protection by it being compromised due to injected fault current infeeds on existing facilities. These infeed lead to the undesired trip of a healthy section of the line, and protection system failure. This paper presents a soft computational approach to adaptive fault classification model on High Voltage Transmission Line (HVTL) with and without RGES-WFG integration topologies, using extracted one-cycle fault signature of voltage and current signals with wavelet statistical approach in Matlab. The results are unique signatures across all fault types and fault distances with distinct entropy energy values on proposed network architecture. The supervised machine learning algorithm from Bayesian network classified 99.15 % faults correctly with the operation time of 0.01 s to produced best-generalized model with an RMS error value of 0.05 for single line-to-ground (SLG) fault identification and classification. Best suitable for adaptive unit protection scheme integration.

A Robust Protection Scheme Based on Hybrid Pick-Up and Optimal Hierarchy Selection of Relays in the Variable DGs-Distribution System

The increasing proliferation of distributed generators (DGs) demands a robust and comprehensive design of the communication-based adaptive protection scheme, which must be able to not only deal with the known changes in the DGs-distribution system but also handle the unknown changes due to variations in the operating mode, network configuration, and number, type, and size of DGs. On one side, with the increasing installations of DGs, the deployment of the communication system in protection is increasing to monitor the system status and select the relays’ settings accordingly. However, on the other side, if information flow does not happen due to the presence of pre-fault failure of the relay-agents and/or communication links, a protection scheme may fail to provide the suitable protection. This paper proposes a centralized adaptive protection scheme to deal with such failures and varying operating conditions. It provides optimal relays settings for varying operating conditions of the DGs-distribution system with the aim of providing fast, comprehensive, and self-adaptive protection. In order to achieve these objectives, two algorithms have been developed: the first algorithm determines optimal hybrid pick-up settings of the relays, and the second algorithm determines the adaptive hierarchies of the relays. With the inclusion of these two algorithms, the relay coordination problem has been formalized linearly. The performance of the proposed scheme has been tested and validated for various known and unknown events with different types of short circuit faults of different fault impedances on the 37-bus IEEE test distribution system in a MATLAB simulation and coding environment. The results show that the proposed method not only provides the optimal relay's coordination in varying situations but also effectively reduces the protection latency due to pre-fault failures of the relays and communication links, and low level of fault currents.

\xb5PMU-based smart adaptive protection scheme for microgrids

The concepts of microgrids (MGs) and smart grid represent the recent targeted revolution towards fully smart electrical network integrated with high penetration of renewable energy sources (RESs). The protection system of MGs becomes a challenge due to variable characteristics of its currents, bidirectional power flow and output power fluctuations of RES, causing selectivity and sensitivity issues for conventional protective devices (PDs) with fixed setting. In this paper, a smart protection scheme (SPS) is proposed using micro-phasor measurement units (µPMUs) to obtain the continuous rapid synchronized phasor measurement data. And it is communicated with a microgrid central controller (MGCC) through highly reliable communication architecture to carry out online smart adaptive protection scheme. Fault index coefficients and abnormality coefficients are calculated for each feeder to detect the fault location and the abnormality case. Detailed modeling of an MG including 10-bus connected distribution system with integrated distributed generation (DG) is simulated using ETAP software. The proposed protection algorithm is modeled and evaluated using MATLAB software. The proposed fault detector and abnormality detector can enable quick and accurate fault identification and isolation.

Graph Theory and Optimization Algorithms Aided Adaptive Protection in Reconfigurable Microgrid

Microgrids interfaced with distributed generators facilitate decentralization of electric power. Bi-directional power flow due to multiple sources and dynamic behaviour of microgrids possess challenges to protection engineers. In this paper, an adaptive protection scheme for a central protection centre (CPC) in a microgrid is proposed. The key functions of the CPC are monitoring the microgrid, identification of fault if any, shortest path identification from a fault to the nearest operating source using Boruvka–Dijkstra graph theory algorithm. It also assigns adaptively the optimized values of time multiplier setting of relays in that path using genetic algorithm, which in turn aids in quick fault clearance. A hardware prototype is developed, tested and validated for a 7-bus microgrid network using Arduino ATmega 1280 for shortest path identification and optimized TMS value assignment for relays in that path using Raspberry Pi Model B+.

Exploiting Idle Capacity in Optical Networks to Pre-Plan as Many Additional Paths as Possible for Enhancing Service Connection Availability

A network is not always fully loaded during operation and may have idle capacity which is neither carrying any network services nor providing protection for working capacities. This idle capacity may be used to pre-plan as many additional paths as possible to enhance service connection availability with only some extra pre-planning in the network central controller. Our proposed adaptive multi-path protection scheme pre-plans additional paths for failure recovery in an elastic optical network over currently idle capacity to improve the overall network service availability significantly.

Adaptive protection combined with machine learning for microgrids

This paper presents a rule-based adaptive protection scheme using machine-learning methodology for microgrids in extensive distribution automation (DA). The uncertain elements in a microgrid are first analysed quantitatively by Pearson correlation coefficients from data mining. Then, a so-called hybrid artificial neural network and support vector machine (ANN-SVM) model is proposed for state recognition in microgrids, which utilises the growing massive data streams in smart grids. Based on the state recognition in the algorithm, adaptive reconfigurations can be implemented with enhanced decision-making to modify the protective settings and the network topology to ensure the reliability of the intelligent operation. The effectiveness of the proposed methods is demonstrated on a microgrid model in Aalborg, Denmark and an IEEE 9 bus model, respectively.

Protection Schemes for Key Service in Optical Networks Secured by Quantum Key Distribution (QKD)

Quantum key distribution (QKD) is considered a secure solution for key distribution and applied in optical networks to overcome security issues by providing key services in different lightpaths. In optical networks, lightpaths in fibers can be used for the delivery of QKD due to their good transmission performance. Accordingly, optical networks secured by QKD have been regarded as an important paradigm, and survivability in this paradigm is an issue worthy of study. In this paper, we focus on the protection schemes for key services in optical networks secured by QKD. Specifically, in consistency with two characteristics of key services (i.e., the key-updating process and key-volume adaptive routing), two key-volume adaptive protection schemes (i.e., dedicated protection and shared protection) are proposed for the networks against link failures. In such scenarios, the designed key-protection threshold can alleviate the tight network resources caused by the key-updating process. Simulation work has been conducted to evaluate the performance of the proposed schemes in terms of blocking probability, resource utilization, and proportion of secret-key consumption with different key-protection thresholds and update periods. Numerical results show that the two proposed schemes are effective in providing protection. Furthermore, evaluating the impact of protection on network security verifies a trade-off that exists between how much protection can be provided for key services versus the overall security of the network, given a certain resource budget.

The Adaptive and Robust Power System Protection Schemes in the Presence of DGs

In recent years, using distributed generations (DGs) has increased in order to compensate the load and consumption growth. Although connecting DG resources to power system has many advantages, it might cause some protective problems such as mis-coordination between network protection devices, due to the changing in the short circuit level of power system. In this paper, two method for restoring the coordination of relays in the presence of DGs by using FCLs are proposed. In both methods, different criteria, such as considering the variation of network topology, optimizing the value and number of FCLs are considered to propose a comprehensive and adaptive protection method. In the first method, an adaptive protection scheme by using FCLs is proposed to active and deactivate FCLs in different topologies to restore the coordination of relays. In addition, the second method proposes a robust method which considers all possible situations and topologies of the power system to maintain the coordination of power system during fault. Finally, the proposed robust and adaptive protection scheme has been compared in terms of cost, the operation time of relays and computation time, and based on the aims of operators in a power system one of these method can be implemented, The proposed methods are implemented on IEEE 14-bus standard network, and all possible topologies of the mentioned network are considered. Simulation results show that the proposed method can maintain the coordination of overcurrent relay protection in the presence of DGs and topology changes. In other words, the proposed method is robust against topologies changes.

A Novel Constraints Reduction-Based Optimal Relay Coordination Method Considering Variable Operational Status of Distribution System With DGs

One of the factors that affect the level of fault currents is the number of short-circuit MVA sources present during the fault. A distribution system with distributed generators (DGs) is a multi-source system, in which DGs can be connected or disconnected to meet the high or low load requirements respectively. Also, during fault conditions, DGs can get disconnected due to their low fault ride-through capabilities. These changes in connections change the number of DGs and the operational status of the system, which in turn change the fault currents seen by relays and the ranges of maximum and minimum fault currents for which the relays settings work coordinately. This paper realizes that an increase in the proliferation of DGs makes the relay coordination problem a highly constrained optimization problem, and changes in the number of DGs make the problem more complex, which can decelerate the overall performance of relays. The aim of this paper is to reduce the complexity and design a fast, robust, and adaptive protection scheme which can efficiently work in the variable environment of the DG-distribution system. This paper proposes a novel constraints reduction-based relay coordination method which selects a small set of constraints out of large set of constraints while determining the optimal relays settings. The relay coordination problem is formulated as a linear programming problem. The performance of the proposed method is tested on the both configurations, radial and meshed, of the IEEE 38-bus distribution system. Comparative studies have been conducted to highlight the advantages of the proposed approach under changing system’s configuration with variable locations and sizes of DGs.

Adaptive Protection Coordination Scheme Using Numerical Directional Overcurrent Relays

Dynamically changing distribution system operating conditions compromises the coordination of the existing protection schemes. This paper proposes an online adaptive protection coordination scheme by utilizing numerical directional overcurrent relays (DOCRs) and commercial A Mathematical Programming Language (AMPL) based Interior Point OPTimization (IPOPT) solver. The proposed scheme also utilizes intelligent electronic devices and a communication channel to obtain real-time system information and to update relays settings. The presented approach is able to handle different operating conditions of the system, including loss of loads, generations, and lines. Further, the miscoordination arising due to injections of distributed generations (DGs) is also handled. The proposed approach has been tested on the IEEE 14-bus system (with and without DG), under various operating conditions. Overall system reliability enhancement using the proposed approach has been analyzed in terms of the amount of energy not supplied. Further, the optimum settings of DOCRs obtained using AMPL based IPOPT solver has been compared with those obtained by General Algebraic Modeling System based Sparse Nonlinear OPTimizer solver, OPTI Toolbox based IPOPT solver, MATLAB based interior point method, and metaheuristic genetic algorithm and differential evolution. It has been found that the proposed coordination approach gives good results in reasonably small time and thus, is suitable for the adaptive protection scheme.

Adaptive Protection Coordination with Setting Groups Allocation

Abstract- Distributed Generations (DGs) plug & play operation changes the fault current levels, which results in Directional Over-Current Relay (DOCR) miss-coordination and non-optimal tripping times. Adaptive protection is a great solution to tackle the adverse effects of DGs on distribution network. Some adaptive protection coordination for all DG connection statuses requires vast communication infrastructure and equipment upgrade where the non-adaptive coordination leads to high operating time of relays. In this paper, a new adaptive protection concept is introduced as a tradeoff where the settings of some relay are adaptively changed based on its neighborhood DGs connection. The number of Settings Groups (SGs) of each DOCR are found by calculating the proposed sensitivity matrix. The SGs are only added in relays experiencing the high changes in short circuit levels. The proposed method is simulated on IEEE-30 Bus and the results indicate the capability of the proposed method in efficient and optimum design of adaptive protection schemes with proper SGs allocation.

Relevance of adaptive protection scheme using phasor measurement unit in Indian power grid

The configuration of the power system is constantly changing due to renewable integration, changing loads, network switching operations or faults. The relays settings based on pre-determined static system conditions that are in general maximum or minimum, may not suffice, leading to inaccurate relay operation for a dynamic power system. Malfunction of conventional protection system has been one of the main causes of cascading catastrophes in power grid. Selection of suitable relay characteristics that will be an appropriate compromise for all loading conditions and contingencies is a matter of concern. The relevance of adaptive relay settings in wide area monitoring, protection, and control (WAMPAC) using synchrophasor is brought out in this paper. The significance of new wide area adaptive protection system (WAAPS) in improving the reliability and safety of power transmission through Indian grid, with a high level of operational uncertainties, is analysed and an architecture is suggested.

Adaptive protection methodology in microgrid for fault location and nature detection using q 0 components of fault current

The dynamic behaviour of microgrid system under faulty conditions makes adaptive protection a general necessity for reliable microgrid operation. In design of adaptive protection, the grid-connected and islanded modes have immense importance including grid-connected mode without distributed generators (DGs) in microgrid. In this study, a new adaptive protection scheme is proposed based on the above-mentioned modes of microgrid operation. The proposed method considers nature of DGs connected, fault location detection and fault nature identification based on quadrature and zero sequence components of fault current considering impact of X/R ratio of DGs. The proposed methodologies for adaptive protection schemes are verified in Matlab-Simulink environment and the results are found to be satisfactory while various faults are simulated at different nodes of the microgrid model. At the time of verification of effectiveness of the proposed methodologies, the time derivative of quadrature and zero-axis components of fault current are considered sufficient to instantaneously detect the fault location and fault nature in microgrid system.