Conventional Protection Schemes Research Articles

Security challenges to smart agriculture: Current state, key issues, and future directions

Smart agriculture integrates a set of technologies, devices, protocols, and computational paradigms to improve agricultural processes. Big data, artificial intelligence, cloud, and edge computing provide capabilities and solutions to keep, store, and analyze the massive data generated by components. However, smart agriculture is still emerging and has a low level of security features. Future solutions will demand data availability and accuracy as key points to help farmers, and security is crucial to building robust and efficient systems. Since smart agriculture comprises a wide variety and quantity of resources, security addresses issues such as compatibility, constrained resources, and massive data. Conventional protection schemes used in the traditional Internet or Internet of Things may not be useful for agricultural systems, creating extra demands and opportunities. This paper aims at reviewing the state-of-the art of smart agriculture security, particularly in open-field agriculture, discussing its architecture, describing security issues, presenting the major challenges and future directions.

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.

Toward an adaptive protection scheme in active distribution networks: Intelligent approach fault detector

Conventional protection schemes have proven insufficient for the protection of Active Distribution Networks (ADN). Novel protection schemes with an adaptive approach should be developed to guarantee the protection of ADN under all their operating conditions. This paper proposes an ADN adaptive protection methodology, which is based on an intelligent approach fault detector over locally available measurements. This approach uses Machine Learning (ML) based techniques to reduce the strong dependence of the adaptive protection schemes on the availability of communication systems and to determine if, over a fault condition, an Intelligent Electronic Device (IED) should operate considering the changes in operational conditions of an ADN. Additionally, the methodology takes into account different and remarkable recommendations for the use of ML techniques. The proposed methodology is validated on the modified IEEE 34-nodes test feeder. Additionally, it takes into consideration typical features of ADN and micro-grids like the load imbalance, reconfiguration, changes in impedance upstream from the micro-grid, and off-grid/on-grid operation modes. The results demonstrate the flexibility and simplicity of the methodology to determine the best accuracy performance among several ML models. Besides, they show the methodology’s versatility to find the suitable ML model for IEDs located on different zones of an ADN. The ease of design’s implementation, formulation of parameters, and promising test results indicate the potential for real-life applications.

Impact of TCSC on Directionality of Traveling Waves to Locate Faults in Transmission Lines

The use of devices based on power electronics has been widely spread to improve the transmission lines performance. However, the inclusion of these compensators, named Flexible AC Transmission Systems, produces adverse effects on conventional protection schemes. For instance, it modifies the apparent impedance of transmission lines. This condition produces malfunction in conventional distance protection. This paper presents an algorithm protection for power transmission lines, compensated with a Thyristor-Controlled Series Capacitor. The proposed algorithm is capable of discriminating the directionality of traveling waves as well as detecting and locating eleven types of faults. The impact of the Thyristor-Controlled Series Capacitor device in the directionality of traveling waves is analyzed and separated for developing the protection. The obtained results show that the directionality of the algorithm is not affected by the presence of Thyristor-Controlled Series Capacitor. In order to validate the algorithm, several study cases are considered. The error calculating distance to fault is smaller than 1.25%

Integration of a Heuristic Multi-Agent Protection System into a Distribution Network Interconnected with Distributed Energy Resources

In conventional method protection schemes are devised for certain operation conditions with fixed settings throughout their operation life, however, protection systems in interconnected distribution networks rely on a detailed analysis of fault current contribution and variation in operation conditions under real-world scenarios. In fact, the concept of Adaptive Protection System (APS) and possibility of the adjustment for protection settings within modern Intelligent Electronic Devices (IEDs) have introduced desired functionalities for protection systems to cope with complex operation scenarios envisioned within future power system networks. In this paper, a novel protection system based on Multi-Agent System (MAS) and heuristic decision-making is proposed to update protection settings of the protection IEDs with respect to prevailing operation conditions in an interconnected distribution network. The adopted methodology is reliant on real-time simulation of a distribution network interconnected with Doubly-fed Induction Generator (DFIG) wind farms where different fault scenarios are applied to evaluate the functionality and performance of the proposed Multi-Agent Protection System (MAPS). In addition to that, combination of knowledge sharing between different protection IEDs and logic reasoning are integrated to fulfill protection task under real-world operation scenarios. The significance of the proposed MAPS is the improvement in protection system of the interconnected distribution network.

A Robust Adaptive Overcurrent Relay Coordination Scheme for Wind-Farm-Integrated Power Systems Based on Forecasting the Wind Dynamics for Smart Energy Systems

Conventional protection schemes in the distribution system are liable to suffer from high penetration of renewable energy source-based distributed generation (RES-DG). The characteristics of RES-DG, such as wind turbine generators (WTGs), are stochastic due to the intermittent behavior of wind dynamics (WD). It can fluctuate the fault current level, which in turn creates the overcurrent relay coordination (ORC) problem. In this paper, the effects of WD such as wind speed and direction on the short-circuit current contribution from a WTG is investigated, and a robust adaptive overcurrent relay coordination scheme is proposed by forecasting the WD. The seasonal autoregression integrated moving average (SARIMA) and artificial neuro-fuzzy inference system (ANFIS) are implemented for forecasting periodic and nonperiodic WD, respectively, and the fault current level is calculated in advance. Furthermore, the ORC problem is optimized using hybrid Harris hawks optimization and linear programming (HHO–LP) to minimize the operating times of relays. The proposed algorithm is tested on the modified IEEE-8 bus system with wind farms, and the overcurrent relay (OCR) miscoordination caused by WD is eliminated. To further prove the effectiveness of the algorithm, it is also tested in a typical wind-farm-integrated substation. Compared to conventional protection schemes, the results of the proposed scheme were found to be promising in fault isolation with a remarkable reduction in the total operation time of relays and zero miscoordination.

An adaptive distance protection scheme for high varying fault resistances: Updated results

The conventional distance protection scheme is usually affected by uncertainties associated with transmission line parameters and some uncontrolled parameters like fault resistances. By varying the fault resistances, errors are introduced in the fault distance estimation because the apparent impedance measured in the relay terminal is not proportional to the line length between the relay and fault location. This paper presents an adaptive protection scheme using Artificial Neural Network (ANN) to address the problem. The proposed scheme automatically adjusts its relay settings based on the fault resistance calculated using the acquired data obtained by the remote terminal unit RTU connected to field instruments at the local end. Communication between both ends is through fiber optic. A MATLAB based adaptive distance relaying scheme is developed using the ANN. PSCAD/EMTDC software is used to generate the current and voltage signals for specified lines which are used for subsequent ANN training and testing of the proposed algorithm. The proposed non-conventional adaptive scheme was validated with different high fault resistances that occurred on the 132 kV Aba - Owerri, and Aba-Umuahia transmission lines in Nigeria between January 2019 and June2019.The results show the ability of ANN to correctly detect, classify and localized fault under varying fault resistance.

Fault detection scheme based on feeder buses impedance angles discriminator in smart microgrid

Abstract Smart Grid (SG) or a modern electric grid system is becoming a priority for most developed countries. SG describes the integration of elements connected to the electric grid with an information infrastructure through intelligent communication systems to offer numerous benefits for both the provider and consumers of electricity. Thus, the conventional protection schemes have to be moderated for a reliable operation. This paper proposes a new central protection scheme for typical SG with hybrid distributed generations and energy storage. The proposed algorithm employs the available data through the SG communication facilities in three sequentially steps, namely fault detection, bus current direction and faulty feeder selection followed by the proper relay action. Line terminal voltage and current signals are continuously recorded, sampled and transmitted to the main protection centre in form of movable window patterns. The bus impedance angles are estimated and its deviations are tracked. Accordingly, a proposed discriminator is applied to evaluate and identify each bus flow direction during the fault either in forward or reverse direction with respect to the installed protective relay. Finally, the faulty feeder is selected and the required relay action is taken by tripping for the internal fault feeder and blocking for external faults.

Single‐end protection algorithm for HVDC transmission lines based on the current difference

This study presents a single-end protection algorithm for current source converter (CSC) high-voltage direct current (HVDC) transmission lines to solve shortcomings such as inadequate sensitivity, low speed and the need for communication link of conventional protection schemes. The proposed algorithm uses the average of DC line current at the rectifier terminal, sampled at 4 kHz within a 5 ms window, for simultaneous fault detection and faulted pole selection. For fault discrimination, the algorithm uses the average of second-order difference of the sampled current data. The algorithm is verified by extensive simulation studies using a CSC-HVDC test system modelled in PSCAD, as well as field data. The simulation results show fast and reliable protection of CSC-HVDC lines under different fault conditions including high-fault resistances. Moreover, the novel protection algorithm is stable against resistive–inductive faults, power flow changes, change of data window length, lightning interference and size of smoothing reactor. The algorithm does not require a communication link as used by numerous previous methods. It has a low computational burden, low sampling frequency and can be easily implemented in practical CSC-HVDC systems without extra arrangements as the required signals are readily available in the existing measuring hardware platforms.

New approach to intermittent earth fault detection with admittance criteria

Admittance based tripping criteria afford reliable earth fault protection of MV distribution feeders. Although highly effective for persistent earth fault detection, they often fail in the case of intermittent arcing faults when employed in the conventional protection schemes. In this paper the new approach to persistent and intermittent earth faults detection is proposed. The method is based on calculation of the cumulative intermittent arcing fault duration time. The validation based on data from numerical modeling of earth faults in EMTP as well as data recorded in real MV networks confirms the effectiveness of the approach.

Communication-less protection scheme for AC microgrids using hybrid tripping characteristic

Conventional protection schemes are not effective in microgrids due to the possibility of bi-directional current flow and fault level reduction in the islanded mode caused by converter interfaced Distributed Generations (DGs). This paper proposes a hybrid tripping characteristic based protection scheme for microgrids. The proposed characteristic uses both voltage and current measurements to decide the tripping time, thus it is called hybrid tripping characteristic. Same relay setting is used in both grid connected and islanded mode of operation of the microgrid. Therefore, communication facilities are not required in the proposed scheme unlike many existing communication-based solutions. Voltage measurement helps in differentiating low-fault-current situation from overloading condition. It also helps in the reduction of the operating time in islanded mode. Acceptable relay operating time is achieved in both grid connected and islanded mode. A coordination problem is formulated and solved with the proposed hybrid characteristic. The obtained protection coordination is independent of the operating mode of the microgrid. The performance of the scheme is evaluated using both PSCAD simulations and hardware experiments. It is found that the proposed protection scheme performs satisfactorily for various fault impedance values, fault locations, DG combinations, overload situations and measurement errors. The performance of the scheme has been compared with the existing schemes.

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.

A pilot protection algorithm for TCSC compensated transmission line with accurate fault location capability

This paper introduces a communication-aided scheme to enhance the fault detection, and fault location calculation for a thyristor-controlled series capacitor (TCSC) compensated transmission lines. In the proposed method only the current data at the remote-end should be synchronously sent to the local-end. Since the remote-end voltage data do not use in local-end, compared with the conventional pilot impedance-based protection schemes, the proposed method significantly reduces the requirement of data transmission bandwidth. The proposed algorithm is independent of fault resistance, power flow direction, and pre-fault condition. In the proposed method the TCSC parameters are not utilized in the derived fault location formula and as a result, the performance of the proposed method is not impacted due to variations in TCSC parameters. Several major factors are taken to investigate the accuracy of the proposed method, including measurement errors and power swing conditions. The simulation results prove the high accuracy and acceleration of the proposed scheme during all fault cases.

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.

Quaternary Protection Scheme with Optimal Dual-Directional Overcurrent Relay Setting for Smart Microgrids

The implementation of the microgrid concept with flexible grid-connected and islanded operation in distribution networks creates a variety of protection problems, including mis-coordination, protection blinding, and false tripping. Conventional protection schemes that use traditional overcurrent protective relays cannot respond to the microgrid operations in the manner of short-circuit current changes. In this paper, a novel quaternary protection scheme, along with intelligent electronic device-based dual-directional overcurrent relays, is developed for protecting against faults in microgrids with distributed generations. The proposed protection scheme provides the optimal relay setting groups that rely on the dynamic changes in the microgrid system states and the characteristics of forward and reverse short-circuit currents. The optimal protection coordination is formulated as a non-linear programming optimization problem, which is solved by evolutionary programming. The proposed approach is tested on the IEEE 34-node test feeder, which is modified as the microgrid operation equipped with multiple synchronous-based distributed generations. Test scenarios, including the implementation of different protection schemes and protective devices, are analyzed with different fault locations. The simulation results show that the quaternary protection scheme can overcome all the protection problems. In addition, the significant reduction in the total relay operating times indicates that the proposed protection scheme provides fast fault clearing when compared to the conventional protection approach.

Fault location in UPFC compensated double circuit transmission line using negative sequence current phasors

Double-circuit transmission lines are used in modern power systems to enhance the transmission capability and to improve system reliability and safety. However, the protection of double-circuit lines is a challenging task as the presence of flexible ac transmission system (FACTS) in modern power grid impairs the performance of the conventional distance protection schemes. Moreover, the high impedance faults cannot be detected by relays as they become under-reach. This paper proposes a negative sequence current based scheme for locating faults and identifying faulty circuit/ line in double circuit transmission line compensated by UPFC at one end. In the proposed scheme the current signals are collected from both ends of the line to be protected. Then the negative sequence components of the currents are calculated. The discrimination between internal and external fault is achieved from the phase angles of the negative sequence currents and the fault location is determined from the ratio of the negative sequence currents. Prior knowledge about the type of fault is not required for fault location estimation. Extensive fault simulation studies including high impedance faults have been performed. The scheme is immune to the fault inception angle and fault resistance.

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.

Implementation of Optimal Protection Coordination for Microgrids with Distributed Generations Using Quaternary Protection Scheme

The flexible operation of microgrids, along with the availability of distributed generation (DG) units, causes a variety of changes in short-circuit current levels, magnitudes, and directions, which has undesirable effects on the operation of protection systems. Conventional protection schemes use typical directional overcurrent relays (DOCRs) with limited operating capability, unable to respond to microgrid operations in the manner of short-circuit current changes. In this paper, a quaternary protection scheme implemented with dual-directional overcurrent relays (dual-DOCR) and a protection control strategy is developed for protecting against faults in microgrids, taking into account the existence of DGs and connection and disconnection of DG units. The optimal dual-DOCRs setting and coordination are formulated as an optimization problem solved by evolutionary programming to minimize the relay operating times. The proposed protection scheme is implemented with a centralized protection control system based on the smart grid concept to increase the adaptability of the dual-DOCRs, which have multiple relay setting groups in accordance with system state changes. The simulation case studies are performed using the IEEE 14-bus test system, which is modified as a meshed microgrid operation. Test scenarios, including possible operations of microgrids, DGs availabilities, and different fault events, are analyzed and discussed. The comparative studies and simulation results show that the proposed scheme provides efficient coordination between the primary and backup relays and increases the responsibility of the protection system, which can be observed from the significant reduction in the relay operating times, resulting in the enhancement of selectivity, sensitivity, and speed of microgrid protection systems.

Adaptive distance relaying: Solution to challenges of conventional protection schemes in the presence of remote infeeds

Adaptive distance relaying: Solution to challenges of conventional protection schemes in the presence of remote infeeds

A Fault Detection and Classification Scheme for Unified Power Flow Controller Compensated Transmission Lines Connecting Wind Farms

In recent years, there is an increasing trend of integrating large capacity offshore wind farms into power grids through UPFC compensated TLs for accommodating large flow of power. The nonlinear fluctuations of output power due to unpredictable variation of wind speed and the different operating modes of the UPFC greatly affect the performance of the conventional distance relaying-based TL protection scheme. This article investigates the impact of such TLs on distance relay performance and proposes a two criteria-based new fault detection and classification scheme. The method utilizes the sign of the change in the magnitude of positive-sequence current at both ends of the line for fault detection and the transient monitor index derived from the locally measured three-phase current for fault classification. The performance of the proposed scheme is evaluated on different fault and nonfault transients generated on two standard test systems through EMTDC/PSCAD during different operating modes of UPFC and at different wind speed. The performance of the proposed scheme is further validated through dSPACE DS 1103-based real-time digital simulation platform. Finally, the comparative assessment results with some important existing methods justify the effectiveness of the proposed method.