Directional Overcurrent Protection Research Articles

Optimal coordination of directional overcurrent protection relays using hybrid optimizer

In order to minimize or maximize an objective function, electrical engineering problems might benefit from optimization methodologies inspired by nature. This study employs a hybrid particle swarm optimizer (HPSO) to get rid of local optimum solutions and find the best global one for directional overcurrent protection relays (DOPR) protection. DOPR coordination is a highly constrained, mixed-integral nonlinear optimization problem. An adaptive defense method has been created to counteract the intentionally challenging design. Therefore, design variables such as time multiplier setting (TMS) and plug setting (PS) are utilized for each relay in the circuit. The goal function is to reduce the amount of time spent to trace the fault by all the relays. Reducing the time required for each relay to trace the fault is the aim of function. After analyzing and comparing two test studies of the IEEE benchmark using various optimization strategies, we found that the results for the IEEE 15-bus system has minimum time of 8.9 s, which is improved by 22.92% to 82.89%, and those for the IEEE 30-bus system minimum time of 22.45 s that is improved by 4.41% to 39.6%. In terms of overall DOPR operation and computational time needed to get the global optimum solution, the acquired results are demonstrably superior to those obtained using conventional and state-of-the-art methods.

Overcurrent and Directional Overcurrent Protection for Microgrid

Microgrids will become common in future electrical distribution networks. Numerous operating modes that occur in microgrids make the development of protection schemes and settings challenging. This paper aims to develop a simple protection scheme for the Microgrid IEC Benchmark without any expensive equipment such as communication apparatus. The scheme consists of directional and non-directional overcurrent relays with standard inverse characteristics. For the simulation tool, Digsilent powerfactory is employed. Four operating modes of the microgrid are applied to verify the relays’ coordination. The results show that the proposed scheme successfully protects the microgrid during short circuit faults with acceptable time margins.

Protection Scheme based on Artificial Neural Network for Fault Detection and Classification in Low Voltage PV-Based DC Microgrid

With the expansion of the DC distribution market, protection, and operational concerns for Direct Current (DC) Microgrids have increased. Different systems have been investigated for detecting, finding, and isolating defects utilising a variety of protective mechanisms. It might be difficult to locate high-resistance faults and shorted DC faults on low-voltage DC (LVDC) microgrids. Therefore, in this study, a Field Transform Technique like Short-Time Fourier Transform (STFT) is proposed for detecting the Fault Current (FC). This method detects the faults Pole-ground (PG), pole-pole (PP), and Arc fault are the major fault types in the DC network with PG fault as the most common and less severe. One of the difficulties the DC system faces in the incidence of a malfunction is the protection of essential converters. During this fault, the diodes, being the most vulnerable component of the system, may encounter a substantial surge in current, which can potentially cause damage if the current surpasses double their specified capacity for withstanding. After the Fault detection (FD), a Taguchi-based ANN is presented to classify the detected faults. This method effectively classifies PV-based faults. Then, to safeguard the FC, the Improved Self-Adaptive Solid State Circuit Breaker (I-SSCB) is introduced. It safeguards the FC in the low-voltage PV-based DC microgrid (DCMG) and restricts FC in the DCMG. The suggested approach is evaluated using the Matlab software and the proposed method produces 400A current and 100 KW power during the PV temperature of 25°C. The output current of the ANN is then 1A for a duration of 0.3 to 0.4 seconds. The fault voltage and FC produced in this proposed work are 1900V and 1950A. Therefore, the proposed work's current and voltage values are 21 KV and 0.35 I. Therefore, the proposed method produces more power and limits the FC in the LV-DCMG. In future studies, the improved or modified neural network or machine learning (ML)-based techniques can be utilized which may improve the protection scheme of the work.

Communication-less adaptive directional overcurrent protection strategy considering islanded mode detection in active distribution networks

The integration of distributed energy resources (DERs) in electric distribution networks originates the Active Distribution Networks (ADNs). The presence of DERs introduces challenges to conventional protection schemes due to bidirectional power flows and variations in fault current magnitudes; furthermore, the connection and disconnection of DERs result in multiple ADN operating modes (OMs), deteriorating the effective operation of protective relays. Considering the above, this document presents an adaptive protection strategy to address the challenges related to the variable nature of the ADN operation. The main contribution of the proposed approach is accurate islanded mode detection without requiring communication links, enabling fault detection in all ADN operating modes. The protection strategy maintains directional overcurrent relays' coordination using local voltage and current measurements to continuously estimate the Thevenin equivalent, fault currents, and adaptive coefficients.Relay coordination is maintained through tests conducted on a modified IEEE 34-bus feeder, considering several OMs, fault types, and locations. A comparison between the proposed adaptive protection strategy and a conventional overcurrent scheme shows that relay operating time is better in 100% of the analysed cases for the former strategy. On the other hand, the maximum errors in the fault current estimation using the Thevenin equivalent parameters are between 0.05% to 2.6% for all of the analysed operating modes when compared with the true fault current magnitudes. Finally, the adequate results validate the potential of the proposed communication-less protection strategy for modern protective relaying applications.

Principles for Implementation of Digital Power Direction Control in Microprocessor Current Protections

In the existing microprocessor-based directional current protection lines from phase-to-phase short circuits, digital power direction elements are used, which, as a rule, are switched on at full currents and voltage according to the so-called 90-degree pattern. With this switching scheme, a “dead” zone appears only in case of three-phase short circuits close to the protection installation site, which make up a small fraction of all possible types of such damage. Nevertheless, its presence is a significant drawback of the power direction organs. The principles of organ execution based on digital operations with orthogonal components of input voltages and currents have been considered. The result of the functioning of the power direction body is reduced to the development of an information sign equal to: one – with the direct direction of power; minus one – when it is in the opposite direction. To eliminate the “dead” zone, the work of the organ is organized using the voltage “memory”. In order to obtain the required duration of the “memory”, frequency compensation is implemented. The study of the effectiveness of the decisions made, as well as the behavior of the power direction control in normal and emergency modes, has been carried out by the method of a computational experiment. In the MATLAB-Simulink-SimPowerSystems dynamic simulation system, models of the electrical system and a digital power direction control have been developed. The results of the research have shown that the joint use of the existing and proposed principles for the implementation of a digital power direction control ensures an increase in its technical perfection and eliminates the “dead” zone while maintaining its stable operation for an arbitrarily long period of time.

Development of complex relay protection models in the MATLAB software

In the modern educational process, information technologies are actively used to realize the process of acquiring knowledge at a qualitatively new level, which is especially important for distance learning. The level of their development allows to develop mathematical models of any processes and phenomena. Relay protection schemes are chosen as the subject of research. Based on their functionality, virtual stands have been developed in the MATLAB software package, which allow the user to get closer to the real conditions of laboratory work. The program “Investigation of maximum current protection” allows to investigate the operation of circuit elements as a result of a two-phase short circuit in the electrical system that consists of the generator, power line and load. The symmetric method was used to create a mathematical model of short circuit. When you start the model, windows automatically appear, in which the graphs of the dependence of the currents flowing in each phase and the state of the elements from time to time are built in the form of animations. On the basis of previously developed algorithms of operation of the current relay RT-40 and the power direction relay RBM-178 the scheme “Research of the maximum directed current protection” is developed. The virtual stand considers a two-way power supply network, which includes: symmetrical three-phase AC sources, power lines, high-voltage switches, consumers and directional current protection. To ensure greater functionality, the introduction of the necessary parameters of the elements is provided. With the help of a group of switches, you can simulate a two- and three-phase short circuit in the circuit. When starting the model, the currents flowing in the line in normal, emergency and post-emergency modes are calculated. At the end of the simulation, graphs of the dependence of the currents flowing in each phase and the state of the elements over time appear. The program “Distance Protection Research” uses algorithms for calculating currents of two- and three-phase short circuits developed in previous stands. During the simulation, a panel with the main characteristics of the relay is provided for monitoring the results and recording them. There is a graph on the stand, which shows the angular characteristics and values of resistance at different points of the short circuit. The stands have light indication – lamps color – and visual indication – contacts status.

Mixed Integer Linear Programming Applied to Adaptive Directional Overcurrent Protection Considering N-1 Contingency

This work proposes a methodology for directional overcurrent protection coordination in interconnected transmission systems considering a possible network contingency state. The methodology uses the short-circuit data of the current network topology; however, the maximum load current data in the protection section of each relay is obtained considering the n-1 criterion, already foreseeing the disconnection of some network line. Thus, if a line gets disconnected, other protective devices will not improperly actuate by the redistribution of load currents in the network. The objective is to propose an adaptive protection scheme to redo the coordination for each topological change in the network. To this end, this work considers a smart grid environment with a supervisory system with communication capability between this and the remote devices. To obtain the optimal performance, the coordination problem, originally non-linear and non-convex, is linearized, allowing its formulation as a Mixed Integer Linear Programming problem. The methodology is applied to the 8-bus test system in 3 different cases and the 30-bus test system. Results show that the optimal coordination is obtained in a fast computational processing time, showing the suitability of the methodology for real-time application.

Optimal coordination of directional overcurrent protections considering the occurrence probability of different configurations and the effect of grouping cases

Optimal coordination of directional overcurrent protections considering the occurrence probability of different configurations and the effect of grouping cases

The Hybridization of PSO for the Optimal Coordination of Directional Overcurrent Protection Relays of the IEEE Bus System

The hybridization of PSO for the Optimal Coordination of Directional Overcurrent Protection Relays (DOPR) of the IEEE bus system proposes a new method for coordinating directional overcurrent protection relays in power systems. The method combines the hybrid particle swarm optimization (HPSO) algorithm and a heuristic PSO algorithm to find the minimum total operating time of the directional overcurrent protection relays with speed and accuracy. The proposed method is tested on the IEEE 4-bus, 6-bus, and 8-bus systems, and the results are compared with those obtained using traditional coordination methods. The collected findings suggest that the proposed method may produce better coordination and faster operation of DOPRs than the previous methods, with an increase of up to 74.9% above the traditional technique. The hybridization of the PSO algorithm and heuristic PSO algorithm offers a promising approach to optimize power system protection.

A new coordination scheme of directional overcurrent and distance protection relays considering time-voltage-current characteristics

The power transmission systems are mainly protected by distance relays (DisRs) as a primary protection and directional overcurrent relays (DOCRs) as a backup protection. These two types of relays have a different operation principle that, sometimes, leads to miscoordination problems. In this paper, a new approach for DOCRs and DisRs coordination considering the DOCRs time-voltage-current characteristic (TVC-C) is proposed to fully eliminate the miscoordination problems found in the already published works. The coordination problem is formulated as a mixed-integer nonlinear programming (MINLP) considering a new proposed objective function. Furthermore, two new decision variables related to TVC-Cs are proposed namely: the type and the voltage control variable. An enhanced version of the hybrid GSA-SQP method is proposed to solve the developed optimization problem. In order to check the applicability of the proposed relays coordination method on small and large and more complex systems, the IEEE 9-bus and IEEE 39-bus are used for this task. The obtained results are compared with the published works which show the superiority of the proposed method in terms of satisfaction of all coordination constraints.

Harmonic Dual-Setting Directional Overcurrent Protection for Inverter-Based Islanded Microgrids

Limited fault currents in inverter-interfaced islanded microgrids impose immense challenges on conventional overcurrent protection schemes. This paper proposes a sensitive and selective protection scheme for islanded microgrids using a third harmonic voltage generated by inverter-interfaced distributed generators (IIDGs). The generated harmonic voltage results in a harmonic layer formed during short-circuit faults and is decoupled from the fundamental fault current, i.e., limited by IIDGs. Further, the generated harmonic voltage is adaptively adjusted based on fault severity to enhance protection sensitivity and obtain a universal set of relays’ settings. The proposed protection scheme utilizes harmonic directional overcurrent relays (HDOCRs) equipped with a dual-setting time-current-voltage setting that sense the generated harmonic voltages and currents at the relay location to ensure optimal protection coordination (OPC) of islanded microgrids. The OPC with the proposed dual-setting is formulated as a constrained nonlinear program to determine the optimal forward and reverse relays’ settings. The proposed scheme is tested on the Canadian benchmark urban distribution system and compared to the conventional protection scheme, which relies only on a single time-current-voltage trip characteristic. The results ensure the ability of the proposed scheme to protect islanded microgrids without communication and its capability to reduce relays’ operation times.

Выявление факторов разрыва транзита электроэнергии в системе внешнего электроснабжения и ее подпитки через контактную сеть

One of the most difficult emergency modes is feeding the place of a short circuit in the external power supply system through the contact network in case of disconnection of a transit power line, which causes appearance of equalizing currents. In this case, it is proposed to use a combination of directional current protection that reacts not only to the amount of current in the protected line, but also to the direction of the short-circuit current, i.e., to the phase of the current in the line relative to the bus voltage and protection against excess voltage in any of the phases. In order to determine the signs of the specified mode, mathematical modeling of a section of the electrified 2×25 kV railway was performed in the Fazonord software package. During the simulation, the values of equalizing currents, power over-flows, voltages in the circuit nodes, and voltage asymmetry coefficients of the reverse sequence were obtained for the case of feeding the external power supply system through the contact network. In order to determine the factors that make it possible to identify the phenomenon of recharge of the external power supply system from the contact side when the transit of the power line breaks, it is proposed to use InTer-27.5-FVV terminals in combination with rupture monitoring based on the information and measuring complex «Black Box-2000», by which, based on the calculation of the voltage asymmetry coefficient of the reverse sequence, in cases of exceeding the set point value, a signal is transmitted to the control room.

Methodology to assess performance indexes for sensitivity, selectivity, and speed of coordination of directional overcurrent protections

Many algorithms for the coordination of directional overcurrent protections (DOCP) have been proposed in literature claiming that optimal solutions are reached, even though there are different reported solutions for the same problem. A new method to evaluate the quality of solutions for the coordination of DOCP is proposed. Three indexes are defined for selectivity, sensitivity, and speed, as desirable features of the coordination of protections. The use of performance indexes to evaluate the response of DOCP systems has not been previously considered in the literature. Given time dial and pick-up settings provided by any program or algorithm, uniformly distributed fault locations are simulated in each transmission line in order to determine the operation times as well as the separation times between main and backup relays. For each fault, the trip sequence of each relay pair is identified and classified according to 15 possible outcomes. To illustrate the method, indexes were computed from seven different coordination solutions reported in literature over the same test system. Results show interesting trade-offs among the three indexes, suitable to be presented as three independent axes; consequently, a given solution could be better in one feature (e.g., speed) but worse in others (e.g., selectivity and/or sensitivity). • There was no method to evaluate the quality of protection coordination solutions. • A novel and integral assessment of sensitivity, selectivity, and speed of solutions is shown. • The assessment is performed using an exhaustive analysis of possible fault locations. • Seven existing coordination solutions over the same case study are impartially assessed. • Conflicts among resulting sensitivity, selectivity and speed indexes are analyzed.

Effects of fault type and pre-fault load flow on optimal coordination of directional overcurrent protections

• This paper is on optimal coordination of directional overcurrent protections (OC-DOCP). • Effects of fault type and pre-fault load flow on OC-DOCP are analyzed. • Changes in optimal settings can be considerably greater than changes in short-circuit currents. • Changes in objective functions can be considerably lower than changes in short-circuit currents. This short article shows an analysis of the effects of fault type and pre-fault load flow on the optimal coordination of directional overcurrent protections. A well-known case from the literature is taken as an example, because this case has been previously solved considering only three-phase faults and only one pre-fault load flow. The fault type and the pre-fault load flow have an influence on the results of short-circuit currents and, consequently, on the results of the optimal coordination of directional overcurrent protections. It is shown herein that the effects of pre-fault load flow and single-line-to-ground faults can be important on the results of optimal coordination. For the analyzed cases, the percentage changes in the optimal results of time delay settings can be considerably greater than the percentage changes in short-circuit currents. On the other hand, the percentage changes in optimal results of objective functions can be considerably lower than the percentage changes in short-circuit currents for the analyzed cases.

An Improved Technique of Hybridization of PSO for the Optimal Coordination of Directional Overcurrent Protection Relays of IEEE Bus System

The use of a directional overcurrent protection relay (DOPR) to protect an electrical power system is a crucial instrument for keeping the system dynamic and avoiding undue interruption. The coordination of a DOPR’s primary and backup relays is modelled as a highly constrained optimization problem. The goal is to determine an ideal value that will reduce the overall working time of all primary relays. The coordination is accomplished by the use of particle swarm optimization hybridization (HPSO). Comprehensive simulation experiments are carried out to evaluate the efficacy of the proposed HPSO by employing the time multiplier setting (TMS) and plug setting (PS) as an optimization variable and constant, respectively. The HPSO has been examined satisfactorily utilizing certain IEEE benchmark test systems (9-bus and 14-bus). The outcomes are contrasted with earlier heuristics and evolutionary approaches. Based on the acquired findings, it is clear that the obtained results exceed the other conventional and state of the art procedures in terms of total DOPR operation and the computing time necessary to achieve the global optimal solution.

Hybridization of PSO for the Optimal Coordination of Directional Overcurrent Protection Relays

In the electrical power system, the coordination of directional overcurrent protection relays (DOPR) plays a preeminent role in protecting the electrical power system with the help of primary and back up protection to keep the system vigorous and to avoid unnecessary interruption. The coordination between these relays should be pursued at optimal value to minimize the total operating time of all main relays. The coordination of directional overcurrent relay is a highly constrained optimization problem. The DOPR problem has been solved by using a hybridized version of particle swarm optimization (HPSO). The hybridization is achieved by introducing simulated annealing (SA) in original PSO to avoid being trapped in local optima and successfully searching for a global optimum solution. The HPSO has been successfully applied to five case studies. Furthermore, the obtained results outperform the other traditional and state of the art techniques in terms of minimizing the total operating of DOPR and convergence characteristics, and require less computational time to achieve the global optimum solution.

Podešavanje usmerenih zemljospojnih zaštita u prenosnoj mreži korišćenjem unapređene metode diferencijalne evolucije

The paper presents the procedure of directional ground overcurrent protection setting calculation in the transmission network by using classical calculation procedure and by using an advanced algorithm of differential evolution. To meet the basic requirements of relay protection systems such as speed, selectivity, coordination and sensitivity, the conditions that need to be considered when setting directional ground overcurrent protection are defined. By using the optimization method, the problem was solved in two ways. In the first case, the settings are designed to minimize the total response time of directional ground overcurrent protection to remote-end high-resistance faults, whereas in the second case the settings are designed so that the maximum response time to remote-end high-resistance fault is minimal. The results obtained using the classical approach are compared with the results obtained using the optimization method and the advantages and disadvantages of both approaches are highlighted.

Optimal restoration of directional overcurrent protection coordination for meshed distribution system integrated with DGs based on FCLs and adaptive relays

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

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.

Voltage Function in Directional Over-Current Protection to Enhance the Sensitivity and Coordination Problem in Microgrid with High Penetration of Inverter-Based Resources

Voltage Function in Directional Over-Current Protection to Enhance the Sensitivity and Coordination Problem in Microgrid with High Penetration of Inverter-Based Resources