Overcurrent Protection Relay Research Articles

Design and Development of Overcurrent Protection Relay Inverse Definite Minimum Time Type Based on Arduino Uno

An overcurrent protection relay is an essential component in electrical system to protect devices from damage due to excessive current. The Inverse Definite Minimum Time (IDMT) type has a trip time that depends on the magnitude of the overcurrent, with faster trip times for higher overcurrent levels. Arduino Uno can be used as a microcontroller platform to build an IDMT with relatively low cost and ease of implementation. This research aims to design and construct an Arduino Uno-based IDMT. The system consists of a current sensor, Arduino Uno, and a relay. The current sensor is used to detect the current flowing through the load. The Arduino Uno processes the data from the current sensor and determines if the current exceeds a predefined limit. If the current exceeds the limit, the Arduino Uno will activate the relay to cut off the current flow to the load. The IDMT trip time is implemented using an algorithm that considers the magnitude of the overcurrent and the minimum trip time. The system is tested using a simulator and actual load. Test results show that the Arduino Uno-based IDMT system works well and can protect the load from damage due to overcurrent.

A hybrid physical and co-simulation modern adaptive power protection testbed for testing the resilience of smart grids under cyber-physical threats

Power protection systems play a critical role in ensuring the safe and reliable operation of modern power grids. With the increasing complexity of grid topologies and the integration of Distributed Energy Resources (DERs), traditional protection schemes face challenges in maintaining effective coordination among relay systems. This paper presents a new adaptive Overcurrent Relay (OCR) protection and investigates the resilience of different traditional and new adaptive OCR protection schemes against various cyber-physical threats in a smart grid environment. Key contributions include the implementation of a novel adaptive protection scheme designed to dynamically adjust OCR settings based on real-time grid conditions, improving flexibility and responsiveness in managing grid variations induced by DER integration and operational changes. The proposed scheme is validated and implemented using the Multifunction Protection Relay SIEMENS 7SJ62, following to the programming standards of IEC 61131–3, ensuring the reliability and practical applicability of the adaptive OCR scheme in real-world scenarios. Additionally, a dedicated testbed is developed to simulate real-time cyber-physical interactions, incorporating hardware components such as the SIEMENS 7SJ62 and OMICRON-256 test device, along with high-performance computers and communication networks to facilitate comprehensive evaluations of adaptive OCR schemes under varying operational conditions. The study also examines the implications of real-time cyber-attacks on power system operations and the effectiveness of adaptive OCR protection schemes, addressing cybersecurity concerns and proposing mitigation strategies to the system resilience.

Review on Coordination of Time Overcurrent Relays in Electrical Distribution Network

Integration of distributed generators in micro grid causes bidirectional current flow as a result of the need for readjustment of the setting of the overcurrent protective relays in the electrical network. Adaptive coordination is one of the solutions that adjust the setting of protective relays according to the dynamics of the distribution network. Various algorithms had been reported on the adaptive coordination of time overcurrent relays. This paper reports a survey about the coordination of time overcurrent relays in micro grid electrical distribution network. The review found that there is limited research on distributed control rules of the multi agent coordination of protection relays. Furthermore, it was found that the trend of coordination algorithms focused on the nature inspired algorithms.

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.

Coordination Tool for Overcurrent and Earth-Fault Relays at A 33/11 KV Power Distribution Substation in Basrah City

The coordination of overcurrent relay protection in the power framework is crucial for preserving electrical distribution systems. It ensures that both primary and backup protection are provided to the system. It is essential to maintain a minimal level of coordination between these relays in order to reduce the overall running time and guarantee that power outages and damage are kept to a minimum under fault conditions. Proper coordination between the primary and back-up relays can minimize the operation duration of overcurrent with instantaneous and earth fault relays by selecting the optimum TMS (Time Multiplier Setting) and PS (Plug Setting). The present study investigates the difficulty associated with determining the TMS and PS values of earth-fault and overcurrent relays at the 33/11 kV power distribution substation in Basra using the instantaneous setting element. Overcurrent and earth fault relays were simulated in two scenarios: one with a time delay setting and one with an immediate setting. This procedure was carried out to generate Time Current Characteristics (TCC) curves for each Circuit Breaker (CB) relay took place in the Nathran substation, which has a capacity of 2×31.5 MVA and operates at a voltage level of 33/11 kV. The substation is a part of the Basrah distribution network. The short circuit current is estimated at each circuit breaker (CB), followed by the simulation of protection coordination for the Nathran substation using the DIgSILENT Power Factory software. This research is based on real data collection, and the setting considers the short-circuit current at the farthest point of the longest feeders. The results show the effectiveness of the proposed coordination scheme, which reduced trip operation time by 20% compared to the presented case study while maintaining coordination between primary and backup protection.

The Performance and Robustness of Power Protection Schemes for Grid‐Connected PV Systems Under Varied Smart Inverter Controllers

The increasing use of inverter‐based distributed generation requires a comprehensive study of its effects on fault analysis and the effectiveness of protection systems in distribution networks. This study examines the impact of different inverter control modes on multiple types of protective relay schemes. These include different overcurrent relay (OCR) schemes, both standard and nonstandard tripping characteristics, optimal coordination approaches, and different grid operation scenarios. The investigation is conducted through the utilization of grid‐connected and islanding operation modes, with fault resistance values of 0 and 5 Ω. The study is carried out on a 14‐bus CIGRE network which includes two photovoltaic (PV) farms with a capacity of 10 MVA each. The research provides several significant contributions, including the analysis of fault current contributions, examination of issues in OCR protection, investigation of the influence of fault impedance levels on OCR performance, evaluation of ideal coordination methods, and carrying out a comparative analysis utilizing optimization technique by using the water cycle optimization algorithm (WCA) and the particle swarm optimization algorithm (PSO). In addition, to guarantee the robustness of the suggested protection strategy, this work adopts a hardware‐in‐the‐loop approach. The OMICRON‐256 system is utilized to carry out real‐time testing on a SIPROTEC 7SJ62 multifunction protection relay, which validates the effectiveness of the proposed method in protecting microgrids under different PV control strategies. The total operating time for the nonstandard tripping scheme was 12.077–12.3003 s for PSO and WCA, respectively, while for the standard tripping scheme, it was 12.1226 and 12.1564 s. Moreover, these findings offer practical insights that can assist operators in effectively designing the power networks with grid‐connected PV systems by showing OCR miscoordination and no tripping events in power systems with PVs under inverters controllers.

Smart Grid Resilience for Grid-Connected PV and Protection Systems under Cyber Threats

In recent years, the integration of Distributed Energy Resources (DERs) and communication networks has presented significant challenges to power system control and protection, primarily as a result of the emergence of smart grids and cyber threats. As the use of grid-connected solar Photovoltaic (PV) systems continues to increase with the use of intelligent PV inverters, the susceptibility of these systems to cyber attacks and their potential impact on grid stability emerges as a critical concern based on the inverter control models. This study explores the cyber-threat consequences of selectively targeting the components of PV systems, with a special focus on the inverter and Overcurrent Protection Relay (OCR). This research also evaluates the interconnectedness between these two components under different cyber-attack scenarios. A three-phase radial Electromagnetic Transients Program (EMTP) is employed for grid modeling and transient analysis under different cyber attacks. The findings of our analysis highlight the complex relationship between vulnerabilities in inverters and relays, emphasizing the consequential consequences of affecting one of the components on the other. In addition, this work aims to evaluate the impact of cyber attacks on the overall performance and stability of grid-connected PV systems. For example, in the attack on the PV inverters, the OCR failed to identify and eliminate the fault during a pulse signal attack with a short duration of 0.1 s. This resulted in considerable harmonic distortion and substantial power losses as a result of the protection system’s failure to recognize and respond to the irregular attack signal. Our study provides significant contributions to the understanding of cybersecurity in grid-connected solar PV systems. It highlights the importance of implementing improved protective measures and resilience techniques in response to the changing energy environment towards smart grids.

Adaptive overcurrent protection scheme coordination in presence of distributed generation using radial basis neural network

The operational performance of conventional overcurrent protection relay coordination connected to a distribution network is adversely affected by the penetration of distributed generators (DG) at different buses in the network. To address this problem, this paper proposes a novel adaptive protection coordination scheme using a radial basis function neural network (RBFNN), which automatically adjusts the overcurrent relay settings, i.e., time setting multiplier (TSM) and plug setting multiplier (PSM) based on the penetration of DGs. Short circuit currents and voltages measured at different buses are acquired using the remote terminal units (RTU) connected to different buses within the terminal network. Communication between the various remotes and local end station RTUs is through hybrid communication systems of fiber optic and power line communication system modules. The new adaptive overcurrent protection scheme is applied to the IEEE 33-bus distribution network with and without DGs, for single and multi-DG penetration using both the ETAP and MATLAB software. The simulation results show the proposed scheme significantly improves the protection coordination.

Overcurrent and ground fault relay protection settings at tranformator-1 150kV/20kV Braga substation

The occurrence of a malfunction at the substation results in power outages and losses in the electrical energy distribution system to consumers. Many tests are carried out to see the performance of the protection system, including the parameters of the over current relay (OCR) and ground fault relay (GFR) in the electrical energy distribution system. This research aims to analyze OCR and GFR values, analyze OCR setting, drop-off, and pick-up values, and analyze OCR time characteristics using DigSilent Power Factory 15.1 software based on existing equipment specification data at the Braga substation. The results show an OCR accuracy level of around 94% on the 20 kV and 150 kV sides. Meanwhile, 92.39% on the 20 kV GFR side and 94.87% on the 150 kV side. The setting value for the pick-up current is 0.92 A on the 20 kV side of the GFR and the drop-off current is 0.85 A on the 150 kV side with a pick-up current of 0.39 A and a drop-up current of 0.37 A. Setting a value on the 20kV side is greater than on the 150 kV side due to the difference in current transformer ratio values. The simulation results show that the OCR and GFR characteristic curves on both sides meet the criteria for a protection system with good performance.

Adaptive real-time protection scheme for distribution networks with high penetration levels of renewable energy resources

The increasing demands of electrical power have imposed a necessity to integrate renewable energy power sources (REPS) into electrical power networks. The presence of REPS within electrical distribution networks mandated an update in the settings of the overcurrent protection relays. In this paper, a real-time adaptive protection scheme is proposed to redefine the settings of the overcurrent protection relays by replacing the traditional time multiplier setting (TMS) with a newly proposed real-time adaptive time multiplier setting (ATMS). The proposed ATMS is formulated as the product of two factors namely; the acceleration factor (AF) and the tuning factor (TF). The AF is set as the ratio of the impedance seen by the relay during a fault to the pre-fault impedance. The TF is a multiplication constant that is determined offline prior to operation in order to optimize ATMS. The scheme was tested upon different radial and meshed bench-mark testing systems; the IEEE 34 system and the IEEE 30 bus system employing MATLAB software package. The proposed scheme proved its capability of optimizing the response of overcurrent relays and minimizing total operating time. In addition to its adaptability to different operational and loading conditions during the day.

A new methodology for optimization of overcurrent protection relays in active distribution networks regarding thermal stress curves

In this paper, a novel method for optimizing and coordinating directional overcurrent relays in active distribution networks considering thermal equivalent short-circuit current is proposed. A modified genetic algorithm is used as a tool in order to simultaneously minimize the operating times of the primary relays and maximize the time delay between the operation of backup relays and their respective protected elements’ thermal stress curves. In other words, the objective function to be minimized is defined as the sum of the operating times of all primary relays and the reciprocal sum of the thermal violation check. The latter part is necessary because a protection engineer needs to be sure that the operation of a backup relay is as far as possible from the thermal stress curve of the protected element. Needless to say, for every solution, the algorithm ensures the proper coordination between primary and backup relay pairs throughout the network. The simulation is carried out for a closed loop medium voltage distribution network and the results are presented to demonstrate the effectiveness of the proposed approach. The main benefit of this optimization process is that it indicates whether the existing protection system can operate safely below the thermal stress curves of the protected elements’ or whether additional measures are required.

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.

Accurate power sharing for islanded DC microgrids considering mismatched feeder resistances

Accurate load power sharing and bus voltage regulation are two critical control objectives for ensuring power quality and reliable operation of DC microgrids. Although regulating the DC Bus voltage can be achieved by adopting an external secondary control loop, inaccurate load power/current sharing among converters is a prominent issue due to feeder resistances mismatch. This can lead to undesired overloading of converters, triggering over-current protection relays, and potentially resulting in cascading failure of the whole system. Existing literature uses virtual resistance techniques to improve the power sharing accuracy; however, so far, no explicit relation between the values of the virtual resistances and the feeder resistances mismatch has been formulated, opening the possibility to enhance power sharing even further. Therefore, this paper proposes an accurate power sharing strategy in which the virtual resistances are chosen to account for the feeder resistances mismatch. The proposed technique relies on the optimal tuning of the virtual resistance assigned to the local controller of each converter. An online estimation algorithm of the physical feeder resistances, required for virtual resistance tuning, is embedded into the control loop of each converter. Thus, prior information about the feeder resistances in the design stage is not required. The proposed approach is validated through simulation and experimental results from a Hardware-in-the-Loop setup of a typical islanded DC microgrid. The results demonstrate the approach merits, achieving accurate power sharing among converters and ensuring robust operation, even in scenarios involving communication failures.

Impact of an Unsymmetrical Fault on the Controller of the DFIG Wind Farm

Objectives: DFIG-based wind farms are predominant in their performance when compared to other types of generators. In the field study, due to transient events, converters at the machine side and grid side are affected. To protect the converters from an abnormal operation, overcurrent protective relays have to be designed and incorporated. Unsymmetrical fault analysis are help in the design of protective devise and speed sensors. Methods: DFIG-based wind systems are developed using the DIgSILENT power factory software and EMT simulations are executed during the unsymmetrical faults applied near the Machine Side Converter (MSC) and Grid Side Converter(GSC). Findings: During the simulation studies, various parameters are transient time, maximum current, steady-state, and voltage drop identified near the MSC and GSC. The short circuit parameters are attenuated during the unsymmetrical faults and the rotor maximum current increases by 2 to 3 times the rated current per unit, 40% to 50% voltage dip, and the current reach the steady state value after 1.213 sec during the fault. The parameters are affected more when a fault occurs near the GSC when compared to a fault near MSC. Novelty: These research findings will contribute to a better understanding and improvement of sensor sensitivity, as well as the development of control mechanisms, and protection tactics in designing more accurate and appropriate for DFIG-WT. Keywords: DoublyFed Induction Generator; Machine Side Controller; Grid Side Controller; Unsymmetrical Fault; Sensor

Analysis of the Integrated Effect of Temporary Overvoltages, PV Transformer Connection and Overcurrent Protection in Hybrid PV-Wind Energy System

The integration of solar and wind energy in hybrid PV/Wind energy systems (HPWES) have allowed it to be more reliable renewable energy source. However, the overvoltage protection for HPWES is scarcely covered in literature. To fill this gap, an investigative analysis of the effect of temporary overvoltages (TOVs) in HPWES is presented in this paper. Sources of TOV considered were ground faults and load rejection events. The HPWES was simulated and tested for TOVs under different fault conditions. The results showed that the TOV response was dependent on three more elements; overcurrent protection relays (OCRs), surge protective devices (SPDs) and the type of the PV transformer connection. The analysis showed that an interactive effect between these three elements after the occurrence of TOVs. This interactive effect has affected the tripping time of the OCRs which in turn affected the TOV duration and the energy absorbed by SPDs. It was concluded that the impact of the type of transformer connection and OCR tripping settings upon SPD could be critical that in some cases could lead to SPD failure. Conclusions are presented to the designers of HPWES to consider them during the design phase to overcome possible failures of SPDs.

The Use of Instantaneous Overcurrent Relay in Determining the Threshold Current and Voltage for Optimal Fault Protection and Control in Transmission Line

When a fault occurs on the transmission line, the relay should send the faulty signal to the circuit breaker to trip or isolate the line. Timely detection is integral to fault protection and the management of transmission lines in power systems. This paper focuses on using the threshold current and voltage to reduce the time of delay and trip time of the instantaneous overcurrent relay protection for a 330 kV transmission line. The wavelet transforms toolbox from MATLAB and a Simulink model were used to design the model to detect the threshold value and the coordination time for the backup relay to trip if the primary relay did not operate or clear the fault on time. The difference between the proposed model and the model without the threshold value was analysed. The simulated result shows that the trip time of the two relays demonstrates a fast and precise trip time of 60% to 99.87% compared to other techniques used without the threshold values. The proposed model can eliminate the trial-and-error in programming the instantaneous overcurrent relay setting for optimal performance.

A novel cyber‐attack modelling and detection in overcurrent protection relays based on wavelet signature analysis

AbstractCyber attacks can disrupt the digital protection relays and change their output command to the circuit breaker. The aim of this research is to provide new condition monitoring for overcurrent relays during cyber treatments. This research is modeled three common types of attacks with randomize concept and its detection method via MATLAB/SIMULINK software into IEEE 3‐machine 9‐bus model that is applicable in real time situation. Finally a new index has been defined for detection that employs wavelet analysis of the substation currents and its energy which has been called cyber attack detection index (CADI). Proposed index is robust to variation of sampling signal, sampling rate, cyber attack type and current transformer saturation. The results show that the index has an acceptable performance with accuracy of 100% without any false trigger. This method is not dependent on operating point, relay protection scheme and attack type and also could distinguish the abnormal actions of breakers due to unexpected cyber contingencies caused by natural disasters or software malfunctions rather than cyber attacks in a certain operating points. The level of CADI curve in cyber attacks is always higher than symmetrical fault and current signal detects them more quickly and clearly than other signals.

A Communication-less adaptive protection scheme for Self-Healing distribution systems

Network reconfiguration has allowed supply restoration to disrupted areas after fault events. However, changes in network topology can alter the direction and magnitude of fault currents and jeopardize the coordination of overcurrent relays. Adaptive protection schemes using system-wide communications have been developed to solve this issue by performing dynamic relay recalibration. Unfortunately, system-wide communications are also associated with huge economic costs, data integrity issues, and limitations of infrastructures. Moreover, in less developed communities, such schemes are less applicable. Although various communication-less schemes have been proposed, they mainly focused on adapting overcurrent relay protection for different distributed generation penetrations and microgrid islanding statuses. Currently, no communications-less adaptive protection method has been proposed to address the miscoordination of protection relays caused by network reconfiguration for supply restoration. Thus, this paper presents a communication-less adaptive protection scheme to maintain relay coordination in a reconfigurable distribution network that performs supply restoration. The scheme deploys microcontroller units to predict the correct relay settings by monitoring load flows through the relays. The scheme is demonstrated on the IEEE 33-bus and 69-bus test distribution systems using two different relay placement strategies, non-directional and directional relays. The proposed scheme achieved up to 10.8 times lower disruptions than the existing system in N-1–1 contingency scenarios. Overall, the scheme provides a simple and low-cost alternative to improve the effectiveness of power system protection in a reconfigurable network.© 2017 Elsevier Inc. All rights reserved.

Overcurrent Relay for Generation Distribution Utilization

Distributed Generation (DG) is the production of electricity from a variety of renewable energy sources that is closer to the customer and load. The addition of distributed generation sources to the distribution networks alters the characteristics of distribution system and has an influence on its protection coordination. Relay protection plays a critical function in protecting a power system from various problems. Relay protection coordination reduces relay operating time and avoids relay failure. As a result, a fault analysis of the distribution network with and without distributed generation installation is required to determine the effects of installing DG at the radial system on overcurrent relay protection. The software programmed ETAP version 19.0 was used to represent an actual distribution system in this research paper. The consequences on the overcurrent protection relay were discovered as a result of the analysis. Simultaneously, the presence of an overcurrent relay following the installation of DG may no longer be dependable. As a result, it is critical to assess the effects of DG installation in order to verify that the protective zone can be properly protected.

A coordinated relay protection strategy of distribution network based on fault current limiting

In order to solve the problem of difficult coordination of traditional overcurrent relay protection caused by short supply radius and little difference of fault current along urban distribution network, a coordinated relay protection strategy based on economical fault current limiter (FCL) is proposed. The FCL device is configured at the export of the main transformer, by using quick fault identification method, setting different protection current value and relay protection delay time, once the fault occurs, the FCL can quickly limit the fault current first then cooperate with the circuit break and switches on the feeder line to achieved the coordinated relay protection. Combining with faults occurring at different locations along the feeder line, the composition and basic working principle of the FCL are discussed, the theory of fast fault identification method and the setting method of the coordinated relay protection parameters are emphatically discussed. The simulation results show that the proposed current limiting coordinated relay protection strategy can effectively reduce the short-circuit current level and bus voltage drop during the fault handle processing, thus reduce the damage to the distribution system and influence range of the fault, greatly improve the selectivity of the relay protection finally.