Settings Of Overcurrent Relays Research Articles

Stability-Constrained Settings of Directional Overcurrent Relays With Shifted User-Defined Characteristics for Distribution Networks With DERs

Stability-Constrained Settings of Directional Overcurrent Relays With Shifted User-Defined Characteristics for Distribution Networks With DERs

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.

The Evaluation of Over Current Relay and Ground Fault Relay Settings on Power Transformers

Power transformer is an important component of the substation and has an important role in the electric power distribution system. During operation the power transformer can’t be isolated from distribution system when abnormal conditions or faults occur. A fault in the power transformer will have huge impact on the power transformer itself. The substation has an installed capacity of 60 MVA of power transformers, and during operation there is a possibility of relay failure, which may interrupt the power distribution process to the load. To avoid this failure, it is necessary to analyse the settings of Over Current Relay (OCR) and Ground Fault Relay (GFR) on the 60 MVA transformers. The analysis was carried out by simulating short circuit faults of the electrical system in the ETAP software application, and then configure the setting of the relay by referring to the magnitude of the short circuit current value for phase to phase and phase to ground. The results of this analysis are used as a reference to determine the OCR and GFR relay values in the power transformer. The results obtained show that the recommended value for OCR setting on 150 kV power transformers is 0.92 second while for GFR is 0.96 second, and for the 20 KVA power transformers the OCR and GFR setting values are 0.40 and 0.20 seconds respectively. Comparison based on the results of the setup data and the analysis data has carried out, there is difference in the working time of the relay, with a difference of 5%, where the value of the analysis results is not much different from the conditions in the field.

ANALISA SETTING PROTEKSI OVER CURRENT RELAY (OCR) PADA GENERATOR 30 MW UNIT PLTA POSO PT. POSO ENERGY

To ensure that the performance of the protection system is still good or not in terms of protection, calculations and adjustments must be made to the safety relay settings, especially the over current relay. In the research, analysis of the over current relay protection settings on the 30 MW generator at the Poso 1 PT PLTA unit. Poso Energy obtained that the maximum load current data on the generator was 2042 A, while the calculation results obtained were 2041.7 A. For the relay (top) operating time in the specification data, the value was 1.4 s, while in the calculation results it was 1.3 s. And for the setting current (Is) in the specification data the value is 4.7 A, whereas in the calculation results it is 4.28 A. Over current relay (OCR) or over current relay is an auxiliary relay from the differential relay, the over current relay is used to secure the generator of the overcurrent in the Poso 1 PLTA is PCS-985GE-EN-H2-110V-5A. In the specification data, the TMS value is 0.15 s, while in the calculation results it is 0.14 s. This means that data in the field is slower to protect components from interference by 0.01 s. However, overall the overcurrent relay settings on the generator at the Poso 1 PLTA are still in good condition.

Machine-Learning-Based Adaptive Settings of Directional Overcurrent Relays With Double-Inverse Characteristics for Stable Operation of Microgrids

Machine-Learning-Based Adaptive Settings of Directional Overcurrent Relays With Double-Inverse Characteristics for Stable Operation of Microgrids

Optimal data-driven adaptive overcurrent relay coordination for active distribution networks

Massive integration of distributed generation originates the active distribution networks, introducing new control, protection and operation challenges. This paper proposes a strategy for adaptively protecting active distribution networks that undergo frequent changes in operating conditions. Numerical overcurrent relays capable of storing multiple setting groups, each with different settings designed to address various operating conditions, are used to overcome this issue. The proposed strategy uses locally acquired voltage and current measurements to accurately identify the operating conditions during fault occurrence. The identified condition is then used to select the appropriate overcurrent relay settings using a strategy which includes signal characterisation, data recognition, and optimisation to minimise the operating time for both primary and backup relays. Validation of the protection strategy is conducted on the IEEE 34-Bus test system, and the results indicate its ability to accurately detect different operating conditions in both connected and islanded operating modes, even in the presence of high-impedance faults and load variation. The performance rate exceeds 97.27% for all analysed cases, and the proposal identifies the operating condition in less than 20 ms after fault inception, demonstrating its low computational burden and suitability for implementation in field applications.

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.

Optimal overcurrent relay coordination for interconnected power systems: A proper approach and improved technique

The optimum setting of directional overcurrent relays (DOCRs) is required to avoid miscoordination and avail fast response. To fulfill these requirements, it is required to prefer optimization techniques and modifications in objective functions (OF). Many researchers have adopted soft computing techniques and suggested modifications in the objective function for problem formulation of overcurrent relay coordination. Though these modifications and suggestions attain an optimum value of relay parameters, unfortunately, some of them don't follow the fundamental requirements of overcurrent relay coordination. This paper reflects on such modified objective functions and conveys a proper approach. Further, the paper proposes a new objective function as per the overcurrent relay coordination criteria. The novelty of the paper is to modify the existing objective function as per overcurrent relays coordination criteria and to add a new term in it to avoid miscoordination. The proposed objective function (POF) is applied on two power system test networks and results reveal that it is efficient and accurate.

Smart Protection System for Microgrids with Grid-Connected and Islanded Capabilities Based on an Adaptive Algorithm

This work proposes a smart protection system for microgrids, which relies on an adaptive metaheuristic for the automatic calculation of optimal settings for directional overcurrent relays (DOCRs). The adaptive fuzzy directional bat algorithm (AFDBA) associated with a fuzzy inference system (FIS) is used for this purpose. A prominent advantage of this solution is that there is no need for an initial tuning of the parameters associated with the algorithm, unlike many traditional approaches reported in the literature. Such a metaheuristic is used in the conception of an adaptive protection system (APS) in the context of a microgrid while taking into account the connection status of distributed generation (DG) units under distinct scenarios. A performance comparison with a protection system with fixed optimal settings (PSFOS) is also presented. The results demonstrate that the proposed APS outperforms the PSFOS while providing faster response, higher reliability and less susceptibility to miscoordination. In other words, it presents a shorter trip time when compared with the PSFOS, with a reduction of 6.83% and 26.58% when considering the DG penetration and the islanded microgrid, respectively.

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.

Automated Settings of Overcurrent Relays Considering Transformer Phase Shift and Distributed Generators Using Gorilla Troops Optimizer

The relative protective devices are cascaded in a proper sequence with a proper min/max coordination time margin (CTM) to minimize the outage area of the network in case of fault condition. This manuscript addresses a new methodology based on the gorilla troops optimizer (GTO) to produce the best automated settings for overcurrent relays. In the GTO, the exploration and exploitation phases are realized using five methodologies. Three of them are used in the exploration phase and the other two in the exploitation phase. In the exploration phase, all gorillas are considered as candidate solutions and the best one is considered as the silverback gorilla. Then again, the exploitation phase comprises two steps: (i) the first one is the follow of silverback gorilla, and (ii) the second one is the competition for adult females. The latter mentioned offers an added advantage to the GTO framework to move forward steadily to global minima and to avoid trapping into local minima. Two test cases under numerous scenarios are demonstrated comprising an isolated real distribution network with distributed generations for the Agiba Petroleum company which is in the Western Desert of Egypt. The relay coordination problem is adapted as an optimization problem subject to a set of predefined constraints which is solved using the GTO including fixed and varied inverse IEC curves, in which the practical constraints including transformer phase shift and other scenarios for min/max fault conditions are dealt with. In due course, this current effort aims at proving the best strategy for achieving the smoothest coordination of overcurrent relays (OCRs), with the least obtained value of CTMs for the studied cases being established via the automated relay settings. At last, it can be pointed out that the GTO successfully dealt with this problem and was able to produce competitive answers compared to other competitors.

Adaptive Protection for Active Distribution Networks: An Approach Based on Fuses and Relays With Multiple Setting Groups

Protection schemes are essential in active distribution networks and microgrids’ reliable, efficient, and flexible operation. However, the protection of these networks presents significant challenges due to operational changes, such as variations in topology, distributed energy resources connection/disconnection, and microgrid operating modes, among others. This paper proposes an adaptive protection scheme based on overcurrent devices with several setting groups based on artificial intelligence algorithms. The developed strategy is composed of two stages. In the off-line stage, a clustering technique is employed to group the active distribution network operating scenarios exhibiting similarities. The optimal settings for the protection devices are determined for each set of scenarios. On the other hand, in the on-line stage, the protection strategy’s implementation and operation, considering the active distribution network’s existing communication system, are defined. Furthermore, the approach formulates the overcurrent relay coordination as a mixed-integer non-linear optimization problem, and as a result, the optimal setting of the overcurrent protection devices is obtained. It aims to minimize the operating time, considering the transformers’ thermal limits, fuse operating curves, and overcurrent relay settings. The solution is determined by using an Augmented Lagrangian genetic algorithm. The presented protection scheme is validated on the modified IEEE 34 node test feeder, considering the main operating scenarios of the active distribution networks, such as topology changes, distributed energy resource connection/disconnection, and microgrid operating modes (on-grid and off-grid). The results obtained and its easy implementation indicates the high potential for real-life applications.

A multi-objective optimization of FCL and DOCR settings to mitigate distributed generations impacts on distribution networks

Despite providing increased reliability and power quality in meeting the load demand, the integration of DGs has imposed challenges on the protection system. High penetration of DGs changes the overall network impedance and increases the fault current level in the network. Consequently, some buses are exposed to critical conditions, violate the circuit breakers (CB) handling capacity, and affect the existing relay coordination settings. To mitigate these adverse impacts, fault current limiters (FCL) can be a potential solution to minimize the short circuit current within permissible switchgear-rated limits. Due to its expensive cost, it is crucial to ensure the optimal FCL placement and sizing, and at the same time maintain the effectiveness of the protection performance during various network operation states. This research formulates FCL and directional overcurrent relay (DOCR) settings as a combined protection coordination scheme optimized by a multi-objective hybrid optimization technique. The proposed formulation aims to determine the minimal FCL sizing with minimum investment cost to satisfy the relay coordination constraints at high fault-level buses, irrespective of DG locations and network operating state. User-defined relay characteristics (UDC) are employed to intensify the DOCR coordination performance and obtain minimum operating time, where the conventional inverse relay constants (A&B) are optimized with (TSM & Ipu). The combined UDC relay settings and FCL problem formulation solution attained by MO-hybrid optimization can lessen the escalated electromagnetic stresses, costly switchgear replacement, and relay maloperation. The performance of the proposed technique is assessed by implementing it on the radial (IEEE-33 Bus) and meshed (IEEE 30-Bus) DNs with optimized FCL sizing and relay settings. The optimal results demonstrate the effectiveness of the proposed technique in maintaining the relay coordination performance in the presence of DGs and FCL under an ON/OFF grid connection.

Optimal coordination of directional overcurrent relay based on combination of Firefly Algorithm and Linear Programming

Optimal coordination and settings of directional overcurrent relays (DOCRs) are crucial task to ensure reliable and effective protection in power system networks. The settings of DOCRs are plug setting current (PSC) and time multiplier setting (TMS). The DOCRs coordination is well-known as a highly constrained nonlinear optimization problem. Its complexity in terms of non-linearity increases along with the network size increment. This paper proposes a hybrid optimization algorithm which consists of Firefly Algorithm and Linear Programming (FA-LP) to relax the search space by linearizing the equation of the DOCRs coordination to attain an optimal solution. Furthermore, this paper also considers a mixed type of IEC relay characteristics to attain effective relay operation. The proposed method is tested on the IEEE 8-, 15- and 30-bus test systems. The results show the reduction of total relay operating time between 15.6% and 85.5% as compared to other techniques in the literature and also being verified using the ETAP software.

Hierarchical Clustering Cuckoo Search Optimization Implemented in Optimal Setting of Directional Overcurrent Relays

This study has proposed a hierarchical clustering cuckoo search optimization (HCSO) to solve the optimal setting problems of directional overcurrent relays (DOCRs) in the power system. Different from the randomly generated stepsize θ in traditional CSO, stepsize θ in HCSO is updated by a hierarchical clustering mechanism, which can balance the searching priority of exploration and exploitation for each solution. The superiority of HCSO is evaluated by solving the DOCRs coordination problem with the 3-bus, 8-bus, and 9-bus system, presented by linear programming (LP), nonlinear programming (NLP), and mixed integer nonlinear programming (MINLP) forms. Results show that under the same parameter setting conditions, the minimum value of the objective function by HCSO has reduced by 10.93 % , 2.93 % , and 0.46 % , respectively, compared to that of CSO in the experimented cases 2, 3, and 4. It verifies that HCSO is more competitive than CSO in solving the DOCRs optimal setting problem irrespective of the DOCRs number and formulation type.

Adaptive fuzzy directional bat algorithm for the optimal coordination of protection systems based on directional overcurrent relays

Despite bringing several benefits to modern power systems, distributed generation (DG) and microgrids cause a significant impact on the operation of power distribution networks, especially with regard to the protection system. The topological evolution of power distribution networks comprising DG units and the islanding capacity of microgrids have lead to significant changes in the magnitudes of short-circuit currents, consequently affecting the reliability of protection systems in terms of loss of selectivity (false tripping and/or sympathetic tripping), sensitivity (blind protection), and dynamic response (delayed trip). In this new scenario, the adoption of smart protection systems capable of incorporating advanced control and protection mechanisms is of paramount importance for ensuring the automatic reconfiguration and restoration of the power grid when undesirable phenomena like faults occur. Considering this scenario, this work proposes a novel metaheuristic called adaptive fuzzy directional bat algorithm (AFDBA), which can calculate optimal settings for directional overcurrent relays (DOCRs) in any power grid topology without the need for tuning the initial parameters. The technique is applied to three case studies, that is, the 3-bus, 9-bus, and 30-bus test systems. The algorithm performance is compared with that of genetic algorithm (GA), particle swarm optimization (PSO), differential evolution (DE), bat algorithm (BA), and directional bat algorithm (DBA). The results evidence that the proposed approach has high convergence speed, high robustness, and acceptable computational burden, while providing the proper coordination of protection systems.

Comparative Study of Relay Coordination in a Microgrid with the Determination of Common Optimal Settings Based on Different Objective Functions

This study aims to analyze the optimal settings of directional overcurrent relays (DOCRs) for the protection of an alternating current (AC) microgrid in both islanded and grid-connected operation modes. In this context, two different types of objective functions are used for comparing the total operating time of all primary DOCRs. The optimal settings obtained in either mode of the microgrid are different due to the variable magnitude of fault currents. The proposed protection coordination scheme is formulated as a mixed-integer non-linear programming problem, and the settings are obtained using various optimization techniques such as firefly algorithm, simulated annealing algorithm, and genetic algorithm. The results show that the settings obtained in common operation modes are robust as no miscoordination of relays occurs in any of the operation modes.

Protection Coordination Index Assessment Using Fuzzy Logic Controller

This paper proposes the assessment method of the protection coordination index (PCI) for overcurrent protection relay and upstream relay. The protection coordination index is an indicator of how properly the equipment is protected by protective relay. The PCI is used to check the appropriateness of the protection coordination for both the component-wise and pair-wise. The protection index of each protection component of the integrated digital relay is assessed by a fuzzy logic controller. Then the device-level protection index and the composite protection coordination index between up and downstream relays are also assessed. Since the setting criteria of the overcurrent relays are given in a certain range rather than a crisp value, it is difficult to indicate the protection level of the protective system as an index. Currently, there is no way of knowing how well the overcurrent relay setting is. Thus, a method was proposed to evaluate the protection index of overcurrent systems using fuzzy logic. This is the unique research result of this paper.

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.