An adaptive overcurrent protection in smart distribution grid

More and more maritime applications as marine vessels and offshore platforms need an adaptive protection power system. However, the adaptive protection is yet to be implemented in the maritime sector. Usually, the adaptive protection implies the existence of a central control unit that monitors the entire electrical network and changes the relay settings accordingly, but this approach is not adequate for the maritime power systems. This paper propose a decentralized adaptive protection method, where each protection relay is able to identify by itself the network status without the need of a central control unit. The new adaptive protection method is based on communication between the overcurrent relays and the equipment that could affect the protection system, such as circuit breakers and generators. Using PSCAD, the proposed method is implemented in a test medium voltage maritime power system that possess some of the characteristics of the maritime applications, as variable generation and network reconfiguration.

The integration of distributed energy resources (DERs) into medium-voltage (MV) distribution networks is a key challenge in the ongoing digitalization of power systems, requiring new approaches to optimize network resilience and control. This study aims to systematically evaluate the impact of typical MV distribution network wiring configurations on DER accommodation, with a particular focus on cyber-physical performance under both normal and adverse scenarios. To achieve this, a comprehensive hybrid simulation framework combining electromagnetic transient modeling, high-fidelity network emulation, and precision time synchronization is established. Parallel co-simulation and hardware-in-the-loop interfaces are employed to replicate real-world operational dynamics and validate digital control strategies. Empirical results from CIGRE MV testbed trials demonstrate that, compared to the traditional radial structure with manual control (average configuration time 4.3 minutes), the combination of ring network topology and software-defined networking (SDN) controllers reduces the average configuration time to 2.7 minutes, a reduction of approximately 37%. This configuration also significantly enhances cyber-attack resilience and DER hosting capability. These findings provide a quantifiable foundation for optimizing the design, automation, and secure operation of digitalized MV distribution networks to meet the demands of modern power systems.

With large-scale distributed energy resources (DERs) being integrated into distribution networks (DNs), the coordinated optimal power flow (OPF) of high voltage (HV) and medium voltage (MV) DNs becomes challenging due to enhanced uncertainties and nonlinearity. This paper presents a hierarchical distributed chance-constrained OPF model for HV and MV DNs based on a nonlinear adaptive data-driven method. The HV master problem aims to minimize the overall operational costs, and is transformed into mixed-integer convex problem via second order cone programming. A model-free chance-constrained optimization sub-problem is established to tackle inaccurate model parameters issues and DER uncertainties in MV DNs and realize rapid response to control schemes from HV DN. The nonlinearity of power flow is approximately depicted by a data-driven incomplete dimension lifting power flow (IDL-PF) constraint, which is integrated into the MV DNs optimization model. A novel multi-parameter programming (MPP)-based distributed algorithm is proposed to solve the coordinated OPF model, which can significantly accelerate the iterative speed between the master and sub-problems. Finally, the convergence, efficiency and optimality of the proposed method are validated by numerous simulations in a practical DNs in China.

Increasing levels of inverter-based distributed energy resources (IBDERs) impact the legacy overcurrent distribution protection systems. The fault current injections of IBDERs are limited to between 1.25–2.25 p.u. of the rated current. The combination of the limited fault current and varying system load makes it increasingly difficult to reliably set the overcurrent protection. To address this challenge, researchers are proposing adaptive overcurrent protection mechanisms that can adapt to changing system conditions. Accurate modeling of IBDERs is required to develop reliable protection schemes. This paper presents a photovoltaics-based IBDER model in OpenDSS for adaptive overcurrent protection. The paper presents the validation of the proposed IBDER model against a detailed model in electromagnetic transient programs. Protection analysis of the Electric Power Research Institute J1 feeder with the proposed IBDER model is also presented.

The transition from big conventional bulk generation to small dispersed renewable electricity production coupled at medium and lower voltage levels resulted in bi-directional power flow and an active distribution network, which was previously considered to be a passive network. This paradigm shift brings many challenges for protection performances and coordination. As a result, this paper first investigates the impacts of Distributed Energy Resource (DER) integration on distribution protection and then applies the hardware SEL 451 relay for validation. Two of the most common protection failures with DER integration, namely, reverse power flow and sympathetic tripping cases, are examined for a microgrid in this study. Firstly, the system is modeled in PowerFactory for short circuit calculation and protection coordination study. With the help of PowerFactory simulation, coordinated relay settings are subsequently extracted for validation in hardware in the loop testing with SEL 451 relay in real-time digital simulation (RTDS). Both simulation case studies and hardware tests have shown that the DER contribution in healthy conditions as well as during the fault can result in maloperation of the relay. Different from the traditional power amplifier-based testing, the hardware in the loop testing in this work uses Low Energy Analog (LEA) signals output from the GTAO card of RTDS feed directly to SEL 451 relay. Two different feedback methods with Digital Input (DI) and IEC GOOSE signal are tested to compare the time of operation in each case.

A notable spread of Dispersed Generation (DG) power plants, connected at Medium Voltage (MV) distribution grids, takes place in the Italian power system, with a big impact on the operation, both in normal and in emergency conditions, especially during transients determining frequency variations. Enel Distribuzione, the biggest Distribution System Operator (DSO) in Italy, proposed to install some special devices, on its distribution grid, to improve the effectiveness of management of DG and loads, during frequency transients in automatic way. The paper describes the solution proposed by Enel Distribuzione, that gives the possibility to better manage the DG and loads connected in MV in favor of the whole power system in presence of frequency transients, as the Italian Transmission System Operator (TSO) with its Defense Plan (DP) requires. Some numerical results for demonstrating the need and effectiveness of the application of the proposed solution in the real operation of the system are reported.

Distributed energy resources (DERs) can improve the performance of radial distribution systems. The nonlinear power flow constraints, multi-objective trade-offs, and network reconfiguration scenarios for DER placement and sizing call for the formulation of optimization problems. Most of the times optimization algorithms suffer from premature convergence and poor exploration-exploitation balance. These problems exhibit an inherent internal structural symmetry. In order to overcome the above problem, this study uses the Multi-Objective Archimedes Optimization Algorithm (MAOA) to optimally allocate DERs in the Radial Distribution Networks (RDNs), moreover the performance of the proposed MAOA is compared with the other well established algorithms including Particel Swarm Optimization (PSO), Whale Optimization Algorithm (WOA), Shuffled Frog Leaping Algorithm (SFLA), Atom Search Optimization (ASO), and Butterfly Optimization Algorithm (BOA) on the IEEE-33 RDN. The comparison is made for the four cases (S1: DER Only), (S2—Network Reconfiguration Only), (S3—DER Followed by Reconfiguration), and (S4—Reconfiguration Followed by DER) considering factors like voltage profile, network reconfiguration, active and reactive power loss reduction, carbon emission DER utilization and Cost reduction. The MAOA is observed to provide better results among all the other benchmark algorithms. In S3, the active power loss is reduced by 68.41%, whereas the reactive power loss is reduced by 57.44% and the MAOA algorithm improves the voltage by 3.98%. The minimum voltage of the network is also improved by 6.28%. The algorithm improves convergence with a percentage of 18.50% enhancing the system’s operational symmetry and stability, while satisfying all constraints. At Bus 3 and Bus 6 of IEEE-33 bus radial distribution network (Baran–Wu test system), DG capacity is allocated to be 3.8 MW and 2.1 MW, respectively.

Comparison of Programmable Logic and Setting Group Methods for adaptive overcurrent protection in microgrids

The increasing installation of distributed energy resources (DERs) by end consumers introduces new operational challenges to distribution networks. Although several studies investigate these impacts, most proposed control strategies are implemented independently, focusing on individual elements such as substation voltage adjustment, network reconfiguration, or inverter-based DER controls. These approaches often overlook both the interactions among different control mechanisms and the interests of end consumers, concentrating primarily on the system operator’s perspective. As a result, their potential to achieve more balanced and effective solutions is limited. This paper proposes a coordinated multi-objective optimization approach that integrates substation voltage adjustment, network reconfiguration, and the determination of Volt-Var and Volt-Watt control setpoints. By combining these strategies, the search space is expanded, enabling the identification of superior solutions that better balance the competing objectives of minimizing power losses, increasing DER hosting capacity, and maximizing the active power supplied by DERs. The multi-objective optimization problem is formulated with these three objective functions and a set of operational constraints, explicitly considering the interests and requirements of both end consumers and system operators. Furthermore, uncertainties related to load demand and DER generation are addressed using a Monte Carlo method. The proposed methodology is applied to the IEEE 69-bus distribution system and the optimization problem is solved using the Multi-objective Cuckoo Search Algorithm. The results demonstrate that the coordinated strategy outperforms isolated approaches by completely eliminating violations and reducing losses by 47.60%, while incurring only a 7.27% reduction in active power injection from DERs.

This paper introduces a Relay Integrity and Anomaly Detection (RIAD) scheme designed to enhance the reliability of Setting Group‐based Adaptive Overcurrent (SGAO) protection systems. The RIAD mechanism improves relay configuration awareness and mitigates potential failures due to misconfigured relays or cyber intrusions targeting relay settings. To validate the performance of SGAO and the proposed RIAD, a comprehensive cyber‐physical power system testbed was developed and implemented within the CIGRE 7‐bus AC microgrid. This field‐level testbed, featuring IEC 61850‐based Hardware‐in‐the‐Loop (HIL) experimentation with Real‐time Digital Simulation (RTDS) and industry‐grade relays such as SEL 421, 751, and 311C, along with an automation controller (SEL RTAC 3530‐4) for logic implementation, provides a precise timeline analysis of events. The testbed highlights the significance of validating enhanced SGAO schemes under real‐world conditions, ensuring robust relay settings and coordination even in the presence of communication failures, misconfigurations, or cyber‐attacks.

Distributed Energy Resources (DERs) installed on low-voltage distribution systems, both utility-owned and nonutility owned may be employed to make improvements to system resiliency and power quality, in addition to simply serving load demand. By selectively dispatching active and reactive power from these existing DERs, improvements in voltage profiles and service availability during adverse events may be achieved. Further benefits can be gained by optimally choosing which DERs to dispatch power from, and the distribution of power from those DERs. For a given operating condition, using Linear Programming methods, optimal power dispatch values for individual DERs can be determined, while considering variables such as voltage gains, losses in the lines and the DERs, and DER reserve capacities. One such optimization technique is developed in this paper, and results from a real-time simulation study on a modified IEEE 13-bus distribution system with three DERs, are being presented. The operation of the optimized DER selection and dispatch algorithm is shown during normal operation of the transmission system when the DERs operate in grid-connected mode. Similar analyses can drive decision making during transmission system failure when the DERs operate in grid-forming or islanded mode.

Integration of flow battery for resilience enhancement of advanced distribution grids

Distributed energy storage planning in soft open point based active distribution networks incorporating network reconfiguration and DG reactive power capability

This paper presents a new adaptive and optimal overcurrent protection for large-scale wind farms using hybrid Grey Wolf Optimizer and rule-based Fuzzy Logic Controller (GWO-FLC) scheme. The proposed GWO-FLC based adaptive protection scheme overcomes the limitation of conventional protection scheme that suffers from maloperation of relays that damages the power components in the system during fault. Furthermore, due to the intermittent nature of wind, the generated current feeding the grid during extreme high and low wind speeds, creates a significant difference in magnitudes of the generated current. Thus, the existence of only one group of settings for the Overcurrent Relays (OCRs) would cause drastic miscoordination and false tripping during fault. In order to test the performance of the proposed GWO-FLC scheme several OCRs based on standard Schweitzer Engineering Laboratories industrial protection relay (SEL-751) are developed in Matlab/Simulink. A large-scale wind farm model is also developed to perform fault analysis, relay setting and coordination calculation. The GWO is implemented to attain optimal OCR coordination for the defined quadruple group settings for all relays, and the FLC is developed to provide adaptive feature for the relays so that the OCR group settings for each relay are intelligently updated according to the variation of wind speed. Finally, in a laboratory environment the proposed protection scheme is implemented in real-time using FPGA DE2-115 board equipped with Cyclone IV-E device (EP4CE115F29C7). It is found from both simulation and experimental results that the performance of the proposed hybrid GWO-FLC is robust, reliable, efficient and extremely satisfactory.

In this paper the performance of three algorithms for frequency estimation is evaluated and they are applied in an adaptive protection scheme (APS) which was proposed to determine the instantaneous overcurrent relay setting. The APS will monitor system modifications done from the estimation of the fundamental frequency. For this, three methods of fundamental frequency estimation such as: (a) zero-crossing, (b) adjustment of points to a pure sinusoidal waveform method (APPSW), and (c) algorithm based on discrete Fourier transform (DFT). Here, these algorithms were applied in distribution systems with distributed generation (DG), and were compared and analyzed the behavior of the APS. The proposed adaptive protection method by frequency estimation was applied in a real Brazilian sub-transmission system, owned by Eletrobrs Distributer of Alagoas (EDAL). APS was built using ATP/MODELS. The evaluation methodology for the frequency estimators is based in statistical error such as mean square error. The DFT based estimator presented better results in comparison with the other evaluated algorithms. Therefore, the application of the DFT method to the adaptive overcurrent protection presented good results of the relays settings and on the protection of the system.