During recent years, microgrids have been found to be one of the emerging concepts that have been prominently influencing power system engineering [1][2]. Recent demands for sustainable and resilient energy infrastructure have made microgrids one of the prominent enablers for improving reliability, resiliency, and sustainable designs for the power system. Microgrids can be generally defined as a mini power system with multiple DERs such as synchronous generators, solar panels (PV), wind turbines, and battery energy storage systems providing service to local loads enclosed by a microgrid boundary [3].

Contrary to traditional central power grids, microgrids have the advantage of dynamically switching between operating modes, which can be both grid-connected and islanded, as depicted in [4]. During grid-connected mode, microgrids can, with optimum utilization, transfer power to and from the central utility grid. During islanded modes, microgrids can effectively stand-alone without any connection to the utility grids. This makes microgrids especially interesting for hospitals, universities, and even military installations and remote regions, which require an uninterrupted power supply [5][6].

However, with increasing penetration by renewables and distributed generation, the operation and protection systems face substantial challenges. The intermittency inherent in renewable energy sources, with power fluctuations during their operations, causes variation in voltage and frequency. Additionally, because of distributed generation, bidirectional power flow can hinder fault detection, coordination, and selectivity. Conventional protection concepts, originally developed for radial distribution networks with one-way current flow, might not effectively ensure fault selectivity in microgrids [7]. Consider, for example, when there is a fault in one feeder, current contribution can come both from the utility grid and DER units; thus, it will be hard to identify the actual fault and classify it as internal versus external [8][9].

This can be made even more evident, which shows a simplified protection coordination scheme for a microgrid. Based on [10][11], it can be noted how all these devices have to work in sync with each other for efficient fault isolation with minimal disruption to the supply for the non-affected feeders. Uncoordinated performance between these devices can cause problems such as nuisance tripping, instability, or even a cascading disconnection.

Therefore, there is a growing requirement for intelligent and adaptable protection logic, which is able to dynamically adjust itself based on system characteristics and fault types. These protection logics must be capable of combining real-time values, signal processing, and decision algorithms to distinguish between actual in-feeder faults and sympathetic/external fault types. Notably, by including variables such as residual current and minimum phase current in advanced fault detection algorithms, improved sensitivity and selectivity can be attained [10][12][13].

This work is concerned with simulating a protection logic process for in-feeder fault detection. The model developed includes actual system components like synchronous generators, transformers, RL loads, lines, and a point of grid connection (PCC). The proposed protection scheme employs current detection logic, which includes the residual current value I0 and the minimal phase current. Using simulation, it is demonstrated how this protection logic can be used for avoiding false operations and for improving selectivity.

The current research work will help in providing an applied framework for understanding and verifying micro-grid protection strategies by using simulation environments. The research will help in improving fault discrimination accuracy by analyzing actual and false fault circumstances.

Although the suggested dual-threshold protection logic is aimed at improving selectivity and reliability in microgrid earth fault protection, the paper also strongly analyzes its trade-offs, including the loss of sensitivity to low-intensity internal faults. This paper does not just make a presentation of a protection scheme, but rather offers a systematic characterization of the scheme performance during different fault scenario, the limitation of the scheme and the way forward to improve the scheme. This would make sure that the findings are placed not as the ultimate answer, but as a moderate evaluation of a workable, computationally light approach to protection, fit to be used in a microgrid applications in real-time.

The following section is dedicated to a literature review and related studies on micro-grid protection, pointing out critical developments and current research gaps.

With regards to modern power systems, there has been extensive research work conducted on micro-grid protection and fault detection, in addition to integration with distributed energy, due to the increasing trend towards a decentralized and renewable energy-powered grid. Recent literature has emphasized improved micro-grid stability, intelligence, and robustness with regard to control and security strategies for both grid-connected and islanded micro-grids. This article will provide a brief summary on recent literature work to outline the research gaps that this work attempts to bridge.

Recent literature has focused on addressing vulnerabilities of distributed generation systems. Maghami et al. (2025) discussed in considerable detail vulnerability assessment for grid-connected distributed generation systems subject to coordinated cyber-attacks. Their work showed that sensitivity to 10% communication delay resulted in 6% variation in voltage levels for DER-based networks, which can have adverse effects on overall system robustness. The current subject matter highlights the need for implementing protection levels for smart grids and micro-grids against cyber-physical threats [14].

Discussing the implication of energy storage systems (ESS) for supporting grid stability, Mushid and Khan (2025) conducted a thorough literature review on battery energy storage systems (BESS) for supporting ancillary service functions in the distribution networks. The findings revealed that with the implementation of BESS, it is possible to alleviate up to 18% of the overall peak load demands and enhance system frequency by 25% during transient disturbances. Nonetheless, it was highlighted by these authors that technological issues such as aging effects and compatibility with traditional protection relays have not been properly addressed [15].

Another research stream involved the introduction of a Proximal Policy Optimization (PPO)-based controller by Hasheminasab et al. (2025) for improving the accuracy and transient response in microgrids. The simulation outcome revealed a 45% improvement in steady-state error and 32% improvement in dynamic response time with the proposed PPO controller compared to conventional control approaches based on traditional droop control strategies. This research work highlights the increasing use of reinforcement learning algorithms for improving microgrid flexibility [16].

Momesso et al. (2024) investigated the effects caused by transportable battery energy storage systems (BESS) on protection systems used in conventional distribution networks. According to this research, it has been found that with mobile BESS, fault current levels can vary by 20%, which causes issues with the coordination timing of overcurrent protection relays if traditional coordination is adopted [17].

Similarly, Dai et al. (2025) proposed a fault section location scheme for active distribution networks by designing a new subtraction-average-based optimizer (SABO). The experimental result showed that the proposed scheme can locate fault sections with an accuracy of 96.8%, which is about 9% better than other heuristic approaches. This improvement proves that hybrid optimizers are useful in fault detection and isolation for active micro-grids [18].

Despite these developments, there is a gap in literature with regards to a systematic approach that incorporates adaptive protection logic with real-time coordination between feeders and microgrid interfaces. Most approaches have been geared towards ensuring fault detection accuracy or control stability without considering issues related to dynamic interactions between protection relays, fault current, and coordination delay for multi-feeder micro-grids.

Hence, this current research work intends to design and verify an intelligent protection logic for micro-grid feeders, which should have the ability to identify actual in-feeder fault occurrences and external sympathetic disturbances. The current research work is going to bridge this significant research gap by combining both time delay blocking concepts and logical fault identification.

The research paper uses a digital simulation research approach to design and experiment with a customized Earth fault Protection (EFP) logic on an AC microgrid.

MATLAB/Simulink software was developed to create the simulation environment because it has sophisticated software to model an electrical system and analyze its behavior across different operating conditions.

The methodology incorporates a new logic algorithm into the network model to assess its capability to discriminate between true Earth Faults and sympathetic zero sequence currents, which may result into the failure of the traditional protection systems.

The implementation of the methodology was carried out in two major stages:

The initial step consisted in creating an interactive MATLAB interface (GUI) that would create experimental signals of line and neutral currents and test the logic of proposed protection.The second step was concerned with the implementation of this logic into a realistic Simulink model of a microgrid to verify the behavior of protection in a variety of operating conditions (true fault, sympathetic state, and normal operation).

The approach will offer an empirical insight into how the system will react to the different variables that include current thresholds and time barrier (T1), which can make the accuracy and reliability of the protection system to be enhanced in advance before the actual deployment of the system on the ground.

This part of the research work intends to investigate the performance of the proposed Earth Fault Protection (EFP) algorithm on a real microgrid model developed in a MATLAB/Simulink environment. Operating scenarios simulating actual situations commonly found in earth fault protection for microgrids, such as earth fault and symmetrical zero current (I₀) due to fault on other feeders, have been developed. The assessment of these scenarios is important for testing the proposed algorithm’s selectivity towards actual and false events.

Figure 2 illustrates a representation of the dynamic performance of the tap changer prior to and during the operating scenario. From this figure, one can see that there was minimal change in the taps without shifting between different levels. Such performance is indicative that the supply voltage levels for testing purposes are nearly 400 V, which is significant because voltage stability does not allow for any indirect effect on the value for zero current (I₀) or sub-phase current (I_min). Lack of sharp change in thetap levels implies that there was no voltage effect on protection levels, and any variation in I₀ or I_min value for subsequent readings will only occur due to the fault. From this reading, it can be concluded that there is efficiency in voltage control practices for this test scenario, and earth fault protection is conducted under ideal electro-mechanical conditions. Such a scenario gives more authenticity to the reading and does not allow for the possibility that protection failure could have resulted due to adverse voltage levels. Hence, it is significant to conclude that it is necessary to have such elements for the ideal functioning of the algorithm with a goal to fairly test performance levels for 200 A and 350 A thresholds that have been used for controlling protection levels.

At the same time, however, the voltage levels for both regulation points remained in their normal operating ranges without any irregular fluctuations or sudden drops/peaks. This is imperative for guaranteeing the authenticity of the protection evaluation process because any deviation in voltage levels can have both effects on fault currents and the corresponding direction of sympathetic current flowing. As one can see, because there are no significant deviations in terms of voltage levels, it is clear that it is due to the effective functioning of the AVR system in regulating and maintaining a constant 400 V during this test process. This ensures all protection reactions can be exclusively related to the functioning process of Earth Fault Logic algorithm implementation without any interference. At the same time, this process signifies that it is free from any adverse effects on I_min values, which is imperative because I_min is considered to be a critical parameter in distinguishing between local and sympathetic fault reactions. The one significant observation related to this figure is that it clearly indicated that the voltage effect is entirely decoupled, and it occurred in a stable environment, thus enabling a scientific process for protection logic evaluation, which is clearly evident in Figure 3.

Figure 2. Tap changer operating position under normal system conditions.

Figure 3. Voltage profile at the regulating points of the microgrid.

The analysis results derived from the proposed logic of earth fault protection are found to be highly selective and reliable, especially during the detection of true in-feeder faults and sympathetic zero sequence currents. This result goes hand-in-hand with the analysis presented in the existing literature to some extent but varies in terms of methodology and applications. For example, Gang (2024) has successfully utilized ANFIS intelligent techniques with the aid of PMU technology data to pinpoint arc faults with improved sensitivity. In contrast to his presentation, though the current protection scheme is more reliable in terms of non-trip action during sympathetic faults without utilizing AI techniques, it lacks sensitivity to low-intensity in-feeder faults due to the use of the predefined “I_min” threshold level .

In the same vein, Xie et al. (2025) introduced topology flexibility and model-driven approaches to the interphase fault location problem within distribution networks, establishing that there is merit in incorporating dynamic structural variations within the algorithm in terms of improving fault detection accuracy. In contrast to the above-mentioned method, the designed protection logic in this research is static in terms of topology and uses current magnitude criteria instead. However, the designed logic has shown excellent robustness to external disturbances, consistent with Xie’s results that the underlying application environment has an impact on accuracy .

Moreover, the increasing efficacy of artificial-intelligence-based and optimization-driven approaches to ensure fault detection reliability in contemporary power grids was brought to light by Pijarski and Belowski in 2024 [21]. The issue with standard threshold-triggered protection in complex operating conditions was highlighted by his research to be particularly evident in smart and micro-grids with multiple active sources—the same problem that needs to be addressed within the current study’s real A-G fault case, with the unchangeable I_min threshold that prevents triggering with the clear zero-sequence current increase. Instead, the sympathetic current case illustrated outstanding non-tripping reliability to match the selectivity advantage conventionally cited to be realized with the aid of optimizations and artificial intelligence techniques. In summary, in the current study cited in contemporary research works, the proposed protection logic achieves simplicity and selectivity within sensitivity factors but may be further enhanced by applying adaptive/intelligent thresholding techniques to reflect the sensitivity achieved by AI-based protection schemes.

The logic proposed was also put into context by comparing its performance to the conventional directional overcurrent relays (67-type devices) and the AI-based fault detection techniques. Although a traditional directional relay might theoretically be able to distinguish between internal and external faults based on measuring the phases, the operation in microgrids dominated by inverters and low fault currents can be difficult because it requires a voltage measurement subject to distortion during faults. However, the suggested logic exploits only measurements at present time making implementation simpler at the expense of sensitivity. In comparison to the AI-based solutions like ANFIS or reinforcement learning-based detectors, the proposed method does not require a large amount of training data, high computational resources, and complicated real-time signal processing. Nevertheless, it has fixed thresholds restricting flexibility as demonstrated in the sensitivity analysis. Future research might consider hybrid designs in which lightweight AI modules dynamically update thresholds based on real-time system conditions and in this way reduce simplicity and adaptability trade-offs.

The outcome of this research work has successfully proved that the designed Earth Fault Protection (EFP) logic is highly selective and reliable with robust operational characteristics to microgrid protection applications, especially during the differentiation process between real in-feeder earth faults and sympathetic zero-sequence currents that tend to falsely trip the circuit breakers within normal main protection techniques. In fact, the application of the double-threshold strategy within the logic utilizing both I₀ and I_min values have shown excellent results in the complete prevention of unwanted tripping with full immunity to sympathetic current disturbances while maintaining stable operation irrespective of variations in microgrid operating conditions. This paper has shown that although the dual-threshold EFP logic is a simple, computationally efficient and highly selective method of preventing false trips caused by sympathetic currents, the use of a fixed I_min threshold predetermines low sensitivity to low-magnitude internal faults. This trade-off is quantitatively verified in the sensitivity analysis and shows the sensitivity of selecting the threshold in the protection design. The future research should be aimed at coming up with adaptive threshold mechanisms - perhaps using lightweight machine learning or rule-based corrections - to improve sensitivity without decreasing selectivity. Moreover, it is suggested to compare the proposed logic with directional overcurrent relays and AI-based approaches in the same conditions of a microgrid to comprehensively benchmark the viability of the practical use of the proposed logic. In effect, the sensitivity analysis in this research has shown that there was always a limitation to the detection sensitivity to microgrid internal faults with low magnitude due to the preset magnitude values within the SI zone defined by the use of the fixed threshold I_min, signifying the existence of trade-offs between sensitivity and selectivity. In terms of comparison with other techniques and approaches already re-ported within current international research understandings linked to microgrid applications such as AI-based arc current detection techniques with topology flexibility incorporated in microgrid fault location analysis; within research approaches oriented towards microgrid protection strategy optimizations; the adopted proposed microgrid Earth Fault Protection logic has various superior advantages due to simplicity, clearness, low computations required during analysis processes without the need to use complex models and technology owing to its direct application within real-time processes without needing additional intelligent sensing technologies. As further improvements within microgrid Earth Fault Protection strategy applications in attempts to increase its efficiency within practical applications to protect microgrids; further research is recommended to explore the use of dynamically set thresholds within the SI zone defined within the preset magnitude limits defined within the use of the I_min threshold; development and research within the adoption of microgrid Earth Fault Protection strategy that retains simplicity while optimizing microgrid sensitivity; scaling up simulation processes to test within varied microgrid fault resistances; and development within practical validation attempts to assess microgrid Earth Fault Protection strategy within real-world microgrid applications.