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A New Adaptive Protection Framework for Enhanced Coordination of Overcurrent and Ground Fault Relays With Non-Standard Curves and Dynamic Group Settings
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DOI：10.1109/access.2026.3719866.png)
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Abstract
En 中文
Ground fault relays (GFRs) in distribution networks can fail to detect single-line-to-ground (SLG) faults when fault currents fall below pickup thresholds. High-impedance grounding configurations and limited fault-current contribution of inverter-based distributed generation (DG) exacerbate this issue. This paper presents a new adaptive protection framework that enables phase overcurrent relays (OCRs) to serve as local backup protection for GFRs without relying on external communication infrastructure. The key novelty lies in a communication-free, three-tier group setting (GS) architecture, where the optimal relay time multiplier settings (TMS) and pickup currents for each GS are determined offline via a genetic algorithm (GA) and stored in the relay for real-time activation based solely on the measured fault current magnitude relative to pre-stored phase and ground fault pickup thresholds. GS1 employs an extended standard OCR (SOCR) characteristic with the inverse-time region expanded to 100 times the pickup current, eliminating premature transition to definite-time operation and reducing total network fault clearance time from 11.032 s (industrial SOCR) and 9.448 s (extended SOCR) to 8.732 s, representing improvements of 20.8% and 7.6%, respectively. GS2 incorporates a non-standard OCR (NSOCR) logarithmic characteristic, achieving a 17.6% reduction in total operating time compared to the SOCR curve while preserving all coordination time interval (CTI) margins above 0.198 s. GS3 addresses high-resistance fault scenarios by lowering the 51P pickup threshold to match the 51N level, enabling successful detection of single line to ground (SLG) faults at fault resistances up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$60~\Omega $ </tex-math></inline-formula>, where conventional settings result in no-trip conditions. The IEC modified 6-bus distribution network implemented in ETAP 22.6 is used to evaluate the proposed scheme under both solidly grounded and isolated neutral configurations, as well as with PV-based DG integration. Scalability is further validated on the IEEE 30-bus system, where all coordination constraints are satisfied across four fault resistance levels without modifying the base relay settings, confirming the framework’s applicability to larger meshed networks. Results confirm that the proposed framework significantly improves protection selectivity, sensitivity, and fault clearance speed across a wide range of fault conditions.
Keywords:
Adaptive protection
ground fault relay (GFR)
fault detection
group settings (GSs)
hybrid protection
non-standard tripping characteristics
overcurrent relay (OCR)
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3.6
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9.7W
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29.4W
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