Protection strategy for ADN based on overcurrent relay with adaptability unit using local measurements

Traditional overcurrent protection strategies encounter significant challenges when implemented in active distribution networks (ADNs) owing to the dynamic operating modes and the variability of short-circuit levels of these electric systems. Consequently, adaptive protection mechanisms that operate autonomously are needed to ensure coordination and optimal response times in scenarios with high penetration of distributed energy resources (DERs). This paper introduces an adaptive protection strategy relying on local measurements. The approach utilises reference coordination to calculate a real-time adaptability coefficient, dynamically adjusting to the current system's operating mode. The proposed coefficient facilitates updating operating times in anticipation of potential faults. In addition, the proposed strategy amalgamates detection, directional computation, fault classification modules, the proposed adaptability mechanism, and the trip unit within a unified protective scheme. The proposed adaptive protection strategy is tested in a modified IEEE 34-bus test feeder, including synchronous and inverted-based DERs. Out of the 90 cases analysed, the strategy successfully adapts and maintains the expected relay operating times in 100% of instances, even with high fault resistance values. The previous results satisfy the protection requirements, in contrast to conventional protection strategies, which often present selectivity problems in the presence of DERs in connected and islanded operating modes. The considerable variation in short-circuit levels, a typical characteristic of ADNs, highlights the present strategy as a viable alternative for real-world application in distribution networks. • Use local measurements, avoiding communication links, which reduces costs and facilitates implementation in real systems. • Proposes an adaptive adjustment before the fault occurrence. • Ensures coordination regardless of operation mode, fault type and fault resistance value. • Allows online parameter updating with low computational burden using only local measurements. • Integrates adaptability, fault detection, fault direction calculation, fault classification and tripping units.