An advanced dual-setting protection scheme for microgrid resilience based on nonstandard tripping characteristics of overcurrent relays

Nowadays, the capacity of Distributed Generation (DG) in the power network is increasing, which increases the challenges and complexity of having a fast and reliable power protection system. Several studies on microgrid protection have been conducted, including advances in overcurrent relays (OCRs) and dual-setting protection schemes. However, there is a gap in the literature on developing an innovative protection scheme with dualsetting for directional or non-directional overcurrent relays, taking into account the limitations of the standard tripping characteristics, OCRs coordination problem due to the stochastic behaviour of DG, and the high energy not supplied because of the setting of primary and backup protective relays. This work aims to fill this gap by developing a novel optimal dual-setting protection scheme based on the nonstandard tripping characteristics of overcurrent relays for highly sensitive and reliable microgrid protection. The proposed dual-setting scheme takes advantage of modern communications techniques to provide high reliability and security and reduce unnecessary feeder outages. In addition, the dual-setting OCRs coordination problem is formulated as an optimization problem and solved by the Water Cycle Algorithm (WCA) to find the optimal relay setting to achieve the minimum overall tripping time of OCRs. The proposed innovative optimal dual-setting protection scheme is compared with conventional OCRs and the dual-setting approach. The effectiveness of the proposed scheme is analysed and investigated on the IEEE-9 and 30 Bus systems equipped with photovoltaic (PV) energy and inverter-based DG under different fault scenarios and grid operation modes. The proposed approach successfully achieved 100% power continuity without any cases of energy not being supplied at different fault locations and recorded a 46.2% reduction in the total tripping time compared to conventional approaches, which will help to increase the stability of the power grid.