Protection Solutions for Embedded Distribution Networks

Conventional protection schemes based on nondirectional overcurrent relays (OCRs) cannot provide adequate protection against bidirectional and relatively small fault currents from Distributed Generators (DGs) connected to the distribution system. To address this limitation, various solutions involving the placement of relays based on reliability indices and economic factors have been proposed. However, the performance efficacy and applicability of these solutions in embedded networks where parts of the network may continue to operate during fault contingencies have not been thoroughly investigated. This paper addresses this gap by proposing a range of protection solution scenarios involving different combinations of additional OCRs and directional overcurrent relays (DOCRs). These solutions aim to provide protection against bidirectional faults while allowing parts of the embedded network to operate in islanded mode. The placement of relays in each scenario is determined based on the equal distance of network segments. Additionally, this paper comprehensively assesses the techno-economic performance of new solution scenarios, mainly the impact on supply reliability and economic benefits compared to a baseline scenario with conventional OCR protection. The analysis shows that the proposed solution scenarios significantly enhance supply reliability and lead to substantial savings in energy-not-supplied (ENS) costs.