Protection of Distribution Systems with Distributed Energy Resources

The usage of Distributed Energy Resources (DER) in utilities around the world is expected to increase significantly. The existing distribution systems have been generally designed for unidirectional power flow, and feeders are opened and locked out for any fault within. However, in the future this practice may lead to a loss of significant generation where each feeder may have significant DER penetration. Also, utilities have started to investigate islanding operation of distribution systems with DER as a way to improve the reliability of the power supply to customers.<br/><br/>This report is the result of 17 months of work of the Joint Working Group B5/C6.26/CIRED “Protection of Distribution Systems with Distributed Energy Resources”. The working group used the CIGRE report TB421 “The impact of Renewable Energy Sources and Distributed Generation on Substation Protection and Automation”, published by WG B5.34 as the entry document for the work on this report. In doing so, the group aligned the content and the scope of this report, the network structures considered, possible islanding, standardized communication and adaptive protection, interface protection, connection schemes and protection concepts and future trends accordingly.<br/><br/>The report is structured as follows:<br/><br/>After this preface (chapter 1), the scope of the technical brochure according to the Terms of Reference (TOR) is stated (chapter 2). Then, in the glossary, symbols and abbreviations used throughout the technical brochure are listed (chapter 3).<br/><br/>The first main part of the report starts with a summary of the backgrounds on DER and current practices in protection at the distribution level (chapter 4). This chapter contains an analysis of CIGRE TB421, protection relevant characteristics of DER, a review of current practices for distribution system protection and a summary of country specific approaches for protection in distribution systems. These country specific protection approaches are given in more detail in the Annex in an aligned format.<br/><br/>The second main part of the report describes issues of protection of distribution schemes that include DER (chapter 5). It features the impact of DER on distribution system protection and sums up recommended best practices for reliable island detection.<br/><br/>The third main part offers a proactive approach to technology trends (chapter 6), under consideration of new applications of teleprotection and the use of communication (e.g. IP, PLC, BPL…). Moreover, protection schemes for future distribution networks that include DER are presented.<br/><br/>The report closes with a summary and an outlook (chapter 7), as well as a bibliography (chapter 8).