DER tripping in distribution networks: Root causes and classification framework

Distributed Energy Resources (DERs) are increasingly prevalent in distribution networks due to technological advances, economic factors, and shifting energy policies. A key challenge in DER-rich distribution network operation involves DER tripping during normal operating conditions or following disturbances at the distribution or upstream transmission network levels. DER tripping poses significant risks to stable distribution network operation and overall system stability. However, a clear understanding of DER tripping root causes and corresponding mitigation solutions is still lacking. This paper introduces a systematic classification framework addressing potential root causes of DER tripping, covering both expected and unexpected instances, including DER response characteristics, DER network location, system contingency size, and physical properties of upstream transmission networks (system strength and inertia levels). A detailed classification is proposed, categorizing DER tripping root causes based on the instant of tripping: before the fault, during the fault, and during the fault recovery interval. The practical relevance and comprehensive nature of the proposed classification framework are demonstrated through analysis and rigorous discussion of several real-life DER tripping events, further underscoring its applicability. Simulation results obtained from combined transmission-distribution network analysis highlight significant risks of widespread DER tripping in networks with high DER penetration, potentially compromising grid stability. Lastly, potential strategies employed by industry to mitigate DER tripping in distribution networks are reviewed and compared from both device-level and system-level perspectives, ultimately offering a comprehensive approach to enhancing overall system stability.