Enhanced Protection for Photovoltaic DC Grid-Connected Systems: Identifying Incipient Faults with Fault Arc Energy Analysis

In photovoltaic DC grid-connected systems, inter-pole short-circuit faults pose a significant risk, potentially causing system-wide outages if line protections fail to isolate the fault branch before the converter blocks. This study proposes a proactive approach to enhance system resilience by identifying incipient faults (IFs) before they escalate. While traditional electrical quantity characteristics alone are insufficient for reliable IF detection, this research investigates the interaction between electromagnetic and temperature fields during IFs. By analyzing these characteristics, the study demonstrates the applicability of fault arc energy for IF identification. To accurately extract fault arc energy during the IF process, a novel algorithm is developed that combines current and temperature measurements. This algorithm represents a breakthrough in characteristic volume extraction approaches. Based on the fault arc energy mutation characteristic, an active protection criterion is proposed. Laboratory experiment-in-loop tests and simulations validate the effectiveness of the proposed criterion, demonstrating its ability to reliably identify and isolate IF branches. This significantly reduces the probability of short-circuit occurrence, thereby ensuring the safe and efficient operation of RES-DC grid-connected systems.