A Compatibility Analysis on NEC, IEC, and UL Standards for Protection Against Line-Line and Line-Ground Faults in PV Arrays

Expeditious progress in global photovoltaic (PV) power generation is considerably challenged by electrical fault occurrences in PV arrays; particularly, line-line (LL) and line-ground (LG) faults. Therefore, the compatibility of LL/LG fault protection standards recommended for PV arrays needs decisive evaluation in various unique operating characteristics of PV generating systems. In this context, the existing works in the literature primarily investigates the standards specified in NEC (National Electrical Code) article 690 only. However, apart from NEC 690, protection standards like IEC 62109-1, IEC 62109-2, IEC 602696, UL 1741, and UL 2579 also detail various LL/LG protection aspects for PV arrays. Hence, this paper briefly analyzes the features, investigates the protection challenges, and scrutinizes the potency of NEC 690, IEC 62109-1, IEC 62109-2, IEC60269-6, UL 1741, and UL2579 protection standards for LL/LG fault detection. Extensive simulation and experimental analysis have been carried out in this paper to evaluate the effectiveness of these standards at various practical PV operating conditions: 1) Varying mismatch levels, 2) impact of MPPT controllers, and 3) changing irradiation levels. Overall, this paper is envisioned to assess the necessity of improvements in fault detection standards for PV systems and also to set some valuable benchmarks to avail reliable protection.