Extended analysis on Line-Line and Line-Ground faults in PV arrays and a compatibility study on latest NEC protection standards

Even with the expeditious progress in global Photovoltaic (PV) power generation, faults occurring in PV systems pose excessive challenges to the productivity and reliability of PV installations. Though specific installation standards have been developed for the protection of PV systems, the compatibility of these standards to cope with the unique operating characteristics of PV generating systems is questionable and hence, needs critical evaluation. Therefore, this paper briefly analyzes the standards available for the protection of PV systems, investigates the protection challenges and inspects the compatibility of latest National Electric Code (NEC) standards to protect PV arrays against Line-Line (LL) and Line-Ground (LG) fault occurrences. In particular, this article conducts a detailed behavioral study on LL and LG faults and evaluates the compatibility of NEC standards in the context of: (1) Varying mismatch levels, (2) Impact of Maximum Power Point Trackers (MPPTs) and (3) Changing irradiation levels. Detailed simulations as well as experimental analysis have been carried out to clearly portray the challenges in LL/LG fault detection despite by following new NEC recommendations. Further, based on the implications attained, some suggestions for reliable fault detection have also been presented that are expected to enhance the reliability of LL/LG fault detection in PV systems.