A dc series arc fault is difficult to detect and localize due to the lack of a current zero crossing point. Unless there is an adequate protection, these faults can pose a threat to the stable operation of a photovoltaic (PV) system. A detection method for series dc arc faults in a PV system based on time and frequency characteristics of a parallel capacitor current is proposed. Series and parallel solar panel array systems are constructed, and a capacitor is parallele. A dc series arc fault is difficult to detect and localize due to the lack of a current zero crossing point. Unless there is an adequate protection, these faults can pose a threat to the stable operation of a photovoltaic (PV) system. A detection method for series dc arc faults in a PV system based on time and frequency characteristics of a parallel capacitor current is proposed. Series and parallel solar panel array systems are constructed, and a capacitor is paralleled with the load. Series arc faults are generated at different locations in the PV system, including locations between panels, on the PV bus and the load side. When a series arc is generated in the system, the high frequency components of the current will pass through the dc bus capacitor. The polarity and amplitude of capacitor currents as well as the integration of the frequency spectrum of capacitor currents are analyzed and identified as key attributes to differentiate dc series arc faults from other system changes. The impact of the harmonics generated by a converter is analyzed. The results indicate that the proposed approach and apparatus could be used to detect and localize series arc faults.••••A dc arc fault detection method using parallel capacitor current is proposed.••The difference of integrated spectrum of capacitor current has a certain range.••The polarity of the capacitor current pulse can localize the series arc fault.••Arc fault in a PV string can be localized comparing capacitor current amplitudes.DC series arc faultPhotovoltaic systemTime and frequency characteristicsParallel capacitor currentWith the growing demand of renewable energy, more and more PV systems are connected with the power grid. The stable and safe operation of PV systems is essential to the power grid, since faults in the PV system may disturb the normal operation of the power grid and cause equipment damage (Khan et al., 2015, Park and Candelaria, 2013). Series dc arc faults are commonly generated in PV systems due to the vibration of connected joints or insulation degradation (Garoudja et al., 2017). A dc arc is different from an ac arc since it does not have current zero crossing points. Thus, ac series arc interruption approaches cannot be directly used for dc arcs. In addition, the sustained dc series fault current may easily initiate a fire (Kostyantyn et al., 2013). For instance, a fire hazard was caused by an arc fault in the Mont Soleil PV power station in Switzerland (Novak, 2012). The 2010 U.S. National Electrical Code (NEC) requires that a PV system with a voltage higher than 80 V must have an Arc-Fault Circuit Interrupter (AFCI) (Artale et al., 2014, Seo et al., 2012, UL standard for safety for arc-fault circuit-interrupters, UL, 2008). Therefore, it is critical to develop a reliable detection and localization method for series dc arc faults in PV systems.Series dc arc fault characteristics has been studied and a heuristic model appropriate for simulation studies has been developed (Uriarte et al., 2012). R. This paper mainly focuses on the investigation of physical characteristics of dc series arcs in two PV systems as well as the development of the series arc fault detection and localization method. The impact of the converter and inverter in the PV system is ignored in this section. A load switch and load resistor are used to regulate the system current. Two test scenarios are implemented as shown in Fig. 1. Scenario 1 is a series panel array system, which consists of four series solar panels, a load switch, and a load resistor. Scenario 2 is a series/parallel panel array system, which consists of two parallel strings with three series panels in each string, a load switch, and a load resistor (this will be referred to simply as the parallel array). The rated output power of each solar panel is 120 W with rated voltage of 17.0 V and rated current of 7.1 A. The open-circuit voltage and short-circuit current of each panel are 21.5 V and 7.9 A, respectively.Series arc faults are generated by a test setup, as shown in Fig. 2. Brass electrodes are connected in series with the rest of the circuit in the PV system. The movable electrode is controlled by a step motor, and the moving distance and velocity can be programmed by a controller. In this paper, the moving distance and velocity of the electrode are set to be 2 mm and 2 mm/s, respectively. It should be noted, this is a similar experimental approach to tha.
