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Solar photovoltaic (PV) arrays behave distinctively from conventional power sources so that they need special consideration in fault analysis and protection. The faults inside PV arrays usually cause overcurrent that may damage PV components. This paper focuses on the challenges to overcurrent protection devices (OCPDs) in a PV array under two types of unique fault scenarios. One is a line-line fault that occurs under low irradiance conditions. In this circumstance, the fault current may not be large enough to trip the OCPDs in the PV array, even when high irradiance occurs later in the day. The other fault scenario is that when PV blocking diodes are used in the PV array, the reverse current may be greatly limited. However, OCPDs might not detect the reverse current properly. In both fault scenarios, the fault may not be cleared successfully by conventional OCPDs. Therefore, faults may remain undetected, which could lead to reduced system efficiency, reduced system reliability, and even unexpected safety hazards.