Modification to Wiring and Protection Standards of Photovoltaic Systems

In a photovoltaic (PV) array, some shading profiles can produce abnormal overcurrent, which is in contrast with the general comprehension of partial shading. Under this condition, the magnitude of the overcurrent surpasses the ampacity of a standard wiring system. Since partial shading is not considered as a fault condition, the system should keep working until the shadow leaves the PV array. Even if the system is designed based on standard recommendations, this unique condition may lead to wiring system failure or nuisance trip of the protection system. This paper reviews the overcurrent occurrence at partial shading and analyzes the minimum requirements of wiring and protection based on valid standards of PV systems. Then, through experimental tests, it is proved that the minimum requirements for wiring and protection systems established by standard may not provide safe and durable working condition for a PV array. Finally, some suggestions are presented for possible slight modifications in the PV standard.