Investigation on Lightning-Induced Voltage for Photovoltaic System Considering Electromagnetic Coupling of Rooftop Structure

Considerable photovoltaic (PV) panels are installed on building roof, which are exposed to lightning strike at a high risk. Lightning electromagnetic (EM) field will induce a high voltage, which can damage the electronic devices of PV system. By using the method of moments, the EM coupling among the lightning channel and roof structure is modeled, and the induced voltage of PV array is calculated. The influences of building structure, roof material, and shape are discussed. The induced voltage is strongly dependent on the induced current on rooftop generated by the lightning EM field. Since the induced current produces an opposite magnetic field, it weakens the original lightning magnetic field and the presence of roof can lower the induced voltage. Occasionally, the induced voltage becomes higher for the roof with many crossbars and supporting legs, especially for the metal rooftop. The voltage rises as the roof height increases. Compared to the sloped roof, the distance between the flat roof and PV array is greater, and the effect of roof is relatively minor. To reduce the induced voltage, the arrangement of PV panels is investigated. The results can provide guidance for lightning protection design of rooftop PV system.