Lightning Protection of Rooftop Photovoltaic Systems: A Scientific Approach

The increasing of photovoltaic microsystems in Brazil follows global trend for low-cost panels and efficient cells. Although the solar modules are located on roofs and lightning strikes can damage all components of PV System (PVS). The Lightning Protection Systems (LPS) associated with Surge Protection Device (SPD) are the effective protection against electromagnetic effects. This study estimated the values of overvoltage and overcurrent induced by lightning in 2.65 kW PVS under different configurations, with or without LPS, by Faraday's Law of Induction. The estimation of the difference of potential on soil is according to the Law of Ohm and Maxwell equation. Thus, the purpose of this publication is to support the LPS design and SPD specification for PVS. The simulation considered the DC wiring design, distances from LPS and tilt angle of solar modules. The results pointed out that impulse rate of 200 kA/µs induces peaks up to 201,6 kV and 28,3 kA in DC circuits by lightning strikes and up to 82 kV in AC terminals of DC/AC converter transferred from soil by grounding systems. In conclusion, the main protection system against lightning damages is LPS associated with SPD that can protection against abnormal values of induced voltage and current. In addition, equipotentialization is necessary to complement the effective protection using a unique grounding system in accordance with the guidelines of the international standards IEC and ABNT.