Researchers in Indonesia found that higher soil resistivity significantly increases lightning-induced overvoltage in PV systems. Their simulations also showed that multiple grounding points and connections closer to the lightning strike location can substantially reduce transient voltages.
A research team in Indonesia has proposed a novel grounding strategy to mitigate lightning-induced overvoltage in PV systems by identifying optimal grounding-point locations and evaluating different grounding configurations.
“Previous research has generally protected solar panels using a Lightning Protection System (LPS) with lightning rods connected to down conductors, such as Franklin rods,” the scientists emphasized. “This study considers the possibility of direct lightning strikes on solar panels or their supports, even if an LPS is installed. This occurrence allows current to flow through the solar panels to the grounding point.”
The researchers developed an equivalent electrical circuit model to investigate the transient overvoltage response of PV systems to lightning strikes. The simulated array comprised ten solar panels, each rated at 200 W, representing a section of a larger PV installation. Using ATPDraw 7.2 software, they modeled the electrical characteristics of the PV frames, mounting structures, grounding conductors, and electrodes through equivalent resistance, inductance, capacitance, and mutual inductance parameters.
Lightning strikes were simulated using a Heidler current source with a peak amplitude of 50 kA and an impulse waveform of 1.2/50 μs. Two configurations were investigated: direct grounding through the PV module frames and grounding through the mounting structures. The simulations assessed the effects of soil resistivity, grounding-point location, and the number of grounding connections on transient voltage distribution.
The researchers varied grounding-point locations to determine how the electrical path between the lightning strike location and the grounding connection influences overvoltage levels. They also compared single- and dual-grounding arrangements to assess the benefits of additional connections. The model assumed electrically interconnected metallic PV frames and evaluated voltage differences relative to a reference potential, excluding physical damage mechanisms and potential differences involving PV power conductors and inverters.
The results showed that increasing soil resistivity from 30 Ωm to 3,000 Ωm significantly raised transient voltage levels in both configurations. At lower resistivities, the highest voltages occurred near the lightning injection point, whereas at 3,000 Ωm, they shifted toward the grounding connection. Grounding through the mounting structures generally resulted in lower maximum voltages due to their lower electrical resistance.
At a constant soil resistivity of 30 Ωm, maximum voltages ranged from 1.97 MV to 2.64 MV for frame grounding and from 2.14 MV to 2.43 MV for mounting-based grounding, depending on the connection location. In both cases, positioning the grounding point closest to the lightning injection point minimized peak voltages by shortening the current discharge path and reducing its impedance.
Introducing a second grounding point further reduced transient voltages by 47.5% to 54.8% for frame grounding and by 43.2% to 50.7% for mounting-based grounding. The researchers attributed these improvements to lower grounding impedance and more efficient lightning current dissipation. The simulated peak current reached 48.78 kA, which the researchers described as being within the safety limits of IEEE Std 80, the IEEE Guide for Safety in AC Substation Grounding.
The findings indicate that grounding-point location and the number of connections have a greater influence on transient voltage mitigation than the choice between frame- and mounting-based grounding. In particular, shorter discharge paths, lower grounding resistance, and multiple grounding connections can substantially improve grounding performance.
Overall, the study highlights the importance of strategically positioned grounding points, low-resistivity soil conditions, and multipoint grounding in reducing lightning-induced overvoltage and improving the reliability of PV installations.
The new methodology was presented in “Study of the selection of an individual grounding location point against direct lightning strikes on solar panel systems,” published in Results in Engineering. The research group comprised scientists from Indonesia’s Institut Teknologi Sepuluh Nopember and Universitas Hasanuddin.
This content is protected by copyright and may not be reused. If you want to cooperate with us and would like to reuse some of our content, please contact: [email protected].