The remote locations, expansive layouts, and exposed surfaces of solar photovoltaic (PV) power plants make them highly vulnerable to environmental hazards — especially electrical storms. One of the biggest risks is damage caused by direct or indirect lightning strikes, which can lead to extended system downtime, inverter failure, and major revenue losses.
To mitigate these risks, it’s crucial to install surge protection devices (SPDs) for solar PV systems at strategic points, including the solar inverter and array junction boxes. These solar surge protection solutions act as a first line of defence, preventing destructive overvoltages from damaging sensitive equipment.
Photovoltaic systems operate under specific conditions that require PV surge protection devices specifically engineered for high-voltage DC applications — often up to 1500V. Unlike AC systems, the DC environment in solar arrays is continuous and presents unique challenges.
To choose the correct SPD for your solar PV system, consider the following critical factors:
The lightning flash density in the installation area
The system’s operating temperature range
The system’s DC voltage rating (often up to 1500V)
The short-circuit current (Isc) of the PV array
The type of overvoltage exposure (transient, direct or indirect lightning)
The required nominal discharge current (In) and protection class (e.g. Type 1+2 SPD)
To ensure effective protection, the voltage protection level (Up) of the selected SPD must be at least 20% lower than the dielectric strength of the connected equipment, such as the inverter or combiner box.
Implementing the right lightning protection for solar PV is not just a safety measure — it’s essential for maintaining system uptime, extending equipment lifespan, and protecting your investment in renewable energy.
It is important to use an SPD with a short circuit withstand current greater than the short circuit current of the solar array string that the SPD is connected to. The SPD that is provided on the dc output must have a dc MCOV equal to or greater than the maximum photovoltaic system voltage of the panel.
When a lightning strikes at point A (see Figure 1), the solar PV panel and the inverter are likely to be damaged. Only the inverter will be damaged if the lightning strikes at point B. However, the inverter is typically the most expensive component within a PV system, which is why it is essential to properly select and install the correct SPD on both the ac and dc lines. The closer the strike is to the inverter, the more damaged the inverter will be.
Surge-protection devices are installed on the DC and AC sides of central and string inverters, in combiner boxes and to protect signal lines (measurements and communications). Depending on the atmospheric exposure of the PV plant to lightning, engineering, procurement and construction (EPC) contractors and designers may prescribe either standard type 2 IEC SPDs (indirect impact 8/20 μs) or more robust type 1+2 SPDs (tested to withstand direct lightning impacts in 10/350 μs waveform).
DC side protection at combiner boxes and inverters typically has a Y-connection DIN-rail configuration in order to provide common and differential mode protection.
On the AC side, overvoltage protection of the inverter is likewise required. Whether at the inverter itself or at the AC combiner box, exposure to voltage surges is generally addressed by using standard DIN-rail type 2 SPDs in TN S, IT or even TT configurations.
Moreover, depending on the PV installation, type 1+2 AC may be favored in some cases by EPC contractors and designers, in order to achieve a longer lifetime for SPDs and even protection where conditions are harsher in terms of the expected direct lightning impact. This will typically be the case in areas with a very high isoceraunic level, often associated with high altitudes.
