Like all outdoor structures, photovoltaic (PV) installations are exposed to the risks posed by lightning strikes. Lightning discharges cause high transient overvoltages that are potentially destructive for the PV modules, inverters, monitoring equipment, and other electronics that make up a PV system.
In situations where the produced PV energy is self-consumed, meaning that the PV installation is physically connected to the building electrical installation, these surges may damage not only the PV installation equipment, but also the sensitive devices inside the building.
Putting preventive and protection measures in place can keep electrical equipment safe.
Ensure equipotential bonding between all conductive parts
Your first safeguard should be to ensure equipotential bonding between all conductive parts in the electrical installation including the PV system. The aim is to connect all grounded conductors and metal parts to create equal potential at all points. This measure includes the power lines, including the DC side of the photovoltaic installation, as well as the data lines.
Protect against transient overvoltages with surge protection devices
In a building without an external lightning protection system, surge protection devices (SPDs) are required in three areas:
- • On the DC side of the PV installation
- • On the AC side of the PV installation
- • On the wired communication lines
Even in the presence of a lightning protection system, SPDs may be required as well unless a risk analysis demonstrates that this is not necessary.
Protection on the DC Side
The SPD on the DC side should be specially designed for PV installations because of the very specific electrical setup of such installations. Generally, the International Electrotechnical Commission recommends in IEC 60364-7-712.534, its standard for solar PV power supply systems, that these should be class 2 devices.
The SPD on the DC side should be installed as close as possible to the inverter. If the distance between the SPD and the PV modules is greater than 10m, an additional SPD should be installed closer to the modules. As shown in the figure below, SPD 2 is the device required on the DC side. SPD 1 is the device that should be added if the distance between the PV generator and the SPD exceeds 10m.
The SPDs should be installed in an electrical panel inside the building. If the panel is outdoors, it must be waterproof. Using iPRD-DC withdrawable surge protective devices allow rapid replacement of damaged cartridges and alerts personnel through remote reporting of information, such as by sending the message “cartridge to be changed.”
Protection on the AC Side
The requirements for surge protection device on the AC side are defined by IEC 60364-5-53 and IEC 60364-4-44-443.
The surge protection device on the AC side can be class 1 or class 2 depending on whether there is a lightning rod on the building or in nearby proximity, and the lightning density value.
The SPD should be installed on the LV switchboard to which the PV system is connected, which usually is the main panel. If the cable length between the main LV switchboard and the inverter is greater than 10m, an additional SPD should be installed on the AC output of the inverter.
As shown in the figure, SPD 4 is the required device on the AC side. SPD 3 is the device that should be added if the distance between the main LV switchboard and the inverter exceeds 10m.
Click here to discover a full range of surge protection devices.
Protecting wired communication lines
Surge protection devices are needed not only on the power supply lines. Their installations is recommended as well on wired communication lines, such as RS485 and ethernet. Requirements for the selection of surge protection devices connected to telecommunications and signaling networks are covered by IEC 61643-22. Schneider Electric offers a variety of surge protection devices for digital networks.
How to build a protection plan in installations with solar self-consumption
The integration of photovoltaic production into electrical installations requires specific safety measures. Watch the short video “How to protect electrical installations with photovoltaic production” to learn more about
- Loss-of-mains protection
- Rules for overcurrent protection placement on the AC side
- Isolation and switching of the photovoltaic supply system
You can also consult the Surge Protection for Photovoltaic Applications web page on the Schneider Electric Installation Wiki to get more information on transient overvoltage protection.