More and more people are thinking about installing their own solar mini-power plant. The location of photovoltaic modules is usually the roof of a house or a personal plot. And since sudden surges in voltage can lead to the failure of the solar battery, the system will need reliable protection against thunderstorms and high-voltage atmospheric discharges.
Danger of lightning strike
There are two options for exposing solar panels and ancillary equipment to this disaster.
1. Direct lightning strike.
The place of a lightning discharge strike can be a lightning conductor of a grounded roof of a building or a power line connected to the house.
In the first case, the voltage of the solar battery will jump abruptly due to the fact that part of the charge will spread along the cables laid inside the house. In the second, high currents will flow to the photovoltaic cells directly through the power transmission lines.
Both options, if you do not protect the equipment with additional protective measures, are very dangerous. The worst scenario is a fire in the wiring, which threatens to lose not only an expensive solar system, but also a fire in the house itself.
2. Indirect lightning strike.
Do not think that when a super-powerful discharge hits the ground or a tree standing nearby, solar panels are not needed. The induced electromagnetic field under similar circumstances causes voltage surges in a radius of tens, and sometimes hundreds of meters. The elements of the SPP may not fail. But the danger to all sensitive electrical equipment in the home will be high.
We provide multi-layered protection
The first “level of defense” is grounding itself. It will prevent a direct lightning strike directly in the panel. For this you will need:
- metal receiving rods;
- down conductors;
- grounding devices.
Each rod must be placed no closer than half a meter from the photovoltaic modules. If this is not possible, an external solar lightning protection system is led directly to the frame from one side. Desirable – as close to the down conductor as possible. This ensures that the high voltage is removed from the working part of the panel.
The second level is the installation of SPDs (surge voltage protection devices). Such devices are usually divided into three categories.
- The first one protects directly from a lightning strike. It is compulsorily installed in ASU (input-distribution devices) during the construction of multi-storey buildings and industrial buildings. A similar solution will be required for a private house or summer cottage.
- The second one is mounted in an internal switchboard. It guarantees voltage protection not only of the solar panels themselves, but also of other sensitive elements of the SES – primarily the inverter and the controller.
- The third contains fuses and / or switches, protecting the current-consuming devices directly at the input.
Important! When choosing an SPD device to protect the panel system, its voltage is selected as the sum of all open circuit voltages of the combined Uoc modules with a 20% margin. In other words, for a system of 10 24V batteries each, you will need an SPD of at least (10 * 24) + 20% = 288 volts.
In addition, experts recommend installing combined-type SPDs in a switchboard. This will prevent an impulse voltage surge not only from the outside, but also from the inside of the network.
In this article, we considered the protection of solar panels and auxiliary equipment only for the standard version of the SES and energy-consuming electrical appliances. For branched circuits, with additional devices, more complex, individual solutions may be required. It is advisable to trust the installation of such a multi-level security system only to professionals.
The arrangement of such a complex of protective equipment should be taken seriously. Only its presence, correct selection and placement of all elements guarantees the safe operation of your solar power plant.