According to the relevant part of IEC61643-12, the selection and installation of solar surge protector used to protect photovoltaic systems depends on many factors, but the main factors are as follows:
1. The ground lightning density N1/(km year) or the annual average thunderstorm day T (the number of thunderstorm days per year);
2. The characteristics of the low-voltage power system (such as overhead lines or underground cables) and the characteristics of the equipment to be protected;
3. Whether an external lightning protection system is installed to protect the photovoltaic system from direct lightning strikes.
Solar surge protector requirements when installing an external lightning protection system depend on:
1. Select the level of lightning protection system
2. Whether the requirements for safe separation distance are met between the lightning protection system and the photovoltaic system (isolated/non-isolated lightning protection system).
In order to obtain the best overvoltage protection effect of the inverter, it is recommended to connect the grounding of the photovoltaic surge protector and the grounding of the inverter directly.
We also need to understand several situations that are prone to overvoltage in photovoltaic systems.
The following conditions can cause overvoltages in photovoltaic systems:
1. Direct lightning strike (S1) to the external lightning protection system of the building or lightning strikes near the building and/or photovoltaic system (S2)
2. Lightning direct strike current (S3) and lightning induced current (S4) scattered into AC and DC power grids;
3. Overvoltages caused by the distribution network eg due to switching operations.
4. Special consideration should be given to repetitive operating overvoltages (spikes) generated by the electronic inverter/rectifier on the AC side when selecting the solar surge protector.
The surge protection requirements in this section are based on the assumption that cables connecting the DC components of a PV system can be adequately protected from the risk of direct lightning strikes by means of proper wiring or shielding measures, such as the use of an appropriate cable management system.
After understanding the situation that overvoltage is prone to occur in photovoltaic systems, we will describe in more detail the location and requirements for the installation of surge protectors in different photovoltaic systems
In addition to the installation requirements of surge protection devices in different photovoltaic systems above, surge protectors used in telecommunications and signal networks in photovoltaic systems should also be considered.