For complex systems like solar power plants, it is necessary to assess the risk of damage due to lightning strikes in accordance with IEC 62305-2 (EN 62305-2), and the results must be considered in the design. The protection objectives for solar power stations are to protect the power plant's buildings and photovoltaic arrays from fire (direct lightning strike) damage, and to protect electrical and electronic systems (inverters, remote diagnostic systems, generator mains) from lightning electromagnetic pulses (LEMP).
In order to prevent the photovoltaic array from being directly struck by lightning, it is necessary to arrange the solar module within the protection range of the isolated flashing device. According to the VdS Guiding Principles 2010, photovoltaic equipment larger than 10KW should be designed as a "Class III" lightning protection system. For the corresponding protection level, the rolling ball method is used to determine the height and number of lightning rods. In addition, in accordance with IEC 62305-3 (EN 62305-3), care must be taken to maintain the isolation distance between the photovoltaic bracket and the lightning rod. Similarly, the lightning protection of the operating room is also "Class III". The down-conductor is connected to the grounding system through the ground bus. Due to the risk of soil or cement corrosion, the grounding busbar port must be protected with corrosion-resistant materials or with galvanized steel (such as sealing tape or heat-shrink tubing).
The grounding system of photovoltaic equipment is designed as a circular ground electrode (horizontal ground electrode), and the network size is 20m × 20m. The metal brackets holding the photovoltaic modules are connected to the grounding system approximately every 10m. The grounding system of the plant uses a basic grounding electrode in accordance with DIN 18014 (German standard). The photovoltaic equipment and the grounding system of the plant are connected to each other through a conductor (V4A steel bar, 30mm × 3.5mm, or galvanized steel). Interconnecting the various ground systems can significantly reduce the total ground resistance. The grounding system interconnected with each other in a mesh shape can form an equipotential surface, which can significantly reduce the overvoltage generated by the lightning effect on the connecting cable between the photovoltaic array and the plant building. The horizontal ground electrodes are laid in soil at least 0.5M deep, and are connected to each other in a grid shape using cross clamps. The joints in the soil must be wrapped with corrosion-resistant tape. This also applies to V4A steel bars laid in the soil.
In principle, all conductive parts entering the building from the outside must generally be connected to an equipotential bonding system. The way to complete these equipotential connection requirements is: all non-electrical metal parts are directly connected to the equipotential system, and live parts (such as cables) are indirectly connected to the equipotential connection system by installing a surge protector. Equipotential bonding is best performed near the building entrance to prevent some lightning currents from entering the building. In this case, the low-voltage power supply system in the plant can be protected by a multi-pole composite lightning current and a surge protector.
In addition, the input DC wire of the photovoltaic inverter in the plant must be protected by an adapted lightning current protector based on spark gaps, for example: using a composite lightning current and surge protector.
When a lightning strike device is struck by lightning, in order to reduce the mechanical stress generated by the solar module, a surge protector with a thermal monitoring function is installed in the generator junction box as close to the photovoltaic generator as possible. For DC generator voltages up to 1000V, install a surge protector between the positive and negative poles to ground. Because the photovoltaic panel is within the protection range of the external lightning protection device, this SPD is sufficient to meet the protection requirements.
In order to extend the interval of the periodic on-site inspection of the protective device, it has been proved in practice that using a surge protector with floating contacts to indicate the working status of the thermal trip device is an effective method.
The surge protector in the generator junction box basically controls the regional protection of photovoltaic equipment, and ensures that interference related to wires and electromagnetic fields will not cause arcing in photovoltaic equipment.
Lightning protection for so-called "thin-film photovoltaic modules" is beyond this consideration.
The factory has a remote diagnostic system for simple and fast functional inspection of photovoltaic equipment. Interference to photovoltaic equipment can be detected and eliminated by the operator early. The remote monitoring system can continuously provide performance data of photovoltaic equipment in order to optimize the output of photovoltaic equipment. External sensors at the photovoltaic device can measure wind speed, module temperature, and ambient temperature.
These measurements can be read directly from the data acquisition unit. The data acquisition unit can also be connected to a computer PC and / or modem through an interface such as RS 232 or RS 485, so that maintenance engineers can determine the cause of the fault and eliminate the fault through remote diagnosis. Regulatory Modem A network terminal device (NTBA) connected to an ISDN access port. Like photovoltaic modules, wind speed and module temperature measurement sensors are also installed in the lightning protection range. In this way, there will be no lightning current in the measurement line, but there may be transient overvoltages related to the connection wires, which is the induction effect in the isolated lightning-receiving device during a lightning strike. For reliable, trouble-free and continuous transmission of measurement data to the measurement unit, it is necessary to install a surge protector in the cable of the sensor introduced into the building. When selecting a surge protector, you must ensure that the measured values are not affected. ISDN modems that forward measurement data via telecommunications networks must also be secure and reliable in order to continuously control and optimize equipment performance. For this purpose, a surge protector is installed in the UKO interface of the ISDN modem upstream of the network terminal equipment. This surge protector also protects the network terminal equipment (NTBA) 230V power supply.