How Should Photovoltaic Power Plants Prevent Lightning Strikes During the Rainy Season?

How should photovoltaic power plants prevent lightning strikes during the rainy season?

Lightning will cause a lot of harm to photovoltaic power plants. For example, solar modules are extremely vulnerable to direct lightning strikes and cause the entire system to be paralyzed. After a photovoltaic controller is struck by lightning, the charging system will be charged or not charged, and it may also cause damage to the battery and inverter. If the battery is always in a charging state, overcharging will shorten the service life of the battery and reduce the capacity, and cause the battery to explode, causing damage to the entire system and casualties. In addition, if the inverter cannot invert the voltage, the DC voltage on the solar panel will be directly used by the load, and the high voltage of the solar panel will directly burn out the electrical equipment.

So, how does a photovoltaic power station prevent lightning?

In the current lightning protection measures, the most effective and extensive method is to connect the metal parts of electrical equipment to the earth. The grounding system consists of four parts: the grounding equipment, the grounding body, the lead-in wire and the earth. Good grounding is an important basis for the success of lightning protection measures. There are three main grounding methods.

1. Community grounding

The specific installation process of the grounding body is to dig a hole with a diameter of about 30cm on the ground, and lay some salt on the bottom of the hole, and then put the grounding body into it. Use a PVC pipe to cover the grounding body, and then fill and compact the gaps around the grounding body with soil. Finally, put gravel on top for watering and reinforcement. Use the same method to ground the other ground bodies. Form an isosceles triangle layout, and then use 35mm copper wires to connect. Form a grounding body inside the photovoltaic electric field.

This grounding can effectively ground all metal parts of the photovoltaic power plant. This method can solve the grounding problem without burying many grounding bodies. But also effectively control the resistance value within 4n. The metal shells of all equipment in the photovoltaic field, lightning protection devices, metal frames of solar panels, inverters and many other equipment can be directly connected to the same grounding body. When there is no lightning strike, it can be used simply as ground protection and neutral wire. Once a lightning strike occurs, it can be used as a lightning protection grounding device.

2. Monomer grounding

Some areas are affected by the geographical environment. The poles inside the photovoltaic field are often struck by lightning. And the location of the lightning strike is relatively fixed and will not move. For these special poles, lightning protection devices should be installed separately. Burying the corresponding grounding body can effectively prevent the occurrence of lightning strikes. The grounding body usually uses galvanized angle steel or flat steel with a length of about 2m.

3. Combined grounding

Combined grounding consists of multiple grounding bodies. The installation layout is usually arranged in a circular or square radial form and other forms. When the grounding body is arranged in a ring, it is necessary to ensure that there are no openings in the ring line, which is to reduce the mutual shielding effect. The actual distance between two adjacent grounding bodies cannot be less than 3m. The upper end of the grounding body should be reinforced with galvanized angle steel, and the distance from the ground should be less than 1m.

Lightning protection electromagnetic pulse lightning

Electromagnetic pulse strikes are not as strong as direct lightning strikes, but the probability of occurrence is very high. At present, the commonly used protective measures mainly include equipotential bonding, shielding and installation of surge protectors. In order to reduce the potential difference and fault voltage hazards between different metal objects, good equipotential connection measures should be taken for aluminum alloy frames, brackets, metal casings of controllers, combiner boxes, and inverters, metal shielding layers of metal tube cables, and lightning protection belts, etc. according to regulations.

In order to reduce electromagnetic interference, the home wiring of solar panels should be laid in a suitable path and well shielded. Cables should be cables with metal shielding layers and laid through metal pipes. At the interface of the lightning protection zone, the metal shielding layer of the cable and the metal pipe (both ends of the metal pipe should be grounded) should be equipotentially connected and grounded. Household lines and lightning protection connecting lines must be laid separately, keeping a minimum parallel spacing of 1m and a minimum crossing spacing of 0.3m. In order to prevent the overvoltage and overcurrent generated by the lightning electromagnetic pulse from invading and damaging the indoor photovoltaic power generation equipment through the home line, the cables of the photovoltaic power generation system should be equipped with multi-level anti-surge protection devices for lightning protection.

First of all, a DC arrester should be installed on the DC input line of the solar cell array. According to the line length and working voltage, select the SPD surge protector with a nominal discharge current ≥ 10kA, and the surge protector should include a differential mode filter inside. This can help eliminate the electromagnetic interference conducted on the line, and install an AC arrester on the AC output power supply line of the photovoltaic power station.

Secondly, since the controller and the inverter are both expensive devices, a second-level power surge protector should be installed in the controller and the inverter to have lightning protection. If the inverter is output to some important load equipment, a third-level power surge protector should also be installed at the output end of the inverter. When installing multi-level SPDs in power systems and electronic systems, multi-level matching issues need to be considered.

Lightning can cause severe damage to buildings and electrical equipment. In the lightning protection design of independent photovoltaic power plants, reasonable design schemes should be selected and effective measures should be taken. Do a good job in the lightning protection design of independent photovoltaic power plants to prevent direct lightning strikes, induced lightning, and lightning waves from damaging independent photovoltaic power plant equipment, so as to ensure long-term stable, safe and reliable operation of independent photovoltaic power plants and provide users with high-quality electric energy.