Lightning Protection Technology for Photovoltaic Power Stations

Solar energy is an inexhaustible renewable resource. Due to its complete cleanliness, adequacy, and potential economics, its application is accelerating globally. One of the most important ways to use solar energy is solar power. The absolute advantages of not using fuel, noise, and environmental pollution make solar power generation technology widely used in industry, agriculture, national defense, communications, and transportation. However, photovoltaic power stations are mostly built on rooftops or in remote locations, and are vulnerable to lightning strikes, which can cause equipment damage, power outages, and even personal safety. Therefore, lightning protection grounding technology for photovoltaic power generation systems is crucial in the entire system.

The composition of solar photovoltaic power station system: Solar power station system consists of solar module square array, combiner box, DC distribution cabinet, grid-connected inverter, AC distribution cabinet, booster, operation monitoring and detection system, communication system, lightning protection And grounding system.

According to the standard:

1) "Lightning Protection Design Code for Buildings" (GB50057-94 (2010))

2) "Technical Specifications for Lightning Protection of Building Electronic Information Systems" (GB50343-2012)

3) "Overvoltage Protection for Photovoltaic (PV) Power Generation Systems - Guidelines" SJ/T 111-1997

4) "Civil Electrical Design Code" (JGJ/T16-92)

5) "Surge protector (SPD) for low voltage distribution system Part 12: Guidelines for selection and use" GB/T18802.12 -2006

6) "Low-voltage surge protectors - Part 21: Surge protectors (SPD) for telecommunications and signal networks - Performance requirements and test methods" GB/T 18802.21 -2004

7) "Lightning Protection and Grounding Installation" D501-1~4

8) "Design Specification for Low Voltage Distribution" GB 50054-95

9) "Protection of lightning electromagnetic pulses" IEC 61312

External direct lightning protection

Design content: The so-called lightning protection: it is the lightning protection system that consists of lightning rods (or lightning protection belts, lightning protection nets, lightning rods), down conductors and grounding systems, mainly to protect buildings from lightning accidents and personal safety accidents. In the 0-level protection area is external passive protection, mainly lightning rod (network, line, band) and grounding device (ground line, ground).

2. Equipotential bonding: Equipotential bonding between metal objects is achieved to prevent flashover or breakdown between them. The key part of the lightning protection system is all the metal structures of the solar photovoltaic grid-connected power generation system and the equipment enclosure connected and grounded.

3. Shielding: Realize the electromagnetic shielding of buildings, circuits and devices from the outside world to prevent electromagnetic pulse and induced high voltage. Shielding is to protect the system by reducing the interaction between the electromagnetic field and the transmission line of the system when the thunderclouds near the ground of the system pass through the thundercloud in the vicinity.

4. Surge protection: By installing a surge protector on the live cable, reduce the surge and lightning overvoltage damage to the device. The lightning surge invasion route of solar photovoltaic grid-connected power generation system includes distribution lines and grounding lines in addition to the solar cell array.

Grounding design of solar photovoltaic power stations: Lightning protection grounding of photovoltaic power stations includes lightning rods, lightning protection nets, lightning protection strips, lead wires, grounding wires, and grounding bodies. Good grounding reduces the grounding resistance. In order to prevent various damages caused by lightning and other factors and the safety of national livelihoods, grounding devices are essential in photovoltaic power plants. The power generation equipment of the solar photovoltaic power station and the grounding system of the power distribution room and other buildings are interconnected by galvanized steel to form an integral grounding system. Through the grounding device, lightning-induced overcurrent can be introduced into the earth. In the photovoltaic power station, independent lightning rods (wires) shall be provided with an independent centralized grounding device, and the grounding resistance must be less than 10Ω. The deflectors coming from lightning arrestors such as lightning rods, lightning protection nets, and lightning conductors also use round steel and flat steel. However, round steel is preferred. In addition to the use of hot-dip galvanized or painted steel in its own steel reinforced concrete, in the more corrosive environment, the underwire should be increased in cross-section and other anti-corrosion measures. In regions where salt corrosion is strong in the coastal area or where the earth resistivity is high and it is difficult to meet the grounding resistance requirements, the grounding body should adopt a non-metallic grounding body with corrosion resistance and good moisturizing performance.

The key part of the lightning protection system is all the metal structures of the solar photovoltaic grid-connected power generation system and the equipment enclosure connected and grounded. In order to prevent lightning induction, all metal objects of the entire photovoltaic power generation system, including the aluminum frame of the assembly, the outer casing of the electrical equipment, and the square array bracket of the solar module, must be reliably grounded and connected to the joint grounding body to achieve the potential of each metal. Equipotentials between objects prevent flashovers or breakdowns between them.

Solar power systems have been used more and more widely due to their stable and reliable performance, easy installation, and simple operation and maintenance. Due to the particularity of the installation location and environment of the solar photovoltaic power generation system itself, the hidden dangers of the equipment being damaged by lightning electromagnetic pulses are becoming more and more prominent. Therefore, according to the actual situation, the qualified design of lightning protection for solar photovoltaic power generation system will help improve the safe and efficient operation of the entire power generation equipment system. When necessary, the soil resistivity is measured at the site to provide reliable data for lightning protection grounding design. The lightning protection grounding design of photovoltaic grid-connected power stations relates to the safe operation of the entire power plant and can ensure the safety of the protected equipment. Therefore, in the design of the entire photovoltaic power station, lightning protection grounding design is of utmost importance and must be highly valued to provide a favorable guarantee for the safe and reliable operation of solar photovoltaic power plants in the future.