As the core equipment of a photovoltaic power generation system, the photovoltaic boost box substation requires a multi-layered lightning protection system to address risks such as direct lightning strikes, induced lightning strikes, lightning surge intrusion, and ground potential rise, ensuring equipment safety and stable system operation.
Direct lightning strike protection is the first line of defense in the lightning protection system, requiring lightning rods to conduct the lightning current to the ground. Photovoltaic boost box substations typically have lightning rods or lightning protection strips installed on top, and their protection range must cover the entire substation area. For open-air substations, early discharge lightning rods can be used to expand the protection radius and reduce the probability of lightning strikes by forming an upward leader in advance. The lightning rod must be reliably connected to the grounding grid via galvanized flat steel or copper cable to ensure rapid discharge of lightning current. Induced lightning protection requires equipotential bonding and shielding measures to eliminate electromagnetic induction overvoltage. All metal casings, equipment supports, cable trays, etc., within the photovoltaic boost box substation must be connected through an equipotential bonding terminal box to form a unified potential reference point, preventing equipment damage caused by potential differences.
Meanwhile, both DC and AC side cables must be shielded cables, with both ends of the shield grounded to reduce electromagnetic induction coupling. For signal lines, such as monitoring systems and communication modules, dedicated signal SPDs must be installed to prevent lightning surges from entering the equipment through the signal channel. Lightning surge intrusion protection requires energy suppression through multi-stage SPDs. On the DC side, DC SPDs must be installed at the combiner box and the DC input terminal of the inverter. Their nominal discharge current must match the system voltage; for example, for a 1000V or 1500V DC system, the protection level must be controlled within the equipment's withstand voltage range. On the AC side, AC SPDs must be installed at the inverter output terminal and the AC distribution cabinet input terminal. Type 2 or Type 1+2 level SPDs are typically selected, providing common-mode and differential-mode protection to prevent lightning surges from entering the transformer substation through the collector lines. Furthermore, surge arresters must be installed at the high-voltage side outgoing terminals to prevent lightning surges generated by lightning strikes on overhead lines from entering the transformer substation and damaging the transformer insulation.
The grounding system is the foundation of lightning protection, and the grounding resistance must meet standard requirements. Photovoltaic boost box substations typically employ a combination of horizontal and vertical grounding electrodes. The horizontal grounding electrode is made of galvanized flat steel, while the vertical grounding electrode is made of galvanized angle steel or copper-clad steel rod. The burial depth must meet the specifications. In areas with high soil resistivity, resistance-reducing agents, grounding modules, or extended grounding electrodes can be used to lower the grounding resistance, ensuring the overall grounding resistance is ≤4Ω. Grounding down conductors must be short and straight, avoiding right-angle bends. Connections must be welded or bolted and treated with anti-corrosion measures to ensure long-term stable operation.
Ground potential backflash protection must be achieved through independent grounding and equipotential bonding. The lightning protection grounding, working grounding, and protective grounding of the photovoltaic boost box substation should share the same grounding system to avoid potential backflash caused by separate grounding. For independent lightning rods or towers, the distance between their grounding electrodes and the main grounding grid must be ≥3m to prevent ground potential rise during lightning current discharge, which could damage the equipment. Simultaneously, all equipment casings and metal components inside the substation must be reliably connected to the grounding system to ensure potential balance during lightning strikes and prevent secondary discharge.
Operation and maintenance management is crucial for the continued effectiveness of lightning protection systems. Regularly check grounding resistance to ensure its value is less than or equal to the design value; inspect SPD status indicator lights, test residual voltage and leakage current, and replace faulty components promptly; check for lightning strike burns on module surfaces and water ingress corrosion of junction boxes. For large photovoltaic power plants, lightning monitoring systems can be deployed to monitor surrounding lightning strikes in real time, and, combined with meteorological early warning information, automatically cut off system power before severe thunderstorms, achieving intelligent protection.
The lightning protection system for photovoltaic boost box substations needs to construct a closed-loop protection system from multiple dimensions, including direct lightning strike protection, induced lightning suppression, lightning surge intrusion blocking, grounding system optimization, ground potential backflash prevention, and operation and maintenance management. By selecting appropriate lightning protection equipment, standardizing construction processes, and improving operation and maintenance systems, the lightning strike failure rate can be significantly reduced, ensuring the long-term safe and stable operation of the photovoltaic power generation system.
