As the Flood Season Approaches, Dual Protection Guide for PV System Waterproofing and Lightning Protection to Safeguard Power Generation Safety

As the flood season draws near, severe rainfall, thunderstorms, and flash floods occur frequently. For outdoor-installed PV systems, waterproofing and lightning protection are the two most critical priorities. Core components such as PV modules, inverters, and junction boxes are mostly exposed to the elements. Inadequate waterproofing can lead to rainwater seepage, causing equipment short circuits, damage, and direct losses in power generation efficiency—even potential safety hazards. Meanwhile, the instantaneous high voltage from thunderstorms can breakdown PV system circuits, resulting in irreversible equipment failures. This guide details specific waterproofing and lightning protection measures for PV systems during the flood season, applicable to both household and industrial/commercial PV setups, helping you safeguard power generation safety and extend equipment service life.

I. Waterproof Protection of PV Systems During the Flood Season: Block Every "Water Seepage Loophole"

Water seepage risks in PV systems are mainly concentrated in key areas such as module connections, line interfaces, and equipment installation gaps. This risk is particularly high for rooftop distributed PV systems, which are affected by roof slope and seal aging. The core of waterproof protection lies in "adequate sealing, unobstructed drainage, and timely inspections," which can be broken down into the following four key steps.

1. Module Installation and Sealing: Build the First Waterproof Barrier

While PV modules themselves have inherent waterproof performance, the connection points between modules and the roof, as well as between modules, are most vulnerable to water seepage. First, ensure the roof base is flat and dry before installation. If cracks or damage exist on the roof, repair them in advance with waterproof rolls and sealants to prevent rainwater from seeping into the building through the base. Second, use weather-resistant, high-performance sealants (preferably silicone or butyl sealant) at the contact points between module frames and the roof, applying them evenly to eliminate gaps and bubbles and block rainwater penetration.

For color steel tile roof PV systems, use special fixtures to fix modules without damaging the roof’s coating, and install waterproof gaskets between fixtures and the color steel plate. For concrete roofs, properly waterproof the connection points between module brackets and the roof—install a waterproof base and seal the edges with sealant for double protection against seepage. Additionally, use waterproof terminal blocks for inter-module connections and wrap them tightly with insulating waterproof tape to prevent rainwater from entering the terminals and causing short circuits.

2. Inverters and Distribution Boxes: Ensure "Moisture-Proof Sealing" to Avoid Water Damage

Inverters and distribution boxes are the "brain" of a PV system—water ingress can directly burn out the equipment, resulting in significant losses. Focus on two key protection measures during the flood season: First, install them in high-lying, well-ventilated, and dry areas, avoiding low-lying spots. For household PV systems, this can be a well-ventilated rooftop area or a dry indoor corner; for industrial/commercial systems, ensure the inverter room has unobstructed drainage to prevent rainwater backflow. Second, check that the sealing covers of inverters and distribution boxes are tightly fastened and that their seals are not aged or damaged. Replace worn seals promptly to prevent rainwater seepage through gaps.

Install a waterproof baffle at the inverter’s heat dissipation port to block rainwater from entering the equipment. Place desiccants inside distribution boxes to absorb moisture and prevent internal components from dampness and oxidation. In case of heavy rain, temporarily cover inverters and distribution boxes with waterproof cloth for extra protection.

3. Lines and Junction Boxes: Ensure "Waterproof Wrapping" to Eliminate Line Water Ingress

PV system line connections are complex, and junction boxes, cable joints, and exposed outdoor lines are weak points in waterproofing that require special protection. First, use junction boxes with a waterproof rating of IP65 or higher, ensuring they are firmly fixed with wiring ports facing downward to avoid direct rainwater scouring. Second, use waterproof connectors for cable joints, wrapping them double with waterproof tape and heat-shrink tubing to eliminate gaps and prevent rainwater from seeping into cables, which could cause short circuits or leakage.

Additionally, secure outdoor cables firmly to prevent scouring and soaking by rainwater, and route them away from waterlogged areas. If cables need to pass through the roof or walls, install waterproof sleeves at the penetration points and seal the gaps between the sleeves, walls, and cables tightly with sealant to eliminate seepage risks.

4. Daily Inspection: Double Inspections Before and During the Flood Season to Rectify Hidden Dangers in Time

The key to effective waterproof protection is "prevention first." Before the flood season, conduct a comprehensive inspection of the PV system’s waterproof condition: check for cracked or peeling sealant on module frames, ensure junction boxes and cable joints are well-sealed, look for signs of water seepage on inverters and distribution boxes, and verify that roof drainage pipes are unobstructed. Replace aged or cracked sealant promptly, and clear blocked drainage pipes to ensure smooth rainwater discharge and prevent roof water accumulation from soaking PV modules.

During the flood season, inspect the PV system immediately after each heavy rainfall. Focus on checking for water accumulation under modules and around inverters, as well as signs of seepage or dampness at wiring points. If hidden dangers are found, cut off the power supply immediately and rectify the issue promptly to avoid further damage.

II. Lightning Protection of PV Systems During the Flood Season: Resist Lightning Strikes and Safeguard Equipment Safety

Thunderstorms are frequent during the flood season. The instantaneous high voltage and strong current generated by lightning can damage PV components, inverters, controllers, and other equipment through atmospheric discharge and line conduction—even triggering fires and electric shocks. PV system lightning protection follows the principle of "all-round protection and graded current discharge," constructing a complete lightning protection system through three key aspects: external lightning protection, internal lightning protection, and grounding protection.

1. External Lightning Protection: Intercept Lightning to Avoid Direct Strikes on PV Modules

The core of external lightning protection is preventing direct lightning strikes on PV modules and brackets. Common measures include installing lightning rods or lightning strips. For rooftop distributed PV systems with existing lightning strips, reliably connect PV brackets and module frames to the lightning strip to ensure modules are within its protection range (calculated per relevant standards; generally, the lightning strip should be higher than the highest point of the modules). If no lightning strip exists, install a lightning rod on the roof tall enough to cover the entire PV array and prevent direct strikes.

Note that lightning rods and lightning strips must be installed in compliance with relevant standards to avoid ineffective protection. Use galvanized flat steel or round steel to connect PV brackets to lightning strips/rods, ensuring firm connections and anti-corrosion treatment to prevent rust and breakage, which would compromise lightning protection effectiveness.

2. Internal Lightning Protection: Suppress Lightning Overvoltage and Protect Equipment Circuits

Even without direct lightning strikes, induced overvoltage from lightning can travel through lines and damage internal PV system equipment. Therefore, install lightning arresters (surge protectors) at key points to achieve graded current discharge and suppress overvoltage. Specific installation positions are as follows:

• Between module strings: Install DC lightning arresters between the positive/negative poles of module strings and the ground to protect modules and inverters from DC-side induced overvoltage;

• Inverter input and output ends: Install DC lightning arresters at the DC input and AC lightning arresters at the AC output to prevent lightning overvoltage from entering the inverter and damaging its core components;

• Inside the distribution box: Install a main lightning arrester at the incoming line end to protect the entire system circuit and prevent lightning overvoltage from spreading to the PV system through the power grid.

Select lightning arresters that match the PV system’s rated voltage and current. Ensure firm wiring and good grounding during installation, and regularly check the arrester status. Replace damaged or ineffective arresters promptly to maintain protection.

3. Grounding Protection: Build a Complete Grounding System to Quickly Discharge Lightning Current

Grounding protection is a critical link in lightning protection, with the core function of quickly discharging lightning current into the ground to avoid internal accumulation and overvoltage. Construct a "combined grounding body" for the PV system, reliably connecting all metal components (PV brackets, module frames, inverters, distribution boxes, lightning arresters, etc.) to the grounding body. Ensure the grounding resistance meets standard requirements (no more than 4Ω for household PV systems, and no more than 1Ω for industrial/commercial systems).

Install the grounding body in an area with low soil resistivity. If soil resistivity is high, reduce it by increasing the number of grounding electrodes or laying resistance-reducing agents. Regularly inspect grounding connections to ensure they are firm and free from loosening or rust. Rectify excessive grounding resistance promptly to ensure the grounding system operates normally.

III. Emergency Response for PV Systems During the Flood Season: How to Deal with Hidden Dangers

Even with comprehensive protection, emergencies may still occur during the flood season. Master the following emergency response methods to avoid further damage and safety accidents:

1. In case of thunderstorms, immediately cut off the PV system’s main power supply to stop power generation and prevent lightning damage. After the thunderstorm ends completely, reclose the switch and check if the system operates normally.

2. If water seepage, short circuits, or equipment damage are found, cut off the power supply immediately. Do not disassemble or repair the system without authorization—contact professional maintenance personnel promptly to handle the issue on-site and avoid electric shocks, fires, or other accidents.

3. If the PV system is submerged by floodwater, wait for the water to recede completely before having professionals conduct a comprehensive inspection, drying, and maintenance. Restart the system only after confirming no safety hazards exist.

IV. Summary: Prevention is Better Than Cure for Flood Season Protection

The core of PV system waterproofing and lightning protection during the flood season is "preliminary inspection, comprehensive protection, and timely disposal." For household PV users, follow this guide to conduct pre-flood inspections and protective measures, strengthen in-season patrols, and address hidden dangers promptly. For industrial/commercial PV projects, establish a professional maintenance team, formulate comprehensive flood protection and emergency response plans, and conduct regular system inspections and maintenance to ensure safe and stable operation during the flood season.

After all, the safe operation of your PV system is not only related to power generation benefits but also to personal and property safety. As the flood season approaches, proper dual protection of waterproofing and lightning protection will help your PV system safely "survive the flood season" and continue generating green energy benefits.