Taizhou 22kW distributed photovoltaic power station combiner box application case

Project Description
To reduce electricity costs, a manufacturing company in Taizhou constructed a 22kW distributed photovoltaic power station on its factory roof. The project utilizes 110 monocrystalline silicon modules (200W, 19.8V each), requiring efficient string current aggregation and safe transmission to the inverter. The client required a combiner box with high protection, intelligent monitoring capabilities, and adaptability to the high corrosion and typhoon-prone coastal environment. 

Customer Pain Points and Needs
1. Environmental Adaptability: Taizhou has a coastal climate, and the equipment must meet IP65 protection and salt spray corrosion resistance standards.
2. Operation and Maintenance Efficiency: Real-time monitoring of each string status is required to quickly locate faults.
3. Future Expansion Needs: Space must be reserved for future expansion of photovoltaic panels.

Solution: Customized 16-input, 1-output smart PV combiner box and AC distribution box services.

1. PV Combiner Box Product Configuration
Model: Longqi LQT-DC1000V-16-input, 1-output smart combiner box (actually uses 12 inputs, with room for expansion).
Core Configuration:
Electrical Performance: Rated current of 15A per channel (designed for 1.25 times the string short-circuit current), using a DC1000V 32mm fuse base (with room for expansion) and a 15A fuse element for overcurrent protection. Intelligent Monitoring: Utilizing Longchi's built-in RS485 communication module, the system collects current and voltage in real time (with an accuracy of ±1%) and connects to the customer's inverter cloud platform via RS485.
Protective Design: Stainless steel enclosure (thickness ≥ 2mm), T2 surge protector (Up ≤ 5.3kV), and reverse polarity diodes. Heat Dissipation Module: A hollow aluminum metal module maintains a normal internal temperature.
2. AC Distribution Box Product Configuration
Model: Longqi LQX-AC
Core Configuration:
Incoming Switch: 63A 3P AC disconnect switch, main on/off switch for the inverter AC output.
Lightning Protection Module: T1 T2 composite type, Imax 60kA/phase, response time ≤25ns, to protect against direct lightning-induced overvoltages.
Meter: Bidirectional energy meter (0.5S accuracy), separate metering for self-generation and consumption/surplus power grid connection.
Load Branch: 2 x 32A 2P MCBs (for critical factory loads), independently protecting key equipment.
Grid-Connected Branch: 40A 4P leakage protection device (delay 300mA), grid-side connection, to prevent backflow.
Enclosure Structure: IP65, PC ABS material, lifespan >20 years.
3. Installation Services
Customized Layout: Seven combiner boxes are distributed and installed on rooftop brackets (each box connects to 15-16 modules) to minimize line losses.
Typhoon Resistance:
The box features a bottom-fixed lateral support structure, with a wind pressure resistance of ≥2400 Pa5.
Cables are provided with extra clearance to prevent strain, and the tightening torque of waterproof connectors is ≥25 N·m15.
Safety Commissioning:
Insulation testing (≥100 MΩ), phase sequence verification, and lightning protection grounding (grounding wire diameter ≥16 mm²) are performed.

Project Highlights:
Intelligent Operation and Maintenance: A monitoring module collects data and uploads it to the cloud. Customers can monitor the string dispersion rate using a mobile app (detection accuracy 0.5%), reducing fault location time to 10 minutes.
Wind and Corrosion Resistance: The box has passed the ISO 12944 C5-M salt spray test and is suitable for coastal applications with a 25-year lifespan. Convenient Capacity Expansion: Reserved input ports support future capacity expansion of 20%.

Project Achievements
System Efficiency: Reduced string mismatch losses, achieving a system efficiency of 96.5%, and increasing annual power generation by 12% (compared to traditional solutions).
O&M Costs: Manual inspections reduced by 70%, saving approximately ¥5,000 annually.
Long-Term Reliability: The equipment has a 5-year warranty and a 30-year design life, meeting the stringent standards for scenarios such as fish-solar hybrid systems.