Choosing the right PV grid-connected cabinet is critical for a solar plant. The cabinet protects inverters, metering devices and grid connection equipment. This guide explains how to size and select the right cabinet for your project.
What Is a PV Grid-Connected Cabinet?
PV grid-connected cabinet sits between the solar inverter and the utility grid. It contains AC breakers, surge protection, metering, isolation switches and sometimes power quality devices. It ensures safe and compliant grid connection.
Key Factors for Sizing
1. System Power and Current
Calculate the maximum current. For a 100 kW three-phase system at 400V, current is about 144A. Choose a cabinet rated at least 25% above this value for future expansion and safety margin.
2. Number of Inverters
Each inverter needs its own AC breaker. If you have 4 inverters, the cabinet needs 4 breaker ways plus a main breaker. Plan for spare ways if you may add inverters later.
3. Grid Code Requirements
Different countries have different grid codes. Some require anti-islanding protection, power factor control, or remote trip capability. Make sure the cabinet includes required protection relays and meters.
4. Environmental Conditions
Outdoor cabinets need IP54 or higher protection. Coastal or dusty sites need IP65. Indoor cabinets can be IP30 or IP40. Temperature range matters too: outdoor cabinets need fans or heaters for extreme climates.
Typical Cabinet Components
| Component | Purpose |
|---|---|
| Main AC breaker | Isolate the whole plant from grid |
| Inverter breakers | Individual isolation for each inverter |
| AC surge protector | Protect against grid surges |
| CTs and meter | Measure exported energy |
| Isolation switch | Visible break for maintenance |
| Protection relay | Anti-islanding, over/under voltage/frequency |
Sizing Example
For a 500 kW solar plant with 5 x 100 kW inverters:
- Main breaker: 1000A, 3-phase
- Inverter breakers: 5 x 250A
- AC SPD: 40kA, Type 2
- Meter: 0.5S class CT meter
- Cabinet size: ~800x600x2000mm
Where to Buy
Buy from a manufacturer that understands your local grid code. Chinese manufacturers offer good value for OEM/ODM projects. Look for certifications like IEC, CE and local grid approvals.
Frequently Asked Questions
Can I use a standard LV switchgear cabinet?
You can, but PV applications need specific protection functions like anti-islanding. A purpose-built PV grid cabinet is safer and simpler.
What IP rating do I need outdoors?
IP54 minimum for covered outdoor installation. IP65 if fully exposed to rain and dust.
Do I need a protection relay?
In most countries, yes. Grid codes require anti-islanding and over/under voltage protection. Check your local utility requirements.
Conclusion
Sizing a PV grid-connected cabinet requires careful calculation of current, breaker ways and protection requirements. Plan for expansion, match local grid codes, and buy from an experienced manufacturer.
Electric-GS designs and builds PV grid-connected cabinets from 100 kW to multi-MW systems. The company provides OEM/ODM service from Yueqing, China. Contact info@electricgs.com or WhatsApp +86 135 8897 8050 for a custom quote.