Integrated Solution: Pad Mounted Transformers Enhancing Efficiency and Reliability in Distributed Solar PV Systems

1. The Core Role of Pad Mounted Transformer (PMT) in Distributed PV Systems​

A Pad Mounted Transformer (PMT) is a fully sealed, box-type transformer installed directly on a ground-level concrete pad (pad). It is suitable for voltage step-up and grid interconnection in distributed photovoltaic (PV) power plants. Its primary functions include:

• ​Voltage Transformation:​​Steps up the low-voltage electricity output from PV inverters (e.g., 0.8kV) to 10kV or 35kV to meet grid interconnection requirements.
• ​System Integration:​​Integrates high-voltage switches, protection devices, and metering equipment, reducing the footprint and enhancing system reliability.
• ​Safety Isolation:​​The fully enclosed design provides dustproof, moisture-proof, and corrosion-resistant capabilities, enabling operation in harsh outdoor environments.

2. Pad Mounted Transformer Key Technical Parameters and Selection Guidelines​

2.1 Capacity Matching Principle​

• ​Capacity Calculation:​​Must be slightly larger than the PV system's maximum output power (typically configured at 1.1~1.2 times the rating).

• Example: A 19.9MW PV project equipped with 8 units of 2.5MVA PMTs (total capacity of 20MVA).
• ​Voltage Level:​​Select 10kV or 35kV based on the grid connection point voltage (e.g., an 8.3MW project in Shanghai utilizes 10kV grid connection).

​2.2 Core Selection Parameters​

2.3 Compatibility Design​

• ​Inverter Matching:​​The input voltage range must cover the inverter's output voltage (e.g., 0.8kV → 10kV).
• ​Protection Device Integration:​​Built-in fuses, surge arresters (lightning arresters), and temperature sensors; interfaces for external anti-islanding protection and fault isolation devices.

3. Pad Mounted Transformer System Integration Schemes​

​Intelligent Monitoring Integration​

• ​Sensor Configuration:​​Real-time monitoring of temperature, current, and voltage.
• ​Communication Interface:​​Supports Modbus or IEC 61850 protocol for integration into PV monitoring systems (e.g., Acrel-1000DP).
• ​Safety Protection:​​

Anti-islanding device:Disconnects within 0.5 seconds after detecting grid power loss.

Arc detection:AI-enabled intelligent arc fault identification (e.g., Huawei solution).

4. Pad Mounted Transformer Typical Application Case Studies​

4.1 19.​9MW Distributed PV Project​

• ​PMT Configuration:​​8 units of 2.5MVA pad-mounted transformers, deployed near 4 substations for close connection to 10kV distribution rooms.
• ​Results:​​Annual power generation of 14.95 million kWh, system efficiency >80%, reduced cable length by 30%.

4.2 ​Shanghai 8.3MW Rooftop PV Project​

• ​Solution Features:​​
  • 5 PMTs (2 units of 2.5MVA + 2 units of 1.6MVA + 1 unit of 0.8MVA) matched to groups of inverters with different capacities.
  • Fiber optic ring network for data transmission, enabling remote power forecasting and dispatch response.

4.3 ​Environmental Interference Resistance Design​

• ​High Wind Areas:​​Strengthened mounting bracket fixtures (e.g., wind load-resistant components).
• ​High Humidity Environments:​​Use anti-salt spray coatings (for coastal projects) and inverters with Potential Induced Degradation (PID) recovery function.

5. Economic Benefits and O&M Optimization​

5.1 ​Investment Return (ROI):​​

• Changchun 500kW Project:Annual generation 584,000 kWh, self-consumption rate of return 12.2%, payback period ≈5.3 years.

5.2 ​Operations & Maintenance (O&M) Strategy:​​

• Intelligent Diagnostics:IV curve scanning for real-time fault component localization.
• Preventive Maintenance: Overload risk alerts for transformers based on temperature data.