• Zhejiang Zhilu Transmission and Distribution Equipment Co., Ltd

Joint Commissioning Scheme for Photovoltaic Prefabricated Substations and Inverters

1. Introduction

2. Pre - commissioning Preparation

2.1 Equipment Inspection

• PV Prefabricated Substation:

• Check the integrity of high - voltage switchgear, transformers, low - voltage distribution equipment, and protection relays.

• Verify that the substation's rated voltage, current, and short - circuit withstand capacity match design specifications.

• Inverter:

• Inspect internal components (IGBT modules, capacitors, cooling systems) for physical damage or loose connections.

• Confirm the inverter's rated power, maximum power point tracking (MPPT) range, and grid - connection compatibility.

2.2 Document Review

• Examine installation records, equipment certificates, and wiring diagrams for both the substation and inverter.

• Ensure compliance with relevant standards (e.g., IEC 62116 for anti - islanding protection, IEEE 1547 for grid - connection requirements).

2.3 Site Condition Verification

• Confirm that grounding resistance of the substation and inverter is ≤ 4 Ω, as per safety regulations.

• Check the insulation resistance of power cables and electrical equipment (≥ 10 MΩ for 10kV systems; ≥ 0.5 MΩ for 0.4kV systems).

3. Commissioning Procedures

3.1 Isolated Component Testing

• PV Prefabricated Substation Tests:

• Test the functionality of circuit breakers, contactors, and power distribution panels.

• Measure the voltage and current balance of three - phase outputs.

• Conduct withstand voltage tests on circuit breakers, isolators, and transformers at 1.1 times the rated voltage for 1 minute.

• Verify the operation of protection relays (overcurrent, differential, earth fault) by simulating fault conditions.

• High - voltage Section:

• Low - voltage Section:

• Inverter Tests:

• Perform no - load tests to check the operation of the control system, fan, and display interface.

• Simulate MPPT operation under different irradiance and temperature conditions to verify power extraction efficiency.

3.2 Joint System Integration Tests

• Power Flow Verification:

• Connect the inverter output to the low - voltage side of the prefabricated substation.

• Gradually increase the PV array input to the inverter and monitor the power flow from the inverter to the substation, ensuring stable voltage and frequency at the substation's output.

• Protection Coordination:

• Trigger fault simulations (e.g., short - circuit, overvoltage) at the inverter or substation side and verify that protection devices (circuit breakers, relays) trip within specified time limits.

• Test anti - islanding protection by disconnecting the grid connection and confirming that the inverter shuts down within 2 seconds, as required by IEEE 1547.

• Communication and Monitoring:

• Check the data exchange between the inverter's control system and the substation's monitoring unit (e.g., via Modbus, CAN bus protocols).

• Ensure real - time transmission of key parameters (voltage, current, power, temperature) to the central control system.

3.3 Grid - connection Tests

• Synchronization Verification:

• Adjust the inverter's output voltage, frequency, and phase angle to match the grid's parameters.

• Monitor the inrush current during grid connection; the peak value should not exceed 1.2 times the rated current.

• Grid - code Compliance:

• Test the inverter's response to grid voltage fluctuations (e.g., voltage sags, swells) and frequency variations, ensuring it meets grid - code requirements (e.g., maintaining operation within ±10% voltage and ±0.5 Hz frequency deviations).

• Verify reactive power compensation capabilities by adjusting the inverter's power factor setpoints.

4. Test Records and Acceptance Criteria

4.1 Test Records

• Document all test results, including voltage, current, power measurements, protection device response times, and communication data.

• Record any abnormal phenomena during commissioning, along with corrective actions taken.

4.2 Acceptance Criteria

• Electrical Performance:

• The voltage deviation at the substation's output should be within ±5% of the rated voltage.

• The inverter's efficiency should be ≥ 98% under rated load conditions.

• Protection Functionality:

• All protection devices (circuit breakers, relays) should operate correctly within specified time - current curves.

• Anti - islanding protection should detect and isolate the system within the required time limits.

• Communication and Monitoring:

• Data transmission between the inverter and substation should be error - free, with a response time ≤ 1 second.

• The central control system should accurately display real - time operating parameters of both the inverter and substation.

5. Safety Precautions

• Ensure all commissioning personnel are trained and equipped with appropriate personal protective equipment (PPE), including insulated gloves, safety helmets, and voltage testers.

• Isolate power sources before performing any maintenance or testing on live equipment.

• Establish emergency procedures for handling electrical faults, fires, or equipment malfunctions.

6. Conclusion