• Zhejiang Zhilu Transmission and Distribution Equipment Co., Ltd

Development of Annual Maintenance and Service Plan for Photovoltaic Dedicated Prefabricated Substations

Development of Annual Maintenance and Service Plan for Photovoltaic Dedicated Prefabricated Substations

1. Introduction

2. Maintenance Objectives

1. Reliability Assurance: Minimize unplanned outages by detecting and rectifying potential faults proactively.

2. Safety Enhancement: Ensure all components comply with electrical safety standards and reduce risks of electrical hazards.

3. Performance Optimization: Maintain high - efficiency power conversion and transmission, reducing energy losses.

4. Lifespan Extension: Mitigate wear and tear through regular upkeep, thereby reducing long - term replacement costs.

3. Maintenance Scope and Components

• High - Voltage Section: Circuit breakers, isolators, voltage/current transformers, surge arresters, and busbars.

• Transformer: Oil - immersed or dry - type transformers, including insulation, cooling systems, and tap changers.

• Low - Voltage Section: Switchboards, circuit breakers, contactors, power distribution panels, and power factor correction devices.

• Protection and Control Systems: Relays, monitoring units, communication modules, and control panels.

• Enclosure and Auxiliary Equipment: Weatherproof housing, ventilation systems, heating/cooling units, and grounding systems.

4. Annual Maintenance Procedures

4.1 Visual Inspection

• High - Voltage Equipment:

• Check for signs of arcing, corrosion, or discoloration on busbars, connectors, and switchgear contacts.

• Inspect SF6 - filled circuit breakers for gas leakage (using gas detectors) and oil - filled devices for leakage or contamination.

• Transformer:

• Examine the transformer tank for oil leaks (if oil - immersed), and check the insulation for cracks or degradation.

• Verify the proper operation of cooling fans, pumps, and temperature indicators.

• Low - Voltage Section:

• Inspect circuit breakers and contactors for burnt contacts, loose connections, or mechanical wear.

• Check the integrity of busbars, cable terminations, and insulation materials.

4.2 Electrical Testing

• Insulation Resistance Measurement:

• Test the insulation resistance of transformers, switchgear, and cables using a megohmmeter. Acceptance criteria: ≥10 MΩ for high - voltage equipment and ≥0.5 MΩ for low - voltage equipment.

• Contact Resistance Testing:

• Measure the contact resistance of circuit breakers, isolators, and connectors. Values should not exceed manufacturer - specified limits (e.g., ≤50 μΩ for high - current contacts).

• Functionality Tests for Protection Devices:

• Simulate fault conditions (overcurrent, overvoltage, earth fault) to verify the correct operation of relays and protective tripping mechanisms.

• Check the accuracy of voltage and current transformers through calibration tests.

4.3 Mechanical Maintenance

• Moving Parts Lubrication:

• Lubricate the operating mechanisms of circuit breakers, isolators, and tap changers using approved lubricants.

• Fastener Tightening:

• Re - torque all electrical connections, busbar joints, and mechanical fasteners to manufacturer - recommended torque values (e.g., M24 bolts: 800–1000 N·m).

• Enclosure Inspection:

• Seal any gaps or cracks in the substation enclosure to maintain IP protection (e.g., IP54/IP65). Replace worn - out gaskets and weatherstripping.

4.4 System Calibration and Software Update

• Instrument Calibration:

• Calibrate voltage and current meters, power quality analyzers, and temperature sensors to ensure accurate monitoring.

• Firmware and Software Update:

• Update the control system firmware of protection relays, monitoring units, and communication modules to the latest version, addressing security vulnerabilities and performance issues.

5. Maintenance Schedule and Task Allocation

6. Safety Precautions

1. Personal Protection:

• Ensure maintenance personnel wear appropriate PPE, including insulated gloves, safety boots, and arc - flash suits.

2. Isolation Procedures:

• Completely isolate the substation from power sources (PV arrays, grid connections) before starting maintenance. Verify zero voltage using a voltage detector.

3. Emergency Response:

• Have fire extinguishers (e.g., dry powder type for electrical fires) and first - aid kits readily available. Establish a clear emergency evacuation plan.

7. Record - Keeping and Documentation

• Maintain detailed records of all maintenance activities, including test results, replaced parts, and corrective actions.

• Use a computerized maintenance management system (CMMS) to track maintenance history, schedule future tasks, and generate reports for regulatory compliance and performance analysis.

8. Conclusion