1. Daily Inspection
Daily inspection is the basic work of box-type substation maintenance, aiming to detect potential problems early and prevent failures. Based on xinhong electrical’s operating experience, daily inspection includes:
Appearance check: Check whether the enclosure is deformed, damaged, rusted, or leaking. Ensure the enclosure is well sealed, and door locks and sealing strips are intact to prevent ingress of rain, dust, and small animals. Ventilation louvers and heat dissipation holes should be unobstructed.
Temperature check: Use an infrared thermometer to measure temperatures of key parts such as the transformer, switchgear, and cable joints to ensure they are within normal ranges. The top oil temperature of the transformer should generally not exceed 85°C, and low-voltage terminal temperature should not exceed 70°C.
Sound check: Listen for abnormal noises from the transformer and switchgear, such as irregular humming, discharging, or cracking sounds. Investigate any unusual noise promptly.
Instrument check: Check whether readings of voltmeters, ammeters, power meters, etc., are normal. Verify three-phase voltage balance and that currents are within rated values, and record relevant data.
Environment check: Check that the area around the substation is clean, free of debris, and well ventilated. Ensure the base is not settled or tilted, and the grounding device is firmly connected.
2. Periodic Maintenance
Periodic maintenance is an important part of box-type substation maintenance. xinhong electrical recommends performing it according to equipment operating time or cycles. Contents include:
Cleaning: Regularly clean dust and dirt inside and outside the enclosure, especially on the transformer and switchgear surfaces, to prevent dust accumulation from affecting heat dissipation. For dry-type transformers, use compressed air to blow off dust.
Tightening check: Inspect and tighten all electrical connections, such as cable joints and busbar connections, using a torque wrench to specified values to prevent poor contact or heating due to loosening.
Insulation check: Use an insulation resistance tester to measure insulation resistance of the transformer, cables, switchgear, etc., ensuring compliance with standards. Use a 2500V megger for the high-voltage side (resistance ≥1000MΩ) and a 500V megger for the low-voltage side (resistance ≥0.5MΩ).
Oil level and oil quality check (for oil-immersed transformers): Regularly check that the oil level is between 1/4 and 3/4 of the oil gauge, and that the oil color is transparent without blackening or turbidity. Refill or sample oil for testing (breakdown voltage, moisture content, etc.) as needed.
Protection device check: Inspect the operating status of relays, circuit breakers, fuses, etc. Test whether their operating values match set values to ensure reliable operation.
3. Fault Handling
Various faults may occur during operation of box-type substations. Timely fault handling is an important part of maintenance. xinhong electrical recommends the following steps:
Fault diagnosis: Based on fault phenomena, combined with instrument readings and protection device actions, preliminarily determine the cause. Common box-type substation faults include overheating, tap-changer issues, tripping, and oil leakage. For low-voltage main circuit breaker tripping, check factors such as overcurrent, oil over-temperature, and pressure relief device operation.
Isolate the fault: After identifying the fault point, isolate the faulty equipment promptly to prevent the fault from spreading. For trip faults, perform detailed external checks; if no obvious abnormality, de-energize and further inspect the high-voltage compartment, transformer compartment, and low-voltage compartment.
Repair the fault: Take appropriate corrective actions based on the cause, such as replacing damaged components, repairing insulation, adjusting protection devices, or tightening loose connections. For overheating faults, promptly clean residual materials inside and maintain good heat dissipation.
Test run: After repair, conduct a test run to verify that all parameters are normal and the equipment is restored to proper working condition before returning to service.
4. Preventive Maintenance
Preventive maintenance identifies potential problems in advance through regular inspections, tests, and analysis to prevent failures. xinhong electrical recommends the following preventive maintenance activities:
Periodic testing: Perform periodic preventive tests on transformers, switchgear, etc. Transformer tests include winding insulation resistance (absorption ratio), winding DC resistance, dielectric loss factor, insulating oil chromatography, and withstand voltage tests. Switchgear tests include insulation resistance, loop resistance, and protection relay calibration.
Data analysis: Analyze data from daily inspections, periodic maintenance, and fault handling to identify patterns and potential problems, providing a basis for optimizing maintenance strategies.
Spare parts management: Establish a spare parts inventory for commonly used items (such as fuses, circuit breakers, temperature controllers, etc.) to enable timely replacement during faults and reduce downtime.
Technical training: Provide regular technical training for maintenance personnel to improve their skills in maintenance and fault handling, ensuring that maintenance work is standardized and efficient.
5. Maintenance in Special Environments
Box-type substations may operate in high-temperature, high-humidity, dusty, or other special environments. xinhong electrical recommends the following measures for such conditions:
High-temperature environments: Enhance heat dissipation measures, regularly check cooling fans for proper operation, and ensure thermostats can automatically start fans during over-temperature. Keep ventilation louvers unobstructed to maintain natural ventilation.
High-humidity environments: Enhance moisture-proof measures, regularly check insulation resistance to prevent equipment from becoming damp. Install heaters in high/low voltage compartments to prevent condensation and corrosion. After rain, focus on checking enclosure seals and cable joints for moisture ingress.
Dusty environments: Increase cleaning frequency, regularly remove dust to prevent accumulation that affects heat dissipation and insulation performance. Regularly clean high-voltage insulators and bushings using an insulating rod.
6. Records and Reports
xinhong electrical emphasizes that maintenance work should be thoroughly documented, including inspection records, maintenance records, fault handling records, etc. Each record should include equipment name, inspection items, results, corrective actions, and personnel information. Regularly prepare maintenance reports to analyze equipment operating status and propose improvement recommendations. A complete record system helps trace equipment operating history, evaluate maintenance effectiveness, and provide data support for future preventive maintenance.
7. Safety Precautions
Safety is the primary consideration during maintenance. xinhong electrical reminds maintenance personnel to strictly comply with the following safety rules:
Personnel qualification: Operation and maintenance personnel must hold a valid high-voltage electrician certificate, be familiar with the structure and operating procedures of the substation. Unqualified persons are not allowed to contact the equipment.
Work procedures: For maintenance requiring power outage, strictly follow the process of "disconnect power – verify de-energized – tag – ground". High-voltage work must be de-energized from the supply side; wear insulated gloves when operating mechanically driven switches or disconnectors.
Two-person rule: For repairs, two or more persons should work together – one operator and one supervisor. Avoid working alone. When inspecting high-voltage compartments, maintain a safe distance of at least 0.7 meters from live parts.
Personal protective equipment (PPE): Maintenance personnel must wear necessary PPE, such as insulated gloves, insulated shoes, safety helmets, etc. For cable head work, discharge phase by phase and attach grounding wire.
Warning signs: Prominent "Danger – High Voltage" signs should be placed on the enclosure. In the maintenance area, hang warning signs such as "Man at work – Do not close".
xinhong electrical, as a professional manufacturer of box-type substations, is committed to providing customers with high-quality products and comprehensive maintenance technical guidance, contributing to the safe and stable operation of power systems.
