Oil-Immersed Transformer Maintenance Plan

　　As a core component of the power system, the operational stability of oil-immersed transformers directly impacts power supply quality and safety. A scientific and systematic maintenance plan can extend equipment lifespan, reduce failure rates, and enhance operational efficiency. Below is a detailed maintenance plan covering five key dimensions: daily inspections, periodic maintenance, preventive testing, emergency response, and personnel training.

　　I. Daily Inspections: Real-Time Monitoring to Prevent Issues

　　Visual Inspections

　　Oil Level and Color: Observe the oil level via the oil gauge to ensure it falls within the normal range (typically between 1/4 and 3/4 of the gauge). The oil should appear transparent and slightly yellow, without turbidity, sediment, or discoloration. If the oil level drops abnormally or the oil turns black, investigate for oil leaks or oil degradation.

　　Oil Leak Checks: Focus on inspecting the tank, valves, flange connections, and radiator seals. Address any leaks immediately to prevent insufficient oil levels that could compromise insulation.

　　Breather and Silica Gel: Verify that the breather is unobstructed. The silica gel should be blue (indicating dryness); if it turns pink (indicating saturation), replace it promptly.

　　Operational Parameter Monitoring

　　Temperature: Record oil and winding temperatures using a thermometer or online monitoring system to ensure they do not exceed rated values (typically oil temperature ≤85°C, winding temperature ≤105°C).

　　Load: Monitor the load ratio to avoid prolonged overloading (short-term overloading must comply with equipment specifications, e.g., 160% rated capacity for 15 minutes).

　　Sound and Vibration: Normal operation should be free of abnormal noises or vibrations. If the "humming" sound intensifies, discharge sounds occur, or mechanical vibrations are detected, shut down the unit for inspection.

　　Environmental Adaptability Checks

　　Rain and Dust Protection: For outdoor transformers, confirm that rain covers and dust screens are intact to prevent foreign objects from entering the tank.

　　Corrosion Prevention: Check for coating peeling on the tank surface and repaint corroded areas.

　　II. Periodic Maintenance: In-Depth Care to Extend Lifespan

　　Oil Quality Testing and Treatment

　　Reference Standards: Breakdown voltage ≥35 kV (for equipment below 220 kV), moisture content ≤15 mg/L.

　　Sampling and Testing: Collect oil samples every 1–3 years for laboratory analysis of breakdown voltage, moisture content, acid value, and dielectric loss.

　　Oil Filtration or Replacement: If oil quality is substandard, use a vacuum oil purifier for filtration. Replace the oil if degradation is severe (e.g., acid value >0.1 mg KOH/g).

　　Seal Replacement

　　Rubber Gaskets: Replace sealing gaskets on the tank, valves, and other components every 5–8 years to prevent aging-related leaks.

　　Welded Seals: Perform non-destructive testing (e.g., ultrasonic flaw detection) on welded areas and repair cracks promptly.

　　Radiator Cleaning

　　Natural Convection Radiators: Clean dust from radiator fins annually using a high-pressure air or water gun to ensure proper ventilation.

　　Forced Air-Cooled Radiators: Clean fan blades and filters every 2 years, and inspect motor operation.

　　Buchholz Relay (Gas Protection) Maintenance

　　Operation Testing: Conduct light gas activation tests every 2–3 years to verify signal transmission functionality.

　　Gas Disposal: If gas accumulates in the relay, analyze its composition (e.g., combustible gas content) to diagnose internal fault types.

　　III. Preventive Testing: Early Warning to Eliminate Hidden Risks

　　Electrical Tests

　　Insulation Resistance Testing: Measure winding-to-ground insulation resistance using a megohmmeter; values should be ≥1000 MΩ (at 20°C).

　　DC Resistance Testing: Test high-/low-voltage winding DC resistance; the three-phase imbalance ratio should be ≤2% (for copper windings) or ≤4% (for aluminum windings).

　　Dielectric Dissipation Factor Testing: Measure the tanδ of winding insulation, which should be ≤0.5% (at 20°C).

　　Mechanical Performance Checks

　　Core Grounding Current: Measure the current in the core grounding wire using a clamp meter; it should be ≤0.1 A to prevent localized overheating caused by multiple grounding points.

　　Fastener Inspection: Check and tighten bolts and nuts annually to prevent contact failures due to vibration-induced loosening.

　　IV. Emergency Response: Rapid Actions to Minimize Losses

　　Fault Classification and Handling

　　High Oil Level: Check oil temperature and breather blockages; drain oil to the normal range if necessary.

　　Low Oil Level: Replenish oil to the standard level immediately and investigate leak sources.

　　Oil Level Anomalies:

　　Temperature Overload: Reduce load, enhance ventilation and cooling, and shut down the unit for inspection if temperatures continue to rise.

　　Internal Faults: If the Buchholz relay activates or the pressure relief valve discharges oil, de-energize the unit immediately, collect oil samples for analysis, and contact professionals for repairs.

　　Emergency Supplies Preparation

　　Stock adequate supplies of transformer oil, sealing gaskets, and filter paper.

　　Equip field personnel with portable oil quality testers and infrared thermometers for rapid diagnostics.

　　V. Personnel Training and Safety Management

　　Operational Standard Training

　　Regularly train maintenance personnel on standards such as the Power Transformer Operation Code and Preventive Testing Code for Electrical Equipment.

　　Conduct practical drills for oil sampling, testing operations, and fault handling to improve skill proficiency.

　　Safety Precautions

　　De-energize, label, and ground equipment before maintenance; use insulated tools.

　　Wear safety harnesses for high-altitude work and ensure ventilation/oxygen detection for tank internal operations.

　　VI. Maintenance Schedule and Record Management

　　Maintenance Schedule

　　Record Management

　　Maintain equipment archives documenting inspection data, test reports, maintenance records, and fault resolutions.

　　Use data analysis to predict equipment lifespan and optimize maintenance plans.

　　Conclusion

　　A scientific maintenance plan for oil-immersed transformers integrates daily monitoring, periodic upkeep, preventive testing, and emergency management into a closed-loop system. Through meticulous operations and maintenance, failure rates can be significantly reduced (e.g., <0.5% annually in a wind farm case study), and equipment lifespan extended (e.g., >10 years without insulation failures), ensuring stable power system operation.