Transformers serve as the heart of electrical power networks, and their reliable operation is fundamental to system stability. Ensuring their long-term performance requires implementing a comprehensive life-cycle management strategy centered on preventive measures and conditioned-based maintenance. This approach encompasses multiple aspects including daily operation, routine maintenance, diagnostic testing, and protection configuration, with specific adjustments made according to transformer type.
Routine inspection and basic maintenance form the foundation of transformer health management. This work relies heavily on daily observational rounds where technicians assess transformer condition through visual checks, auditory monitoring, and measurement. Visual inspection involves examining the exterior for oil leaks, corrosion, deformation, verifying oil levels, and checking bushings for cracks or discharge marks. Auditory monitoring means listening for uniform operating sounds and identifying abnormal noises like cracking discharges or mechanical impacts. Measurement includes recording oil temperature, winding temperature, and three-phase current/voltage data to ensure they remain within design limits. Periodic basic upkeep is equally crucial: cleaning accumulated dust to maintain insulation integrity, tightening electrical connections to prevent overheating from contact resistance, and inspecting breather silica gel desiccant and cooling fan operation.
For the most common oil-immersed transformers, maintenance focuses on managing the insulating oil and solid insulation system. The insulating oil acts not only as a dielectric medium and coolant but also as a carrier of fault-related information. Regular oil sample analysis is therefore critical for diagnosing internal transformer health. Dissolved gas analysis is particularly important, capable of detecting minute traces of hydrogen, hydrocarbons, and other gases in the oil, providing early warning of hidden faults such as winding overheating or partial discharge. Simultaneously, monitoring the oil's breakdown voltage and water content ensures its dielectric strength. When oil quality deteriorates, prompt vacuum filtering or reconditioning is necessary. For on-load tap changers, periodic inspection of switching contact erosion and replacement of the diverter switch oil based on operation count is essential to prevent major failures.
Dry-type transformer maintenance concentrates on winding cleanliness, dryness, and moisture prevention. Since windings are directly exposed to air, dust accumulation can severely impede heat dissipation and potentially cause tracking faults. Thorough cleaning of windings and air ducts using a vacuum cleaner or dry compressed air is mandatory. The operating environment should remain well-ventilated, avoiding humidity and corrosive gases. In damp locations, insulation resistance must be checked before energization and after extended shutdowns, with heating devices used when necessary to remove moisture and prevent condensation from compromising insulation.
Gas-insulated transformers using SF6 require maintenance emphasis on gas tightness and quality. Continuous monitoring of SF6 gas pressure and density is vital to maintain insulation strength. Periodic leak checks at pipe joints, valves, and other potential leak points using specialized detectors are indispensable. Simultaneously, SF6 gas requires purity analysis and moisture content testing, as excessive moisture can generate corrosive compounds under arcing, severely damaging internal components.
Regarding protection systems, transformers are equipped with multiple electrical and non-electrical protection layers forming a reliable defense network. Primary protection, the first line of defense, includes differential protection and Buchholz relay protection. Differential protection rapidly clears various internal short-circuit faults and faults on transformer terminals. The Buchholz relay offers unique, sensitive protection for oil-immersed transformers: its light-gas element signals for minor internal faults, while the heavy-gas element trips immediately during serious internal failures. Backup protection such as overcurrent and earth-fault protection handles disturbances from external grid faults. Non-electrical protection is equally important: temperature protection alarms or trips during overheating, pressure relief devices operate to prevent tank rupture during intense internal pressure surges, together creating a comprehensive and dependable protection system.
Finally, all maintenance and protection activities must adhere to the principle of safety first. Any field work, especially during de-energized maintenance and testing, must strictly follow safety procedures including isolation, voltage verification, and grounding to ensure safety of personnel and equipment. Maintaining detailed equipment health records that log every inspection, test, and maintenance action allows for trend analysis and scientifically guides condition-based maintenance decisions. This facilitates the transition from time-based maintenance to precision maintenance, ultimately safeguarding the reliable operation of transformers and the entire power system.