鈴木 拓真

Under normal conditions, transformer oil is not replaced on a fixed calendar like engine oil. Utilities rely on condition based maintenance using trends from moisture, acidity, dielectric losses, and DGA. Oil may last decades if kept dry and stable. Replacement or regeneration is considered when acidity rises, interfacial tension drops, tan delta worsens, moisture remains high despite drying, or DGA indicates abnormal fault activity. Practical decisions also depend on transformer age, criticality, leak history, and whether oil treatment can restore performance without full replacement.

Transformer oil has two primary jobs: electrical insulation and heat removal. As an insulating liquid, it increases dielectric strength around energized parts and helps prevent arcing and partial discharge, especially at high voltages. As a coolant, it transports heat from the windings and core to radiators or coolers so the transformer stays within thermal limits. Oil also supports arc quenching in tap changers and helps protect solid insulation by limiting oxygen and moisture exposure when the system is well sealed. Its condition directly affects reliability and allowable loading.

Specifications define dielectric strength, moisture limits, acidity, dielectric dissipation factor, resistivity, interfacial tension, viscosity, density, oxidation stability, flash and fire points, and corrosive sulfur behavior. They also define cleanliness, inhibitor content if inhibited, and acceptance testing for new oil. Some specifications include compatibility requirements with paper insulation and gaskets, plus guidance for handling and storage. Compliance is confirmed by certificate of analysis and standardized testing, ensuring the oil provides reliable insulation and cooling throughout the expected service conditions.

Oil filled transformers are favored for outdoor substations, transmission networks, power plants, and high MVA industrial loads. Dry type designs are preferred in hospitals, commercial buildings, tunnels, and indoor installations where fire safety and oil spill concerns dominate. Voltage level, power rating, space constraints, environmental risk, and maintenance policy determine selection. For high voltage and bulk power transfer, oil filled transformers remain the dominant solution.

DGA indicates internal faults by identifying which gases are present, their concentrations, their growth rates, and their ratios. Different fault mechanisms crack oil and paper differently, creating characteristic gas patterns. Analysts compare results to historical data for the same transformer, typical limits for similar units, and ratio methods that classify likely fault types. Sudden rises or persistent growth trends are often more important than a single high value, because they show active fault progression.

The transformer steps up line voltage to high voltage and delivers it to electrodes with a controlled gap. The high electric field ionizes air and creates an arc that ignites the fuel spray. Reliable ignition comes from stable secondary voltage, adequate current, and good insulation that prevents internal breakdown. Proper electrode alignment, clean insulators, and dry wiring prevent spark loss to ground. Burner controls time the ignition period and ensure flame verification, improving safety and reducing nuisance lockouts.

Prices in India range ?7.5-15 lakh for a 3,000 L/h transformer oil filtration machine. Fluidex and their regional partners offer CE-certified units with BDV test ports, DGA sampling, and optional trailer mount.