Oil transformers: reliability and efficiency for your project
2026-05-27
I. What is an oil transformer?
An oil transformer is an electrical equipment in which the windings and core are completely immersed inmineral insulating oil. Insulating oil has two main functions:
- Isolation environment: increases the dielectric strength between the windings and in relation to the ground;
- Cooling and heat removal: dissipates the heat generated during load losses by circulating the oil (ONAN/ONAF cooling methods).
II. Main technical characteristics
| Characteristics | Description |
|---|---|
| Wide power range | Standard 50kVA ~ 2500kVA (distribution transformers); large power transformers up to 10 MVA ~ 240 MVA. |
| Voltage classes | 10 kV / 20 kV / 35 kV (high voltage side), 400 V / 690 V (low voltage side); Custom production is possible. |
| Cooling methods | ONAN (oil natural cooling with natural air convection) / ONAF (oil natural cooling with forced air convection), adapt to different loads. |
| Insulating properties | Complies with IEC 60076 / GOST 1094 standards, high dielectric strength. |
| High overload capacity | The oil-filled design has a large thermal capacity, and the short-term overload capacity is higher than that of dry transformers of the same power. |
| Long service life | Estimated service life under normal operating conditions ≥ 25 years. |
III. Typical Applications
- ⚡Power grid substations(step-down distribution 66 kV/35 kV/10 kV)
- 🏭Industrial enterprises(power supply for steel, chemical, cement and mining enterprises)
- 🏢Infrastructure facilities(external power supply to airports, ports and large shopping complexes)
- 🌊Boosting renewable energy substations(voltage increase from 0.69 kV to 35 kV for wind and solar power plants)
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