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A Comprehensive Guide To Oil-immersed Transformers
Classification:
Industry News
Release time:
2026-06-03
How to Properly Select and Maintain Oil-immersed Transformers
In everyday power systems, Oil-immersed Transformers are an extremely common type of electrical equipment. Whether in industrial production, commercial buildings, or residential power supply, reliable and durable Oil-immersed Transformers are indispensable. What are the key advantages of this equipment? What should you pay attention to when selecting and maintaining them? This article will provide detailed answers.
What Is an Oil-immersed Transformer?
As the name suggests, an Oil-immersed Transformer is a power distribution device in which the internal core and windings are completely immersed in specialized insulating mineral oil. The insulating oil contained within the tank serves a dual core function: on one hand, it acts as an insulating medium, creating electrical gaps between the windings and the core, as well as between the windings themselves, thereby preventing short circuits and breakdowns; on the other hand, it efficiently dissipates heat generated during operation through convective circulation, rapidly removing temperature rises and ensuring the unit’s long-term, stable, and reliable continuous operation. Compared to dry-type transformers that rely on natural air cooling, oil-immersed transformers feature higher rated capacity per unit, excellent short-term overload tolerance, and outstanding environmental adaptability. They are widely deployed in outdoor open-air substations and enclosed dedicated distribution rooms.
Four Core Advantages of Oil-immersed Transformers
- Outstanding Heat Dissipation: Insulating oil efficiently dissipates residual heat from the unit. Combined with cooling fins or forced oil cooling structures, this ensures the equipment can operate continuously at full load.
- Cost-effective: For the same power specifications, the production cost of this equipment is lower than that of dry-type transformers, offering outstanding value for money.
- Excellent Short-Term Overload Capacity: The oil’s ample thermal capacity ensures that short-term overloads are unlikely to cause component damage.
Long Maintenance Intervals: With a streamlined design and advanced sealing technology, qualified products can operate continuously year-round, requiring very infrequent major overhauls.
The following parameters should be prioritized during selection:
- Rated capacity (kVA): Allow a 20%–30% margin based on total load power
- Voltage rating: High- and low-voltage sides must match the grid
- Connection group: Commonly Dyn11 or Yyn0; affects system grounding configuration
- Impedance voltage: Affects short-circuit current and voltage regulation
Additionally, select oil-immersed transformers manufactured by reputable manufacturers in compliance with national standards (GB/T 6451), and verify the type test report.
To extend the service life of oil-immersed transformers, routine maintenance is essential:
- Regularly check the oil level: The oil level gauge should remain within the normal range; if too low, replenish with insulating oil of the same grade
- Monitor oil temperature: The top-tank oil temperature should generally not exceed 85°C; set the alarm threshold to 95°C
- Take oil samples for testing: Conduct dielectric strength and chromatographic analysis at least once a year to determine if there is internal discharge or overheating
- Check for leaks: Prevent moisture and air ingress, which can cause a decline in insulation
- Listen for sounds and inspect the exterior: Abnormal “buzzing” sounds, oil leaks, or discoloration require immediate shutdown and repair
Summary
Oil-immersed transformers dominate medium- to large-capacity power distribution applications due to their superior heat dissipation, lower cost, and robust overload capacity. Proper selection, standardized installation, and regular maintenance can significantly enhance power supply reliability and extend equipment lifespan. If you are planning a power system, consider oil-immersed transformers as your preferred solution—they will be your most reliable power partner.
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