Deep Analysis of Oil Immersed Transformers: Structural Principles, Technical Advantages, and Global Application Trends (2026 Edition)

1.Industry background and hot trends

With the acceleration of global power grid upgrades, integration of renewable energy into the grid, and expansion of distribution networks in developing countries, oil immersed transformers remain the mainstream choice in the fields of medium and low voltage as well as medium and large capacity.

In the current market, hot topics mainly focus on three aspects:

• Low loss and energy efficiency rating (IEC/DOE/EU Ecodesign)
• Environmentally friendly insulating oil (mineral oil vs natural ester oil)
• Intelligent monitoring and digital operation and maintenance (DGA online monitoring)

Oil immersed transformers are still irreplaceable in power grids, industrial and mining enterprises, photovoltaic and energy storage systems due to their strong heat dissipation capacity, high overload capacity, long service life, and excellent cost-effectiveness.

2.Basic structure and working principle of oil immersed transformers

2.1 Core Structure Composition

Oil immersed transformers mainly consist of the following parts:

Component	Function
Core	High-grade silicon steel to reduce no-load loss
Windings	Copper or aluminum conductors for energy conversion
Insulating Oil	Electrical insulation and heat dissipation
Tank	Sealed or conservator-type oil tank
Cooling System	ONAN / ONAF options
Protection Devices	Buchholz relay, pressure relief valve, temperature indicators

2.2 Brief description of working principle

Transformers work through the principle of electromagnetic induction:

• Primary winding energized → generates alternating magnetic flux
• Magnetic flux is transmitted in the iron core → Induced voltage in the secondary winding
• Oil serves as both an insulation and heat exchange medium

3.Types and technological differences of insulating oil (industry hotspots)

Oil Type	Characteristics	Typical Applications
Mineral Oil	Cost-effective, mature technology	Standard distribution networks
Natural Ester Oil	High flash point, biodegradable	Urban and eco-sensitive areas
Synthetic Ester Oil	High thermal stability	Heavy industrial applications

Trend interpretation:
In the European and North American markets, the demand for natural ester oil immersed transformers continues to grow, especially in hospitals, subways, and commercial construction projects.

4.Matching cooling method and capacity

Cooling Type	Full Name	Features
ONAN	Oil Natural Air Natural	Simple, low maintenance
ONAF	Oil Natural Air Forced	Suitable for medium capacities
OFAF	Oil Forced Air Forced	Large power transformers

Reasonable selection of cooling methods can significantly improve load capacity and lifespan.

5.Technical advantages of oil immersed transformers

1.Superior heat dissipation performance: high oil circulation efficiency
2.Strong overload capacity: suitable for fluctuating loads
3.Long operating life: up to 25-40 years
4.Low cost per unit capacity
5.Maintain mature system

6.Typical application scenarios

• State Grid/Distribution Network
• Industrial factories and mines
• Photovoltaic booster station
• Energy storage system matching
• Peripheral power supply for data center

7.Future Development Direction

• Lower no-load/load losses
• Intelligent sensors+online monitoring
• Comprehensive replacement of environmentally friendly insulating oil
• Customized export standards (IEC/ANSI/GOST)

Luoyang Datang Energy Technology Co., Ltd. is a high-tech enterprise integrating R&D, manufacturing and supply of power equipment such as transformers, new energy components, distribution cabinets and inverters. With technological innovation as the core, we focus on creating high-reliability and high-performance power solutions to serve global customers. With a strict quality control system and international standard certification, we continue to output excellent products and enable customers to build safe and stable power systems.