The insulating oil circulates quietly inside the transformer, and the synergistic design of high-efficiency silicon steel sheets and cooling oil channels converts electrical energy loss into subtle heat dissipation. A new energy-efficient transformer saves enough electricity each year to power dozens of households for a year.
Transformer oil, through its excellent cooling and insulation properties, directly reduces the no-load and load losses during transformer operation. New-generation transformers using high-efficiency silicon steel sheets and optimized core structures have no-load losses that are 35% to 45% lower on average than previous generations, and load losses that are 20% to 30% lower on average.
The new national standard GB 20052-2020 sets higher requirements for the energy efficiency of power transformers, promoting Level 1 and Level 2 high-efficiency energy-saving transformers as the market mainstream.
01 Energy Efficiency Core
Transformer oil plays a dual critical role in power equipment. As an insulating medium, it protects the windings and core from electrical breakdown; as a coolant, it continuously transfers the heat generated during operation to the external environment.
This dual function directly determines the energy efficiency performance of the transformer, especially under long-term operation and heavy load conditions.
The energy efficiency improvement of oil-immersed transformers is achieved through material innovation, structural optimization, and intelligent operation and maintenance. Currently, more than 80% of the transformers operating in the power grid use oil-immersed designs, most of which rely on natural oil circulation cooling.
This design balances efficiency and reliability, becoming the mainstay of the power system.
02 Heat Dissipation Mechanism
The cooling efficiency of transformer oil is directly related to the energy efficiency of the equipment. The insulating oil, through thermal convection and radiation, transfers the heat generated during transformer operation from the core and windings to the oil tank wall, and finally dissipates it into the surrounding air.
Oil-immersed transformers use a unique cooling design, usually reserving dedicated oil channels between the windings, allowing the hot oil to rise naturally, cool down, and then descend, forming a continuous circulation.
To improve heat dissipation efficiency, modern transformers employ various innovative designs. Increasing the number of oil channels can increase the contact area between the oil and air; optimizing the oil channel layout can avoid local overheating. Large transformers also incorporate cooling oil channels in their cores to ensure that heat is adequately dissipated by the circulating oil flow.
03 Material Synergy
The high energy efficiency performance of transformer oil is inseparable from its synergistic work with other advanced materials. Modern high-efficiency transformers use high-quality cold-rolled grain-oriented silicon steel sheets as core material. This material features high magnetic permeability, high resistivity, and low eddy current loss.
High-efficiency silicon steel sheets typically have thinner thicknesses and more optimized grain orientation, allowing magnetic flux to flow more smoothly within the core.
The core structure design is also carefully optimized, using multi-stage joints and fully mitered joints to ensure that the magnetic flux direction aligns with the grain orientation of the silicon steel sheets.
The transformer windings are made of high-purity, low-resistance wires, reducing resistance losses during current transmission. The synergistic effect of these materials with transformer oil collectively improves the overall energy efficiency of the equipment.
04 Loss Control
Energy losses during transformer operation are mainly divided into no-load loss and load loss. No-load loss refers to the energy consumption when the transformer is connected to the power supply but without a load, mainly caused by hysteresis and eddy current effects in the core.
Load loss is related to the power transmitted by the transformer and varies with the load size.
The new generation of energy-efficient transformers has made significant progress in loss control. Taking a common 800kVA transformer as an example, the S20 type has a total loss of 6630W, while the previous generation S11 type reached 10380W, saving 3750W of electricity per hour.
After the implementation of the new national standard GB 20052-2020, the energy efficiency requirements for power transformers have been further improved. Level 1 energy efficiency products have 30% lower no-load loss and 15% lower load loss compared to Level 3 energy efficiency products.
05 Environmental Trends
With increasing environmental requirements, transformer oil is developing in a more environmentally friendly direction. Natural ester insulating oil is emerging as a substitute for mineral oil. This insulating medium extracted from plants is biodegradable, has a flash point of up to 360°C, significantly reducing fire risk and environmental hazards. The Gaoxiang Substation in Wuxi, Jiangsu Province, has put into operation the world's first 110 kV natural ester oil transformer, contributing to the creation of a zero-carbon substation.
This environmentally friendly transformer not only uses natural ester oil but also considers carbon reduction throughout its entire product lifecycle, including the use of non-fossil fuel power sources. The power industry is using product certification methods to identify and evaluate energy-saving indicators, and qualified energy-saving products can be marked with an "energy-saving" certification label.
With the advancement of the transformer energy efficiency improvement plan, the proportion of high-efficiency energy-saving transformers in operation is planned to increase by 10% by 2023, with the proportion of newly added high-efficiency energy-saving transformers reaching over 75% in that year.
The first 110 kV "zero-carbon" substation in China has adopted natural ester oil transformers, whose insulating medium comes from renewable plant extracts, with a flash point approximately 150℃ higher than traditional mineral oil.
Power grid companies are gradually replacing old transformers with new energy-efficient models, and the line loss rate in some areas has decreased from 6.2% to 4.8%. As night falls and the city lights up, these transformers immersed in insulating oil continue to work, delivering electricity with higher energy efficiency to every corner that needs light.
