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Views: 0 Author: Site Editor Publish Time: 2026-01-14 Origin: Site
This passage explains how picking the correct transformer cooling way—ONAN or KNAN—directly influences performance, safety, cost, and environmental compliance. It compares ONAN’s cost-effective, mineral-oil-based cooling suited for outdoor installations with KNAN’s ester-fluid system offering higher fire safety, biodegradability, and reliability for indoor or sensitive environments. The article highlights application scenarios, regulatory standards, and cost–benefit trade-offs, concluding that ONAN fits budget-driven outdoor projects, while KNAN is preferable for fire-critical, environmentally regulated, or mission-critical applications.
Cooling plays a critical role in setting a transformer’s work strength, efficiency, and durability. Transformers make much heat for core loss and copper loss. If this heat is not effectively dissipated, it accelerates thermal aging of insulation systems and increases the likelihood of insulation failure, which is a leading cause of transformer breakdown.
Good transformer cooling reduces thermal pressure on windings and core builds, slowing down the degradation of insulation materials. On the other side, a weak cooling plan can cause hot spots that harm dielectric strength, raise partial discharge work, and finally cut the transformer’s work life.
Besides, strong cooling betters load handling power. For example, epoxy resin cast dry transformers can run at 120% rated load if under the condition of forced air cooling. This shows how cooling shapes load power and performance margins.
The choice of transformer cooling ways greatly affects setup difficulty, running costs, and risk handling. Cooling systems influence not just equipment space but also the need for auxiliary parts like radiators or fans.
From the perspective of safety, using flammable insulating oils brings fire dangers. For instance, mineral oil in ONAN transformers has a lower fire point than ester-based liquids in KNAN setups, making it less suitable for inside or crowded people areas.
In nature-sensitive spots or tasks with strict rule needs, liquid breakdown in nature becomes key. Ester fluids used in KNAN configurations are not only biodegradable but also compliant with ISO 14000 environmental standards. The chosen cooling way must also match local fire safety and ecological regulations to stop legal problems and keep working for long time.
ONAN stands for Oil Natural Air Natural, describing a passive cooling system wherein heat is transferred from transformer windings to oil via natural convection, then from oil to air through external radiators.
This method typically uses mineral oil as both the insulating and cooling medium. Oil immersed transformer use oil as the main insulation medium and rely on oil as the cooling medium. It adopts a sealed structure to completely isolate the transformer oil from the surrounding air, making the operation of the transformer safer, more reliable, and easier to maintain.
ONAN transformers are favored in cost-sensitive installations due to their lower capital expenditure and simple construction. Oil transformer will be maintenance-free. They are especially suitable for outdoor applications where space is not a constraint and ventilation is sufficient.
However, mineral oil’s flammability brings big risks. Mineral oil is flammable and poses environmental risks if leaked. Besides, its lower fire point limits use in closed inside spaces or places with strict fire safety rules. Mineral oil leaks can also cause envoronmental harm.
KNAN shows a configuration where K-class insulation liquids—often natural or synthetic esters—work with natural air flow for heat diffusion.
These liquids break down in nature, have higher fire points (usually over 300°C), and show better water handling. This betters work safety and reduces risks from water entry or the situation of wetness.
KNAN systems offer substantial safety improvements in critical environments. Their higher fire point makes them perfect for inside setups like hospitals or substations in business buildings. Also, ester liquids are sustainable. Biodegradability in nature aids following nature laws.
The primary trade-off lies in cost. K-class fluids are more expensive than traditional mineral oils. Additionally, retrofitting existing transformers requires material compatibility checks due to different chemical interactions between esters and materials like gaskets or cellulose paper.
Transformer location greatly influences the choice between ONAN and KNAN setups. ONAN-cooled units fit open-air substations with enough space from buildings and personnel areas.
On the other hand, KNAN transformers work best for inside substations or spots near sensitive tools because of their fire-resistant raits. Places like data centers or underground transit systems need this level of safety .
KNAN configurations fit better with green energy plans and lasting aims. Ester liquids follow ISO 14000 marks and lower risks of ground or water harm if leaks happen.
For installations near wetlands, forests, or city areas with strict environmental controls, KNAN turns into a legal necessity rather than a choice.
KNAN systems outperform ONAN in challenging environments such as coastal regions or high altitudes. Esters’ superior moisture absorption capability ensures dielectric performance even under humid conditions.
Conversely, ONAN units may require enhanced monitoring or additional dehumidification mechanisms when deployed in such climates.
ONAN transformers offer financial advantages during procurement and installation phases. For instance:
l SHENGTE low loss, energy-saving oil-immersed transformer features a laminated iron core structure designed for superior performance.
l The coil and core are vacuum-dried, and the transformer oil is filtered and injected through a vacuum process—ensuring durability without additional costs of advanced fluids.
KNAN systems may yield savings over time via reduced maintenance needs and longer insulation life due to lower thermal aging rates. In mission-critical infrastructure where downtime incurs high penalties, KNAN’s reliability justifies its initial investment.
l IEC 60076-2: Defines temperature rise limits for liquid-filled transformers under standard loading.
l IEC 60076 7: Offers loading guidance based on thermal models specific to oil-immersed transformers.
l IEC 60296: Details specifications for unused mineral insulating oils suitable for ONAN systems.
l IEC 61099: Provides criteria for synthetic ester insulating liquids applied in KNAN designs.
l IEEE C57.12.00: Establishes general requirements for liquid-filled distribution transformers across cooling types.
l IEEE C57.147: Offers guidelines for acceptance testing and maintenance practices specific to natural ester fluids used in KNAN transformers.
There are two products produced by SHENGTE, which are worth purchasing. The specific information is as follows:
The S11 500kVA 10kV/400V Silicon Iron Core 3-Phase ONAN Distribution Transformer, featuring a compact design with a high-efficiency silicon steel core, is an ideal and cost-efficient solution for outdoor distribution networks with moderate load demands.
Designed for large-scale industrial or utility applications, the S11 2500kVA 10kV/400V 3-Phase ONAN Step-Down Distribution Transformer is a high-capacity solution offering robust thermal performance under ONAN cooling, making it an economical choice for outdoor installations where space is available.
While SHENGTE currently lists ONAN-cooled models publicly, customized solutions using K-class insulating fluids are available upon request through SHENGTE’s engineering team. These are recommended for:
l Indoor substations in commercial buildings.
l Renewable energy plants located near water bodies or forests
l Critical infrastructure where fire safety is paramount.
Q: Can an existing ONAN transformer be retrofitted to use KNAN cooling?
A: Changing an existing transformer from mineral oil to K-class fluid may work but needs match checks on seals, gaskets, paper insulation, and tank materials because of different chemical traits.
Q: What are the key indicators that a project should use KNAN instead of ONAN?
A: Projects placed indoors, near people or tools, in nature-sensitive zones, or needing higher fire safety marks should choose KNAN cooling systems.
Q: Does SHENGTE offer transformers pre-filled with natural ester fluids (KNAN)?
A: While current online listings focus on ONAN models, SHENGTE supplies custom transformer answers including those using K-class breakdown liquids upon request through their technical support ways.
