The KNAN (Ester natural Air Natural Cooling) method is adopted, and the natural convection of ester insulating liquid is utilized to achieve heat dissipation.
The flash point of FR3 ester insulating liquid is as high as 360℃ (while mineral oil is only 170℃), significantly enhancing its fire safety
oil immersed distribution transformer designed for high-temperature outdoor applications, featuring FR3 natural ester fluid, Dyn11 vector group, 4% impedance, KNAN cooling, SS304 stainless-steel enclosure and 120% oil containment.
This customized transformer is designed for outdoor power distribution where high ambient temperature, environmental protection, fire safety, oil containment and equipment durability are important project requirements.
The transformer is rated at 500 kVA with an 11 kV primary voltage and 433 V secondary voltage, and is designed for operation in ambient temperatures up to 50°C.
The transformer is engineered according to the customer's project-specific technical requirements.
| Item | Specification |
|---|---|
| Rated Power | 500 kVA |
| Primary Voltage | 11 kV |
| Secondary Voltage | 433 V |
| Phase | Three Phase |
| Frequency | 50 Hz |
| Vector Group | Dyn11 |
| Impedance Voltage | 4% |
| Tap Changer | Off-circuit, ±2 × 2.5% |
| Insulating Fluid | FR3 Natural Ester Fluid |
| Cooling Method | KNAN |
| Maximum Ambient Temperature | 50°C |
| Winding Temperature Rise | 55°C |
| Oil Temperature Rise | 50°C |
| Enclosure Material | SS304 Stainless Steel |
| Enclosure Protection | IP53 |
| Oil Containment Capacity | 120% of transformer oil volume |
| Enclosure Colour | RAL7033 |
| Oil Temperature Indicator | Alarm + Trip |
| Oil Level Indicator | High + Low Level |
| Pressure Protection | Pressure Relief Device |
| Warranty | 12 months after commissioning |
FR3 is a natural ester insulating fluid used in liquid-filled transformers as an alternative to conventional mineral insulating oil.
For outdoor transformer applications, FR3 can be attractive when the project places greater emphasis on fire safety, environmental considerations and biodegradable insulating fluids.
1. Improved fire-safety characteristics
Natural ester fluids generally have a significantly higher fire point than conventional mineral oil, making them attractive for installations where fire risk is an important design consideration.
2. Environmental advantages
FR3 natural ester fluid is derived from renewable vegetable-based feedstocks and is biodegradable, making it suitable for projects with environmental requirements.
3. Suitable for environmentally sensitive installations
The combination of natural ester fluid and a dedicated oil containment system provides an additional layer of environmental protection for outdoor installations.
One of the important requirements of this project is the 50°C maximum ambient temperature.
A transformer operating in a high-temperature environment has less margin for dissipating heat compared with a transformer operating under standard ambient conditions.
For this reason, the thermal design needs to consider:
This transformer is specified with:
Winding temperature rise: 55°C
Oil temperature rise: 50°C
This specification provides a clear thermal design basis for engineers evaluating transformer performance in hot outdoor environments.
The transformer enclosure incorporates an integrated oil bund.
The oil containment capacity is designed to hold 120% of the transformer oil volume.
The purpose of the containment system is to help prevent insulating fluid from spreading into the surrounding area in the event of an oil leak.
For outdoor transformer installations, oil containment can be particularly important for:
The transformer is also specified with no oil leakage during operation, making sealing and oil-tight construction important parts of the manufacturing and inspection process.
The 500 kVA transformer is equipped with several monitoring and protection devices.
The oil temperature indicator provides:
This allows the transformer monitoring system to respond to abnormal oil temperature conditions.
The oil level indicator provides:
This helps operators identify abnormal oil-level conditions during operation and inspection.
A pressure relief device is installed to provide protection against excessive internal pressure.
The transformer also includes:
The oil sampling location is clearly marked:
“SAMPLING POINT”
This makes routine oil sampling and transformer condition monitoring easier for maintenance personnel.
For an outdoor transformer, protection is important, but maintenance accessibility is equally important.
This transformer uses four bolted doors to provide access for inspection and maintenance.
The HV and LV maintenance doors include:
The enclosure also includes an internal walking platform above the oil containment area.
The internal grounding system uses:
70 mm² PVC grounding cable
These details are designed to make inspection and maintenance operations more convenient while supporting site safety requirements.
The transformer incorporates multiple safety-related design features.
The external enclosure is also marked with warning signs on all sides to make electrical hazards clearly visible to personnel working around the transformer.
This type of 500 kVA 11kV/433V oil immersed transformer can be considered for applications requiring medium-voltage power distribution and outdoor installation.
Typical applications include:
The final application depends on the project's electrical system, load characteristics, environmental conditions and applicable standards.
For EPC contractors, the transformer is not just another electrical component. It has to survive harsh outdoor conditions, protect the surrounding environment, provide safe access for maintenance, and integrate smoothly into the overall project.
Our 500 kVA oil-immersed transformer is engineered as a complete outdoor transformer package to address these challenges.
This product uses FR3 natural ester vegetable oil as the insulating and cooling medium. FR3 oil is derived from 100% renewable vegetable oil and features an extremely high flash point and ignition point (50 ° C higher than synthetic esters), significantly reducing the risk of fire and explosion, Meanwhile, FR3 oil is biodegradable, harmless to the environment, and can actively absorb moisture in cellulose insulation, extending the lifespan of insulating paper by 5 to 8 times
KNAN means:
K — natural ester insulating liquid
N — natural circulation of the liquid
A — air as the external cooling medium
N — natural circulation of air
In practical terms, the transformer uses natural liquid circulation and natural air circulation without forced fans or pumps.
A 120% containment capacity provides additional volume to contain the transformer's insulating fluid in the event of an oil leak.
This can help reduce the risk of oil spreading into the surrounding installation area and supports environmental and site-safety requirements.
The transformer uses Dyn11.
This means the high-voltage winding is connected in delta, while the low-voltage winding is connected in star with a neutral point.
The “11” represents the corresponding phase displacement according to the clock notation used for transformer vector groups.
