Transformer Dielectric Fluid Comparison
Compare the typical characteristics and performance of mineral oil, FR3® natural ester fluid, synthetic ester fluid, and silicone transformer oil.
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| Mineral Oil | FR3® Dielectric Fluid Natural Ester | Envirotemp® 360 Fluid Synthetic Ester | Silicone Transformer Oil | |
|---|---|---|---|---|
| Base Fluid | Petroleum oil | Plant oil | Hydrocarbons | Polydimethylsiloxanes |
| Voltage Class Applicable | Any, including extra high voltage AC and HVDC | Any, including extra high voltage AC and HVDC | Any, including extra high voltage AC | Mostly limited to 66 kV |
| Fire Point | 160°C | 360°C | >315°C | 343°C |
| Flash Point | 140°C | 330°C | >260°C | 324°C |
| Density at 20°C | 880 kg/cm3 | 920 kg/m3 | 960 kg/m3 | 960 kg/cm3 |
| Pour Point | -35°C | -21°C | <-48°C | -55°C |
|
Kinematic Viscosity 100°C 40°C -20°C |
2 – 3 mm2/sec 8 – 9 mm2/sec 230 mm2/sec |
7.7 – 8.3 mm2/sec 32 – 34 mm2/sec 500 mm2/sec |
6 mm2/sec 34 mm2/sec 1700 mm2/sec |
20 mm2/sec 45 mm2/sec 200 mm2/sec |
| Toxicitya | Potentially toxic | Non-toxic, non-hazardous in soil & water | Not classified as hazardous according to GHS | Potentially toxic |
| Biodegradabilityb | Readily biodegradable; ultimately biodegradable | Readily biodegradable | Not biodegradable (only oxidegradable) | |
| Biobased | No | Yes | No | No |
|
Oxidation Stability Non-free-breathing Free-breathing |
Very good Good |
Very good Not recommended |
Very good Good (moisture control recommended) |
Very good Not recommended |
| Temperature Limits for Normal Lifespan (TUK Paper) |
65 average winding rise 110°C hottest spot |
85 average winding rise 130°C hottest spot |
65 average winding rise 110°C hottest spot |
65 average winding rise 110°C hottest spot |
| Degradation Effects/Consequences | Average; reduces dielectric capacity and produces sludge | Best; long-term impact in viscosity with no formation of sludge | Better; may produce minimal sludge | Average; may produce sludge |
| Transformer reliability | Declines with aging as moisture content in paper and oil increases | Preserves dielectric capacity due to continuous drying of insulation system | May decline as moisture content in paper increases | Typically only used up to 66 kV; no available information |
| Application Location | Indoor & outdoor; requires complex containment & fire mitigation systems | Indoor & outdoor; highly simplified containment & fire mitigation systems | Indoor & outdoor; highly simplified containment & fire mitigation systems | Indoor & outdoor; requires containment system |
a. “Non-toxic” classification for FR3 fluid and Envirotemp 360 fluid is according to IEC6770 requirements and revised EPA definition. “Non-hazardous in water and soil” classification for FR3 fluid Envirotemp 360 fluid is according to GHS.
b. See OECD 301 B (Readily) and Environmental Protection Agency OPPTS 835.3110 (Readily) and 835.3100 (Ultimately).
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