Number

295-EN

Section

General Section

Use

Abstract

It was estimated that globally each year about 5.7 million tons of fresh transformer oil is needed. Substitution of mineral oil by vegetable oil would be an important contribution to sustainable development.

Substituted substances

Alternative Substances

Reliability of information

Evidence of implementation: there is evidence that the solution was implemented and in use at time of publication
Evidence of assessment: there is evidence of an official (positive) assessment of the substitution

Reason substitution

CMR

Hazard Assessment

Substance to be substituted: Petroleum may cause cancer cat. [1B/ 1A], according to Annex VI of Regulation (EC) No 1272/2008 (CLP Regulation). It fulfils the criteria to be listed in the Substance Database according to SUBSPORTplus Screening Criteria (SDSC). Alternative substance: The soybean oil has no official classification and is not listed in the Substance Database according to SUBSPORTplus Screening Criteria (SDSC).

Description of Substitution

On 28 June 2007 a transformer caught fire on the ground of a power plant in Germany (Krümmel). The fire was caused by a short circuit that inflames the mineral oil inside of the transformer. The transformer was filled with mineral oil. Typically, petroleum-based mineral oil is used as insulation and cooler inside transformers. It has a flashpoint of 145 ° C, and is therefore highly flammable and, burns for a long period. The fire in Krümmel lasted for two days (minimum of two days). A fire has always been a problem in transformers in former times. During the mid-20th century, PCBs (polychlorinated biphenyls) were commonly used as a dielectric fluid in transformers because of their non-flammable nature and chemical stability. PCB was banned in the 1970s because of its carcinogenity and negative impact on the environment. As alternatives there are silicone oils and synthetic esters on the market. A sustainable solution can be the use of vegetable oils for transformer fluid. Substitution of mineral oil by vegetable oils has started in the USA about fifteen years ago and is now also done in Europe. The electrical characteristics of vegetable (soybean oil) and mineral oil are equivalent, but there are important differences in the physical and the environmental data (see following Table).

Physical data	Soybean oil	Mineral oil
Flash point [°C]	324	147
Fire point [°C]	360	165
Viscosity (cSt) 40°C	33	9.2
Viscosity (cSt) 100°C	8,0	2,3
Pourpoint [°C]	-21	-50
Biochemical oxygen demand [ppm] 5 days	>200	<6
Biodegradability [%] 21 days	>99	25,2

Compared to mineral oil are the vegetable oils:
•biodegradability
•sustainability
•non toxicity
•highly flammability
•long term stability of cellulose

Disadvantages of vegetable oils are still:
•high viscosity
•high pour point, poor low temperature properties Based on current researches it can be expected that the disadvantages will be solved soon.

Case/substitution evaluation

This case story describes a replacement of mineral oil based on petroleum in transformers by safe alternative. Soybean oil consists primarily of the glycerides of fatty acids linoleic, oleic, palmitic and stearic.

State of implementation

In use

Date and place of implementation

1997 in USA

Type of information supplier

Research

Further information

Carl von Ossietzky Universität Oldenburg
Fakultät V - Organische Chemie
https://uol.de/chemie/

Publication source: author, company, institute, year

Metzger J. O. (2009) Pflanzenöle und Transformatoren. HighChem hautnah - Aktuelles zur Nachhaltigen Chemie. Gesellschaft DEer Chemiker

Publication source

Type of publication and availability

http://archiv.aktuelle-wochenschau.de/2008/woche52/woche52.html

Date, reviewed

November 26, 2021