Influence of thermal ageing and electrical discharges on uninhibited olive oil properties

• Published in: IET science, measurement & technology measurement & technology, 2016-10, Vol.10 (7), p.711-718
• Main Authors: Reffas, Abderrahim, Idir, Omar, Ziani, Abderrahmane, Moulai, Hocine, Nacer, Azzeddine, Khelfane, Ilhem, Ouagueni, Mourad, Beroual, Abderrahmane
• Format: Article
• Language: English
• Subjects: acid number; ageing; Aging; breakdown voltage; cinematic viscosity; colour index; complex dielectric permittivity; Dielectric constant; Dielectric loss; dielectric loss factor; dielectric losses; discharges (electric); Electric fields; Electric power; electrical discharges; electrical resistivity; electrical stress; Engineering Sciences; flash point; frequency 20 Hz to 1 MHz; frequency domain spectroscopy; insulating oils; Low energy; Olive oil; Permittivity; resistivity; temperature 110 degC; thermal ageing; thermal stress; Thermal stresses; uninhibited olive oil properties; vegetable oils; viscosity; water content
• ISSN: 1751-8822; 1751-8830; 1751-8830
• DOI: 10.1049/iet-smt.2016.0045

In recent years, significant attention has been paid to biodegradable vegetable oils as an alternative to mineral insulating oils. This study presents the influence of electrical discharges and thermal stress on the variation of the properties of uninhibited olive oil. This latter constitutes a serious environmentally friendly and renewable substitute for currently used mineral oils. The investigated properties are: dielectric loss factor and permittivity, resistivity, acid number, cinematic viscosity, water content, breakdown voltage, flash point and colour index. To analyse the effect of thermal stress, the uninhibited olive oil was aged in sealed bottles at 110°C for durations up to 716 h. As concerns the electrical stress, series of 200 up to 1600 low energy discharges are applied under 50 Hz alternating divergent electric field. Frequency domain spectroscopy has also been performed in order to assess the oil behaviour in a large frequency range (20 Hz–1 MHz). The real part of the complex dielectric permittivity of oil tends to increase with ageing. The obtained results show an acceptable stability with regard to thermal ageing and even an improvement of the oil key properties when submitted to discharges of controlled low energy level.