Caracterização físico-química e dielétrica de óleos biodegradáveis para transformadores elétricos

Abstract

R ESU M OO óleo mineral, originário do petróleo, é o fluido isolante tradicionalmente utilizado em transformadores elétricos. Diante do apelo por fontes de energia limpa e renovável o setor elétrico também é pressionado a apresentar alternativas ao fluido de origem fóssil. Neste estudo, óleos de algodão, babaçu, girassol, milho e soja, foram avaliados quanto ao seu potencial para utilização como fluido dielétrico. As propriedades avaliadas foram densidade, viscosidade, acidez, tensão de ruptura, fator de perda, teor de água e corrosividade. Os resultados obtidos foram comparados aos limites estabelecidos na NBR 15422. Os óleos vegetais apresentaram densidade e viscosidade dentro dos limites recomendados; além disso, não se mostraram corrosivos mas devem ser submetidos a tratamentos específicos que os conduzam a atender outras especificações; o tratamento dos óleos com solução de hidróxido de sódio diminuiu a acidez, melhorou a tensão de ruptura e diminuiu o fator de perda. Palavras-chave: óleo mineral, óleo isolante vegetal, transformadorPhysico-chemical and dielectric characterization of biodegradable oils for electric transformers A B ST R A C T The mineral oil, originated from petroleum, is the insulating fluid traditionally used in electrical transformers. Responding to appeals for clean and renewable energy sources, the electrical sector is also under pressure to present alternatives to the fluid of fossil origin. In this study, cotton, `babassu', sunflower, corn and soybean oils were evaluated for their potential of utilization as a dielectric fluid. The properties investigated were density, viscosity, acidity, breakdown voltage, loss factor, water content and corrosivity. The results were compared with the values of the limits established in NBR 15422. Vegetable oils showed density and viscosity within the limits set by standard, however, higher than those presented by the studied mineral oil. It was found that vegetable oils have to pass through improvements to meet other specifications required. The treatment of oils with sodium hydroxide solution reduced the acidity, improved the breakdown voltage thereby lowering the loss factor.

Quality of Glycine max (soybean) and Helianthus annuus (sunflower) oils stored in different environments and their suitability for consumption

“…Results allied to those obtained in the present research were reported in the study conducted by Silva et al (2012) with the aim of characterizing the physical-chemical and dielectric constituents of biodegradable oils that obtained acid level around 0.14 mg/KOH for sunflower oil and 0.2 mg/KOH for soybean oil. Similarly, Almeida et al (2013) when evaluating the physical-chemical characterization of mixtures vegetable oils for food purposes, obtained acid index of 0.17mg/KOH.…”

Characterization of Soybean Cultivars for Biodiesel Production

“…The data obtained in the experiment also overcame those presented by Costa et al (2001), which were 0.64 to 0.88 mg KOH g -1 and the 0.2 mg KOH g -1 acidity index indicated by Silva et al (2011).…”

“…The The highest results were at the lower limit of Brazilian standardization, which recommends the specific mass variation between 919 and 925 kg m -3 ; according to normative instruction n 0 49, MAPA/Brazil. Likewise, they did not reach the 920 kg m -3 reached by Sahoo et al (2015) nor the 924 kg m -3 presented by Silva et al (2011).…”

Influence of refining on the properties of buriti oil (Mauritia flexuosa L.f.)

“…Other two parameters that weren´t presents variation during the treatments were the relative density and refraction index. According to Silva, Carvalho, Conrado, Fook and Leite (2012), the density of an oil is a key-factor, since, in smaller values present a higher oil fluidity increasing its applicability. In turn the refraction index, is specific for each oil and can suffer alterations by thermal and oxidative processes (Jung, Park & Yoon, 2016).…”