Dielectric properties of virgin coconut oil
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Date
2018-06
Authors
Siti Syafiqah Mat Sauki
Journal Title
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Abstract
The transformer has become one of the most important equipment in electrical
power system, especially in power distribution system. Therefore, the application of
liquid insulator such as mineral oil (most commonly used) is very important to reduce the
failure, ageing effect, increase the life span and act as a cooling medium (heat transfer
agent). Mineral oil has a good dielectric strength and cooling performance, but it has
serious negative environmental impact such as non-biodegradable, non-renewable
resource and difficult to dispose when the mineral oil deteriorates completely. As a result,
three tests, breakdown voltage, water content and viscosity are carried out to investigate
the dielectric properties of virgin coconut oil since it biodegrades completely without
toxic and easy to obtain in the tropical country. However, the moisture ingress into the
insulation oil can alter the hydrocarbon bond of the fatty acid and lowering the breakdown
voltage. Therefore, this paper presents a study about the effect of the moisture level of
VCO on breakdown voltage and kinematic viscosity. The breakdown voltage (BDV) is
conducted according to IEC 601566 standard, while water content and kinematic
viscosity follow ASTM D1533 and ASTM D445 respectively. The result obtained for
BDV, water content and viscosity of VCO are 22.9kV 1235ppm and 22.9cSt respectively.
However, dry VCO has higher BDV which is 99.8 kV. Also, the decrease of breakdown
voltage was proportional to the increase of moisture, but the kinematic viscosity was
slightly changed. The kinematic viscosity of mineral oil varied ±1.282% in descending
order while VCO varied (-0.873 to 1.31) % in ascending order. These happened due to
the high intermolecular forces in VCO. Then, the rate of breakdown voltage decrease with
the increasing of moisture for VCO is lower than mineral oil. Therefore, the VCO has
good breakdown voltage with the ability to absorb a lot of moisture keeping the Kraft
paper dry. However, high kinematic viscosity making it not favorable to be used as
insulation in transformer.