Abstract:
Power transformer is one of the most
expensive components in electrical network. Frequent
breakdown of power transformers are reported mainly
due to the failure of electrical insulation. Many
researchers are working towards improving the electrical
insulation properties of transformer oil. Present nano
technology confirms that addition of nano fillers in the
transformer oil provide superior electrical insulation
properties. Recent concern towards environmental and
fire safety of transformer operation has led to the
development of natural ester based liquid insulation for
power transformers. Hence it is important to evaluate the
electrical insulation characteristics of nano modified
natural ester based liquid insulation system. In this work,
laboratory experimental works are carried out to
understand the electrical insulation parameters such as
power frequency breakdown voltage (BDV), volume
resistivity, dielectric loss factor, relative permittivity,
flash point, fire point, viscosity and lightning impulse
streamer propagation characteristics of corn oil filled
with SiO2 nano fillers at different %wt concentration such
as 0.01%, 0.05% and 0.1%. Lightning impulse withstand
tests are conducted at both needle/plane and
needle/sphere electrode geometry with 1.2/50 μs
waveform at both positive and negative polarity. It is
noticed that addition of SiO2 nano filler at lower %wt
concentration in the range of 0.01% - 0.05% has
significant influence in improving the BDV, volume
resistivity, flash point, fire point, lightning impulse
withstand and breakdown strength of corn oil. Results
also reveal that the nano modified corn oil considerably
reduces the dielectric loss factor and lightning streamer
propagation velocity. Improvement in dielectric, thermal
and LI streamer characteristics gives confident that nano
modified corn oil may be considered for transformer
applications.
