| Summary: | Insuring reliable operation of high voltage electrical equipment, such as transformers and cables,
is of great importance to the power industry. This is done by monitoring the equipment. A large
portion of this monitoring includes analyzing the quality of the insulating oils and observing
various compounds formed in the oils during aging. Most often, transformer monitoring
includes routine oil sampling and analysis, which has proven to be very effective at diagnosing
faults and determining the insulation condition. Many techniques have been demonstrated for
the purpose of online monitoring, and various commercial products are available. However,
utility companies are still looking for more cost effective methods to monitor their equipment
between sampling intervals. The work presented here was performed in order to investigate the
use of refractive index for monitoring insulating oils. The refractive indices of various oil
samples obtained from the field were measured and differences were observed. Accelerated
aging experiments were conducted in a laboratory and increases in the refractive indices of these
artificially aged oils were observed. Experiments were conducted to determine what by-products
would contribute to this increased refractive index by investigating the effects of individual
groups on the refractive index change. These groups included aromatic compounds, polar
compounds, furans, acid, and fault gases. We observe that the formation of furans, acids, and
fault gases cannot be detected using refractive index for the concentrations typically found in the
field. We conclude that changes in the refractive index of an oil can be used as an indicator of
the oil’s aging and its break down and the formation of aromatic and polar compounds. === Applied Science, Faculty of === Electrical and Computer Engineering, Department of === Graduate
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