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Evaluation of aged transformer oils by microwave absorption measurements. Schroeder, Edgar Henry
Abstract
The deterioration of electrical insulating oils results in the formation of complex oxidation products, many of which are polar in structure. The significance of the microwave-frequency dielectric-loss measurement, when applied to the evaluation of aged transformer oils, is investigated. A cylindrical cavity, operating in the TE₀₁ mode, is used to measure the loss tangent of aged transformer oils. Q-factor measurements are made by a dynamic method which is described. The problem of mode interference in the cavity is investigated in detail. It is found that the loss tangent of transformer oils, measured at X-band, increases as the oil deteriorates through oxidation. The increase is influenced by several factors but closely parallels the increase in acidity. Sludge particles do not in themselves cause a significant increase in the dielectric losses. An indirect correlation between the loss tangent and the sludge content of an oil may exist but has not been established. The change in the dielectric constant of an oil caused by the presence of dissolved water, or by the ageing process, is too small to be measured by the method used. A small but measureable increase in the loss tangent is produced by the presence of water in concentrations of approximately 75 parts per million.
Item Metadata
Title |
Evaluation of aged transformer oils by microwave absorption measurements.
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1964
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Description |
The deterioration of electrical insulating oils results in the formation of complex oxidation products, many of which are polar in structure. The significance of the microwave-frequency dielectric-loss measurement, when applied to the evaluation of aged transformer oils, is investigated.
A cylindrical cavity, operating in the TE₀₁ mode, is used to measure the loss tangent of aged transformer oils. Q-factor measurements are made by a dynamic method which is described. The problem of mode interference in the cavity is investigated in detail.
It is found that the loss tangent of transformer oils, measured at X-band, increases as the oil deteriorates through oxidation. The increase is influenced by several factors but closely parallels the increase in acidity. Sludge particles do not in themselves cause a significant increase in the dielectric losses. An indirect correlation between the loss tangent and the sludge content of an oil may exist but has not been established.
The change in the dielectric constant of an oil caused by the presence of dissolved water, or by the ageing process, is too small to be measured by the method used. A small but measureable increase in the loss tangent is produced by the presence of water in concentrations of approximately 75 parts per million.
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Genre | |
Type | |
Language |
eng
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Date Available |
2011-10-05
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0104936
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.