Electrical and capacitive methods for detecting degradation in wire insulation

dc.contributor.advisor Nicola Bowler
dc.contributor.author Sheldon, Robert
dc.contributor.department Electrical and Computer Engineering
dc.date 2018-08-11T20:31:05.000
dc.date.accessioned 2020-06-30T02:44:25Z
dc.date.available 2020-06-30T02:44:25Z
dc.date.copyright Sun Jan 01 00:00:00 UTC 2012
dc.date.embargo 2013-06-05
dc.date.issued 2012-01-01
dc.description.abstract <p>Motivated by a need within the aerospace industry to detect and characterize degradation in the insulation of onboard wires, this thesis reports testing of several extant methods and development of novel capacitive sensors. This work focuses on measuring the electrical parameters resistance and capacitance that are directly related to the material parameters conductivity and permittivity, respectively, of the insulation. It is shown that the measured electrical parameters successfully indicate degradation in the wire insulation.</p> <p>Insulation resistance tests were performed on 17 wire samples, removed from various locations on a retired aircraft, and compared with those conducted on pristine wire samples, in order to assess any change in conductivity exhibited by degraded insulation. Timed resistance tests were also performed to determine the dielectric absorption of the insulation. Curved patch-electrode sensors were applied in order to measure the capacitance and dissipation factor of the same wires. Results from the resistive and capacitive tests both identified wire samples that were apparently significantly degraded, as indicated qualitatively by visual inspection.</p> <p>Further, a novel cylindrical interdigital capacitive sensor was developed. The interdigital sensor is designed with the goal of achieving a good signal-to-noise ratio, the lowest instrument error possible at 1 MHz, full circumferential coverage of the wire, and the ability to adjust the penetration depth of the electric field into the insulation layer by adjusting the separation of the sensor digits. With the aim, ultimately, of quantitative measurement of insulation complex permittivity, a numerical model was developed using a cylindrical Green's function and the Method of Moments to calculate theoretically the capacitance of the interdigital sensor. Benchmark experiments were carried out on large-scale dielectric-coated conductive cylinders to test the validity of the model. Experimental results agreed with measured results to within 5% for sensor configurations with 22 and 30 digits of each polarization, tested on insulation polymers acetal copolymer, acrylic and polytetrafluoroethylene. A design method by which the penetration depth of the electric field into the insulation layer may be optimized is also introduced.</p> <p>Plans for future work, to develop interdigital capacitive sensors with a convenient hand-held clamp design for in-situ testing of aircraft wiring insulation, are also presented.</p>
dc.format.mimetype application/pdf
dc.identifier archive/lib.dr.iastate.edu/etd/12681/
dc.identifier.articleid 3688
dc.identifier.contextkey 4186436
dc.identifier.doi https://doi.org/10.31274/etd-180810-1782
dc.identifier.s3bucket isulib-bepress-aws-west
dc.identifier.submissionpath etd/12681
dc.identifier.uri https://dr.lib.iastate.edu/handle/20.500.12876/26870
dc.language.iso en
dc.source.bitstream archive/lib.dr.iastate.edu/etd/12681/Sheldon_iastate_0097M_12927.pdf|||Fri Jan 14 19:27:17 UTC 2022
dc.subject.disciplines Electrical and Electronics
dc.subject.disciplines Mechanics of Materials
dc.subject.keywords capacitive
dc.subject.keywords dielectric
dc.subject.keywords insulation
dc.subject.keywords interdigital
dc.subject.keywords sensor
dc.subject.keywords wire
dc.title Electrical and capacitive methods for detecting degradation in wire insulation
dc.type article
dc.type.genre thesis
dspace.entity.type Publication
relation.isOrgUnitOfPublication a75a044c-d11e-44cd-af4f-dab1d83339ff
thesis.degree.level thesis
thesis.degree.name Master of Science
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