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High Frequency Characterisation of Water-treed XLPE Cables
KTH, Superseded Departments, Electrical Systems.
KTH, Superseded Departments, Electrical Systems.
2003 (English)In: PROCEEDINGS OF THE 7TH INTERNATIONAL CONFERENCE ON PROPERTIES AND APPLICATIONS OF DIELECTRIC MATERIALS, VOLS 1-3, 2003, 187-190 p.Conference paper, Published paper (Refereed)
Abstract [en]

Time Domain Reflectometry (TDR) has been used for localisation of transmission line discontinuities in various applications. One of the challenges when applying TDR is to obtain knowledge of the high frequency characteristics of both the degraded and the undegraded sections of the cable. The wave propagation characteristics of water-treed XLPE cables are investigated in this study. The parameters are extracted from the cable S-parameters measured with a Network Analyzer (NA) in the frequency range from 300 kHz to 300 MHz. The cable samples are characterised at different temperatures and with different water content of the water trees. The effect of the application of nominal voltage for extended period on the cable wave propagation characteristics is also shown. High voltage dielectric spectroscopy is used as a reference method for estimation of the level of water tree deterioration.

Place, publisher, year, edition, pages
2003. 187-190 p.
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-5125DOI: 10.1109/ICPADM.2003.1218384ISI: 000186114700045ISBN: 0-7803-7725-7 (print)OAI: oai:DiVA.org:kth-5125DiVA: diva2:7909
Conference
7th International Conference on Properties and Applications of Dielectric Materials NAGOYA, JAPAN, JUN 01-05, 2003
Note
QC 20101012Available from: 2005-05-18 Created: 2005-05-18 Last updated: 2010-10-12Bibliographically approved
In thesis
1. Techniques for Localization of Insulation Degradation along Medium-Voltage Power Cables
Open this publication in new window or tab >>Techniques for Localization of Insulation Degradation along Medium-Voltage Power Cables
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Time Domain Reflectometry (TDR) has been used for localization of transmission line discontinuities in diverse applications. Various challenges have to be addressed when applying TDR for localization of insulation degradation in power cables. The dominant problem is that TDR detects reflections coming from insulation changes, but it also records reflections related to geometrical irregularities along the cable length and, in some cases, surrounding medium variations. It is realized that one can compare TDR measurements before and after changes have occurred or have been induced in the aged sections. Thus the signals from the deteriorated insulation can be distinguished from other reflections that are constant.

The measurement technique to localize water-treeing in cross-linked polyethylene (XLPE) insulation is based on the voltage nonlinearity of water trees. TDR measurements have been performed before, after and during the application of high AC voltages. The high stresses affect the cable characteristic impedance and speed of wave propagation in the water-treed region. The possibility to detect local changes in the velocity of wave propagation has been presented as a technique for localization of insulation ageing. Localization of impedance changes related to water treeing and water ingress in mass impregnated paper insulated cables has also been achieved.

To characterize the power cables in the high frequency domain two parameter extraction methods have been developed. The first one uses TDR measurements and analyses short pulse propagation along the cable. The second one is based on the S-parameter measurements in the frequency domain. The methods extract the complex propagation constant and the characteristic impedance, as well as the LCRG Telegrapher's Equation parameters for the frequencies between 300 kHz and 300 MHz.

The dependence of the high frequency power cables properties on the metallic screen design and cable surrounding medium has been studied. The cable characteristics are modeled using time- and frequency-domain numerical simulations. This is required due to the complex spiralized structure of the outer metallic screen. It is established that this screen design causes a dependence of the cable characteristics on the surrounding medium.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. xii, 114 p.
Series
Trita-ETS, ISSN 1650-674X ; 2005:03
Keyword
Electrical power technology, Attenuation measurement, cross-linked polyethylene insulation, discontinuities, localization, mass-impregnated insulation, numerical analysis, parameter estimation, power cable metallic screen, scattering parameters, time domain reflectometry, velocity measurements, water treeing, Elkraftteknik
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-207 (URN)91-7178-044-0 (ISBN)
Public defence
2005-05-27, E1, Lindstedtsvägen 3, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20101012Available from: 2005-05-18 Created: 2005-05-18 Last updated: 2010-10-12Bibliographically approved

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