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On-line time domain reflectometry diagnostics of medium voltage XLPE power cables
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
2006 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

Degradation of XLPE insulated power cables by water-trees is a primary cause of failure of these cables. The detection of water-trees and information about the severity of the degradation can be obtained with off-line measurement using dielectric spectroscopy. In many situations only a limited part of the cable may be degraded by the water-trees. In such a situation a method for localization of this water-treed section would be desirable. On-voltage Time Domain Reflectometry (TDR) diagnostics proved to be capable of localizing the water-tree degraded sections of the cable. The possibility of using on-voltage TDR as a diagnostic method opens up as a further step for the development of an on-line TDR method where the diagnostics are performed using pre-mounted sensors on the operating power cable. The benefits with such a method are: ability to perform diagnostics without disconnecting the cable from a power grid; the diagnostics performed during a longer period of time could give an extra information; no need for an external high-voltage supply unit.

In this thesis the sensors for the on-line TDR are investigated in terms of sensitivity and bandwidth. High frequency models were built and the simulation results in frequency and time domains were verified by measurements. Results of the on-voltage TDR measurements on the degraded XLPE cables in laboratory as well as on-site are presented.

The on-line TDR system and the results of a four-days on-line measurement sequence are presented. Variations due to load cycling of the cable were observed, where an increase in the cable temperature cause an increase of the pulse propagation velocity in the cable.

A method has been developed for high frequency characterization of power cables with twisted screen wires, where the measurements are performed using inductive strip sensors. This technique allows the high frequency parameters of the selected section of the cable to be extracted. The high frequency parameters are extracted from frequency domain measurements of S-parameters as well as from TDR measurements.

Place, publisher, year, edition, pages
Stockholm: KTH , 2006. , xi, 69 p.
Series
Trita-EE, ISSN 1653-5146 ; 2006:010
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-3921ISBN: 91-7178-327-X (print)OAI: oai:DiVA.org:kth-3921DiVA: diva2:10027
Presentation
2006-04-27, Sal D2, KTH, Lindstedtsvägen 5, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100709Available from: 2006-04-12 Created: 2006-04-12 Last updated: 2010-11-11Bibliographically approved
List of papers
1. Couplers for on-line Time Domain Reflectometry diagnostics of power cables
Open this publication in new window or tab >>Couplers for on-line Time Domain Reflectometry diagnostics of power cables
2004 (English)In: 2004 ANNUAL REPORT CONFERENCE ON ELECTRICAL INSULATION AND DIELECTRIC PHENOMENA, 2004, 210-214 p.Conference paper, Published paper (Refereed)
Abstract [en]

This paper investigates three types ofcouplers for sending and receiving a Time DomainReflectometry (TDR) signal to and from a cable on-line.Transfer functions of the couplers were estimated andlumped element models were built. The couplers wereplaced on a power cable with High Voltage (HV)terminations. Measurements were performed at a HVsimulating realistic conditions. In this cable weinvestigated voltage pulse injection, propagation, anddetection for different coupler topologies and HVterminations.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-5603 (URN)000225187200050 ()2-s2.0-17744397723 (Scopus ID)0-7803-8584-5 (ISBN)
Conference
Annual Conference on Electrical Insulation and Dielectric Phenomena (CEIDP) Location: Boulder, CO Date: OCT 17-20, 2004
Note
QC 20100709Available from: 2006-04-12 Created: 2006-04-12 Last updated: 2011-10-24Bibliographically approved
2. Technique Employing Inductive Coupler for Propagation Constant Extraction on Power Cables with Twisted Screen Wires
Open this publication in new window or tab >>Technique Employing Inductive Coupler for Propagation Constant Extraction on Power Cables with Twisted Screen Wires
2005 (English)In: Proceedings of the Nordic Insulation Symposium, 242-245 p.Article in journal (Refereed) Published
Abstract [en]

This paper investigates a new propagation constant measuring technique in which an inductive coupler allows only the selected part of the cable to be measured. The propagation constants are extracted from frequency and time domain measurements. The extracted propagation constants from measurements with an inductive coupler are compared with the reference propagation constant obtained from direct measurements on the cable. The dependence of the extracted propagation constant accuracy on the measured cable part length is investigated.

Place, publisher, year, edition, pages
Trondheim, Norway: , 2005
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-9866 (URN)
Note

QC 20100709

Available from: 2009-01-20 Created: 2009-01-20 Last updated: 2017-04-25Bibliographically approved
3. High-Frequency Model of the Rogowski Coil With a Small Number of Turns
Open this publication in new window or tab >>High-Frequency Model of the Rogowski Coil With a Small Number of Turns
2007 (English)In: IEEE Transactions on Instrumentation and Measurements, ISSN 0018-9456, Vol. 56, no 6, 2284-2288 p.Article in journal (Refereed) Published
Abstract [en]

In this paper, the Rogowski coil is modeled as adistributed-element transmission line. The elements in the distributedtransmission line are modeled using physically basedequations. It allows self and transfer impedances of the Rogowskicoil to be modeled using the physical dimensions and the materialproperties of the coil. The models of the impedances were verifiedby measurements in the frequency domain on three Rogowskicoils. The coils mounted on the power cable were modeled andsimulated in the time domain and afterward compared with themeasurements.

Keyword
distributed element model; high-frequency measurements; Rogowski coil; simulations
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-9867 (URN)10.1109/TIM.2007.907965 (DOI)000251745500024 ()2-s2.0-37249043656 (Scopus ID)
Note
QC 20100709Available from: 2009-01-20 Created: 2009-01-20 Last updated: 2010-12-03Bibliographically approved

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