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Development of on-line diagnostic methods for medium voltage XLPE power cables
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

On-line diagnostics of power system components is an important area since it allows the diagnostics to be performed at regular intervals during the normal operation of the components. This combined with reliability centered maintenance could lead to reduced customer outages. In this thesis the on-line diagnostic methods for medium voltage cross-linked polyethylene (XLPE) cables are investigated based on Time Domain Reflectometry (TDR).

Degradation of XLPE insulated power cables by water-trees (WT) is a primary cause of failure of these cables. The detection of WT and information about the severity of the degradation can be obtained with off-line measurements using dielectric spectroscopy.  In many situations only a limited part of the cable may be degraded by the WT. In such a situation a method for localization of this WT section would be desirable.

The developed high frequency measurements superimposed on HV system is presented. It was used to measure the propagation constant of the WT aged cables as a function of the applied HV. This was done in order to study the diagnostic criteria, which could be used for on-line TDR diagnostics of WT aged cables.

A physically based dielectric model of WT was developed in order to explain qualitatively and quantitatively the permittivity and loss of WT at different frequencies and voltages.

The sensors applicable for the on-line TDR were 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.

The developed on-line TDR systems are presented. Their applicability to detect water penetration under the cable sheath and localize the broken screen wires was investigated during the measurements in laboratory environment.

The results of field measurements with on-line TDR 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. The temperature dependent wave propagation in the cable is investigated and explained by modeling.

Place, publisher, year, edition, pages
Stockholm: KTH , 2009. , x, 119 p.
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-9872ISBN: 978-91-7415-220-3 (print)OAI: oai:DiVA.org:kth-9872DiVA: diva2:134377
Public defence
2009-02-13, F3, Lindstedsvägen 26, KTH, Stockholm, 10:15 (English)
Opponent
Supervisors
Note
QC 20100709Available from: 2009-01-29 Created: 2009-01-20 Last updated: 2010-07-12Bibliographically approved
List of papers
1. 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
2. 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
3. Dielectric model of water trees in an XLPE cable
Open this publication in new window or tab >>Dielectric model of water trees in an XLPE cable
2008 (English)In: International Symposium on Electrical Insulating Materials (ISEIM 08), Yokkaichi, Japan, 2008, 448-451 p.Conference paper, Published paper (Refereed)
Abstract [en]

In this paper a water-tree degraded insulation is modeled as a matrix composed of cubic cells. In the model there are three types of cells: pure XLPE, XLPE with water inclusion and the XLPE cell with a cylindrical water channel. Voltage dependant dielectric properties of the water-trees are modeled by an elongation of the inclusions and appearance of the conducting channels caused by the Maxwell stress. Afterwards the modeled effective permittivity of the insulation matrix is compared with the dielectric spectroscopy measurements of a field aged XLPE cable.

Place, publisher, year, edition, pages
Yokkaichi, Japan: , 2008
Keyword
Water trees; model; dielectric permittivity; high voltage; XLPE; power cable
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-9869 (URN)10.1109/ISEIM.2008.4664582 (DOI)000262126300112 ()2-s2.0-58049105879 (Scopus ID)978-4-88686-005-7 (ISBN)
Conference
International Symposium on Electrical Insulating Materials Mie, JAPAN, SEP 07-11, 2008
Note
QC 20100709Available from: 2009-01-20 Created: 2009-01-20 Last updated: 2011-03-25Bibliographically approved
4. Temperature influence on wave propagation in XLPE power cables: on-line and laboratory measurements
Open this publication in new window or tab >>Temperature influence on wave propagation in XLPE power cables: on-line and laboratory measurements
2009 (English)Article in journal (Other academic) Submitted
Abstract [en]

This paper investigates the influence of temperature on the wave propagation in medium voltage XLPE power cables. During an on-line time domain reflectometry measurements a periodicity of the pulse velocity was observed. These variations are attributed to the temperature changes of the cable caused by the load cycling. The results of the on-line measurements were verified by laboratory measurements of the propagation constant as a function of temperature in the 0.3 – 500 MHz frequency range. It is shown that the changes in the propagation constant are mainly caused by the temperature dependent permittivities of the semiconducting shields and the XLPE insulation.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-9870 (URN)
Note
QS 20120315Available from: 2009-01-20 Created: 2009-01-20 Last updated: 2012-03-15Bibliographically approved
5. On-line time domain reflectometry measurements of temperature variations of an XLPE power cable
Open this publication in new window or tab >>On-line time domain reflectometry measurements of temperature variations of an XLPE power cable
2006 (English)In: 2006 Annual Report Conference on Electrical Insulation and Dielectric Phenomena, Kansas City, Missouri, USA, 2006, 47-50 p.Conference paper, Published paper (Refereed)
Abstract [en]

In this paper an on-line time domainreflectometry system and a four-days measurementssequence are presented. Detected pulse velocityvariations are attributed to temperature variations of thecable caused by a load cycling. The changes in the pulsevelocity are verified by propagation constantmeasurements of a power cable at differenttemperatures in 300 kHz - 500 MHz frequency range.Also an influence of temperature dependentsemiconducting screens and XLPE insulation to thechanges in the cable's capacitance is investigated.

Place, publisher, year, edition, pages
Kansas City, Missouri, USA: , 2006
Keyword
Computer networks, Electromagnetic waves, Light velocity, Reflection, Reflectometers, Telecommunication cables, Time domain analysis, Walls (structural partitions)
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-9871 (URN)10.1109/CEIDP.2006.312059 (DOI)000242527800011 ()2-s2.0-50549091182 (Scopus ID)1-4244-0546-7 (ISBN)
Conference
Annual Conference on Electrical Insulation and Dielectric Phenomena. Kansas City, MO. OCT 15-18, 2006
Note
QC 20100709 QC 20111006Available from: 2009-01-20 Created: 2009-01-20 Last updated: 2011-10-06Bibliographically approved
6. 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

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