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Partial discharges in cylindrical cavities at variable frequency of the applied voltage
KTH, School of Electrical Engineering (EES).
2005 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

Measurements of partial discharges are commonly used to diagnose the insulation system in high voltage components. Traditionally a single xed frequency of the applied voltage is used for such measurements as in the Phase Resolved Partial Discharge Analysis (PRPDA) technique. With the Variable Frequency Phase Resolved Partial Discharge Analysis (VF-PRPDA) technique the frequency of the applied voltage is instead variable. This technique provides more information about the condition of the insulation than the PRPDA technique. To extract the extra information a physical understanding of the frequency dependence of partial discharges is necessary.

In this thesis partial discharges in cylindrical cavities in polycarbonate are measured using the VF-PRPDA technique in the frequency range 10 mHz { 100 Hz. It is studied how the cavity diameter and height inuence the frequency dependence of partial discharges. Insulated cavities are compared with cavities bounded by an electrode. It is shown that from measurements at variable applied frequency it is possible to distinguish between cavities of di erent dimensions and between insulated and metal bounded cavities.

A two-dimensional eld model of partial discharges in a cylindrical cavity is developed. The sequence of discharges in the cavity is simulated by use of the eld computation program FEMLABR. Discharges are modeled with a voltage and current dependent streamer conductivity and are simulated dynamically to obtain charge and current consistency. It is shown that the frequency dependence of partial discharges is signi - cantly inuenced by the statistical time lag and by the two dielectric time constants related to charge movements on the cavity surface and in the bulk insulation. Simulation results are used to interpret the frequency dependent partial discharge activity in a cylindrical cavity.

Place, publisher, year, edition, pages
Stockholm: KTH , 2005. , viii, 49 p.
Series
Trita-ETS, ISSN 1650-674X ; 2005:13
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:kth:diva-477ISBN: 91-7178-169-2 (print)OAI: oai:DiVA.org:kth-477DiVA: diva2:13853
Presentation
2005-11-11, Sal H1, Teknikringen 33, Stockholm, 13:00
Opponent
Supervisors
Note
QC 20101129Available from: 2005-11-08 Created: 2005-11-08 Last updated: 2010-11-29Bibliographically approved
List of papers
1. Variable frequency partial discharge analysis of in-service aged machine insulation
Open this publication in new window or tab >>Variable frequency partial discharge analysis of in-service aged machine insulation
2003 (English)In: Proceedings Nordic Insulation Symposium, 2003, 29-35 p.Conference paper, Published paper (Refereed)
Keyword
variable frequency, phase resolved, partial discharge, machine insulation
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-8456 (URN)
Conference
Nordic Insulation Symposium, Tampere, June 11-13, 2003
Note
QC 20100722Available from: 2008-05-16 Created: 2008-05-16 Last updated: 2010-11-29Bibliographically approved
2. Modelling of Partial Discharge Spectra Measured with Variable Applied Frequency
Open this publication in new window or tab >>Modelling of Partial Discharge Spectra Measured with Variable Applied Frequency
2003 (English)In: Proceedings of the 7th international conference on properties and applications of dielectric materials, 2003, 839-842 p.Conference paper, Published paper (Refereed)
Abstract [en]

Variable Frequency Phase Resolved Partial Discharge Analysis (VF-PRPDA) is a newly developed method for partial discharge measurements. In this method the frequency of the applied voltage is variable and not fixed at the power frequency as in the standard PRPDA implementation. In this paper, simulations illuminate the frequency dependence of PD of a discharging cavity embedded in an otherwise homogeneous insulation. It is shown how the frequency dependence is influenced by the conductivity of the bulk insulation, the surface conductivity of the cavity walls and the statistical time lag. The results of simulations are compared with result of measurements on an asphalt-mica insulated machine stator bar.

Keyword
Capacitance, Computer simulation, Electric conductivity, Electric fields, Electric impedance, Electric insulation, Electric network analysis, Electric variables measurement, Permittivity
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-8457 (URN)10.1109/ICPADM.2003.1218552 (DOI)000186114700209 ()0-7803-7725-7 (ISBN)
Conference
7th International Conference on Properties and Applications of Dielectric Materials, NAGOYA, JAPAN, JUN 01-05, 2003
Note
QC 20100722Available from: 2008-05-16 Created: 2008-05-16 Last updated: 2010-11-29Bibliographically approved
3. Influence of cavity size and cavity location on partial discharge frequency dependence
Open this publication in new window or tab >>Influence of cavity size and cavity location on partial discharge frequency dependence
2004 (English)In: 2004 ANNUAL REPORT CONFERENCE ON ELECTRICAL INSULATION AND DIELECTRIC PHENOMENA, New York: IEEE , 2004, 438-441 p.Conference paper, Published paper (Refereed)
Abstract [en]

Variable frequency phase resolved partial discharge analysis (VF-PRPDA) is a partial discharge measurement technique where the frequency of the applied voltage is variable. In this paper, the VF-PRPDA technique is applied to a test object containing a cylindrical cavity in an otherwise homogeneous insulation of polycarbonate. The frequency is varied in the range 10 mHz-100 Hz. It is shown how the frequency dependence of PD is influenced by the cavity diameter and the cavity location in relation to the electrodes. The PD frequency dependence is also numerically modeled for an isolated cylindrical cavity with diameter 1.5 mm using a field model.

Place, publisher, year, edition, pages
New York: IEEE, 2004
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-8505 (URN)10.1109/CEIDP.2004.1364281 (DOI)000225187200105 ()2-s2.0-17744387318 (Scopus ID)0-7803-8584-5 (ISBN)
Conference
Annual Conference on Electrical Insulation and Dielectric Phenomena (CEIDP) Boulder, CO, OCT 17-20, 2004
Note
QC 20101129Available from: 2005-11-08 Created: 2005-11-08 Last updated: 2010-11-29Bibliographically approved
4. Field model of partial discharges at variable frequency of the applied voltage
Open this publication in new window or tab >>Field model of partial discharges at variable frequency of the applied voltage
2005 (English)Conference paper, Published paper (Refereed)
Abstract [en]

In this paper the PD frequency dependence of acylindrical cavity in a delaminated insulation issimulated using a field model. It is shown how thestatistical time lag influences the PD frequencydependence. The technique of Variable FrequencyPhase Resolved Partial Discharge Analysis (VFPRPDA)is applied to a test object and measurementdata is compared with the results of the simulations.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-8506 (URN)
Conference
Nordic Insulation Symposium (Nord-IS), Trondheim, Norway, June 2005
Note
QC 20101129Available from: 2005-11-08 Created: 2005-11-08 Last updated: 2010-11-29Bibliographically approved
5. Partial discharges in cylindrical cavities at variable frequency of the applied voltage
Open this publication in new window or tab >>Partial discharges in cylindrical cavities at variable frequency of the applied voltage
(English)Article in journal (Other academic) Submitted
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-8507 (URN)
Note
QS 20120326Available from: 2005-11-08 Created: 2005-11-08 Last updated: 2012-03-26Bibliographically approved
6. Modeling of a discharging cavity in a dielectric material exposed to high electric fields
Open this publication in new window or tab >>Modeling of a discharging cavity in a dielectric material exposed to high electric fields
2005 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Partial discharges are localized electric discharges that do not bridge the electrodes. For high voltage components measurements of partial discharges arecommonly used to diagnose the condition of the insulationsystem. Traditionally partial discharges are measuredat a single frequency of the applied voltage. Howeverthe rather newly developed technique of VariableFrequency Phase Resolved Partial Discharge Analysis(VF-PRPDA) makes it possible to measure partial dischargesat variable frequency of the applied voltage. Thebenefit of varying the frequency is that more informationabout the state of the insulation system is obtainedthan from measurements at a single frequency. This paperpresents a model of partial discharges in a cavity atvariable applied frequency. The aim of the model is to increasethe physical understanding of how the frequencyof the applied voltage affects the partial discharges in thecavity. This paper studies the influence from the statisticaltime lag on the frequency dependent discharge sequenceand results from simulations are compared withmeasurement data. The model is a 2D time dependent FEMLAB model in PDE mode which is handled from aMATLAB script.

Keyword
Insulation diagnostics, partial discharges, variable applied frequency
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-8508 (URN)
Conference
FEMLAB Conference, Stockholm, Sweden, October 2005
Note
QC 20101129Available from: 2005-11-08 Created: 2005-11-08 Last updated: 2010-11-29Bibliographically approved

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Citation style
  • apa
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Output format
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