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Insulation condition assessment of power transformer bushings by utilizing high voltage lightning impulses
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.ORCID iD: 0000-0003-0759-4406
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
2015 (English)In: 2015 IEEE Eindhoven PowerTech, PowerTech 2015, IEEE conference proceedings, 2015Conference paper (Refereed)Text
Abstract [en]

High voltage bushing forms an essential part of a power transformer and its insulation condition is of high importance in a transformer's reliability. Transformer failure statistics indicate considerable contribution from bushing failures, which makes the monitoring of power transformer bushings essential. Several off-line and on-line methods are available for condition assessment of these components. However, most of the on-line methods cannot provide as much information as off-line methods because of the performance limitations. Therefore, condition assessments of these components are mostly done through several on-line methods and decision-making must be done according to majority agreements between different techniques. This paper investigates the possibility of assessing the insulation condition of power transformer bushing through utilizing high voltage transients. They are used as stimuli to get the dielectric response of the insulation system. The investigation is done on two service-aged 150 kV power transformer bushings. The results are verified by comparison with Frequency Domain Spectroscopy (FDS). The proposed application seems promising for monitoring of dielectric properties of power transformer bushings.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2015.
Keyword [en]
Dielectric response, lightning impulse, power transformer bushing, Decision making, Dielectric properties, Frequency domain analysis, Insulation, Lightning, Power transformers, Transients, Condition assessments, Frequency domain spectroscopy, High-voltage transients, Insulation conditions, Performance limitations, Transformer bushings, Bushings
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-181173DOI: 10.1109/PTC.2015.7232724ScopusID: 2-s2.0-84951304792ISBN: 9781479976935OAI: oai:DiVA.org:kth-181173DiVA: diva2:902581
Conference
IEEE Eindhoven PowerTech, PowerTech 2015, 29 June 2015 through 2 July 2015
Note

QC 20160211

Available from: 2016-02-11 Created: 2016-01-29 Last updated: 2016-05-25Bibliographically approved
In thesis
1. Dielectric Response and Partial Discharge Diagnostics of Insulation Systems by Utilizing High Voltage Impulses
Open this publication in new window or tab >>Dielectric Response and Partial Discharge Diagnostics of Insulation Systems by Utilizing High Voltage Impulses
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, power system transients are considered as an opportunity for development of on-line diagnostics of power components and specifically the insulation systems of power transformers and bushings.

A new technique for on-line dielectric response measurement of power transformer bushings is proposed which utilizes natural transients in the power system, such as lightning and switching surges, as stimuli. Laboratory investigations are done on implementation of the proposed technique. Measurement considerations, data acquisition and processing involved in achievement of reasonable accuracy in the Dielectric Response (DR) are presented. Capability of the technique in tracking of the degradation signatures such as moisture content in the insulation has been evaluated and it has shown a good level of accuracy by being compared to the Frequency Domain Spectroscopy (FDS). 

The proposed technique is tested on the service-aged 150 kV bushings and feasibility of the technique for monitoring of dielectric properties of power transformer bushings has been assessed; the results are promising for the technique to be used in the real application. 

Partial Discharges (PD) behavior under transients has been also studied for different materials in this project. PD behavior of different defects, at different insulation condition, responding to the overvoltage transients in form of superimposed impulses on ac voltages was investigated and it was perceived how their distinctive response and the interpretation of  that, can be useful for their identification.

Besides the conventional materials, surface ac PD properties of modified paper with silica and zinc oxide nanoparticles under the superimposed impulses have been assessed in this project. Proper type and optimum concentration level of nanoparticles in the paper are the factors that lead to the improvement of PD behavior in the modified paper under overvoltage transients.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. 79 p.
Series
TRITA-EE, ISSN 1653-5146 ; 2016:080
Keyword
Dielectric Response, Transients, Transformer bushing, Oil-impregnated paper, Moisture content, Partial discharge, Surface PD, Cavity PD, Superimposed impulse, Nanoparticles
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-187632 (URN)978-91-7729-033-9 (ISBN)
Public defence
2016-06-15, sal E3, Osquars backe 14, Stockholm, 14:00 (English)
Opponent
Supervisors
Note

QC 20160525

Available from: 2016-05-25 Created: 2016-05-25 Last updated: 2016-06-16Bibliographically approved

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