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Effect of temperature on surface discharge in oil
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.ORCID iD: 0000-0003-1766-8077
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
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2012 (English)In: 2012 Annual Report Conference on Electrical Insulation and Dielectric Phenomena (CEIDP), IEEE , 2012, 96-99 p.Conference paper, Published paper (Refereed)
Abstract [en]

In this paper surface discharge along the oil-pressboard interface was investigated. Surface discharges were measured both in time domain by means of an oscilloscope and as phase resolve patterns. The effect of temperature from 20°C to 90°C on surface discharge inception, extinction and surface flashover voltage were investigated. Trend of number and maximum magnitude of PD was compared for 20°C and 90°C over time. The effect of voltage rise and surface flashover on number and maximum magnitude of PD were investigated. The results show that PD inception voltage is lower for higher temperature but surface flashover voltage is higher for higher temperature. However for 90°C the final damage due to surface discharge is much severe compared to 20°C.

Place, publisher, year, edition, pages
IEEE , 2012. 96-99 p.
Series
Annual Report - Conference on Electrical Insulation and Dielectric Phenomena, CEIDP, ISSN 0084-9162
Keyword [en]
Effect of temperature, PD inception voltage, Surface flashover, Time domain, Voltage rise
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-105884DOI: 10.1109/CEIDP.2012.6378731ISI: 000316899800020Scopus ID: 2-s2.0-84872085265ISBN: 978-1-4673-1252-3 (print)OAI: oai:DiVA.org:kth-105884DiVA: diva2:572711
Conference
2012 IEEE Conference on Electrical Insulation and Dielectric Phenomena, CEIDP 2012; Montreal, QC; 14 October 2012 through 17 October 2012
Note

QC 20121128

Available from: 2012-11-28 Created: 2012-11-28 Last updated: 2015-02-06Bibliographically approved
In thesis
1. Partial Discharge Signatures of Defects in Insulation Systems Consisting of Oil and Oil-impregnated Paper
Open this publication in new window or tab >>Partial Discharge Signatures of Defects in Insulation Systems Consisting of Oil and Oil-impregnated Paper
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Partial discharge measurement is a common method for monitoring and diagnostics of power transformers, and can detect insulation malfunctions before they lead to failure. Different parameters extracted from the measured PD activity can be correlated to the PD source, and as a result it is possible to identify the PD source by analyzing the PD activity.

In this thesis, possible defects that could cause harmful PDs in transformers were investigated. These defects include corona in oil, a void in pressboard, a metal object at floating potential, surface discharge in oil, a free bubble in oil and small free metallic particles in oil. The characteristics of disturbing discharge sources were analyzed, like corona in air, surface discharge in air, and discharge from an unearthed object near to the test setup.

The PD activity was recorded both in the time domain and phase domain, and possible characteristics for each PD pattern and waveform were extracted in order to find the best characteristic for the purpose of classification.

The results show that in the phase domain parameters such as phase of occurrence, repetition rate and shape of PD Pattern are most suitable for classification while magnitude of discharge can only be useful in specific cases. The results show that the PD waveforms correlated to different defects are similar; however the time domain data include all the information from the phase domain, and also has the power to identify the number of PD sources.

 The PD dependency on temperature was investigated on the four test objects including surface discharges in oil, corona in oil, bubble discharges in oil, and metal object at floating potential. The effect of humidity was investigated for corona in oil. The results show that at higher temperature the corona activity in oil and PD activity due to a metal object at floating potential in oil decrease. However, for a bubble in oil and for surface discharge in oil the PD activity increases with the increase of the oil temperature. It was shown that the amount of moisture in oil has a strong impact on number of corona pulses in oil.

The last part focused on ageing of oil-impregnated paper due to PD activity. Investigation was made of the behavior of PD activity and its corresponding parameters such as PD repetition rate and magnitude, from inception until complete puncture breakdown. The results show that both the number and magnitude of PD increase over time until they reach to a peak value. After this point over time both curves decrease slowly, and eventually full breakdown occurs.

The effect of thermal ageing of oil impregnated paper on time to breakdown and PD parameters was investigated. The results show that thermal aging of oil-impregnated paper increases the number and magnitude of PD. Dielectric spectroscopy was performed on the samples before and after PD ageing and the result was used in order to explain the behavior of PD over time.

Place, publisher, year, edition, pages
KTH, Stockholm: KTH Royal Institute of Technology, 2012. viii, 67 p.
Series
Trita-EE, ISSN 1653-5146 ; 2012:059
Keyword
partial discharge, transformer, oil, ageing, temperature, PD classification
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-105785 (URN)978-91-7501-573-6 (ISBN)
Presentation
2012-12-07, H21, Teknikringen 33, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20121129

Available from: 2012-11-29 Created: 2012-11-26 Last updated: 2015-02-06Bibliographically approved

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Ghaffarian Niasar, Mohamad

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