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Return voltage measurements Diagnostic interpretations based on the dielectric time constants

Patsch R., Kamenka D., Menzel J.

Materials Science Poland

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2009

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Vol. 27, No. 4/2

1157--1169

EN

Return voltage measurements of paper-oil insulations such as medium voltage cables have proven to be a reliable method to determine the actual state of degradation and/or the humidity of the insulation. As a first step, the interpretation of the measurements can be done based on the p-factor. This parameter is sensitive to the dielectric properties and especially the humidity of the solid part of the insulation, whereby aged or humid cables show a higher p-factor. The calculation of the dielectric time constants ?1 and ?2 of the two insulating materials oil and cellulose is unique for the return voltage method and hence exceeds the information extractable from other diagnostic methods.

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Return voltage measurements - diagnostic interpretations on the basis of the dielectric time constants.

Patsch R., Kamenka D., Menzel J.

Prace Naukowe Instytutu Podstaw Elektrotechniki i Elektrotechnologii Politechniki Wrocławskiej. Konferencje

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2007

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Vol. 46, nr 19

58-64

EN

Return Voltage Measurements of paper-oil insulations such as medium voltage cables have proven to be a reliable method to determine the actual state of degradation and/or the humidity of the insulation. As a first step the interpretation of the measurements can be done on the basis of the p-factor. This parameter is sensitive on the dielectric properties and especially the humidity of the solid part of the insulation, whereby aged or humid cables show a higher p-factor. The calculation of the dielectric time constants t1 and t2 of the two insulating materials oil and cellulose is unique for the Return Voltage Method and hence exceeds the information extractable from other diagnostic methods.

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Partial discharge analyses ‒ a comparison of different parameters used

Benzerouk D., Patsch R., Menzel J.

Prace Naukowe Instytutu Podstaw Elektrotechniki i Elektrotechnologii Politechniki Wrocławskiej. Konferencje

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2004

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Vol. 40, nr 15

46-50

EN

In the past many approaches have been made to use partial discharge signals to monitor and characterize degradation processes in electric equipment. For the on-line monitoring of large machines or transformers or periodic off-line inspections in many cases only the change of the phase angle distributions of the occurrence of discharges is taken as an indicator for ageing processes in the insulating system. This is sufficient as an indication for the need of a more detailed examination, but often even with off-line experiments the actual change in the defect and especially its relevance for the service life remains unclear. A more detailed insight into the physics of the local degradation processes and their relevance for the ageing process of the equipment can be gained in most cases only with measurements with a continuously increased voltage load and the evaluation of the data via Pulse Sequence Analysis. The paper will discuss and compare different methods to analyze partial discharge data, starting with 'simple' frequency distributions of different parameters of the externally applied voltage load derived from the data set as a whole. As the main point sequence correlated data such as time differences between consecutive discharges will be discussed. It will be shown that in dependence on the type of defect the significance of different parameters is different.