An assessment of the physical basis for the application of design criteria for dielectric structures

Nelson, J. K.

doi:10.1109/14.42161

Cited by 58 publications

(22 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…This method is based on the fact that the local maximum points of the electric field have the highest probability for partial discharge inception. Indeed, partial discharge is a local phenomenon, and all events are concentrated at high-stress points of the insulation structure [2,14] because one of the most important mechanisms of breakdown initiation is related to the charged particles' behavior. These particles can be swept to the highest stress point and cause a weak link (especially when moisture is present).…”

Section: The Cumulative Stress Methodsmentioning

confidence: 99%

“…The oil gap strength versus the oil gap length is explained by Eq. (1) for a frequency of 60 Hz [2]:…”

Section: Safety Factors Of Creepage Paths With a Uniform Electric Fieldmentioning

confidence: 99%

“…The tangential component of the electric field, E t , has a key role in the initiation and propagation of creepage discharge along the interface [2,11]. Cumulative stress characteristics, defined as the variation of the maximum average tangential electric field versus the length of partial paths inside a creepage path, have been proposed as a design criterion for the insulation structure of high-voltage components [2,12]. In this paper, a criterion is defined as the safety factor of the solid/liquid insulation materials and surfaces against the tangential and normal components of the electric field, which is applicable to the design process of the transformer insulation system.…”

Section: Introductionmentioning

confidence: 99%

“…The electrical stress on the liquid/solid interface contains tangential and normal components. The tangential component of the electric field, E t , has a key role in the initiation and propagation of creepage discharge along the interface [2,11]. Cumulative stress characteristics, defined as the variation of the maximum average tangential electric field versus the length of partial paths inside a creepage path, have been proposed as a design criterion for the insulation structure of high-voltage components [2,12].…”

Section: Introductionmentioning

confidence: 99%

“…The interface between the oil and paper insulation at the edge of high-voltage electrodes is one of the weakest regions of the insulation system in power transformers. The surface partial discharge in this interface is a very important phenomenon in power transformers because the inception voltage of partial discharge in the solid/liquid interface is lower than voltages resulting in partial discharge in both liquid and solid insulation separately [2][3][4]. Investigations have been performed on the initiation, propagation mechanisms, and characteristics of surface discharges in oil/paper interfaces [5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Calculation of creepage discharge safety factors against the tangential component of electric fields in the insulation structure of power transformers

Hekmati¹

2017

Turk J Elec Eng & Comp Sci

View full text Add to dashboard Cite

Abstract:Creepage discharges are a main cause of insulation damage in power transformers during repeated tests or during operation. In this paper, a hazardous region in the insulation structure of power transformers (the interface between solid and liquid insulation at the top edge of a high-voltage electrode) is considered, and the impact of a very important factor of the surface discharge initiation and propagation (the tangential component of the electric field) on the strength of the insulation structure is investigated in power transformers. Insulation system reliability against this tangential component is presented as a safety factor. Two methods based on cumulative stress characteristics and breakdown probability are proposed for safety factor calculation and for the recognition of weak insulation regions. These methods provide essential information on insulation system design and optimization for reducing insulation deteriorations.A case study is performed on the insulation structure of a power transformer that failed during a test at the Iran Transfo Corporation. The redesigned transformer has shown no test failures in the past 10 years.

show abstract

Section: The Cumulative Stress Methodsmentioning

confidence: 99%

“…The oil gap strength versus the oil gap length is explained by Eq. (1) for a frequency of 60 Hz [2]:…”

Section: Safety Factors Of Creepage Paths With a Uniform Electric Fieldmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Calculation of creepage discharge safety factors against the tangential component of electric fields in the insulation structure of power transformers

Hekmati¹

2017

Turk J Elec Eng & Comp Sci

View full text Add to dashboard Cite

show abstract

Isolierstoffe aus Zellulose für die elektrische Isolierung von Leistungstransformatoren

Krause

2012

Elektrotech. Inftech.

View full text Add to dashboard Cite

Degradation of the compression strength of spacers made of high-density pressboard used in power transformers under the influence of thermal ageing

et al. 2023

View full text Add to dashboard Cite

The structural components inside power transformers are commonly made of high-density pressboard, due to its suitable mechanical and dielectric properties. Among these components are the spacers used in the windings of transformers, which are subjected to compressive loading during operation. The spacers are immersed in dielectric liquid and subjected to high temperatures and chemical reactions during the lifespan of the transformer, which result in the degradation of their dielectric and mechanical properties. The performance and reliability of the power transformer greatly depends on its mechanical integrity, so it is necessary to understand how ageing degrades the mechanical response of the high-density pressboard. In this study, spacers made of high-density pressboard and pieces of copper conductor were immersed in uninhibited paraffinic oil and aged at 150 °C for different periods of time, trying to realistically represent the process suffered by a power transformer during its whole lifespan. The evolution caused by the thermal ageing over some chemical parameters (acidity and moisture content) and dielectric properties (AC breakdown voltage, dielectric dissipation factor, resistivity and degree of polymerisation) of the oil and the pressboard was studied experimentally. Compressive mechanical tests were performed on samples of the aged high-density pressboard, and the compressive stiffness during the ageing process was related with other chemical and dielectric parameters.

show abstract

An assessment of the physical basis for the application of design criteria for dielectric structures

Cited by 58 publications

References 17 publications

Calculation of creepage discharge safety factors against the tangential component of electric fields in the insulation structure of power transformers

Calculation of creepage discharge safety factors against the tangential component of electric fields in the insulation structure of power transformers

Isolierstoffe aus Zellulose für die elektrische Isolierung von Leistungstransformatoren

Degradation of the compression strength of spacers made of high-density pressboard used in power transformers under the influence of thermal ageing

Contact Info

Product

Resources

About