Investigation of partial discharges in synthetic ester-pressboard under AC stress
06 Jul 2016-pp 136-140
TL;DR: In this paper, the suitability of synthetic ester as transformer insulation with respect to partial discharge studies was investigated, and the experimental study was carried out in order to analyse the effect of various impurities over partial discharge activity.
Abstract: Pre-compressed pressboard was commonly used in power transformers along with mineral oil. Pressboard in combination with mineral oil is suitable composite insulation for oil filled transformers over several decades. Synthetic ester is a suitable alternative for mineral oil due to its biodegradable and fire resistant property. It is also compatible for transformer insulations as per recent research studies. Intent of this paper is to find out the suitability of synthetic ester as transformer insulation, with respect to partial discharge studies. Understanding partial discharge characteristics of synthetic ester with an influence of moisture, conducting particles and bubbles, the experimental study was carried out. Measurements of PDIV, PDEV, maximum apparent charges, and PRPD patterns were recorded in order to analyse the effect of various impurities over partial discharge activity. Oil moisture has more impact over board moisture.
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TL;DR: In this paper, the effects of different solid and liquid insulation materials on the surface partial discharge (PD) characteristics were investigated using PD inception voltages (PDIV), apparent charges (pC), and phase-resolved PD (PRPD) patterns.
Abstract: The surface discharge along the interface of solid–liquid insulation is one of the main causes of the deterioration of the life of a power transformer. This experimental study investigates the effects of different solid and liquid insulation materials on the surface partial discharge (PD) characteristics. The liquid insulation materials utilized are mineral oil and synthetic ester, whereas the solid insulation materials are cellulose board and Nomex board. The surface PD characteristics in various combinations of solid and liquid insulation materials are investigated using PD inception voltages (PDIV), apparent charges (pC), and phase-resolved PD (PRPD) patterns, and the comparative analysis is presented. Moreover, topography and composition of samples during surface discharges phenomena have been discussed using high-resolution images and chemical composition obtained using the scanning electron microscope (SEM) and energy dispersive spectroscopy (EDAX). The findings of this article will assist in understanding the behavior of surface PDs under various conditions.
5 citations
23 Jun 2019
TL;DR: In this article, the behavior of different rigid insulation materials, not studied until now, during the impregnation process in a synthetic ester compared with a mineral oil was investigated.
Abstract: Although oil-immersed power transformers generally use mineral oil as insulation and cooling fluid, this liquid does not meet the new technical requirements of dielectric fluids such as high biodegradability, non-toxicity and high safety. For these reasons, natural and synthetic esters as alternative to mineral oil have increased their utilization in some transformers installations. Despite the fact that there are several works that have demonstrated the suitability of these insulation fluids from the point of view of their stability, dielectric and thermal properties, there are very few works focused on the study of the effects of these liquids on impregnation process. The aim of this work is provide information about the behavior of different rigid insulation materials, not studied until now, during the impregnation process in a synthetic ester compared with a mineral oil.
2 citations
References
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01 Jan 2003
201 citations
"Investigation of partial discharges..." refers background in this paper
...Effect of various stresses like AC stress, impulse voltage and formation of white marks due to partial discharge and surface flashover studies on mineral and ester based liquids has been investigated [3-6]....
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Book•
01 Dec 1987
TL;DR: In this paper, the physical background of Transformer operation is discussed, including the core, the windings, and the insulation of the Transformer's structural parts, as well as the temperature rise and cooling of Transformers.
Abstract: 1. The Physical Background of Transformer Operation. 2. The Core. 3. The Windings. 4. Stray-Field Losses in Structural Parts of Transformers. 5. Transformer Insulation. 6. Temperature Rise and Cooling of Transformers. 7. Constructional Parts of the Transformer. Subject Index.
184 citations
01 Aug 2005
TL;DR: In this article, the authors present characteristic features aimed at identifying the basic nature of partial discharge-generating defects in oil/paper insulated systems, and highlight characteristic features that can be used to identify the defect type and cause.
Abstract: Partial discharge (pd)-based risk assessment in electrical insulation systems becomes effective only if the nature of the defect generating pd can be ascertained In oil/paper insulation systems this is a fundamental item since eg harmfulness of pd generated by gas bubbles is much smaller than that of pd occurring between paper layers For such reasons, partial discharge analysis of oil/paper insulated systems often lacks a clear correlation between cause (ie, defect type) and effect (partial discharge recording) Results relevant to partial discharge measurements performed on lab-scale objects having different electrode configuration are presented in the paper with the purpose to spotlight characteristic features aimed at identifying the basic nature of partial discharge-generating defects in oil/paper insulated systems
81 citations
"Investigation of partial discharges..." refers background in this paper
...Effect of various stresses like AC stress, impulse voltage and formation of white marks due to partial discharge and surface flashover studies on mineral and ester based liquids has been investigated [3-6]....
[...]
TL;DR: In this article, the authors present experimental studies on streamer and breakdown of synthetic and natural ester liquids with the presence of parallel pressboard interface in a divergent pointplane field under lightning impulse voltage.
Abstract: This paper presents experimental studies on streamer and breakdown of synthetic and natural ester liquids with the presence of pressboard interface in a divergent point-plane field under lightning impulse voltage. Based on the current, light signals and streamer images, characteristics of both positive and negative streamers on pressboard surface were described, which resemble the features of streamers in open liquid gaps. Introducing pressboard in parallel does not influence the streamer stopping length and thus not weaken the oil gap breakdown voltage, under both positive and negative polarities at gap distances up to 75 mm. However, presence of parallel pressboard significantly reduces the acceleration voltage in mineral oil but seems have no influence on ester liquids under positive polarity, while it tends to accelerate the streamer velocity at larger gap distance and under higher voltage in both ester liquids and mineral oil under negative polarity. Generally, streamer on ester/pressboard interface propagates further than on mineral oil/pressboard interface at the same voltage level; both breakdown voltage and acceleration voltage on ester/pressboard interface are lower than those on mineral oil/pressboard interface at the investigated gap distances up to 75 mm.
72 citations
"Investigation of partial discharges..." refers background in this paper
...Streamer attachments observed by the shadowgraphs would suggest that charge carriers were stored on the surface of the solid dielectric barrier [8]....
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TL;DR: In this paper, the authors investigated the physical mechanisms that lead to the initiation and formation of PD pulses in mineral-based oil and reported the results of fundamental investigations concerning the behavior of partial discharges.
Abstract: This paper reports the results of fundamental investigations concerning the behavior of partial discharges (PD) in mineral-based oil with the aim of characterizing the physical mechanisms that lead to the initiation and formation of PD pulses. First the influence of the parameters temperature, moisture, pressure and oil condition on the PD inception voltage, the apparent charge and the number of PD pulses are introduced. Furthermore some results achieved by investigating the shape of PD pulses and the behavior of visible PD channels using the Schlieren technique are explained. The paper ends with a discussion of the obtained results. >
31 citations