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Proceedings ArticleDOI

Nano SiO 2 /epoxy coating effect on creepage discharge characteristics in oil/pressboard composite insulation system

03 Jul 2016-Vol. 1, pp 394-397
TL;DR: In this article, the experimental characterization of creepage discharge to improve the electrical characteristics of oil/pressboard composite insulation system by solid layer coating such as epoxy resin, and nano size silica/epoxy resin composite on PB surface under positive standard lightning impulse voltage (1.2/50 µs) using a needle/bar electrode arrangement in mineral oil.
Abstract: This paper deals with experimental characterization of creepage discharge to improve the electrical characteristics of oil/pressboard (PB) composite insulation system by solid layer coating such as epoxy resin, and nano size silica/epoxy resin composite on PB surface under positive standard lightning impulse voltage (1.2/50 µs) using a needle/bar electrode arrangement in mineral oil. Creepage discharge properties of conventional PB are compared with solid layer coated PB, in terms of discharge final propagation length (l d ) and partial discharge inception voltage (PDIV). As a result, it is found that partial discharge inception probability (P d ) of solid layer coated PB increases at all applied impulse voltage levels compared with that of conventional PB. The result is interpreted in terms of drying effect, surface modification effect and electron suppression effect by nano/epoxy composite coating on PB surface.
Citations
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Journal ArticleDOI
TL;DR: In this article, the effect of temperature on creeping flashover voltage at oil-pressboard interface using the concept of nanofluids is experimentally evaluated using a needle-plate electrode configuration considering 5 mm gap spacing.
Abstract: Creeping flashover (surface discharge) at oil-pressboard interface is considered a serious failure of the insulation system in power transformers. In this paper, creeping flashover voltage at oil-pressboard interface using the concept of nanofluids is experimentally evaluated. The creeping flashover test is carried out using a needle-plate electrode configuration considering 5 mm gap spacing. Three different types of nanofiller (CuO, MgO and ZnO) with different concentration levels (0.05, 0.1, 0.2 g/l) are used for enhancing oil-pressboard creeping flashover voltage. The effect of temperature on creeping flashover voltage is experimentally studied for all nanofiller types at the adopted concentration levels. The considered temperatures are room temperature (30°C), 50 °C, 80 °C and 120 °C. These temperatures are considered to study their effect on creeping flashover voltage taking into consideration a wide range of transformer loading. Average of ten creeping flashover voltages is investigated for all studied conditions. Also, Weibull distribution is used for analyzing the creeping flashover voltages at 10% and 50% probabilities for the studied conditions. Finally, interpretations of the obtained results are presented through a proposed mechanism.

5 citations

Proceedings ArticleDOI
01 Dec 2019
TL;DR: In this paper, the influence of the thickness of the solid insulators on characteristics of creeping discharges propagating over three kinds of solid insulating materials immersed in coconut oil was studied.
Abstract: This paper studies the influence of the thickness of the solid insulators on characteristics of creeping discharges propagating over three kinds of solid insulating materials immersed in coconut oil. A test apparatus based on point plane arrangement connected to an HVAC transformer is used to analyse creeping discharges in term of morphology, length of discharges and the associated amount of ramification. Fractal dimension of experimental discharge patterns, calculated by box counting method is used to index the ramification of the discharges. The results show that the discharge length and the fractal dimension increase when the thickness of the solid material decreases indicating the capacitive effect of the materials.

4 citations


Cites background from "Nano SiO 2 /epoxy coating effect on..."

  • ...In general, the inherent capacitance of the solid insulation affects the discharge inception voltage [16]....

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Proceedings ArticleDOI
01 Jun 2017
TL;DR: In this paper, the effect of nano filler loading in epoxy resin (EP) on creepage discharge properties of the epoxy/silica nanocomposite (EP/S-NC) in mineral oil under standard lightning impulse voltage application using needle-bar electrode arrangement.
Abstract: This paper deals with the effect of the nano filler loading in epoxy resin (EP) on creepage discharge properties of the epoxy/silica nanocomposite (EP/S-NC) in mineral oil under standard lightning impulse voltage application using needle-bar electrode arrangement. Experimental results allow to estimate discharge occurrence probability (P d ) at each voltage level. The relative permittivity e’ r . and dielectric loss are measured at 50 Hz–5 MHz for EP/S-NC with a good dispersion of nanoparticles in the base epoxy matrix. As a result, it is found that P d decreases with increasing the filler loading up to 1 wt%, and then increases. Namely, the nano filler content of 1 wt% produces the best insulation performance in terms of Pd. The relative permittivity of the composite decreases with decreasing the filler loading below 1 wt%, while further increasing nano silica filler loading results in increased e’ r above 3 wt%.

1 citations


Cites background from "Nano SiO 2 /epoxy coating effect on..."

  • ...Our previous work reported that epoxy/silica nanocomposite (EP/S-NC) thinly coated pressboard (PB) exhibits improved insulation performance against creepage discharge in terms of discharge propagation length (ld) and discharge occurrence probability (Pd) in mineral oil [2]....

    [...]

References
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Journal ArticleDOI
T.V. Oommen1, T.A. Prevost
TL;DR: In this paper, the practical aspects of the usage of cellulose insulation in transformers with regard to maintaining the integrity over long periods of time and preserving and extending insulation life are examined and life plots are discussed in more detail.
Abstract: This paper examines the practical aspects of the usage of cellulose insulation in transformers with regard to maintaining the integrity over long periods of time and preserving and extending insulation life. The factors that relate to loss of life are examined and life plots are discussed in more detail.

191 citations

Journal ArticleDOI
TL;DR: In this paper, the influence of moisture content on paper, quality of oil and quality of paper, ageing state and temperature increase on the evolution of gas bubbles in a wet oil-paper insulation system was systematically investigated.
Abstract: This study experimentally investigated and theoretically analysed the evolution of gas bubbles in a wet oil-paper insulation system. Water vapour bubbles significantly decrease the dielectric withstand strength of insulating oil. The influence of moisture content on paper, quality of oil, quality of paper, ageing state and temperature increase on this -Bubble Effect- was systematically investigated. New thermally upgraded paper combined with new insulation oil shows the best resistibility against bubbling because of its microstructure. Paper ageing increases the bubble inception temperature, whereas oil ageing decreases this parameter. Bubbles appear only for a steep temperature rise of more than 3-K/min; for lower values the moisture diffuses into the oil only. An empirical equation that calculates the inception temperature with respect to paper and oil quality and ageing is derived. The evolution of gaseous bubbles constitutes a risk for transformer operation if a steep temperature gradient occurs, if the moisture in paper is above 2- and if bubbles move into an area with high dielectric stress.

43 citations

Journal ArticleDOI
TL;DR: In this paper, the influence of solid surface on the propagation of creepage discharge in liquids was investigated under ac divergent electric field, where Synchronized phase-resolved partial discharge (PD) detection, wideband current measurement and streamer channel visualization were employed to study the differences of discharge patterns between in open gap and on solid surface and explore the mechanisms behind from the linkages between consecutive discharges.
Abstract: The influences of solid surface on the propagation of creepage discharge in liquids were investigated under ac divergent electric field. Synchronized phase-resolved partial discharge (PD) detection, wideband current measurement and streamer channel visualization were employed to study the differences of discharge patterns between in open gap and on solid surface and to explore the mechanisms behind from the linkages between consecutive discharges. It is found that Perspex, glass and pressboard would all promote the propagation of discharges, especially negative discharges, and enable more discharges to occur at lower instantaneous voltages. It is experimentally verified that this promotion effect of solid surface on discharges is caused by the memory effect of solid surface for space charges and residual low density channels.

24 citations

Proceedings ArticleDOI
19 Jul 2015
TL;DR: In this article, the authors investigated the relationship between the insulation failure and the charge transport in polymeric materials, and described the effective methods to improve insulation properties based on the links.
Abstract: The transport of the available charge carriers is a key issue to determine the macroscopic behaviors of insulating materials. Although the rapid developments of experimental and numerical techniques make great contributions to the understanding of the space charge dynamics, the charge carrier mobility and the nature of traps in various situations of electric field and temperature in polymeric materials, the relationship between the insulation failure and the charge transport still remains unclear. As a result, the way continues to further understand the links, particularly in the view of traps. This paper indeed focuses on these significant links and describes the effective methods to improve insulation properties based on the links. The short-term insulation failure including the breakdown and surface flashover, and the significant methods such as employment of nanostructured fillers and surface treatments of polymers, are discussed. Considering the characteristics of charge capture, the effect of trap filling and the numerical techniques with high precision, the charge transport behaviors in polymers are investigated based on surface potential decay (SPD) and bipolar charge transport (BCT) models. The deep trap can effectively reduce carrier mean free path and the energy obtained from applied field. Consequently, the breakdown strength increases as an increase of deep trap. The deep trap can effectively reduce charge mobility and then the conductivity. The trap sites, especially for deep traps, can be modified by employing nanostructured fillers and surface treatments. These modifications can influence the charge injection, the impact ionization within the low-density regions, and the flashover development processes. In this way, electrical breakdown strength and surface flashover performance are improved.

22 citations

Proceedings ArticleDOI
10 Jun 2012
TL;DR: In order to improve the electrical characteristics of transformer oil-impregnated pressboard, transformer oil based nanofluids were used to impregnate the pressboard as discussed by the authors.
Abstract: In order to improve the electrical characteristics of transformer oil-impregnated pressboard, transformer oil-based nanofluids were used to impregnate pressboards. It is found that nanofluid-impregnated pressboard (NP) exhibits substantially higher AC and DC breakdown voltage than that of pure oil-impregnated pressboard (OP). Pulse electroacoustic measurement (PEA) was carried out to study the difference of space charge distribution and decay characteristic in OP and NP. It has demonstrated that NP has a more uniform internal electric field, which is caused by a higher charge transport rate compared to OP, resulting in the improved electrical insulating properties.

18 citations