Effect of Temperature on the Breakdown Probability of Liquid Dielectrics

This paper describes the surface breakdown characteristics of silicone oil which has the possibility of application to innovative switchgears and transformers as an insulating medium. At the first step, we have experimentally studied the impulse breakdown characteristics of the configuration with a triple-junction where a solid insulator is in contact with the electrode. The test configuration consists of solid material (Nomex ® or pressboard) and liquid insulation oil (silicone or mineral oil). We have discussed the experimental results based on the maximal electric field at the triple-junction. As the second step, we have studied the configuration which may improve the surface breakdown characteristics by lowering the electric field on the insulator surface.Index Terms -Surface breakdown, Electric power apparatus, silicone oil, triple junction, discharge inception voltage.

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Surface breakdown characteristics of silicone oil for electric power apparatus

Wada

Nakajima

Miyahara

et al. 2006

“…It is known that temperature affects the conduction and breakdown properties of the insulating liquids, [15,16]. However, a change in temperature of 20 ºC to 80ºC only resulted in a ∼7% decrease in the ac breakdown voltage for mineral oil, [17]. From data in [18] changes of ±5ºC about a temperature of 20 ºC leads to a ∼5% change in measured conductivity.…”

Section: Experimental Arrangementmentioning

confidence: 99%

Dielectric properties of natural ester, synthetic ester midel 7131 and mineral oil diala D

Timoshkin

Wilson

et al. 2014

The insulating liquids used in industrial applications are typically mineral oils. In recent years however, significant attention has been paid to alternative insulating fluids, including synthetic and natural ester liquids. In order to expand their practical applications, it is important to have detailed information on their dielectric properties. In this present paper, the dielectric properties of synthetic ester, Midel 7131; mineral oil, Shell Diala D; and vegetable (rapeseed) oil have been investigated. It has been shown that Midel 7131 has a higher ac breakdown voltage (27.6 kV) as compared with Diala D oil (26.4 kV) and rapeseed oil (24.6 kV). However, the breakdown voltage of the Diala D oil has the smallest standard deviation (7%) amongst the tested liquids (13% for Midel 7131 and 11% for rapeseed oil). Statistical analysis of the breakdown voltages has been conducted and it has been shown that the ac breakdown voltages can be described by a normal distribution. dc I-V characteristics have been measured and the space charge saturation regime has been observed for all three liquids starting from ∼9 kV for positive energisation and ∼10 kV for negative energisation in the point-plane topology. Apparent mobilities of the charge carriers in the tested liquids have been obtained using I 1/2 -V curves; these mobilities can be used for calculation of the space charge influenced distribution of the electric field in liquid insulators stressed with dc voltage. Such analysis can be important for design and exploitation of HVDC power systems.

“…The breakdown probability distribution of the models was analyzed using the Weibull distribution, given by the following equation [4,5]:…”

Section: Submission Proceduresmentioning

confidence: 99%

Insulating System to Reduce the Amount of Oil in Electric Power Apparatus Using Silicone Oil

Miyahara

Nakajima

Ishikawa

et al. 2008

The lightning impulse breakdown characteristics of various combinations of insulation material in silicone oil for use in electric power apparatus were investigated, with the aim of reducing the amount of oil required and thus the cost. Breakdown characteristics were investigated in a system in which an insulating filler was mixed with silicone oil. Tests were conducted on a sphere-plane electrode in a vertical arrangement and a sphere-sphere electrode in a horizontal arrangement. The relation between the breakdown strength and the electric field strength was clarified. Breakdown characteristics were also investigated in a system in which an insulator with low relative permittivity was inserted between a filler with high relative permittivity and the high-voltage electrode. Based on the findings, optimum conditions for the application of silicone oil to electric power equipment are proposed.