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Mineral oil is widely used in the transformers as insulation oil because of its preferable low price, good insulation quality and a relatively low condensation point. However, with the consideration of the fact that it almost does not degrade which can cause the contamination of soil, water and our living environment; While on the other hand that fossil fuel would be a scarce resource for the 21st...
Silicone rubber insulators are widely used in the power grid. An accurate estimation of the insulator aging status is necessary for electric power safety. In this study, a novel unilateral nuclear magnetic resonance (NMR) method to quantify insulator aging status is proposed. Firstly, a unilateral NMR sensor was designed specifically for measuring the transverse relaxation time (T2) of insulators...
Objective: To observe the nutritional support effects of calorie for senile chronic diseases. Methods: The 72 selected senile patients were divided into 2 groups, or the calorie restriction group and the non-calorie restriction group. Nutritional support was given by nasal feeding. The change of the nutritive index and the incidences of complications were observed in the 2 groups. Results: Hematochrome,...
Space charge has been a general concern related with the reliability and the life-time of HVDC components. In this present work, the space charge profiles in oil-impregnated pressboards are investigated by the means of the pulsed electroacoustic (PEA) technique under AC voltage with 50 Hz at the room temperature. It has been observed that the ageing status of the mineral oil and the presence of the...
ZnO varistors are wildly used in power system and electronic system to protect equipments against surges and over-voltage. As there is none series gap in ZnO arresters, the ageing phenomenon of ZnO varistors has attracted great attention. In order to study the principle of pulse degradation of ZnO varistors, the thermally stimulated current (TSC) characteristic, voltage-current (U-I) and pulse electro-acoustic...
Aging performance decides the long-term stable operation of ZnO varistors. This paper applied the Scanning Electron Microscope (SEM) to determine the elements distribution inside ZnO varistors before and after ac aging, based on the Energy Dispersive Spectrometer (EDS) analysis, which consists of point analysis, line scan analysis, and mapping analysis. From experimental results, we can conclude that...
ZnO varistors have high nonlinearly which are widely utilized in protecting power systems and electronic devices against the dangerous over-voltages or surges. In this paper, the thermally stimulated current (TSC) characteristic and U-I characteristic performance of aging ZnO varistors had been investigated in different aging conditions(impulse current amplitude, impulse time). Based on the experimental...
ZnO varistors have high nonlinearity, which are widely utilized in protecting power systems and electronic devices against the dangerous over-voltages or surges, and the ac aging characteristic of ZnO varistors is widely concerned. In this paper, the thermally stimulated current (TSC) characteristic, U-I characteristic and power loss characteristic performance of aging ZnO varistors have been investigated...
ZnO varistors are highly non-ohmic resistor and they are widely utilized in protecting electric power transmission line and electronic device against the dangerous overvoltage or voltage surge, and the AC voltage aging characteristic of ZnO varistors is one of the most concerning performance parameters. In this paper, the thermally stimulated current (TSC) performance of ZnO samples has been investigated...
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