Pressboard

About: Pressboard is a research topic. Over the lifetime, 1123 publications have been published within this topic receiving 9089 citations.

Research on Creeping Flashover Characteristics of Nanofluid-Impregnated Pressboard Modified Based on Fe₃O₄ Nanoparticles under Lightning Impulse Voltages.

Abstract: Creeping flashover of mineral-oil-impregnated pressboard under impulse stress is a common insulating failure in oil-immersed transformers, arousing increasing attention. Recent studies have shown that the breakdown strength of transformer oil under positive lightning impulse voltage can be significantly improved through nanoparticles-based modification, and Fe₃O₄ has shown the best improvement in breakdown strength compared to other nanoparticles that have been used. This paper presents the creeping flashover characteristics of pure oil-impregnated pressboard (OIP) and nanofluid-impregnated pressboard (NIP) based on Fe₃O₄ nanoparticles under positive and negative lightning impulse voltages, respectively. It was found that NIP possessed higher resistance to creeping flashover than OIP. The relative permittivities of oil and oil-impregnated pressboard before and after nanoparticles-based modification were measured, and the results revealed that the addition of nanoparticles led to a better match in relative permittivity between oil and oil-impregnated pressboard, and a more uniform electric field distribution. Furthermore, the shallow trap density in NIP was obviously increased compared to that of OIP through the thermally stimulated depolarization current (TSDC), which promoted the dissipation of surface charges and weakened the distortion of the electric field. Therefore, the creeping flashover characteristics of oil-impregnated pressboard were greatly improved with Fe₃O₄ nanoparticles.

Thermal degradation of transformer pressboard impregnated with magnetic nanofluid based on transformer oil

Abstract: In this paper, the thermal ageing of pressboard impregnated with two kinds of insulation liquids is studied by means of frequency domain spectroscopy which involves the measurement of real and imaginary part of complex permittivity as function of frequency. The magnetic nanofluid was composed by mineral transformer oil as carrier liquid, nanoparticles of magnetite and surfactant. The thermal aging test was performed at the temperature 90°C for 1000 hours. Each sample had two variations, with and without copper, which has function catalyst. Then frequency domain spectroscopy was investigated at 40°C for restriction of moisture influence from surrounding. From the data and curves, it can be shown that the undried samples are dried with the aging time and cooper considerably getting worse the imaginary part of complex permittivity. In case of magnetic nanofluid, the colloidal suspension was unstable after 800 hours of the thermal ageing. There was found much more resistance of moisture at the nanofluids than in case of mineral oil impregnated pressboard.

Analysis of creeping discharges on oil-impregnated pressboard under combined AC and DC voltages

Abstract: This paper presents a comparative analysis of the creeping discharge characteristics on mineral oil-impregnated pressboard (OIP) under combined AC and DC voltages. The creeping discharge behavior at various voltage levels to failure were analyzed using partial discharge (PD) measurements, camera observations, and electric field simulations. It was found that the creeping discharge distribution was significantly influenced by the DC component, and it was difficult to induce failure even on OIP with high moisture under combined AC and DC voltage. The flashover along the free-oil boundary layer above the OIP during creeping discharge occurred much more easily under combined AC and DC than under AC voltage, and the quality of the oil was important to avoid flashover. These differences were attributed to the combined influence of the electric field distribution under DC and space charge accumulation.

Development of a novel dual temperature model for insulation aging in oil immersed transformers

Abstract: Power transformer is one of the most expensive equipments in a high voltage AC power system. Adequate monitoring system for power transformers can help in reducing the failure rate and thereby enhancing system reliability and economic efficiency. The failure of power transformer has serious consequences on system reliability. Long term and comprehensive testing cannot be done in working transformer, so prorated model of transformer is preferred. In the proposed work, a new dual temperature test cell is developed based on IEC 62332 and IEEE C57.100. The cell provides for a current carrying conductor wrapped with insulating paper and further insulation is provided with high-density pressboard as per arrangements in power transformer. In this paper a new mathematical model is developed using activation energy and preexponential constant calculated from experimental results at different temperatures. The expected life based on degree of polymerization (DP) value, shows nonlinear aging of insulation based on investigation carried out on prorated model.

Dielectric spectroscopy of epoxy/glass composite materials

Abstract: Glass fibre reinforced epoxy (GFRE) material is used in pressboard transformers for optical telecommunication systems, typically at voltages between 1 to 2 kV. A programme has been set up to follow the electrical ageing of the GFRE through dielectric and space charge (PEA) measurements. Here we report on the characterisation of the GFRE prior to ageing made by means of linear dielectric spectroscopy. Preliminary results for the aged samples show differences in dielectric response that could be related to debonding at the epoxy-fibre interfaces observed in some failed samples.