Pressboard

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

Thermal insulation structure of oil cylinder of hot press and hot pressboard of hot press

Abstract: The utility model discloses a thermal insulation structure of an oil cylinder of a hot press and a hot pressboard of the hot press. The thermal insulation structure comprises an oil cylinder body, the driving end of the oil cylinder body is connected with the hot pressboard, a backing base which is of a hollow structure is arranged between the driving end of the oil cylinder body and the hot pressboard, and an oil collecting disk is arranged on the part, above the backing base, of the lower end of the oil cylinder body. The arrangement of the backing base of the thermal insulation structure of the oil cylinder of the hot press and the hot pressboard of the hot press enables heat transmission between the oil cylinder body and the hot pressboard to be slow, lowers the working temperature of the oil cylinder and prolongs the service life of the oil cylinder; due to the arrangement of the oil collecting disk, maintenance is convenient, and oil gas pollution of the surface of the hot pressboard is effectively lowered.

Influence of Water and Powder Contaminants on Dielectric Strength of Transformer Oil

Abstract: Transformer failure statistics reveal that most of the transformer failures are due to insulation failures, where a considerable fraction of that percentage is caused by oil contamination. In this paper, the influence of water and powder contaminants on the electrical performance of transformer oil is investigated. The powder contaminant used is the fibrous dust obtained from the pressboard insulation of high voltage transformers. In a transformer, pressboard powder can easily contaminate the oil during the operation due to electrical and thermal stresses. Levels of powder contaminants selected for the research are 20mg, 40mg, and 80mg and added water levels were 1 ppm, 2 ppm, 3 ppm, and 4 ppm for an initial water level of 26ppm. Effect of contamination on AC breakdown voltage and visual streamer inception voltage of transformer oil was measured, and the results were statistically analyzed. This consists of Pearson correlation analysis, one-way multivariate analysis of variance and one-way analysis of variance. The correlation between the measured parameters of powder and water contamination levels was calculated with the Pearson correlation coefficient. The effect size which is a parameter that indicates how much the variance of the response (dependent) variable is described by the predictor(independent) variable was calculated using one-way multivariate analysis of variance and one-way analysis of variance methods. The results obtained from one-way multivariate analysis of variance showed an 86.1 % effect size for the case of powder contamination. For the same case, with univariate one-way analysis of variance results, 88.8% and 96.2% effect sizes were calculated for breakdown voltage strength and visual streamer inception voltage respectively. For the water contamination case, one-way analysis of variance statistical method was utilized, and the effect size was calculated as 99.34% for the response variable (average of breakdown voltage and visual streamer inception voltage). Results of both cases made it evident that there is a significant effect of contamination on the dielectric strength of transformer oil. With a higher number of experimental results, the accuracy of the statistical analysis could be improved and with an increased number of response variables the analysis can be extended.

Researches on the Discharge Characteristics of the Novel 3-Element Mixed Oil-Pressboard Insulation System Under Severe Non-uniform Electrical Field

Abstract: A novel 3-element mixed insulation oil was developed successfully by our team. Its key parameters meet the requirements of IEC 60296:2012. Taking mineral oil-impregnated insulation pressboard as control group, the lightning impulse breakdown voltages of the novel 3-element mixed oil-impregnated insulation pressboard with different thickness were measured by the rising-voltage method. Besides, the partial discharge properties of the novel 3-element mixed oil-pressboard insulation system were also studied under needle-plane electrode configuration. Some key parameters, such as PRPD patterns, maximum pulse amplitude and repetition rate were comparatively analysed between two types of oil-pressboard insulation system. The results show that the discharge properties of the mixed oil-pressboard insulation system are comparatively desirable. There is not significant difference on dielectric strength under lightning impulse voltage between two types of oil-pressboard insulation system. Compared with mineral oil-pressboard insulation, the mixed oil-pressboard insulation system has lower partial discharge inception voltage, higher discharge pulse amplitude and repetition rate in corona discharge, which means it’s relatively more prone to partial discharge under severe non-uniform electrical field for the novel 3-element mixed oil-pressboard insulation system.

A study of oil impregnated pressboard insulation based on ester fluids for an application in HVDC insulation systems

Abstract: Ester-based insulation fluids are increasingly used in high-voltage insulation systems. The reasons for this are the advantages in the area of ecological compatibility and resource-saving provision. The use of ester-based insulation fluids in HVDC equipment is new. For this purpose basic investigations are carried out in the form of conductivity investigations for various insulation barrier systems. In addition, a mineral oil serves as a reference oil for estimating existing insights. The results show the influence of the ester-based insulating liquids on the DC conductivity of pressboard barriers and mixed insulations.