1,782 research outputs found

    Partial Discharge Location within a Transformer Winding using Principal Component Analysis

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    Partial discharge (PD) may occur in a transformer winding due to ageing processes, operational over stressing or defects introduced during manufacture. The presence of PD does not necessarily indicate imminent failure of the transformer but it will lead to serious degradation and ageing mechanisms which can be considered as a precursor of transformer failure. A necessary step is required in order to prevent degradation due to PD activity which may ultimately lead to failure. PD might occur anywhere along the transformer winding, the discharge signal can propagate along the winding to the bushing and neutral to earth connections. As far as maintenance and replacement processes are concerned, it is important to identify the location of PD activity so any repair or replace decision is assured to be cost effective. Therefore, identification of a PD source as well as its location along the transformer winding is of great interest to both manufacturers and system operators. The proposed method for locating PD sources in windings is based on wavelet filtering and principal component analysis. An experiment has been developed based on a high voltage winding section that has been used to produce PD measurement data and to investigate the feasibility of the proposed approach

    Location of Partial Discharges within a Transformer Winding Using Principal Component Analysis

    No full text
    Partial discharge (PD) may occur in a transformer winding due to ageing processes or defects introduced during manufacture. A partial discharge is defined as a localised electric discharge that only partially bridges the dielectric insulator between conductors when the electric field exceeds a critical value. The presence of PD does not necessarily indicate imminent failure of the transformer but it is a serious degradation and ageing mechanism which can be considered as a precursor of transformer failure. PD might occur anywhere along the transformer winding and the discharge signal can propagate along the winding to the bushing and neutral to earth connections. As far as maintenance and replacement processes are concerned, it is important to identify the location of PD activity so any repair or replace decision is assured to be cost effective. Therefore, identification of a PD source as well as its location along the transformer winding is of great interest to both manufacturers and system operators. The wavelet transform is a mathematical function that can be used to decompose a PD signal into detail levels and an approximation. Wavelet filtering is often used to improve signal to noise ratio (SNR) of measured signals, but in this case it is used to identify the distribution of signal energies in both the time and frequency domains. This method produces a feature vector for each captured discharge signal. The use of principle component analysis (PCA) can compress this data into three dimensions, to aid visualisation. Data captured by sensors over hundreds of cycles of applied voltage can be analysed using this approach. An experiment (Figure 1) has been developed that can be used to create PD data in order to investigate the feasibility of using PCA analysis to identify PD source location

    Effects of Organic Load on Basic Geotechnical Properties of Compacted Sand-kaolinite Mixture

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    In the laboratory, four PVC sand-kaolinite mixture columns, each of 150 cm depth and 15 cm diameter, were fed with solutions of sodium acetate equivalent to 20,000 p.p.m., 30,000 p.p.m., 40,000 p.p.m., and 50,000 p.p.m. BOD (biochemical oxygen demand). Soil physical and chemical properties, such as Atterberg limits, specific gravity, soil pH and soil organic content, altered markedly within 40 days of continuous feeding. The results showed that feed with higher BOD values increased the soil organic content as well as soil pH; and thereby the specific gravity and Atterberg limits were lowered

    Mangroves degradation: a local perspective on its awareness

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    Mangroves in Malaysia reside on the coastlines, and the largest areas of mangrove are in the Northern Sabah. Over the past decades, mangrove species have been reported to be disappearing from the globe. It is due to several natural processes that have been inserted to fill the needs of the increased population. These include illegal logging, agriculture activities and urbanisation. In this regards, awareness of the local residents about the problem of mangrove depletion is important to inhibit the problem to prolong further.Therefore, this research was conducted to determine the degree of awareness of local residents on the importance of mangroves in managing environmental quality. Consequently, a questionnaire survey was conducted on 103 respondents to examine their awareness on the subject of mangrove degradation.The respondents were selected randomly among local residents of Kuala Selangor district.It is found that only twenty percent of the total number of respondents are totallyaware of the issue and acted upon it; either taking part in the endeavours made by the government as well as those with the nongovernmental bodies or practicing mangroves replanting at their backyard

    Painting process improvement through six sigma approach in a Malaysian vehicle assembly company

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    Painting is an important process in the automotive assembly to give more attractive appearance to the vehicles and to provide the layer of protection against corrosion and weathering. The objective of this paper is to identify and analyze the factors affecting the quality of painting process at Company RST’s Paint Shop. The paint shop was unable to perform the painting process satisfactorily and deliver the painted vehicle bodies as per customer specifications. The study concentrated on the fiber defect detected at Top Coat Area as the major problem of paint deficiency. Using activities like Genba investigation, data collection, trials and data analysis, the root causes of the problem were identified. Six Sigma DMAIC approach was utilized in conducting the improvement activities. Through designed experiments conducted to determine the best parameter setting of the spray gun used in the painting process, it was found that 3.5 bars for air pressure and 450 ml/minutes for fluid delivery resulted in the lowest paint defect. The use of Six Sigma DMAIC approach had succeeded in helping the company to minimize paint fiber defect per unit (DPU) from 10 to less than 3 DPU. The results from the study have provided an insight on successful deployment of DMAIC through application of its various statistical tools and techniques, and as the systematic problem-solving framework on solving actual industrial issues such as automotive painting problem

    Influence of certain carbon and nitrogen sources on antagonistic potentiality of Trichoderma harzianum and Bacillus subtillus against Botrytis allii the incitant of onion neck rot

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    Gliotoxin Fermentation Agar (GFA) Medium and Nutrient Glucose Agar   (NGA) medium with different carbon and nitrogen sources were used to study the impact of carbon and nitrogen sources on Trichoderma harzianum Rifai and Bacillus subtillus Cohn antagonistic efficiency against growth of Botrytis allii Munn. Results indicated that Trichoderma harzianum gave the highest inhibition % in growth of Botrytis allii when Sucrose was used as a carbon source while the lowest values of inhibition% were appeared by application of Mannitol as a carbon source. Trichoderma harzianum gave the highest inhibition% in growth of B.allii when use Potassium nitrate  as a nitrogen source while the lowest values of inhibition% in growth of B.allii were obtained by application of Beef extract as a nitrogen source. Results showed also that Bacillus subtillus gave the highest inhibition% in growth of B.allii when Mannitol was used as a carbon source while the lowest values of inhibition% in growth of B.allii were appeared by application of Sucrose as a carbon source. Bacillus subtillus gave the highest inhibition% in growth of B.allii when use Glutamic acid as a nitrogen source while the lowest values of inhibition% in growth of B.allii were appeared by application of Tryptophan as a nitrogen source.

    Electrical performance study of a large area multicrystalline silicon solar cell using a current shunt and a micropotentiometer

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    In this paper, a new technique using a Current Shunt and a Micropotentiometer has been used to study the electrical performance of a large area multicrystalline silicon solar cell at outdoor conditions. The electrical performance is mainly described by measuring both cell short circuit current and open circuit voltage. The measurements of this cell by using multimeters suffer from some problems because the cell has high current intensity with low output voltage. So, the solar cell short circuit current values are obtained by measuring the voltage developed across a known resistance Current Shunt. Samples of the obtained current values are accurately calibrated by using a Micropotentiometer (μpot) thermal element (TE) to validate this new measuring technique. Moreover, the solar cell open circuit voltage has been measured. Besides, the cell output power has been calculated and can be correlated with the measured incident radiation

    Mathematical modeling of fructose production by immobilised glucose isomerase as a function of temperature and pH variations

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    Production of fructose from glucose isomerisation process using commercial immobilized glucose isomerase (IGI) was conducted in a batch type of stirred tank bioreactor. A mathematical model was developed to describe the effect of temperature and pH on the kinetic parameters of fructose production. Modified Santos model known as MM3 was used to describe this phenomenon. The influence of temperature and pH was investigated and quantified. The results showed that, even though the highest R2 was at 70°C but based on the IAE of 0.843 and ISE of 0.978, it proved that for enzymatic reaction, it should be carried out below 65°C. Effect of pH for various models have shown that, the IAE and ISE were less than one whereas the R2 were greater than 0.95. This indicates that the model, MM3 is acceptable.Keywords: Batch reactor, fructose, glucose isomerisation, mathematical modeling, pH, temperatur
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