Partial Discharge Location within a Transformer Winding using Principal Component Analysis

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

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

Investigation of graphene channel interaction with yeast cell for cell counting application

Graphene superior and unique properties make it a suitable material for biosensor. In this work, graphene interaction with yeast cell is investigated for development of graphenebased cell counter. The fabricated graphene channel was characterized by means of two-terminal and solution-gated three-terminal measurement setup. The correlation between graphene channel resistance and cell concentration was confirmed. The yeast cell was found to give n-type doping which modulate the conductivity of graphene channel

Design of Serial-Fed Bend-Array and Measured Results

For the next generation mobile system (5G), a cylindrical lens antenna is developed for mobile base station application. As for the feed radiator for this lens antenna, bendarray configuration that produces a bifurcated beam is also developed. The bend-array configuration consisting of four rectangular patch array elements with serial feed network. In previous work, achievement of the bifurcated beam by bendarray configuration was shown by electromagnetic simulations. In this paper, a practical bend-array composed of four numbers of patch elements is fabricated. To verify the radiation characteristics, measured results of antenna input characteristic and radiation pattern are compared with the designed results. Through good agreement of measured and designed results, achievement of practical antenna is ensured

Efecto hepatoprotector del insaponificable de los aceites de oliva, linaza y sésamo contra la lesión hepática inducida por tetracloruro de carbono en ratas

In the present study, the hepatoprotective activity of the unsaponifiable matter (UNSAP) of olive oil, linseed, and sesame oils against CCl4-induced liver toxicity in rats was investigated. In a preliminary antioxidant study, UNSAP showed pronounced DPPH radical scavenging activity (IC50 6.2-10.8 mg/mL). The constituents of UNSAP were determined by GC-MS. The subcutaneous administration of CCl4, caused liver injury. The hepatoprotective effect of UNSAP was comparable to that of α-tocopherol, a standard antioxidant agent. The co-administration of the investigated UNSAP normalized the activities of serum marker enzymes, alanine aminotransferase (ALT), and aspartate aminotransferase (AST). Furthermore, the serum alkaline phosphatase (ALP) activity and hepatic malondialdehyde (MDA) level were found to be alleviated by pre-treatment with the UNSAP. A histopathological evaluation showed marked improvement in the liver of UNSAP- and α-Tocopherol-treated animals. The hepatoprotective effect could be attributed to the antioxidant characteristics of UNSAP.En el presente estudio, se investigó la actividad hepatoprotectora de la materia insaponificable (UNSAP) de los aceites de oliva, linaza y sésamo contra la toxicidad hepática inducida por CCl4 en ratas. En un estudio preliminar de antioxidantes, UNSAP mostró una pronunciada actividad de captación de radicales DPPH (IC50 6.2-10.8 mg / mL). Los constituyentes del UNSAP fueron determinados por GC-MS. La administración de CCl4, por vía subcutánea, causó lesión hepática. El efecto hepatoprotector del UNSAP fue comparable al del α-Tocoferol, un agente antioxidante estándar. La administración conjunta del UNSAP normalizó las actividades de las enzimas marcadoras séricas, alanina aminotransferasa (ALT) y aspartato aminotransferasa (AST). Además, se encontró que la actividad de la fosfatasa alcalina en suero (ALP) y el nivel de malondialdehído hepático (MDA) se mitigan con el tratamiento previo con UNSAP. La evaluación histopatológica mostró una mejoría notable en el hígado de los animales tratados con UNSAP y α-Tocopherol. El efecto hepatoprotector podría atribuirse a las características antioxidantes de UNSAP

Concentrated photovoltaic thermal systems:A component-by-component view on the developments in the design, heat transfer medium and applications

The need of the hour in present world scenario is to reduce the emission of greenhouse gases and environmental pollution whilst satisfying the world energy demands. The most promising and readily available source of energy over the whole world is solar energy. One of the ways of taping this energy into useful energy is using Concentrated Photovoltaic Thermal systems. The paper presents the advanced comprehensive review on the design components of Concentrated Photovoltaic Thermal, heat transfer medium, recent application area such as Tissue Dyeing, domestic hot water, Organic Rankine Cycle, and the economic aspect of the Concentrated Photovoltaic Thermal system. Furthermore, the review paper simplifies the classification into two systems namely thermally coupled and thermally decoupled systems. Concentrated Photovoltaic Thermal shows potential to deliver better gains compared to Concentrated Photovoltaic, Photovoltaic and Photovoltaic Thermal. But matching the different components like the heat transfer component and the medium for specific use is an area that requires research. Therefore, this review concentrates more on the advantages and limitations of using different heat transfer components and heat transfer medium. The benefits of this paper would be the understanding of the components of the heat transport system like fins, microchannel, storage tank and underground heat exchangers and the fluid used in the Concentrated Photovoltaic Thermal integrated system like water, air, nanofluids, Phase Change Materials. It is found that the heat transfer device performance is limited due to its large area, thermal losses, mirror effect on the thermal and electrical efficiencies, and the temperature difference between the sink and device. Likewise, the performance of the heat transfer fluid is dependent on the mass flow rate, thermal mass, viscosity, density, time and the required temperature. Finally, for economic feasibility of the Concentrated Photovoltaic Thermal system requires the need for a grid connected system with properly sized system with feed-in-tariff and carbon incentives. Furthermore, the recommendation for heat transfer device, medium and economic aspect is also presented. However, more experimental research is required to further understand the compatibility of each components with Concentrating Photovoltaic Thermal System as presented in way forward

Prevalence of needle stick injuries and compliance to infection control guidelines among health care workers in a teaching hospital, Malaysia

Introduction: Health care workers (HCW) are constantly exposed to blood-borne illnesses through needle stick injuries (NSI). Despite the increasing trend of NSI, evidence regarding the actual practice of universal precautions among these HCWs is lacking. This study assessed the practice of universal precautions towards prevention of NSI among HCWs in a teaching hospital setting. Methods: This cross-sectional survey involved a newly-designed self-completed questionnaire assessing demographic data, exposure to NSI and practice of universal precautions. Questionnaires were distributed to every ward and completed questionnaires were collected after a period of 7 days. Results: A total of 215 HCWs responded to the survey. 35.8% were exposed to bodily fluid, with 22.3% had NSI in the last 12 months. Blood taking was the commonest procedure associated with NSI. Of practices of universal precautions, recapping needle and removing needle from syringe were still wrongly practiced by the HCWs assessed. Conclusion: NSI among HCW are still common despite the introduction of universal precautions in our hospital. Incorrect practices in handling sharps should be looked into in order to reduce the incidence of blood-borne illnesses through NSI in the hospital

Actividades antioxidantes, antiinflamatorias y citotóxicas de la fracción insaponificable de aceite de oliva virgen extra

The health benefits of olive oil are well-known. In this study, the unsaponifiable fraction of extra virgin olive oil (Unsap) was investigated for reducing power capacity, ferric reducing antioxidant power, fer-rous chelating activity and nitric oxide inhibition. The present study was also designed to evaluate the in vitro cytotoxic effect of the Unsap against human carcinoma cells. The anti-inflammatory potential of Unsap has been determined via the inhibition of Human Cyclooxygenases. The results showed that Unsap is efficient for ferric reducing antioxidant power and nitric oxide inhibition. Unsap has a selective effect as anti-inflammatory agent. The results showed moderate to good in vitro antitumor activities of Unsap against human liver, lung and pancreas cancer cells with IC50 ranging from 19.6 to 30.4 μg/mL and good selectivity index (≥ 2). In conclusion, Unsap represents a promising and safe antitumor and antioxidant material that supports the need for further investigation.Los beneficios para la salud del aceite de oliva son bien conocidos. En este estudio, se investigó la fracción insaponificable del aceite de oliva virgen extra (Insap) para reducir el poder antioxidante férrico, la actividad quelante ferrosa y la inhibición del óxido nítrico. El presente estudio también fue diseñado para evaluar el efecto citotóxico in vitro del Insap contra las células de carcinoma humano. La potencialidad antiinflamatoria del Insap se ha determinado mediante la inhibición de las ciclooxigenasas humanas. Los resultados mostraron que el Insap es eficiente para reducir el poder antioxidante férrico y la inhibición del óxido nítrico. El Insap tiene un efecto selectivo como agente antiinflamatorio. Los resultados mostraron actividades antitumorales in vitro del Insap de moderadas a buenas contra células de cáncer de hígado, pulmón y páncreas humano con una CI50 que varía de 19,6 a 30,4 μg/ml y por su buen índice de selectividad ( ≥ 2). En conclusión, el Insap contiene material antitumoral y antioxidante prometedor y seguro que será respaldado por investiga-ciones adicionales