An Overview of HVDC Power Transmission System with Voltage Source Converter

A general platform is introduced to study thedynamics of power systems with high voltage dc (HVDC) transmission links. Small-signal stability, voltage stability, and interaction phenomena of power systems with both line-commutated-converter HVDC (LCC-HVDC) and voltage-source- converter HVDC (VSC-HVDC) are addressed using the proposed platform. In quest of high efficiency, power density and problems of bulk power transmission over long distance, requirement of full control over power transmission and growing interest to incorporate renewable energy source into the grid has led to develop a new era of high voltage direct current (HVDC) transmission system. The researchers have developed many new HVDC configurations and voltage source converter (VSC) based HVDC transmission is one of them. Their high efficiency, compact size, high reliability, short installation and commissioning period and low operating and maintenance cost make it suitable choice for HVDC transmission. The HVDC system with power converter acts as a backbone and provides high reliability with a long useful life to support the AC electrical system. The power conversion i.e. AC to DC or vice versa is achieved by controllable electronic switches in a 3-phase bridge configuration.The wide spread use of AC-DC converters for various applications has resulted in power quality pollution leading to failure of sensitive equipments, reduced efficiency, etc

STUDIES ON BIOAVAILABILITY ENHANCEMENT OF CURCUMIN

Objective: The objective of the present work was to improve aqueous solubility and in vivo bioavailability of curcumin and structural analogues of curcumin such as potassium, calcium, magnesium salts and nitro derivative. Methods: Structural analogues of curcumin were prepared by reaction of curcumin with potassium chloride, magnesium chloride hexahydrate and calcium chloride dihydrate in a suitable solvent. The nitro derivative synthesized by treating curcumin with sulphuric acid and nitric acid. The prepared analogues were evaluated for melting behavior, solubility, UV spectrophotometry, partition coefficient, moisture content, cellular uptake, FTIR analysis, antimicrobial activity and in vivo bioavailability in the rat. Results: Chemical modification of curcumin increased the saturation solubility to 11.6, 16.5, 21.5, 28.0 µg/ml in calcium salt, magnesium salt, potassium salt and nitro derivative respectively, against 8.6 µg/ml of curcumin. The analogues were chemically stable as curcumin analyzed by FTIR spectrophotometry. Increased cellular uptake, as well as enhanced antimicrobial activity, was demonstrated by modified curcumin analogues. Moreover, significant improvement in plasma levels was estimated with nitro derivative. Conclusion: The present work recommends that nitration of curcumin improves aqueous solubility which may improve absorption and in vivo bioavailability

Improvement in Transformer Diagnosis by DGA using Fuzzy Logic

Abstract -Power transformer is one of the most important equipments in electrical power system. The detection of certain gases generated in transformer is the first indication of a malfunction that may lead to failure if not detected. Dissolved gas analysis (DGA) of transformer oil has been one of the most reliable techniques to detect the incipient faults. Many conventional DGA methods have been developed to interpret DGA results obtained from gas chromatography. Although these methods are widely used in the world, they sometimes fail to diagnose, especially when DGA results falls outside conventional method codes or when more than one fault exist in transformer. To overcome these limitations, fuzzy inference system (FIS) is proposed. 250 different cases are used to test the accuracy of various DGA methods in interpreting the transformer condition

Improvement in Transformer Diagnosis by DGA using Fuzzy Logic

Abstract -Power transformer is one of the most important equipments in electrical power system. The detection of certain gases generated in transformer is the first indication of a malfunction that may lead to failure if not detected. Dissolved gas analysis (DGA) of transformer oil has been one of the most reliable techniques to detect the incipient faults. Many conventional DGA methods have been developed to interpret DGA results obtained from gas chromatography. Although these methods are widely used in the world, they sometimes fail to diagnose, especially when DGA results falls outside conventional method codes or when more than one fault exist in transformer. To overcome these limitations, fuzzy inference system (FIS) is proposed. 250 different cases are used to test the accuracy of various DGA methods in interpreting the transformer condition

A model for understanding electromigration-induced void evolution in dual-inlaid Cu interconnect structures

Electromigration-induced void evolution in various dual-inlaid copper (Cu) interconnect structures was simulated by applying a phenomenological model assisted by Monte Carlo-based simulations, considering the redistribution of heterogeneously nucleated voids and/or pre-existing vacancy clusters at the Cu/dielectric cap interface during electromigration. The results indicate that this model can qualitatively explain the electromigration-induced void evolution observed during experimental in situ secondary-electron microscopy (SEM) investigations as well as in various other reported studies. The electromigration mechanism in Cu interconnect structures and differences in the peculiar electromigration-induced void evolution in various dual-inlaid Cu interconnect structures can be clearly understood based on this model. These findings warrant reinvestigation of technologically important electromigration mechanisms by developing rigorous models based on similar concepts