Multifunction realization of active electronic current transformer
In order to fit for the urgent requirement of the digital substation, the research of electronic current transformer (ECT) attracts more and more attention. The multifunction of ECT is especially studied in order to expand its application range. In this paper, a type of active ECT is introduced firstly. The redundant backup design of high-voltage circuit is presented after that. It will be greatly helpful for the improvement of stability and reliability of active ECT. The multifunction of lowvoltage side circuit is also discussed carefully. The local display, harmonic analysis and remote communication between ECT and master computer are all designed and realized. Therefore, the application field of active ECT will be expanded significantly. The validities of above circuits are all illustrated in Lab at last.
A new calibration method of electronic transformer applied in power system
In this paper, a new calibration method is proposed to fulfill the requirement of calibration of electronic transformer. At first, the fast measurement method of power frequency is presented. And then the principle of Quasi-synchronous DFT algorithm is introduced in order to satisfy the special requirement of fast harmonic analysis during the calibration of electronic transformer. Therefore the amplitude error and phase error of electronic transformer could be obtained based on this new calibration method. The performance of method is verified by simulation results.
A single amino acid substitution in elongation factor Tu disrupts interaction between the ternary complex and the ribosome
Elongation factor Tu (EF-Tu).GTP has the primary function of promoting the efficient and correct interaction of aminoacyl-tRNA with the ribosome. Very little is known about the elements in EF-Tu involved in this interaction. We describe a mutant form of EF-Tu, isolated in Salmonella typhimurium, that causes a severe defect in the interaction of the ternary complex with the ribosome. The mutation causes the substitution of Val for Gly-280 in domain II of EF-Tu. The in vivo growth and translation phenotypes of strains harboring this mutation are indistinguishable from those of strains in which the same tuf gene is insertionally inactivated. Viable cells are not obtained when the other tuf gene is inactivated, showing that the mutant EF-Tu alone cannot support cell growth. We have confirmed, by partial protein sequencing, that the mutant EF-Tu is present in the cells. In vitro analysis of the natural mixture of wild-type and mutant EF-Tu allows us to identify the major defect of this mutant. Our data shows that the EF-Tu is homogeneous and competent with respect to guanine nucleotide binding and exchange, stimulation of nucleotide exchange by EF-Ts, and ternary complex formation with aminoacyl-tRNA. However various measures of translational efficiency show a significant reduction, which is associated with a defective interaction between the ribosome and the mutant EF-Tu.GTP.aminoacyl-tRNA complex. In addition, the antibiotic kirromycin, which blocks translation by binding EF-Tu on the ribosome, fails to do so with this mutant EF-Tu, although it does form a complex with EF-Tu. Our results suggest that this region of domain II in EF-Tu has an important function and influences the binding of the ternary complex to the codon-programmed ribosome during protein synthesis. Models involving either a direct or an indirect effect of the mutation are discussed.