An acoustic emission method for on-line monitoring the contamination-causing flashover of insulator
This paper presents an acoustic emission (AE) monitoring method. When a partial discharge occurs, there is an instantaneous release of energy, some of which is emitted as acoustic energy. The pollution severities of insulators in-service can be monitored and accordingly threaten to the insulation of power grid is evaluated by detecting the sound signals. To prove this AE monitoring method, artificial contaminations experiments are carried out. The essential information about the relationship of AE signal and PD are obtained in different moments of the whole process of flashover. The studied method is a new way of AE technique in monitoring and characterizing defects of electrical power equipments in-service.
Radiating signal model for broadband acoustic emission from high voltage equipment
This paper presents a radiating signal model that simulates the acoustic emission from high voltage equipment. This theoretical model was formulated for radiating signals originate from high voltage equipment such as transformer, insulator and gas-insulated chamber using the numerical method known as the finite-difference time-domain (FDTD) method. The FDTD method has been widely applied in the analysis of electromagnetic waves. Its applications range from the design of antennas to the study of radiation effects on the human body. A simple one source one receiver model was used to demonstrate the capability of the FDTD method. Using the FDTD method to study the theoretical aspects of high voltage acoustic emissions, researchers can better understand the properties and characteristics of the phenomena.
ATP-dependent S-(2,4-dinitrophenyl)glutathione transport in canalicular plasma membrane vesicles from rat liver.
Uptake of the thioether S-(2,4-dinitrophenyl)glutathione (DNPSG) in canalicular plasma membrane vesicles from rat liver is enhanced in the presence of ATP and exhibits an overshoot with a transient 5.5-fold accumulation of DNPSG. Stimulation by ATP is not caused by the generation of a membrane potential, based on responses of the indicator dye oxonol V. ATP-dependent uptake has an apparent Km of 71 microM for DNPSG and a Vmax of 0.34 nmol.min-1.mg of vesicle protein-1. Protein thiol groups are essential for transport activity as indicated by the sensitivity of DNPSG transport to sulfhydryl reagents. There is competitive inhibition with other thioethers, S-hexylglutathione (Ki = 66 microM), the photoaffinity label S-(4-azidophenacyl)glutathione (Ki = 56 microM), as well as with glutathione disulfide (Ki = 0.44 mM) and with the bile acid taurocholate (Ki = 0.61 mM). GSH (2 mM) or cholate (0.4 mM) does not inhibit. Both glutathione disulfide and taurocholate show ATP-dependent transport in the canalicular membrane vesicles which is inhibited by DNPSG. No ATP-dependent transport is found for GSH. Transport of DNPSG is also inhibited competitively by alpha-naphthyl-beta-D-glucuronide (Ki = 0.42 mM) but not by alpha-naphthylsulfate (2 mM), and there is substantial inhibition with the glucuronides from ebselen and p-nitrophenol. The results indicate that the canalicular transport system for DNPSG is directly driven by ATP and that the biliary transport of other classes of compounds may also proceed via this system.