Due to aging and degrading of insulation oil in power transformers, dissolved hydrogen, as a typical fault gas, would produce accompanied by discharges or overheating. Palladium (Pd) film deposited on the surface of chemically etched fiber Bragg grating (FBG) as sensing element by magnetron sputtering process is proposed in this paper. Volume expands when Pd film with 560nm thickness absorbs hydrogen molecules and wavelength shift caused by the strain could be measured. In this principle, hydrogen of low concentration can be obtained through wavelength shift of FBG. Different aspects have been taken into consideration including membrane thickness, polyimide coating and cladding diameter to obtain satisfactory sensitivity. Experimental results in the lab showed that this developed hydrogen could detect 30 μL/L at 1 pm approximately, which proved to be a prospective sensor as a on-line method to be utilized in power transformers.
It was found from the tests in our laboratory that statistic analysis of insulator corona current pulses could identify the existence of faulty insulators on strings or transmission line towers. Some basic researches on corona discharge characteristics of insulators and insulator strings were investigated hrther in terms of polarity, aniplitude, and pulse count of corona current pulses. Insulator corona characteristics are observed to be different from piece to piece. Therefore, a BP network was developed to classify voltage across an insulator and hrther identify the existence of faulty insulators on towers. It is confirmed that the developed BP network method yields satisfactory performance in terms of training time and quality of classification.Porcelain insulators are main insulators used to transmission lines in china. Electric power utilities in china inspect for low and zero resistance insulators on transmission lines once 2 -4 years. The tools widely used to
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