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김경엽,김점배 한국유체기계학회 2004 한국유체기계학회 논문집 Vol.7 No.1
The waterhammer has recently become more important because the pumping stations were big and the systems conveying the fluid through the large and long transmission pipelines were complex. When the pumps are started or stopped for the operation or tripped due to the power failure, the hydraulic transients occur as a result of the sudden change in velocity. As the pressure waves are propagating between the pumping station and the distributing reservoir, the pressure inside the pipe drops to the liquid vapor pressure with the pipeline profile, at which time a vapor cavity forms, and finally the column separation occurs. If the pressure in the pipe is less than the atmospheric pressure, the pipe can be collapsed and destroyed after the water columns separated by the vapor cavity rejoin. During the reverse flow, the pressure is so abnormally increased at the pumping station that the accident of flooding may happen due to the failure of system. In this paper, the field tests on the waterhammer by the startup, stoppage, and power failure of a centrifugal pump were carried out for Yongma transmission pumping station in Seoul. The experimental results were compared with that of the numerical calculations, in which results the procedure of controlled pump normal shut-down and the two-step closing mode of controlling the ball valve for pump emergency stop are proposed to reduce the pressure surge.
전력선 반송통신을 이용한 전기기기 전원 제어 시스템에 관한 연구
김경엽,문복산,유영호 한국마린엔지니어링학회 2001 한국마린엔지니어링학회지 Vol.25 No.4
Recently, a lot of studies on the power line communication(PLC) are being done by many companies and institutes due to its own merit which can use the power line spread widely as a communication channel. But, there are many serious problems about the harsh and unpredictable characteristics, or noise, signal distortion and attenuation to be overcome for commercialization. In this paper, the power line characteristics as the view point of communication channel are investigated and the technologies of PLC are proposed to control the power of electric machineries by using the combined method of ASK modulation and microprocessor technologies. Also experiments are carried out to ascertain performance in case of applying to electric lights control according to various distancea as an example.