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천추 전방에서 발생한 신경절 세포종 : 증례 보고 A Case Report
강현구,이승로,박동우,박충기,함창곡,박용욱 한양대학교 의과대학 2002 한양의대 학술지 Vol.22 No.2
We have experienced a case of presacral ganglioneuroma. So, we report a peripheral ganglioneuroma of sacral origin. The patient is 34-year-old man with intermittent low back pain and right sciatica. Myelographic computed tomography revealed extradural lobulated low attenuated tumor lesion within spinal canal at the level of L5 and S1. Tumor indented the thecal sac to the left side, and extended into the pelvic cavity through the intervertebral foramen between S1 and S2. The mass was surgically excised and turned out to be ganglioneuroma pathologically.
Application of Low Voltage High Resistance Grounding in Nuclear Power Plants
Chang, Choong-Koo,Hassan, Mostafa Ahmed Fouad Korean Nuclear Society 2016 Nuclear Engineering and Technology Vol.48 No.1
Most nuclear power plants now utilize solid grounded low voltage systems. For safety and reliability reasons, the low voltage (LV) high resistance grounding (HRG) system is also increasingly used in the pulp and paper, petroleum and chemical, and semiconductor industries. Fault detection is easiest and fastest with a solidly grounded system. However, a solidly grounded system has many limitations such as severe fault damage, poor reliability on essential circuits, and electrical noise caused by the high magnitude of ground fault currents. This paper will briefly address the strengths and weaknesses of LV grounding systems. An example of a low voltage HRG system in the LV system of a nuclear power plant will be presented. The HRG system is highly recommended for LV systems of nuclear power plants if sufficient considerations are provided to prevent nuisance tripping of ground fault relays and to avoid the deterioration of system reliability.
Chang, Choong-koo,Sulley, Mumuni The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.6
The extension of DC battery backup time in the DC power supply system of nuclear power plants (NPPs) remains a challenge. The lead-acid battery is the most popular at present. And it is generally the most popular energy storage device. However, extension of backup time requires too much space. The lithium-ion battery has high energy density and advanced gravimetric and volumetric properties. The aim of this paper is development of the sizing formula of stationary lithium-ion batteries. The ongoing research activities and related industrial standards for stationary lithium-ion batteries are reviewed. Then, the lithium-ion battery sizing calculation formular is proposed for the establishment of industrial design standard which is essential for the design of stationary batteries of nuclear power plants. An example of calculating the lithium-ion battery capacity for a medium voltage UPS is presented.
Application of Low Voltage High Resistance Grounding in Nuclear Power Plants
Choong-Koo Chang,Mostafa Ahmed Fouad Hassan 한국원자력학회 2016 Nuclear Engineering and Technology Vol.48 No.1
Most nuclear power plants now utilize solid grounded low voltage systems. For safety and reliability reasons, the low voltage (LV) high resistance grounding (HRG) system is also increasingly used in the pulp and paper, petroleum and chemical, and semiconductor industries. Fault detection is easiest and fastest with a solidly grounded system. However, a solidly grounded system has many limitations such as severe fault damage, poor reliability on essential circuits, and electrical noise caused by the high magnitude of ground fault currents. This paper will briefly address the strengths and weaknesses of LV grounding systems. An example of a low voltage HRG system in the LV system of a nuclear power plant will be presented. The HRG system is highly recommended for LV systems of nuclear power plants if sufficient considerations are provided to prevent nuisance tripping of ground fault relays and to avoid the deterioration of system reliability.
Choong-koo Chang,Mumuni Sulley 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.6
The extension of DC battery backup time in the DC power supply system of nuclear power plants (NPPs) remains a challenge. The lead-acid battery is the most popular at present. And it is generally the most popular energy storage device. However, extension of backup time requires too much space. The lithium-ion battery has high energy density and advanced gravimetric and volumetric properties. The aim of this paper is development of the sizing formula of stationary lithium-ion batteries. The ongoing research activities and related industrial standards for stationary lithium-ion batteries are reviewed. Then, the lithium-ion battery sizing calculation formular is proposed for the establishment of industrial design standard which is essential for the design of stationary batteries of nuclear power plants. An example of calculating the lithium-ion battery capacity for a medium voltage UPS is presented.
Analysis of Open-Phase Conditions in Korean Standard Nuclear Power Plants and Fault Detection Scheme
Choong-koo Chang 한국조명·전기설비학회 2017 조명·전기설비학회논문지 Vol.31 No.2
Because of partial losses of power known as “open-phase faults”, controlled reactor shutdown has occurred in nuclear power plants around world. Depending on transformer wiring and loading, such conditions can be difficult to detect, because phase voltage measurements can appear to be normal. Many of the identified events went undetected for several weeks. These findings were sufficient for staff to conclude that an open phase condition is a credible event having safety significance and must be considered in the electric power system design for nuclear power plants. This paper elaborates the processes and results of the open-phase fault studies on the standard nuclear power plants in Korea. The ETAP unbalanced load flow module is used for the system analysis. The analysis described in this paper has been performed to determine the response of unit auxiliary transformers and standby auxiliary transformers during open-phase conditions to aid in the development of system protection schemes designed to detect such conditions.