• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.7
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• pp.577-582
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• 2020

Electricity produced at power plants is distributed to consumers through several stages of substations. At this time, an ultra-high voltage transformer is needed in the initial transmission stage to transmit a voltage suitable for each consumer. A high voltage, non-uniform electric field is formed at the end of the winding of the ultra-high voltage transformer, which carries a risk of dielectric breakdown. The winding of the ultra-high voltage transformer is an electrode, which is the key to converting the magnitude of the voltage. A non-uniform electric field is formed along the shape of the winding end, resulting in high electrical stress. The static ring installed at the upper and lower ends of the winding is used to disperse the stress at the winding end. Several variables should be considered when designing a static ring. Among them, this study examined how the curvature of the static ring, the thickness of the insulating paper, the number of barriers, and barrier thickness affect the electrical stress of the static ring using the Finite Element Method. Suggestions to be considered when designing the static ring are proposed through the FEM results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.10
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• pp.1328-1336
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• 2014

This paper proposes Power System Health Index(PSHI) newly. The paper describes several kind of power system health indices based on two main categories, which are adequacy and security. In adequacy, four kinds of health indices of Frequency, Voltage, Reserve(Operating Reserve Power and Frequency Regulation Reserve Power) and Overload of lines and transformers are proposed. In security, four kinds of health indices of Voltage(154kV, 345kV and 765kV), Overload of lines and transformers, Power flow constraint among areas and SPS are proposed. All indices are mapped with three domains, which are indicated as Health, Margin and Risk, defined with expert interview. While domains of health, margin and risk is defined similar with the conventional well being analysis of power system. The criterion of the domains is proposed using an interview with expert operators and practical reliability codes in Korea. The several kinds of health index functions, which are linear ratio, piecewise linear ration and reverse ratio function etc. are developed in this paper. It will be expected that the developed health indices can help operators to control power system more successfully and also prevent power system from accident as like as black out in future because operator can make a decision immediately based on more easily visual information of system conditions from too much indices acquisition of complex power system.

• Journal of IKEEE
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• v.23 no.1
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• pp.254-260
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• 2019

The failure rate of bidirectional dc-to-dc converter is predicted through the failure mode and effect analysis (FMEA) and the fault-tree analysis (FTA) considering the operational risk. In order to increase the driving voltage of the electric vehicle efficiently, the bidirectional converter is attached to the front of the inverter. It has a boost mode for discharging battery power to the dc-link capacitor and a buck mode for charging the regenerative power to the battery. Based on the results of the FMEA considering the operating characteristics of the bidirectional converter, the fault-tree is designed considering the risk of the converter. After setting the design parameters for the MCU for the electric vehicle, we analyze the failure rate of the capacitor due to the output voltage ripple and the inductor component failure rate due to the inductor current ripple. In addition, we obtain the failure rate of major parts according to operating temperature using MIL-HDBK-217F. Finally, the failure rate and the mean time between failures (MTBF) of the converter are predicted by reflecting the part failure rate to the basic event of the fault-tree.

• The Journal of Korean Medicine
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• v.43 no.1
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• pp.33-41
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• 2022

Objectives: Drug-induced blockade of the human ether-à-go-go related gene (hERG) potassium ion channel causes acquired long QT syndrome, which is known to cause cardiac arrhythmias and be fatal. To establish safety evidence of herbal formulae, we evaluated the effects of 31 herbal formulae on hERG channel activity. Methods: The current through hERG channel was measured by changing the membrane voltage before and after treatment with 31 herbal formulae in HEK 293 cell overexpressing hERG channel using a whole-cell patch clamp system. The current-voltage curves and the activity curves were fitted, and the hERG activity and 50% inhibitory concentration (IC₅₀) according to each herbal formula were calculated. Results: Chokyungjongok-tang, Oncheong-eum, and Cheongsangbangpung-tang strongly inhibited the hERG activity, with IC₅₀ values of 67.67, 141.2, and 296.3 ㎍/mL, respectively. Yeonkyopaedok-san, Eunkyo-san, Ukgan-san gajinphibanha, Daegunjoong-tang (except Oryzae gluten), Insamyangyoung-tang, Banhahubak-tang, SokyungHwalhyul-tang, Jodeung-san, Hyeonggaeyeongyo-tang, and Bangkeehwangkee-tang weakly inhibited hERG activity, with IC₅₀ values ranging from 400 to 1000 ㎍/mL. The other 18 herbal formulae showed very weak hERG activity inhibition of less than 50% at the highest concentration (1000 ㎍/mL). Conclusion: This study provided safety information on cardiotoxicity by cardiac arrhythmia risk assessment of herbal formulae, and is expected to be a reference data for predicting the safety and risk of herbal formulae.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.277-279
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• 2005

Recently, due to the increase of power conversion devices and nonlinear loads with the development of information, communication and control technologies, the instantaneous minute interruption factors such as voltage & current harmonics, surge occurring frequency, instantaneous voltage variation, voltage unbalance, flicker etc. have greatly threatened the power quality, and the deterioration of electric power facilities and the functional error of controllers are increasing. As such an instantaneous minute interruption appears to be small and local, accurate evaluation with measurement is difficult and total analysis system is required through a wide range of power quality effect analysis such as the simultaneous measurement on various power supply phenomena and the analysis on the interrelation with system loads. Most of conventional power quality diagnosis equipments have beer developed and applied, which were able to measure the stability rate of frequency, the stability rate of voltage, the electricity-failure duration etc, However, they were insufficient to analyze the system present situation, understand the cause of the failure occurred by the problem of power quality and analyze out the phenomena. Accordingly, this study will address the development of the system for a wide range of power quality diagnosis over the present level, the system for supporting the determination such as the analysis on risk factors, failure mode and impact, the system for harmonic evaluation based on international standards(IEC 61000 Series) and the total power quality diagnosis network & system with the extension and openness as a local and national-scale broadband power quality diagnosis system.

• Journal of the Korean Society of Safety
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• v.38 no.4
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• pp.8-14
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• 2023

This study presents the characteristics of short circuits (SCs) caused by excessive currents in high-voltage cables used in electric vehicles and emphasizes the need to calculate the cross-sectional areas of these cables according to the SC current. Three direct current power supplies were connected in parallel to test the SC characteristics caused by excessive currents, and a timer and a magnetic contactor were used to deliver the conduction time and SC current. A circular infrared-radiation heater was used to test the temperature-dependent SC characteristics, a thermocouple was used to measure the temperature, and a shunt resistor was used to measure the current. As the SC current increased, the fusing time of the cable decreased. Additionally, a high-voltage cable (with an area of 16 mm² ) used in electric vehicles fused when a current (approximately equal to 55 times the allowable current) flowed for 0.2 s (operating time of the protective device). When the SC current is 10 kA, the cable may fuse during the operating time of the protective device, thus creating a fire hazard. In electric vehicles, the size of the SC current increases in proportion to the capacity of the battery. Thus, the cross-sectional areas of the cables used should be calculated accordingly, and cable operations should be properly coordinated with the surrounding protective devices.

• The Korean Journal of Pain
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• v.31 no.3
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• pp.155-173
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• 2018

Chronic postsurgical pain (CPSP) is an unwanted adverse event in any operation. It leads to functional limitations and psychological trauma for patients, and leaves the operative team with feelings of failure and humiliation. Therefore, it is crucial that preventive strategies for CPSP are considered in high-risk operations. Various techniques have been implemented to reduce the risk with variable success. Identifying the risk factors for each patient and applying a timely preventive strategy may help patients avoid the distress of chronic pain. The preventive strategies include modification of the surgical technique, good pain control throughout the perioperative period, and preoperative psychological intervention focusing on the psychosocial and cognitive risk factors. Appropriate management of CPSP patients is also necessary to reduce their suffering. CPSP usually has a neuropathic pain component; therefore, the current recommendations are based on data on chronic neuropathic pain. Hence, voltage-dependent calcium channel antagonists, antidepressants, topical lidocaine and topical capsaicin are the main pharmacological treatments. Paracetamol, NSAIDs and weak opioids can be used according to symptom severity, but strong opioids should be used with great caution and are not recommended. Other drugs that may be helpful are ketamine, clonidine, and intravenous lidocaine infusion. For patients with failed pharmacological treatment, consideration should be given to pain interventions; examples include transcutaneous electrical nerve stimulation, botulinum toxin injections, pulsed radiofrequency, nerve blocks, nerve ablation, neuromodulation and surgical management. Physical therapy, cognitive behavioral therapy and lifestyle modifications are also useful for relieving the pain and distress experienced by CPSP patients.

• Safety and Health at Work
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• v.4 no.3
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• pp.156-159
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• 2013

Background: Cardiac pacemakers are known to be susceptible to strong electromagnetic fields (EMFs). This in vivo study investigated occurrence of electromagnetic interference with pacemakers caused by common environmental sources of EMFs. Methods: Eleven volunteers with a pacemaker were exposed to EMFs produced by two mobile phone base stations, an electrically powered commuter train, and an overhead high voltage transmission lines. All the pacemakers were programmed in normal clinically selected settings with bipolar sensing and pacing configurations. Results: None of the pacemakers experienced interference in any of these exposure situations. However, often it is not clear whether or not strong EMFs exist in various work environments, and hence an individual risk assessment is needed. Conclusions: Modern pacemakers are well shielded against external EMFs, and workers with a pacemaker can most often return to their previous work after having a pacemaker implanted. However, an appropriate risk assessment is still necessary after the implantation of a pacemaker, a change of its generator, or major modification of its programming settings.

• Tuberculosis and Respiratory Diseases
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• v.48 no.6
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• pp.944-955
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• 2000

Background : In patients with chronic obstructive pulmonary disease(COPD), several factors have been associated with a poor prognosis. These include old age, low $FEV_1$ low diffusing capacity, high alveolar-arterial oxygen pressure difference, and finally cor pulmonale. This study was done to investigate if the ECG signs suggesting cor pulmonale were independent prognostic factors in patients with COPD. Method : We analyzed ECG, pulmonary function data and arterial blood gas values in 61 patients who were admitted through the emergency department with an acute exacerbation of COPD. The ECG signs reflecting cor pulmonale were right strial overloading(RAO), right bundle branch block, right ventricular hypertrophy and low-voltage QRS. The 61 patients were divided into 2 groups ; group I with no ECG signs(n=36) and group II with one or more ECG signs(n=25) suggesting cor, pulmonale. Results : Poor, prognostic factors by univariate analysis were low $FEV_1$, $FEV_1$ % pred., VC % pred., DLco, DLco % pred., $PaO_2$ and $SaO_2$ high $PaCO_2$ presence of ECG signs reflecting cor pulmonale, presence of mental status change, use of mechanical ventilator, and long term use of glucocorticoid. A multivariate analysis indicated that age(risk ratio=1.13, 95% confidence interval 1.05-1.23), DLco % pred. (risk ratio=0,97. 95% confidence interval 0.94-0.99), $PaO_2$ (risk ratio=0.95, 95% confidence interval 0.90-0.99) and RAO(risk ratio=5.27, 95% confidence interval 1.40-19.85) were independent prognostic factors of survival. There was a significant difference in survival between the patients with and without RAO(p=0.038). The survival rates at 1, 2, and 5 years were 94.5%. 81.4%, and 50.0% in patients without RAO and 82.4%, 70.6%, and 27.5% in patients with RAO, respectively. Conclusion : These results suggest that the presence of ECG signs reflecting cor pulmonale is a predictor of survival and that RAO of these ECG signs is a significant independent predictor of survival in patients with COPD.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.408-410
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• 2006

To chase maximum power point at every moment under a conventional MPPT control method, a voltage and current coming out from PV-cell are needed to be feedbacked. So, the structure of control circuit becomes so complex and the MPPT control is in risk of control failure. In the newly developed control method, the current flowing into SPE cell is the only one considerable factor. So, the structure of control circuit becomes simple and the manufacturing cost of the control device decreases. Especially, in case of a huge system of PV-SPE system, because the voltage coming out from PV-cell is not needed to be feed backed, this system can be operated much more safely. In this paper, the PV-SPE system was actually manufactured based on the simulation model of PSCAD/EMTDC program and the results tested were shown. Authors are sure that it is the most useful method to maximize power from PV to SPE with only a feedback of SPE input current.