• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.21 no.5
• /
• pp.60-67
• /
• 2007

In this paper, a simulation method of the internal winding fault is proposed to calculate winding current and electromagnetic force in a distribution power transformer by suing FEM program. The model of the transformer is a single phase, 60[Hz], 1[MVA], 22.9[kV]/220[V], cable-type winding. The short-circuit current and electromagnetic force are calculated by FEM(Finite Element Method) program(Flux2D) and the results we verified with theoretical formula and PSPICE program. The simulation results are fairly good agreement with the other verified methods within 5[%] error rate. The turn-to-turn short-circuit current is 500 times of the rated current and the electromagnetic force is about $20{\sim}200times$. The method presented in this study may serve as one of the useful tools in the electromagnetic force analysis of the transformer winding behavior under the short circuit condition for design of the structure.

• Journal of Korean Neurosurgical Society
• /
• v.29 no.2
• /
• pp.196-202
• /
• 2000

Objective : This study was designed to evaluate the relationship between the initial neurosurgical or psychosocial factors and the psychosocial outcome. Patients and Methods : We analyzed 123 head-injured patients who were referred to the department of psychiatry for the evaluation of psychosocial function. We analyzed initial neurosurgical variables such as Glasgow Coma scale(GCS) score, skull fracture, CT finding, and psychosocial outcomes with regards to psychosis, personality change, depression, anxiety and IQ on Intelligence Scale. Results : Patients with mild head injury(GCS score 13-15, N＝94, 76.4%) had better recovery rate on Glasgow Outcome Scale(GOS), less personality change than those with moderate or severe head injury. However, depression, anxiety and intelligence were not significantly different between two groups. The skull fracture(N＝37, 30.1%) did not influence on the psychosocial outcome with reference to personality change, depression, anxiety and intelligence. The patients with abnormal CT findings(N＝64, 52%) had lower recovery rate on GOS, more frequent tendency in psychosis, personality change and severe depression, less frequent in anxiety and mild depression, than patients with normal CT finding. However, levels of intelligence were not different between two groups. The patients with industrial accidents(IA) had lower educational level, milder head injury, more delay for the psychiatric evaluation (longer treatment period) than those with motor vehicular accidents(MVA). The psychosocial outcome with reference to personality change, depression, anxiety, intelligence were not different between two groups. Conclusion : These findings indicate that the more severe initial trauma, the poorer psychosocial outcome. However, it was frequently observed that patients with mild head injury suffered from mild anxiety and depression. Therefore mild head injury appeared to be more complicated by psychosocial stressors. The patients with IA, despite the fact that initial head injury was mild, required longer treatment period than MVA.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.23 no.12
• /
• pp.191-200
• /
• 2009

This paper, which consists of two parts, dealt with the parameter tuning of the power system stabilizer for a 612[MVA] thermal power plant in KEPCO system and its validation in field test. In Part 1 of the paper, the selection of parameters such as lead-lag time constants for phase compensation, system gain was optimized by using linear & eigenvalue analyses and they were verified through the time-domain transient stability analysis. In part 2, the performance of PSS was finally verified by the generator's on-line field test. Through the comparisons of simulation results and measured data before and after tuning of the PSS, the models of generator and its controllers including AVR, Governor and PSS used in the simulation are validated and confirmed.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.47 no.6
• /
• pp.432-437
• /
• 2021

Objectives: The mandible and other parts of the maxillofacial region suffer significant morbid injuries following road traffic accidents. Our study gives epidemiological description of mandibular fractures in Ghana and also evaluates the relevance of closed reduction and indirect fixation for managing mandibular fractures in low-resource health facilities in low-income countries like Ghana. Patients and Methods: This is a retrospective study involving 268 patients who reported to the Department of Oral and Maxillofacial Surgery of the Sunyani Regional Hospital with mandibular fractures from January 2010 to December 2019. Patient medical records were assessed for information on age, sex, fracture etiology, anatomic location of fracture, time of day of road traffic accident, and other associated injuries. Results: A total of 268 patients were included in this study (males, 216 [80.6%]; females, 52 [19.4%]). Motor vehicular accident (MVA) was the leading cause of mandibular fractures (202 injuries, 75.4%). Other etiologies included assault (39, 14.6%), gunshot (13, 4.9%), falls (12, 4.5%), and industrial accidents (2, 0.7%). Of the 161 male cases caused by MVA, 121 (75.2%) occurred at night and in the evening while the remaining 40 (24.8%) occurred in the morning and afternoon. Among all managed 222 patients, 212 (79.1%) were treated with closed reduction and indirect fixation technique while 10 (3.7%) were treated with open reduction and direct fixation. Conclusion: Closed reduction with indirect fixation could successfully be used to manage mandibular fractures in low resourced health facilities, especially in low-income countries. The poor lightening system on roads in Ghana is a major contributory factor to motor vehicular accidents.

• Proceedings of the KIPE Conference
• /
• 2014.11a
• /
• pp.93-94
• /
• 2014

본 논문의 주제는 가파도 마이크로 그리드에 적용한 1MVA급 배터리 에너지 저장시스템(BESS-Battery Energy Storage System)을 소개하는 것이다. 에너지 저장장치가 디젤발전기와의 연계 및 독립운전 하여 탄소 배출 없이(Carbon-Free) 가파도 전체 부하에 전원을 공급하는 실증 사례를 살핀다.

• Proceedings of the KIPE Conference
• /
• 2013.11a
• /
• pp.119-120
• /
• 2013

Wind turbines as a power distribution system linked to the driving operation according to the characteristics of the distribution system can be adversely affected by a change of circumstances, depending on Distribution Systems with driving characteristics of a wind turbine can be affected. Thus according to the grid-tied wind turbines and transient suppression of the distribution lines and distribution lines outside of the accident in order to maintain stable power supply to supply reactive power efficient system is necessary to keep the voltage constant. In this paper, we substantiated in Jeju Hangwon 12 Unit Level 1MVA STATCOM system configuration, control, configure, and test results will be introduced.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.62 no.1
• /
• pp.6-11
• /
• 2013

In this paper, the temperature characteristics of mold transformer for the distribution power system have been analyzed by using computational fluid dynamics(CFD). The model has been modeled by coil, cores, insulating materials and frames about 3MVA grade mold transformer and analyzed the temperature distribution of the structure with a heat fluid. The fluid, which is incompressible ideal gas, is analyzed as a turbulent flow phenomenon on the assumption that it is natural cooling of transformer cooling system. Through this study, by examining the temperature distribution and hot-spot of the structure field of the mold transformer, cooling design and temperature distribution information, which are demanded for designing are estimated.

• Journal of Electrical Engineering and Technology
• /
• v.8 no.1
• /
• pp.156-162
• /
• 2013

This paper measures the hot spot temperatures in a single-phase, 154 kV, 15/20 MVA power transformer filled with natural ester fluid using optical fiber sensors and compares them with those calculated by conventional heat run tests. A total of 14 optical fiber sensors were installed on the high-voltage and low-voltage windings to measure the hot spot temperatures. In addition, three thermocouples were installed in the transformer to measure the temperature distribution during the heat run tests. In the low-voltage winding, the hot spot temperature was $108.4^{\circ}C$, calculated by the conventional heat run test. However, the hot spot temperature measured using the optical fiber sensor was $129.4^{\circ}C$ between turns 2 and 3 on the upper side of the low-voltage winding. Therefore, the hot spot temperature of the low-voltage winding measured using the optical fiber sensor was $21.0^{\circ}C$ higher than that calculated by the conventional heat run test.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.53 no.1
• /
• pp.24-29
• /
• 2004

A new low cost hybrid active filter for thyristor-controlled rectifier load is presented to overcome the high cost problem of the active or the other hybrid active filters. The proposed hybrid active filter which consists of tuned (5th and 7th harmonics) LC passive filters, power factor improvement(PFI) capacitor bank, and active filter compensates power factor as well as harmonic currents. Since most of harmonic currents are filtered by the passive filter and most of reactive power is compensated by the PFI capacitor bank, the power rating of active filter can be minimized, resulting in cost minimization of the proposed hybrid active filter. A 300kVA hybrid active filter system is implemented and tested using 1MVA thyristor rectifier load to verify the operation and performance.

• Proceedings of the KIPE Conference
• /
• 2015.07a
• /
• pp.105-106
• /
• 2015

본 논문은 1MVA까지 대응구성이 가능한 병렬확장구조를 가진 EES용 PCS의 개발에 관해 기술하고 있다. 시장의 다양한 용량요구에 대응하기 위해 Stack과 필터로 구성된 인버터 Stack 판넬을 설계/구현하였으며 이를 이용하여 1MW까지 병렬구성하여 대응이 가능하다. 높은 시스템 전력밀도와 MTBF, 효율을 구현하였으며 이에 대한 설계 및 시스템 제어, 시뮬레이션 결과에 관해 언급한다.