• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.320-321
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• 2011

As the scale of industries expands, the facilities of the industrial customer become larger and more complex. When a fault occurs in the system, the circuit breakers play an important role in minimizing causalitites by quickly tripping the faulted line. Since the capacity of the receiving-end has increased in size, an examination is needed to be performed between the industrial customers and the conventional circuit breakers. The transient recovery voltage, which is the initial transient characteristics of the voltage across the breaker when tripped, is an important factor in determining the circuit breaker's performance. In this paper, a TRV analysis on the large-scale industrial customer is being performed utilizing PSCAD/EMTDC.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.527-528
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• 2011

송전선로에서 발생하는 고장의 대부분은 낙뢰에 의한 상-대지간 섬락이나 외물접촉, 혹은 애자련의 오손에 의한 절연파괴 등이 대부분이다. 그리고 대분의 고장은 큰 고장전류를 흘리게 되어 보호계전기가 동작하여 고장구간을 신속하게 분리하게 된다. 그러나, 본 고장사례는 매우 희귀한 고장 사례로서, 고저항 아크 지락에 의하여 발생하는 과도회복전압(TRV: Transient Recovery Voltage)이 애자련에 섬락을 일으킨 경우이다. 본 연구에서는 EMTP (Electro-Magnetic Transient Program)를 이용하여 고저항 지락시 아크의 단속에 의하여 과도회복전압이 발생할 가능성이 있음을 보였으며, 고장기록장치(Fault Recorder)에 나타난 파형 기록과의 유사성을 확인하였다. 또한, 고저항 지락에 의하여 직류분이 초기에 방전됨으로써 고장전류 파형에 직류분 오프셋이 나타나지 않게 됨을 밝혔다.

• 한국초전도ㆍ저온공학회논문지
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• 제7권2호
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• pp.35-38
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• 2005

One of the most serious problems in KEPCO system operation is higher fault current than the SCC(Short Circuit Capacity) of circuit breaker. There are many alternatives to reduce the increased fault current such as isolations of bus ties, enhancement of SCC of circuit breaker, applications of HVDC-BTB(Back to Back) and FCL(fault current limiter). But, these alternatives have some drawbacks in viewpoints of system stability and cost. As the superconductivity technology has been developed, the resistance type HTS-FCL(High Temperature Superconductor Fault Current Limiter) can be one of the most attractive alternatives to solve the fault current problem. To evaluate the accurate transient performance of resistance type HTS-FCL, it is needed that the dynamic simulation model considering transient characteristics during quenching and recovery state. Under this background, this paper presents the EMTDC model for resistance type HTS-FCL considering the nonlinear characteristic of final resistance value when quenching and recovery phenomena by fault current injection and clearing occurs.

• 한국기계가공학회지
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• 제17권4호
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• pp.150-159
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• 2018

The present research deals with a finite element analysis and fatigue evaluation of a steam separator of a high-pressure evaporator for the Heat Recovery Steam Generator (HRSG). The fatigue during the expected life of the HRSG was evaluated according to the ASME Boiler and Pressure Vessel Code Section VIII Division 2 (ASME Code). First, based on the eight transient operating conditions prescribed for the HRSG, temperature distribution of the steam separator was analyzed by a transient thermal analysis. Results of the thermal analysis were used as a thermal load for the structural analysis and used to determine the mean cycle temperature. Next, a structural analysis for the transient conditions was carried out with the thermal load, steam pressure, and nozzle load. The maximum stress location was found to be the riser nozzle bore, and hence fatigue was evaluated at that location, as per ASME Code. As a result, the cumulative usage factor was calculated as 0.00072 (much less than 1). In conclusion, the steam separator was found to be safe from fatigue failure during the expected life.

• 전기학회논문지
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• 제67권9호
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• pp.1159-1164
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• 2018

Vacuum circuit breakers(VCB) are widely used for current interruption of high-voltage inductive loads such as induction motors. This VCB can be chopped off before the current zero due to its high arc-extinguishing capability. One of the outstanding features of VCB is that it can cut off high frequency re-ignition current more than other circuit breakers. If the transient recovery voltage generated in the arc extinguishing is higher than the dielectric strength of the circuit breaker, a re-ignition phenomenon occurs. The surge voltage of the re-ignition is very high in magnitude and the steepness of the waveform is so severe that it can act as a high electrical stress on the winding. If the high frequency current of one phase affects the other two phases when the re-ignition occurs, it may cause a high surge voltage due to the virtual current chopping. If the magnitude of the voltage allowed in the motor winding is high or the waveform level is too severe, it may lead to insulation breakdown. Therefore, it is necessary to reduce the voltage to within a certain range. In this study, we briefly explain the various phenomena at the time of interruption, analyzed the magnitude of the dielectric strength and the transient recovery voltage at the simultaneous three-phase interruption that can give the greatest influence to the inductive load, proposed a method to reduce the impact.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.222-223
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• 2011

본 논문은 인천지역 345kV 계통고장전류 저감을 위한 한류리액터 설치에 따른 362kV 50kA 차단기의 과도회복 전압 정격 초과 여부를 EMTP을 활용하여 검토하였다. 과도회복전압(TRV : Transient Recovery Voltage)은 크게 두가지, 최대전압(Vp)과 초기과도회복전압상승율(RRRV:Rate of Rise of Recovery Voltage)로 구분하며, 리액턴스 성분이 증가하며 RRRV가 상승하여 차단기가 고장전류을 차단시 절연파괴(열파괴)로 이어질 수 있다. IEC 62271-100 규정에는 RRRV를 정격차단전류의 100% 크기(T100%) 차단시 2kV/us이내로 규정하고 있으며 이 보다 작은 전류의 T90, T75 차단시의 규정치는 계산식에 의해 정해진다.

• 설비공학논문집
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• 제12권12호
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• pp.1057-1065
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• 2000

A sizing of sensible and latent energy recovery system with condensing heat exchanger is important to the design of a thermally controlled facilities. The transient system simulation program TRNSYS 14.2/IISiBat has been used to evaluate the energy consumptions of a thermally controlled facilities which consist of boiler, chiller and condensing heat exchanger, The boiler and chiller are selected based on the annual peak loads and controlled to maintain the setting temperature of $14~17^{\circ}C$. Simulation shows that the amount of sensible and latent energy recovered by heat exchanger is almost 20% of total heating load.

• Journal of Yeungnam Medical Science
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• 제40권2호
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• pp.212-217
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• 2023

We report a case of transient osteoporosis of the hip with a femoral neck fracture found during follow-up. A 53-year-old man presented with left hip pain without trauma. The pain did not improve after 2 weeks and he was brought to our hospital by ambulance. Magnetic resonance imaging (MRI) of the left hip joint showed diffuse edema in the bone marrow, which was identified by low signal intensity on T1-weighted images, high signal intensity on T2-weighted images, and increased signal intensity on short tau inversion recovery. This edema extended from the femoral head and neck to the intertrochanteric area. He was diagnosed with transient osteoporosis of the left hip. Rest gradually improved his pain; however, 3 weeks later, his left hip pain worsened without trauma. X-ray, computed tomography, and MRI results of the hip joint demonstrated a left femoral neck fracture, and osteosynthesis was performed. Differential diagnoses included avascular necrosis of the femoral head, infection, complex regional pain syndrome, rheumatoid arthritis, leukemia, and other cancers. Transient osteoporosis of the hip generally has a good prognosis with spontaneous remission within a few months to 1 year. However, a sufficient length of follow-up from condition onset to full recovery is necessary to avoid all probable complications such as fractures.

• Journal of Chest Surgery
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• 제27권7호
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• pp.563-570
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• 1994

Effect of ischemic preconditioning on left ventricular function after cardiac arrest in isolated rat heart.Ischemic preconditioning reduces infarct size caused by sustained ischemia. However, the effects of preconditioning on post ischemic cardiac function are not well-known. The objective of the present study was to determine whether preconditioning would improve the recovery of left ventricular functions after cardiac arrest in isolated rat heart model.Isolated rat hearts were allowed to equilibrate for 20 minutes and were then subjected to either 5 minutes of global, normothermic transient ischemia [Group 2 and 4] or not [Group 3]. A stabilization period of perfusion lasting 5 minutes after the termination of transient ischemia was followed by a standard global, normothermic 20 minute-ischemia and 35-minute reperfusion challenge [Group 3 and 4]. These following results were odtained.1. The recovery of left ventricular developed pressures showed no significant differences between Group 3 and Group 4 at 50 [P>0.3] and 85 minute [P>0.2].2. Heart rates showed no significant differences throughout all the course of experiment and between groups [P>0.5].3. The recovery of left ventricular maximum dP/dt showed no significant differences between Group 3 and Group 4 at 50 [P>0.1] and 85 minute [P>0.2].4. The recovery of pressure-rate products showed no significant differences between Group3 and Group 4 at 50 [P>0.5] and 85 minute [P>0.1].These results suggest that ischemic preconditioning does not provide significant benefit for the postischemic left ventricular functions in isolated rat hearts.

• ETRI Journal
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• 제3권4호
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• pp.93-97
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• 1981