• 전기학회논문지
• /
• 제62권2호
• /
• pp.278-283
• /
• 2013

With the increasing power demands, size of the fault current in electrical grids is steadily increasing, and it exceeds the breaking capacity of circuit breakers. To effectively cope with these problems, a high-speed interrupter was suggested. The high-speed interrupter provides fault current with a bypass to a fault current limiter in case of accidents and consequently, fault current can be restricted. In this study, behavioral characteristics of high-speed interrupter were analyzed by accident types occurred in a distribution system. When accidents occurred, a and b contact of the high-speed interrupter were turned-off and then, turned-on. Accordingly, fault current flowed to the circuit connected to a current limiting element, and the fault current limiter restricted fault current to within a half-cycle. Nevertheless, the behavior of the high-speed interrupter was slowed down by a switching surge. As a result, fault current was confirmed to be restricted not to within the anticipated half-cycle, but to after a half-cycle. Moreover, the behavioral characteristics of the high-speed interrupter changed not only by accident types, but by behaviors of R, S, and T phases. This was due to the errors in stroke lengths of the high-speed interrupters, which resulted in a slight time discrepancy among three interrupters. In addition, the switching behaviors of the b and a contact were confirmed not to have coincided due to the switching surge; b contact behaved first and a contact followed. because of this, accuracy of stroke length and switching surges through the solenoid suction increases may be necessary to resolve.

• 전기저널
• /
• 4호통권100호
• /
• pp.48-51
• /
• 1985

• 한국철도학회논문집
• /
• 제9권4호
• /
• pp.394-400
• /
• 2006

Since Seoulmetro built the first line of electric railway at seoul 1974, the passengers of railway have been increased rapidly, and electric railway requires more electric power for the greater capacity of transport. It is important that we prevent the accidents related with the subway, because all systems of subway are constructed in artificial underground structure. Since the previous versions of the earth system were built to meet the old standards of the electric facility for the lightning, some accidents related with the DC earth fault are causing secondary damages to the electric equipments. So, the old grounding system must be improved, and new standards of grounding system are required. We compare the grounding systems of the domestic railway corporations and the accidents that are related with the grounding systems. And we give ideas to improve the grounding systems and present standards which are suitable to electric railway.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년 학술대회 논문집 정보 및 제어부문
• /
• pp.603-605
• /
• 2006

To reduce inference of any power delivery failures in underground power cable, power system operators are trying to find effective way of finding fault location as soon as possible. But it is very difficult to find fault location exactly for underground power cable. We are developing fault location system for underground power cable which can detect its fault location exactly. This new system monitors current and voltage of underground power cable by using low voltage and current sensors and if there are any accidents, it records its transient signal. Fault location is calculated by analyzing recorded signal. To develop fault location system for power cable, we needed fault simulation system and we installed it physically and tested. In this rapers, we describe on describe of fault location system for underground power cable.

• Agricultural and Biosystems Engineering
• /
• 제5권2호
• /
• pp.35-39
• /
• 2004

A review of accidents involving farm machinery, which occurred in Korea during 2002, shows that $90.7\%$ of farm-work accidents and $9.3\%$ of traffic accidents were linked to agricultural machinery. The frequency of accidents per annum amounts to 72.2 out of 10,000 vehicles, $94.4\%$ of which relates to tillers and tractors. An analysis of the causes of the accidents revealed that $49.1\%$ of farm-work accidents were due to the tiller driver's fault or error. In the case of traffic accidents, $83\%$ of farm machinery mishaps were found to be due to violation of traffic regulations while $60.4\%$ of the farm machinery damage resulted from faulty driving or lack of safe driving practices. The average casualty count of farm machinery-related accidents is 1.39 persons per case, which consist of 0.07 deaths, 0.74 serious injuries, and 0.58 slight injuries.

• 한국산업융합학회 논문집
• /
• 제26권2_2호
• /
• pp.315-325
• /
• 2023

Recently, various dynamic risk analysis methods have been suggested for estimating the risk index by predicting the possibility of accidents and damage. It is necessary to maintain and support the safety system for responding to accidents by continuously updating the probability of accidents and the results of accidents, which are quantitative standards of ship risk. In this study, when a LNG leakage that may occur in the LN G Fuel Gas Supply System (FGSS) room during LN G bunkering operation, a reliability physical model was prepared by the change in monitoring data as physical parameters to estimate the accident probability. The scenario in which LNG leakage occur were configured with FT (Fault Tree), and the coefficient of the covariate model and Weibull distribution was estimated based on the monitoring data. The possibility of an LNG leakage, which is the top event of FT, was confirmed by changes in time and monitoring data. A method for estimating the LNG leakage based on the reliability physical analysis is proposed, which supports fast decision-making by identifying the potential LNG leakage at the accident.

• 사물인터넷융복합논문지
• /
• 제8권2호
• /
• pp.7-12
• /
• 2022

케이블 사고의 주요 원인은 케이블 자체 또는 내·외적으로 전기적, 기계적, 화학적, 열적, 수분침입 등으로 인한 열화의 가속화로 절연성능 감소되고 절연파괴가 발생하여 케이블 사고를 유발하게 된다. 케이블 사고는 과전압, 과전류의 영향으로 절연이 불량한 부분에서 발생할 수 있으므로, 변압기, 차단기의 이상여부, 상간불평형에 의한 지락사고 등을 종합적으로 분석할 필요성이 있다. 케이블의 절연파괴에 의한 지락사고는 케이블 자체의 결함, 케이블 시공불량 뿐만 아니라 운영상의 영향, 전기설비(개폐기, 차단기 등)의 운전 시 아크 등에 의해 발생할 수 있어 사고시점을 전후로 운전 데이터 및 사고 이력에 대한 분석이 필요하다. 이 연구에서는 국내의 한 공장에서 발생한 케이블 사고의 분석을 통하여 케이블 사고의 원인을 고찰하고자 한다.

• 한국안전학회지
• /
• 제25권3호
• /
• pp.1-6
• /
• 2010

Ball bearings are one of main components that support the rotational shaft in high speed rotary machinery. So, it is very important to detect the incipient faults and fault growth of bearing since the damage and failure of bearing can cause a critical failures or accidents of machinery system. In the past, many researchers mainly performed to detect the bearing fault using traditional method such as wavelet, statistics, envelope etc in vibration signals. But study on the detection technique for bearing fault growth has a little been performed. In this paper, we verified the possibility for monitoring of fault growth and detection of fault size in bearing outer-race by using the envelope powerspectrum and probabilistic density function from measured vibration signals.

• 한국전기전자재료학회논문지
• /
• 제26권2호
• /
• pp.134-139
• /
• 2013

When the accident occurred in power distribution system, it needs to control efficiently the fault current according to the fault angle and location. The flux-lock type superconducting fault current limiters (SFCL) can quickly limit when the short circuit accidents occurred and be made the resistance after the fault current. The flux-lock type SFCL has a single triggering element, detects and limits the fault current at the same time regardless of the size of the fault current. However, it has a disadvantage that broken the superconductor element. If the flux-lock type SFCL has separated structure of the triggering element and the limiting element, when large fault current occurs, it can reduce the burden of power and control fault current to adjust impedance. In this paper, this system is composed by triggering element and limiting element to analyze operation of limiting current. When the fault current occurs, we analyzed the limiting and operating current characteristics of the two triggering current level, and the compensation characteristics of bus-voltage sag according to the fault angle and location.

• 대한안전경영과학회지
• /
• 제14권3호
• /
• pp.101-109
• /
• 2012

It is commonly recognized that railway is one of the representative transportation and it offers public service based on strategies for being rapid, automation, safety. Since the opening of high speed railway, 3-hundred-million people have used it and acknowledged its efficiency. However, derailed accident at Kwangmyeong station in February, 2011, frequent malfunction of KTX-Sancheon, and accidents by engineer's careless fault damaged on credibility of safety, Especially, spreaded accidents through social networking service by cell phones amplified anxiety of public, being criticized by the press. This study analyzed statistics of past accident and cases of passing-by accident, and surveyed 152 KTX captain engineers about their recognition of the accident by careless fault and experiences of possibility of occurrence for preventing engineer's careless fault and restoring trust According to the analysis, engineers worry about responsibility and disadvantages related to the accidents for the most, and they are nervous about malfunction for the second most. This study presents prevention methods regarding the result. First, it is required to improve mental stability and concentration on their work, secondly, advanced ability to cope with malfunction or error through repetitive education and training are required to increase confidence, and for the last, improvement of operational supporting system such as ATP, GPS to prevent errors by human factors. Improvement of the system is expected to lead engineers to prevent careless fault and regain the reputation of railway.