Analysis of Urban Rail DC Short Circuit Fault and Vehicle-Network Protection Coordination Based on Transient Characteristics

Wang Tingting,Sun Guobin,Cao Hu,Zhang Zhexu,Chen Jinheng 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.3

During the operation of urban rail transit system, if the vehicle traction system has short-circuit fault, the vehicle protection device will act and cut off the short-circuit current. Under some extreme short circuit conditions, the protection device of power supply system will also act, and the whole power supply section will be powered off. This is because the action setting values of vehicle protection device and power supply system protection device are designed respectively, and their matching and reliability need to be analyzed. Based on this, this paper first models the urban rail transit power supply system and vehicle traction system, then compares the calculated mathematical model with the simulation model to verify the accuracy of the simulation model. Finally, the short-circuit current waveforms under different short-circuit conditions are simulated, and the action sequence and protection range of protection devices are analyzed according to the simulation results. The research results are of great significance to the characteristic analysis of short-circuit fault, the selection of vehicle protection devices and the setting of protection parameters of power supply system.

단락흔의 형성 메커니즘 분석

김선재,최경원,공영수,문병선,조영진,임규영 한국화재소방학회 2023 한국화재소방학회논문지 Vol.37 No.1

In this study , short -circuit processes were analyzed via simulations and experiments by applying a principle that caninterpret the short-circuit marks, which are the most basic inspection criteria in fire-scene investigation. According toFleming's left-hand rule, a Lorentz force is generated when current and magnetic fields are applied. Railgun, one of thetypical applications, utilizes the same basic principle for generating trajectories. Using the same concept, it was interpretedthat the molten copper balls generated during a short-circuit process scatter in the load direction similar to a ballistic launch. The simulation and experimental results also confirmed that the copper balls were scattered in the load direction owing tothe Lorentz force. Although it is impossible to examine the source and load during a fire-scene investigation process, thestudy findings will aid in predicting the load by observing the portion where the copper bulbs are relatively frequent. Thus,based on an estimation of the cause of fire, it will be possible to infer reliable results through fire-scene investigation. 본 논문에서는 화재 현장 조사에서 가장 기본으로 검사하는 단락흔을 중심으로 단락 과정을 해석할 수 있는 법칙과 원리를 적용하여 시뮬레이션과 실험으로 분석하였다. 플레밍의 왼손 법칙에서 전류와 자기장이 작용할 경우, 로렌츠의 힘이 발생하게 된다. 이를 응용한 것이 레일 건으로써, 탄도가 발생되는 원리를 적용하였다. 이를 통해 탄도발사와 동일한 형태로, 단락 과정에서 발생되는 용융된 구리 망울이 부하측 방향으로 비산되는 것으로 해석하였다. 시뮬레이션 및 실험 결과에서도 로렌츠의 힘에 의해 구리 망울이 부하측 방향으로 비산되는 것을 확인하였다. 화재조사 과정에서 전원측과 부하측에 관한 검토가 불가능 하더라도, 연구를 통해 얻어진 결론을 적용하여 구리 망울이상대적으로 많이 형성된 부분을 부하측으로 예측할 수 있을 것이다. 이를 통해 발화원인을 추정할 수 있는 근거를마련할 수 있기 때문에 화재 조사의 신뢰성 있는 결과를 추론할 수 있을 것이다.

A multi-domain diagnostic framework for CRD fuel injection systems under water-in-diesel emulsion fuel conditions

Ugochukwu Ejike Akpudo,허장욱 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.2

From a global perspective, combustion emission from diesel engines has negatively impacted our environment as observed from the increasing global warming and other environmental pollution. In the quest for mitigating these consequences, diesel emulsification offers a cost-efficient and eco-friendly alternative but the corrosion, wear, and power loss effects on the engine pose a strong concern for global adoption. In the right proportions and mixing conditions, water-in-diesel (WiD) emulsion fuels can offer long-term solutions to reducing the number of combustion residuals-nitrogen oxides (Nox), particulate matter (PM), carbon oxides (COx) and with appropriate condition monitoring techniques in place, engine efficiency can be maintained. Interestingly, the rail pressure sensor (RPS) of a common rail (CR) diesel engine reflects the underlying transient and spectral dynamics in the CR system at varying engine speeds and WiD emulsion compositions and when properly harnessed can be used for condition monitoring/diagnosis. This paper proposes a machine learning (ML)-based diagnostic framework for CR diesel engines that functions on the use of continuous wavelet coefficients (CWCs) and short-time Fourier transform (STFT) outputs from the first-order derivatives of the RPS signals. Following an investigative experiment on a KIA Sorento 2004 four-cylinder line engine at various WiD emulsion compositions at various engine RPMs, diagnostic results show that exploring a multi-domain approach of feature extraction offers more discriminative diagnostic parameters thereby providing a wider perspective to condition monitoring and with the robustness of ML classifiers, accurate diagnostics can be achieved. A comparative assessment using global and local evaluation tools reveal the diagnostic performances of the ML algorithms and the trustworthiness of the most accurate model- random forest (RF) with a test accuracy of 96.65 % following a grid search against the other widely-used ML-based diagnostic tools.

INVESTIGATION OF SHORT INJECTIONS USING STANDARD AND MODIFIED COMMON RAIL INJECTORS

Ficarella, A.,Giuffrida, A.,Lanzafame, R. The Korean Society of Automotive Engineers 2007 International journal of automotive technology Vol.8 No.2

The control of the fuel to be introduced into the combustion chamber under idling and low-load conditions is known to be a problem in Diesel engines, owing to the relatively small fraction of the full-load fuel needed under light loads. Thus, particular attention should be paid to the behavior of the injector with reference to short injection events. This work presents the results of an experimental campaign carried out with two different types of common rail injectors, a standard injector and a modified one. The latter, coming from a simple modification realized in a standard injector, exhibits linear behavior between injected fuel and solenoid energizing time in the field of short injections. A direct comparison of the two injection behaviors suggests a possible way to better control short or pilot injections.

교류전기철도 레일전위 저감을 위한 통합접지시스템의 횡단접속선 설치기준에 관한 연구

오승현,창상훈 한국산학기술학회 2023 한국산학기술학회논문지 Vol.24 No.11

The aim of this study was to analyze the standards for installing cross-connection lines in the integrated grounding system of AC electric railways in South Korea and to suggest alternatives. Unlike general electricity supply devices, in an electric railway, several kiloamps of operating current flow through the tracks, so direct contact with the human body should be avoided. When a line-to-ground fault or a short circuit occurs, a fault current flows to the track or the ground, causing a potential difference inside and around the electrical equipment, which is a risk for human safety or insulation of the equipment. To prepare for these risks, the AC electric railway uses an integrated grounding method. The amount of rail potential change according to the LTI (Liaison Transversale Integrate) interval in the integrated grounding method shall be analyzed and verified as conforming to KSC IEC62128-1 standard.

The Study and Application of Simple Automatic Welding Device for Small Block

Chul-Sung Park(박철성),Jeong-Soo Lee(이정수) 대한용접·접합학회 2023 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2023 No.10

충돌형태에 따른 자동차 프레임 변형시 변형분석 및 차체수리에 관한 실험적 연구

김태훈,권영신 한국산업안전학회 2002 한국안전학회지 Vol.17 No.2

In present study, the deformation analysis and automotive body repair were analyzed with respect to collision types by case studies. As a result, lots of data for the automobile frame deformation caused by collision were collected and analyzed according to collision types. It was shown from the result that the frame deformation patterns were able to be roughly grouped by collision positions of vehicles. Repair plans of deformed frames could be carried on the measured data. It was shown that the deformed vehicle frames were sufficienty repaired to be normal in driving characteristics from the performance test of repaired vehicles.

산업연관분석에 의한 운송부문별 국민경제적 파급효과의 상호비교 분석

이태우 ( Tae Woo Lee ),장영태 ( Young Tae Chang ),신성호 ( Sung Ho Shin ) 韓國海運物流學會 2006 해운물류연구 Vol.51 No.-