• 한국정보기술학회 영문논문지
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• 제10권2호
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• pp.1-13
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• 2020

This paper presents an emergency brushless synchronous generator having rotating exciter status monitoring and protection functions. For monitoring the rotating exciter status, a wireless rotor status detector and a digital AVR(Automatic Voltage Regulator), which has a wireless communication capability, are proposed. The proposed rotor status detector detects temperatures of exciter armature and main field windings and input voltage and current of the main field. Therefore, it is possible to protect the generator from the over-temperature of windings and detect the exciter bridge diode fault. Furthermore, the proposed digital AVR has rotor status monitoring and protection function, and remote generator tuning, wireless group parallel operation function. So the operator can efficiently operate the generator using a smartphone from a remote area.

• 한국안전학회지
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• 제30권1호
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• pp.28-33
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• 2015

Three phase heaters in 7 buildings of 2 sites were examined for precise diagnosis. The sample size was 626. Precise examinations of current and the heater wiring status revealed contact failures and arcs in equipments that had CUF larger than 10%. Contact failures and arcs may cause electrical fire. Therefore, the correlation between the CUF and the imperfections in heater equipment and its wiring was analyzed for three phase heaters. In addition, the protection devices used for detection of heater imperfections were found to be unsuitable for the purpose. Current status of the protection devices was analyzed, and suggestions for improvements were made for new standards of the protection device selection.

• International Journal of Contents
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• 제1권1호
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• pp.21-28
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• 2005

This paper is about the hardness of Leader Election problem in asynchronous distributed systems in which processes can crash but links are reliable. Recently, the hardness of a problem encountered in the systems is defined with respect to the difficulty to solve it despite failures: a problem is easy if it can be solved in presence of failures, otherwise it is hard [9]. It is shown in [9] that problems are classified as three classes: F (fault-tolerant), NF (Not fault-tolerant) and NFC (NF-completeness). Among those, the class NFC is the hardest problem to solve. It is also shown in [9] that the construction of Perfect Failure Detector (problem P) belongs to NFC. In this paper, we show that Leader Election is also one of NFC problems by using a general reduction protocol that reduces the Leader Election Problem to P. We use a formulation of the Leader Election problem as a prototype to show that it belongs to NFC.

• Journal of Power Electronics
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• 제8권2호
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• pp.181-191
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• 2008

The task performed by induction motors grows increasingly complex in modern industry and hence improvements are sought in the field of fault diagnosis. It is essential to diagnose faults at their very inception, as unscheduled machine down time can upset critical dead lines and cause heavy financial losses. Artificial intelligence (AI) techniques have proved their ability in detection of incipient faults in electrical machines. This paper presents an application of AI techniques for the detection of inter-turn insulation and bearing wear faults in single-phase induction motors. The single-phase induction motor is considered a proto type model to create inter-turn insulation and bearing wear faults. The experimental data for motor intake current, rotor speed, stator winding temperature, bearing temperature and noise of the motor under running condition was generated in the laboratory. The different types of fault detectors were developed based upon three different AI techniques. The input parameters for these detectors were varied from two to five sequentially. The comparisons were made and the best fault detector was determined.

• 전력전자학회논문지
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• 제27권2호
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• pp.100-105
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• 2022

This paper applies the arc detection algorithm to prevent the false detection in photo voltaic series arc detection circuit, which is required not only to detect the series arc quickly, but also not falsely detect the arc for the non-arc noise. For this purpose, this study proposes a rapid and preventive false detection method of single peak noise and short noise signals. First, to prevent false detection by single peak noise, Discrete wavelet transform (DWT)-based characteristic parameters are applied to determine the shape and the amplitude of the noise. In addition, arc fault detection within a few milliseconds is performed with the DWT iterative algorithm to quickly prevent false detection for short noise signals, considering the continuity of serial arc noise. Thus, the method operates not only to detect series arc, but also to avoid false arc detection for peak and short noises. The proposed algorithm is applied to real-time serial arc detection circuit based on the TMS320F28335 DSP. The serial arc detection and peak noise filtering performances are verified in the built simulated arc test facility. Furthermore, the filtering performance of short noise generated through DC switch operation is confirmed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.294_295
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• 2009

Superconducting fault current limiter (SFCL) is an power device of a novel concept. While SFCLs generate no ohmic loss during the operation carrying normal currents, they can limit fault currents very fast making large impedance by their quench characteristics. In 2006, KEPCO has developed a distribution class hybrid type SFCL by a collaborative research project with LS industrial systems. The SFCL has merits in practical and economical points of view. In the SFCL, the superconductor just plays a role of a fault detector and the current limiting is completed by the other current limiting element made of normal metals throu호 the line commutation. As a result, the required amounts of superconductors can be reduced considerably. Consequently, the hybrid SFCL can be fabricated with small size and cost, maintaining perfect current limiting performance. Currently, KEPCO is carrying out a research project at Gochang power test center for the purpose of the verification test of the 22.9 kV/ 630 A class SFCL for the practical application in real grid. Through the project, a long term operational test and fault current test will be done. In this paper, the back ground of development and installation of the SFCL will be explained and the operation plan of the SFCL for the verification test is also introduced.

• 한국화재소방학회논문지
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• 제31권6호
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• pp.67-73
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• 2017

항공기 정비 격납고는 고가의 항공기를 보관하거나 정비, 점검등을 하는 건축물로 화재발생 빈도는 낮지만 화재발생 시 인적, 물적 피해가 매우 클 수 있다. 따라서 본 연구에서는 Fault tree를 이용하여 현재 운용중인 항공기 정비 격납고 소화시스템의 화재 안전성에 대한 정성적 분석을 시행하고, 도출된 기본사상에 대한 고장률 자료를 활용하여 정량적 분석을 실시한 후 정상사상의 발생 확률에 대한 Minimal cut set의 중요도를 분석하였다. Minimal cut set에 의한 정성적 분석결과 항공기 격납고 포헤드 소화시스템의 화재제어 실패로 대형화재로 확대될 수 있는 사고경로는 14개라는 것을 알 수 있었다. 또한 정량적인 분석 결과 대형화재로 확대될 확률은 $2.08{\times}E-05/day$이며, Minimal cut set의 중요도 분석 결과 화재 발생 시 4개의 Minimal cut set 즉, 구역별 화재 감지기 및 포헤드 동작과 항공기 날개 및 Fire plume에 의한 소화약제 차단이 동일하게 24.95%로 대형화재로 확대될 가능성의 대부분을 차지하였으며, 항공기 정비 격납고의 포헤드 소화시스템은 항공기 날개 하부화재에 대한 적응성이 없어 개선이 필요한 것으로 Fault tree를 이용하여 처음 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 C
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• pp.1694-1697
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• 2002

KEPCO is planing to adopt a preventive diagnostic system to obtain the reliability of transformer and GIS in 765kV substation. KEPRI has developed the preventive diagnostic system for 765kV substation since 1997. We used various sensors and fault detecting devices such as a dissolved gas analyzer in oil, a ultrasonic detector and LA leakage current detector, etc., and carried out adaptation tests at the both a laboratory and a site. We developed a data acquisition system, a communication control unit and a server system as well. Furthermore, monitoring program and diagnostic expert system were also developed. This paper describes the preventive diagnostic system for 765kV Sin-Ga-Pyong and Sin-Tae-Baek substations which will be operated from 2004.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 C
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• pp.1612-1614
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• 2003

80pF capacitive couplers were connected to six 6.6kV motor model coil terminals. The voltage applied to the coils were 3.81kv, 4.76 kV and 6.6kV, respectively. These stator coils have various types of artificial insulation defects such as large voids, semi-conductive coating damage and strand insulation fault. Digital PD detector(PDD) and turbine generator analyzer(TGA) were used to measure PD activity. TGA summarizes each plot with two quantities such as the normalized quantity number(NQN) and the peak PD magnitude(Qm). The PD levels in PD were measured with a conventional digital PD detector. Most of the defect mechanism of large motor stator winding can be associated with PD patterns such as internal and slot discharges. PD patterns coincide with PDD and TGA. These instruments have an input bandwidth of 40-400kHz and 0.1-350MHz. Surge testing detects faults in inter-turn winding of high voltage motor model coils.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1948_1949
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• 2009

All the power generating station require dc auxiliary power systems to operate those dc components that must be available if a loss of ac power occur. Some examples of such components are auxiliary motors, circuit breakers, relays and solenoids. The dc source may be one common battery for both power and control or two separate batteries; one for power and another for control. Typically, a dc auxiliary power system is designed as an ungrounded system, instead of grounded system, so that a low-resistance ground fault on one of its two polarities will not affect the operation of the system, thus increasing system reliability and continuity of service. A ground detector should provide a high polarity-to-ground resistance so that a single ground fault occurring on the system will not affect the operation of that system. Sensitive relays have been known to energize momentarily while the cable and capacitive charge to ground shifts[1]. A power station had experienced this kind of incident and performed root cause analysis based on PC based simulation program known as PSpice. This simulation showed adapted relays on the system energize momentarily and design criteria on this relay should be corrected.