• Journal of Advanced Navigation Technology
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• v.28 no.4
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• pp.459-465
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• 2024

The flight control computer applied to manned/unmanned aircraft is one of the key components directly connected to the control of the aircraft, and is generally designed with a redundant architecture so that essential functions for flight can be maintained even if a failure occurs in a single channel. The operational flight program loaded on these redundant flight control computers should be designed considering a time synchronization between channels, input data selection methods from redundant sensors, and fault detection/isolation methods for channels. In this paper, we propose a redundancy management method applied to triplex compact flight control computers for advanced air vehicle. The proposed redundancy management method includes a synchronization algorithm between triplex channels, an input data voting method from sensors, a bus control right selection method for control command output, and a fault detection/isolation method for channels.

• Proceedings of the KIEE Conference
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• 2009.07a
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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.

• Journal of the Korea Safety Management & Science
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• v.14 no.3
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• pp.101-109
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• 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.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.3
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• pp.441-448
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• 2022

In the distribution system, there are multiple power protection systems such as circuit breakers at substations, and reclosers, minimum circuit ampacities, fault interrupters on distribution lines. They are widely used to prevent partial outages, cascading power failure or blackout so that other healthy systems could maintain the integrity in case of the instant fault or permanent failure on the power lines. However, when a fault happens, it could cause a major black out due to the lack of the protection cooperation between the protection relay of the circuit breaker at a substation and a protection system on the distribution lines. To achieve the power system integrity better, it is required to develop the circuit breaker which can be operational within 1 cycle(16ms). In this study, the high speed circuit breaker which is filled up with eco-friendly gas is developed. This equipment achieved an excellent test results based on IEC 62271-111 standard. It is respected that this equipment would contribute to prevent the wide area blackout by isolating a fault area quicker and faster.

• Proceedings of the KIPE Conference
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• 2013.11a
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• pp.81-82
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• 2013

HVDC 시스템은 초고압 직류 송전 시스템으로써, AC를 DC로 변환하여 장거리 송전에 유리한 시스템이다. 현재 대륙간 송전 및 주파수 변환을 위한 BtB Topology에 많이 응용되고 있다. HVDC 시스템의 장점은 일정 송전거리 이상이 되면, DC가 AC에 비하여 손실율이 적고 유리한 장점이 있다. 해당 HVDC Valve는 전력을 AC-DC-AC로 변환하려면, HVDC Valve(Module)이라고 불리는 전력 변환 장치가 필수적이다. 해당 Valve를 현장에 설치하기 전에 IEC 60700-1 또는 CIGRE 같은 국제 표준 규격에 맞추어 Type Test를 진행 후에 통과 시 현장에 설치되어야 한다. 해당 Type Test는 크게 2가지로 분류되며, 절연 성능을 시험하기위한 Dielectric Test 그리고, 실제 Thyristor Valve의 동작을 가혹 한 조건에서 시험하기위한 Operational Test가 필요하다. 본 논문은 IEC 규격 (IEC 60700-1)에 의거 사이리스터 밸브에 대한 Operational Test 중 단락시험방법과 시험내용을 기술하고, 시험결과로 검증한다.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.6
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• pp.762-770
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• 2013

Korean military is currently using and operating a precision approach and landing system, called RAPCON (ASR/PAR), which is imported from overseas. However, drawbacks of this system are operational and cost problems that come along, e.g. straightness of the radio waves, limited ability of narrow searching, lack of interoperability, and high cost of installation and maintenance. Moreover, as the civilian air traffic control uses a similar system compared to the military, the so called DME/VOR/ILS, disturbance between these two systems triggered the consideration of GNSS as alternative system. In this paper, we conduct a research on trends in the field of precise approach and landing systems based on GNSS, analyze weaknesses of GNSS(jamming, fault) and consider possible solutions. Furthermore, we propose the precise approach and landing system based on GNSS to be used by the Korean military as we found it to be also suitable for military purposes. Finally, we examine the benefits of a domestic development with different focuses(development/cost of mass production/operational advantages and potential for increased performance).

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.2
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• pp.664-677
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• 2014

Wind energy has proven its viability by the emergence of countless wind turbines around the world which greatly contribute to the increased electrical generating capacity of wind farm operators. These infrastructures are usually deployed in not easily accessible areas; therefore, maintenance routines should be based on a well-guided decision so as to minimize cost. To aid operators prior to the maintenance process, a condition monitoring system should be able to accurately reflect the actual state of the wind turbine and its major components in order to execute specific preventive measures using as little resources as possible. In this paper, we propose a fault detection approach which combines cluster analysis and frequent pattern mining to accurately reflect the deteriorating condition of a wind turbine and to indicate the components that need attention. Using SCADA data, we extracted operational status patterns and developed a rule repository for monitoring wind turbine systems. Results show that the proposed scheme is able to detect the deteriorating condition of a wind turbine as well as to explicitly identify faulty components.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.5
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• pp.614-621
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• 1999

In this paper, the analytical appproaches are presented for jointly determining the profit-miximizing configuration of the fault-tolerance real time modular cell manufacturing system. The transient(time-dependent) analysis of Markovian models is firstly applied to modular cell manufacturing system from a performability viewpoint whose modeling advantage lies in its ability to express the performance that truly matters - the user's perception of it - as well as various performance measures compositely in the context of application. The modular cells are modeled with hybrid decomposition method and then availability measures such as instantaneous availability, interval availability, expected cumulative operational time are evaluated as special cases of performability. In addition to this evaluation, sensitivity analysis of the entire manufacturing system as well as each machining cell is performed, from which the time of a major repair policy and the optimal configuration among the alternative configurations of the system can be determined. Secondly, the recovery policies from the machine failures by computing the minimal number of redundant machines and also from the task failures by computing the minimum number of tasks equipped with detection schemes of task failure and reworked upon failure detection, to meet the timing requirements are optimized. Some numerical examples are presented to demonstrate the effectiveness of the work.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.811-814
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• 1998

REcent research about current testing($\textrm{I}_{DDQ}$ testing) has been emphasizing that $\textrm{I}_{DDQ}$ testing in addition to the logical voltage testing is necessary to increase the fault coverage. The $\textrm{I}_{DDQ}$. testing can detect physical faults other than the classical stuck-at type fault, which affect reliability. One of the most critical issues in the $\textrm{I}_{DDQ}$ testing is to insert a built-in current sensor (BICS) that can detect abnormal static currents from the power supply or to the ground. This paper presents a new BICS for internal current testing for large CMOS logic circuits. The proposed BICS uses a single phase clock to minimize the hardware overhead. It detects faulty current flowing and converts it into a corresponding logic voltage level to make converts it into a corresponding logic voltage level to make it possible to use the conventional voltage testing techniqeus. By using current mirroring technique, the proposed BICS can work at very high speed. Because the proposed BICS almost does not affects normal operation of CUT(circuit under test), it can be used to a very large circuit without circuit partitioning. By altenating the operational modes, a circuit can be $\textrm{I}_{DDQ}$-tested as a kind of self-testing fashion by using the proposed BICS.

• Journal of Environmental Science International
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• v.25 no.4
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• pp.525-534
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• 2016

The biological wastewater treatment plant, which uses microbial community to remove organic matter and nutrients in wastewater, is known as its nonlinear behavior and uncertainty to operate. Therefore, operation of the biological wastewater treatment process much depends on observation and knowledge of operators. The manual inspection of human operators is essential to manage the process properly, however, it is impossible to detect a fault promptly so that the process can be exposed to improper condition not securing safe effluent quality. Among various process faults, equipment malfunction is critical to maintain normal operational state. To detect equipment faults automatically, the dynamic time warping was tested using on-line oxidation-reduction potential (ORP) and dissolved oxygen (DO) profiles in a sequencing batch reactor (SBR), which is a type of wastewater treatment process. After one cycle profiles of ORP and DO were measured and stored, they were warped to the template profiles which were prepared already and the distance result, accumulated distance (D) values were calculated. If the D values were increased significantly, some kinds of faults could be detected and an alarm could be sent to the operator. By this way, it seems to be possible to make an early detecting of process faults.