• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.432-434
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• 2006

The additional matters appear to be considered in several aspects for building up power-quality measuring system of transmission system(high voltage system) compared to distribution system(middle or low voltage system). Like in distribution system, input signals are also received from PT and CT source of voltage and current respectively in transmission system and applied in accordance with a certain rate. In this case, very big error rate can be occurred according to the specification of the measuring system as the applying rate is bigger than in distribution system beyond comparison. In addition, when the abnormal signal occurred such as sag/swell, interruption, transient etc., power quality of other sires linked to the system also should be checked to find the accurate cause of the abnormal power-quality signals from the corresponding. site. Accordingly, the accurate diagnosis on the condition of power quality for the system depends on the way how the synchronization system is brought along for each site. This paper will suggest the solution for the most effective system building focused on how to solve the problem of the error rate and synchronization described in the above when building up the measuring system of power quality for transmission system.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.107-109
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• 2006

The additional matters appear to be considered in several aspects for building up power-quality measuring system of transmission system(high voltage system) compared to distribution system(middle or low voltage system). Like in distribution system, input signals are also received from PT and CT source of voltage and current respectively in transmission system and applied in accordance with a certain rate. In this case, very big error rate can be occurred according to the specification of the measuring system as the applying rate is bigger than in distribution system beyond comparison. In addition, when the abnormal signal occurred such as sag/swell, interruption, transient etc., power quality of other sites linked to the system also should be checked to find the accurate cause of the abnormal power-quality signals from the corresponding site. Accordingly, the accurate diagnosis on the condition of Power quality for the system depends on the way how the synchronization system is brought along for each site. This paper will suggest the solution for the most effective system building focused on how to solve the problem of the error rate and synchronization described in the above when building up the measuring system of power quality for transmission system.

• Journal of the Korean Society of Safety
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• v.37 no.4
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• pp.28-35
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• 2022

This study is aimed to develop a safety diagnosis system for fire pumps that detects normal and abnormal signals for the stable operation of the system. Hence, the following activities were carried out: first, a threshold value was identified for the normal operation and six abnormal operations (adherence of impeller, absence of water source, separation of pump and motor, run-stop operation, air inflow into the casing, and reverse-phase loss of the power line) reflecting changes in the current, flow and pressure of fire pumps; secondly, based on the identified signals, an algorithm capable of detecting three abnormal signals was developed and in terms of hardware, a current, pressure and flow sensor suitable for the analogue input values of NI-6009 was designed and installed. This combination of the hardware and software is applicable as a diagnosis system to ensure the stable operation of fire pumps.

• 제어로봇시스템학회:학술대회논문집
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• 1995.10a
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• pp.142-145
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• 1995

It is important from prevention of the malfunction and an important accident by the failuer, to detect a failuer in revolution devices. The acoustic emission(AE) method is expected as means that defects an abnormal phenomenon of revolution devices earlily and utilized. Although a research example by the AE method is reported regarding a gears, little reserch has been conducted using the AE method for running gears in a bending fatigue process of spur gear teeth. Therefore, in this report, with two micro AE sensors attached to the side of the gear, AE was measured in a bending fatigue process of a carburizing gear by using the power circurating-type machine and AE source location in gear teeth were required. By various analysis in these data, the AE characteristics in the fatigue damaging process of the gear tooth were determined.

• Journal of Sensor Science and Technology
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• v.14 no.6
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• pp.415-422
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• 2005

Using stretch sensors, a stuttering treatment training device that improve the abnormal breathing of stutterer was designed and developed. To improve stutterer's inadequate breathing method that is one of principal reason of stammering, the device estimates breathing method by checking the changes of the stretch sensor's resistances those are put on the chest and abdomen of user. And a vocal exercise program that carry out exercises only when the user maintains the abdominal breathing was designed. Using a PIC16C711 device that includes an A/D convertor, a main controller was designed and the vocal exercises software was developed using Director and C program with graphic user interface for user convenience. The controller sends the resistance data of sensors to PC through the serial port and the software verifies the breathing method. And the device was designed that the RTS (request to send) pin of serial port in PC is used as a power source so that it can work without any battery or other power source. Three stutterers have carried out the clinical experiments using the implemented device for two months and the results showed it was excellent to alleviate the stuttering.

• Journal of Power System Engineering
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• v.11 no.4
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• pp.65-71
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• 2007

According to the survey, abnormal condition of the system is the main source for interrupting an elevator service, especially faults in worm gears used for the traction machine. Worm gear is popularly used in traction machine for middle and low speed elevators. Elevators need high reliability and stability, because they are closely related to human life. Usually, traction machine is applied to drive the elevators that have height about 35 m and it is an important mechanical unit for riding quality in elevators. There are some research results about types of vibration fault for worm gear in International Association Elevator Engineers (IAEE). But this study concerns with diagnosis of various faults in elevator worm gear using vibration signal. The analysis of fault characteristics is compared with previous researches in traction machine.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.3
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• pp.119-124
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• 2011

Electric night storage heater was introduced and disseminated for power grid balancing and efficient management of power generation facility. But fuel cost for heating has been increased rapidly while the cost of electricity increased slightly. This abnormal rate system caused peak load in winter at last. To solve this problem, application of an air source heat pump was suggested. In the study, the effect of replacing night heater by heat pump and the economics were analysed. In addition the expectation of prospect of heat pump penetration was simulated based on surveyed and investigated data. As a result, fund supporting as well as institutional backing was needed for effective propagation and return of investment.

• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.476-478
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• 2001

Coordination under short-circuit conditions is a systematic application of protective devices in the electrical power system, which, in response to a fault, will remove only a minimum amount of equipment from service. The objective is not only to minimize the equipment damage and process outage costs, but also to protect personnel from the effects of these failures. The coordination study of an electric power system consists of an organizes time-current study of all devices in series from the utilization device to the source. This study is a comparison of the time it takes the individual devices to operate when certain levels of normal or abnormal current pass through the protective devices. The objective of a coordination study is to determine the characteristics, ratings, and settings of overcurrent protective devices that will ensure that the minimum unfaulted load is interrupted when the protective devices isolate a fault or overload anywhere in the system. At the same time, the devices and settings selected should provide satisfactory protection against overloads on the equipment and interrupt short-circuit as rapidly as possible.

• Journal of Korea Multimedia Society
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• v.19 no.12
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• pp.2014-2023
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• 2016

Web presence is one of the key issues for extensive deployment of Internet-of-Things (IoT). An obstacle to overcome for Web presence is relatively low computing power of IoT devices. In this paper, we present implementation of an IoT platform based on Constrained Application Protocol (CoAP) which is a web transfer protocol proposed by Internet Engineering Task Force (IETF) for the low performance IoT devices such as Wireless Sensor Network (WSN) nodes and micro-controllers. To qualify the performance of CoAP-based IoT system for such an application as smart grid, we designed a test platform consisting of Raspberry Pi2, Kmote WSN node and a desktop PC. Using open source softwares, CoAP was implemented on top of the platform. Leveraging the GET command defined at CoAP specification, performance of the system was measured in terms of round-trip time (RTT) from web application to the Kmote sensor node. To investigate abnormal cases among the test results, hop-by-hop delays were measured to analyze resulting data. The average response time of CoAP-based communication except the abnormal data was reduced by 23% smaller than the previous research result.

• Journal of Power Electronics
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• v.15 no.3
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• pp.670-684
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• 2015

The hybrid cascaded multilevel inverter (HCMLI) is a popular converter topology that is being increasingly used in high power medium voltage drives. The intricacy of the control technique for a HCMLI increases with the number of levels and due to fluctuating dc voltages. This paper presents a novel offline quadrant search based space vector modulation technique to synthesize a sinusoidal output from a dispersed pattern of voltage vectors due to different voltages in the auxiliary unit. Such an investigation has never been reported in the literature and it is being attempted for the first time. The method suggested distributes the voltage vectors for a reduced total harmonic distortion at minimal computation. In addition, the proposed algorithm determines the maximum modulation index in the linear modulation range in order to synthesize a sinusoidal output for both normal and abnormal vector patterns. It is better suited for a wide range of practical applications. It is particularly well suited for renewable source fed inverters which utilize large capacitor banks to maintain the dc link, which are prone to such slow fluctuations. The proposed quadrant search space vector modulation technique is simulated using MATLAB/SIMULINK and implemented using a Nexys-2 Spartan-3E FPGA for a developed prototype.