• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.3
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• pp.105-111
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• 2001

The research presented in this paper focuses on a method for the detection of High Impedance Fault(HIF). The method will use the wavelet transform and neural network system. HIF on the multi-grounded three-phase four-wires primary distribution power system cannot be detected effectively by existing over current sensing devices. These paper describes the application of discrete wavelet transform to the various HIF data. These data were measured in actual 22-9kV distribution system. Wavelet transform analysis gives the frequency and time-scale information. The neural network system as a fault detector was trained to discriminate HIF from the normal status by a gradient descent method. The proposed method performed very well by proving the right state when it was applied staged fault data and normal load mimics HIF, such as arc-welder.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.6
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• pp.620-627
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• 2016

This paper proposes an advanced detection technique for cable fault by eliminating the sign of reference signal in STDR(sequence time-domain reflectometry) and SSTDR(spread-spectrum time-domain reflectometry). The proposed fault-detection technique can eliminate the reference signal more effectively than the conventional one since the sign detector can approximately recover the distorted reference signal by cable and connector, and consequently, can detect the reflected signal by fault more effectively than the conventional one. Especially, it is shown that the error rate of proposed technique can be significantly lower than the conventional one in the case of far fault simulation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.5
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• pp.240-246
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• 2014

A fault detector was developed for heat exchangers of a hybrid heat pump (HP) for household. The proposed detector can be applied directly to raw operating data. It is to monitor a tracking error between a measured saturation temperature and its state observer. The observer was estimated from a state-space model simulating dynamics of a heat exchanger. The real hybrid HP was substituted with a dynamic simulator that implemented two-phased heat transfer and was validated by experimental data. And artificial fault data were generated using the simulator. Diagnosing the data showed the following. The residual calculated from the state observer error shows a relatively robust consistency with respect fouling level. The fault detector is practically useful because it detects a threshold fouling beyond which the performance starts to deteriorate significantly.

• Proceedings of the KIEE Conference
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• 2008.04a
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• pp.199-200
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• 2008

Demand for reliability and safety in modem systems has been increased in the research on fault detection and isolation. At traditional approaches to fault detection, redundant sensors have been used. More advanced methods are the residual analysis of signals which are created by the comparison between the actual plant behavior and the output response of a mathematical model. However, mathematical system models are difficult to obtain by using physical laws. These problems can be solved by system identification. In this paper, the transfer function of a direct current motor is estimated by using the system identification. And, the efficiency of the fault detector design is verified by using experiments.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.2
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• pp.356-362
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• 2009

The ELectromagnetic Core Imperfection Detector (EL-CID) test was performed on a small generator in the laboratory and a gas turbine generator in the field to assess the fault condition of generator stator core. Artificial defects with six different sizes were introduced in the small generator. The scan results on six defects show a very large increase in the magnitude of fault current compared to that obtained with a healthy core. After the stator core heats up, a thermal imaging camera was used to detect hot spot on the inner surface of the core for comparison. Several faults were found during inspection of the gas turbine generator with the EL-CID. It has been shown that the existence of a fault can be determined by monitoring the magnitude of fault current.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.5
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• pp.453-456
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• 2016

The major causes of electrical fire in low-voltage distribution lines are classified into short-circuit fault, overload fault, electric leakage, and electric contact failure. The special principal factor of the fire is electric arc or spark accompanied with such electric faults. This paper studies the development of an electric fire prevention system with detection and alarm of that in case of parallel arc fault occurrence in low-voltage distribution lines. The proposed system is designed on algorithm sensing the instantaneous voltage drop of line voltage at arc fault occurrence. The proposed detector has characteristics of high-speed operation responsibility and superior system reliability from composition using a large number of semiconductor devices. A new sensing control method that shows the detection of parallel arc fault is sensed to ripple voltage drop through a diode bridge full-wave rectifier at electrical accident occurrence. Some experimental tests of the proposed system also confirm the practicality and validity of the analytical results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.10
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• pp.1537-1545
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• 1993

In this paper, we design a pattern generator and a fault position detector to implement the proposed fault test algorithms which are Column Weight Sensitive Fault (CWSF) test algorithm and bit line decoder fault test algorithm for performing the Built-In Self Test(BIST) in RAM. A pattern generator consists of an address generator and a data generator. An address generator is divided into a row address generator for effective address and a column address generator for sequential and parallel addresses. A fault position detector is designed to determine whether full occurred or not and to find the position of the fault. We verify the implemented circuits by the simulation.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.2
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• pp.61-68
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• 2011

The circuit breaker of power distribution board is essential part for the protection of electrical disaster from load short, trouble of power system. For the normal operation of circuit breaker, trip coil of the circuit breaker can cut the mechanical contact of circuit breaker from the detection of power system troubles. This paper presents a design and experimental results of trip coil fault detection system for the real time monitoring of the circuit breaker. The designed system is consisted by the trip coil fault detector which is connected to the each circuit breaker and remote monitoring unit. The trip coil fault detector can detect the impedance and operating voltage of the trip coil, and the detected values are compared with the normal state. And the remote monitoring unit can be connected to the 32 channels of trip coil fault detectors by serial communication. From the designed system, the fault and normal states of the trip coil can be remotely monitored in real time. The designed system is verified by the practical circuit breaker of power distribution board. And the results shows the effectiveness of the designed system.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.811-813
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• 1996

High impedance fault can not be easily detected by conventional method. But if it would not be detected and cleared quickly, it can result in fires, and electric shock. In this paper, neural network, which has learning capability, is used for high impedance fault detector. The potential of the neural network approach is demonstrated by simulation using KEPCO's measured data. The instantaneous values and frequency spectrum of current are respectively used as the inputs of neural networks. Also, the methods using combined data to exploit the advantage of each data are proposed. In this paper, back-propagation network(BPN) is used for high impedance fault detector and can use for high speed relay because it detects faults within 1 cycle.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.45-48
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• 2003

This research presents an approach to simultaneously detect the faults and measure the length of the electric cables. This approach is easy to use and inexpensive. Moreover, it can be applied to any kinds and sizes of the electric cable. This paper uses 750V $4{\times}4$ Sq.mm. cables. The concept is to send the 2 kHz pulse into the electric cable. When the pulse bumps into the fault, it bounces back. Then, the total time the pulse travels back and forth and the shape of the pulse after bumping are inspected using the pulse detector and pulse converter. Next, the signal obtained is modulated with 10 MHz carrier pulse to segregate into several small pulses before sending to 8-bit counter. The length of the electric cable can be obtained using microcontroller and the location of the faults can be seen on the LCD screen. This approach can be used to inspect the electric cables with the length of at least 15 m.