• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.7
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• pp.118-126
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• 2003

In this study, a battery charge and discharge regulator of modular type is designed as paralleled bi-directional converter that is possible to provide the power without failure not only in the steady state but also in the transient period by the step load variation or the unexpected faults among the converter modules. Each converter module is designed to get stability, performance, reliability, and maintainability and the average current mode method used for controller has the advantages such as noise immunity, fast response, and the real average current signal acquisition. The equivalent model and small signal model for the paralleled battery chargerIdischarger are presented, and also the transfer functions are analyzed for the CCM(Continuous Charge Mode), CDM(Continuous Discharge Mode) and DDM(Discontinuous Discharge Mode). The experiments of the paralleled bi-directional converter are carried out in the step load variation, and in faults of one converter module respectively. And the performance of paralleled bi-directional converter is verified via the experimental results.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1679-1681
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• 2001

In this paper, As the wavelet transform has the properties of multi-resolution analysis and time-frequency domain localization, application of wavelet transform is used at partial discharge(PD) signal detected by electromagnetic wave detection method to extract PD signal's various frequency component and its time domain. therefore we can analyzed PD signal's time-frequency domain simultaneously. On the other hand, using wavelet transform denoising process, inclued noise signal in detected PD signal is well elimiated. we can propose the true shape of PD signal.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.12
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• pp.2286-2292
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• 2011

In this paper we present the design of Low Noise Amplifier(LNA), mixer and filter for RF front-end part of partial discharge monitoring system. The monitoring system of partial discharge in high voltage power machinery is used to prevent many kinds of industrial accidents, and is usually composed of three parts - sensor, RF front-end and digital microcontroller unit. In our study, LNA, mixer and filter are key components of the RF front-end. The LNA consists of common gate and common source-cascaded structure and uses the resistive feedback for broad band matching. A coupled line structure is utilized to implement the filter, of which size is reduced by the meander structure. The mixer is designed using dual gate structure for high isolation between RF and local oscillator signal.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1540-1542
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• 1994

This paper describes an experimental study of pattern recognition of partial discharge for three different discharge sources by using neural network(NN) system. The NN system is three layer feedforward connections and its learning method is a backpropagation algorithm incorporating an external teacher signal. Input information for NN is a statistical parameters of a discharge magnitude and the number of pulse count. After learning three typical input patterns, NN system offers good discrimination between different defects.

• KIEE International Transactions on Electrophysics and Applications
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• v.4C no.1
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• pp.1-4
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• 2004

This paper presents an investigation of the phase-resolved partial discharge (PD) pattern of PET (Poly Ethylene Telephthalate) films with carbon black particles. The phase-resolved PD pattern and statistical parameter from PET samples according to the number of included semiconductor particles were measured. The measurement system consisted of a conventional PD detector using a digital signal processing technique. The partial discharge patterns of the PET films that include the semiconductor particles were investigated to simulate an actual situation that may exist in the cable. In addition, difference of PD patterns between semiconducting particles in PET films and artificial voids was studied. The relationship between the numbers of semiconductor particles in PET films was discussed through the difference of Ψ-q-n distribution and statistical analysis.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1999.11a
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• pp.136-140
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• 1999

Measurements of AE signals caused by partial discharges were performed by using an ultrasonic measurement technique to diagonise the electrical treeing deterioration in XLPE cable. We also examined the partial discharge magnitude and AE signals(peak-to-peak) with the increase of the deterioration time. From these results, it was found that AE signal due to partial discharge can be greatly detected at the peak value of positive polarities prior to the breakdown voltages, and the magnitude of AE signals was closely related to the current pulses by the increase of deterioration, and it appeared that AE signals(peak-to-peak) was proportional to partial discharge magnitude. Attenuation and time-delaying characteristics of ultrasonic signals propagated in various polymers sample by using ultrasonic oscillation and receiving systems are also reported as a basic data of ultrasonic measurements in XLPE cable.

• Journal of Applied Reliability
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• v.13 no.2
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• pp.129-140
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• 2013

As a fundamental experimental study for reliability improvement of lithium ion secondary battery, degradation mechanism was investigated by microscopic observation and acoustic emission monitoring. Microstructural observation of the decomposed battery after cycle test revealed mechanical and chemical damages such as interface delamination, microcrack of the electrodes, and solid electrolyte interphase (SEI). Acoustic emission (AE) signal was detected during charge and discharge of lithium ion battery to investigate relationships among cumulative count, discharge capacity, and microdamages. With increasing number of cycle, discharge capacity was decreased and AE cumulative count was observed to increase. Observed damages were attributed to sources of the detected AE signals.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.2
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• pp.335-341
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• 2009

Analysis of the partial discharge signal, a technique to diagnose the stator winding insulation is a key function for the diagnosis of high voltage rotating machines and requires high precision. To satisfy this requirement, various denoising techniques such as filtering and differential methods were proposed. However, these techniques can not eliminate a adjacent induction noise that decreases reliability of the diagnosis. A simple novel denoising algorithm, therefore, is proposed for removing the adjacent induction noise in this paper. The algorithm shows good performance in the real partial discharge signals measured by 13kV class capacitive couplers installed at hydro-generator in Dae-cheong Dam.

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.132-137
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• 2003

This paper concerns the prediction of railway noise propagation using scale model experiment in acoustics. In order to make acoustical experiment the digital signal processing technique are applied and spark discharge sound sources have been developed in which impulse response measured in 1/20 scale model railway. In the case of scale model experiment, it is difficult to realize sufficiently small size and directivity and to get sufficient sound energy and to get repeatability. Several type of Spark discharge sound source is made in laboratory. Experiment results are compared with the calculated results by the prediction model. As the results, it was found that railway noise could be predicted in acoustical scale model experiment using spark discharge sound source.

• Transactions on Electrical and Electronic Materials
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• v.7 no.5
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• pp.247-251
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• 2006

The traction DC feeder cable is one of the key devices for the safety operation of subway system, but for low voltage DC feeder cable (<3000 V) for subway, little attention has been paid by investigators on its online monitoring technology. With an introduction of cable laying and operation environment for the cable, this paper investigated the on-line monitoring technology of 1500 V DC feeder cable of subway. Firstly, in the text, the fault model of 1500 V DC cable was proposed based on the analysis of the fault type of the DC feeder cable, and then put forward synthetically on-line monitoring discharge signal and DC leakage current signal to assess DC feeder cable insulating state. The results of laboratory experiment prove that the proposed methods are feasible and can be implemented on-line monitor on DC feeder cable of subway.