• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.05a
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• pp.58-62
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• 2004

The PWM inverter drive my cause motor terminals voltage surge and oscillation(ringing), which impose severe electric stresses on inter-turn insulation of motor windings. This paper describes the technique used to simulate the problems associated with the use of PWM ASD's(Adjustable Speed Drive) to drive induction motor. The characteristic of switching surge was analyzed by EMTP(Electromagnetic transient program) model. The effects of switching surge by surge impedance, rise-time and cable lengths are also discussed.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.5
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• pp.761-769
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• 1994

VCB (Vacuum Circuit Breaker), with the strong arc extinction capability in switching the source of an induction motor, occurs the severe switching surge voltage which can cause the breakdown or the deterioration of motor insulation. Therefore, a method which reduces surge voltage across motor windings is necessary. So, it is analyzed that fast-rise-time surges resulting from VCB switching operations give rise to severe voltage stress on turn insulation. Additionally, the switching surge simulation algorithms using EMTP are developed, and C, R values of surge suppressor minimizing the steep-fronted stress in winding insulation surges are calculated.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.11
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• pp.2089-2092
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• 2010

There are many cases that interrupt the production process because of malfunctions caused by electronic circuit boards which control equipment, but it is difficult to distinctly identify the causes in many cases. Especially, CMOS devices with the control logic circuit return automatically to normal state after their own faults. Therefore it is not easy to analyze the problems with electronic circuit boards. Recently, nuclear power plant experienced a failure due to the malfunction of electronic circuit boards and it was identified that the reason of the malfunction was because of latch-up phenomenon caused by external surge in electronic devices. This paper presents the causes and the phenomenon of latch-up by experiment and also a way using counter EMF diodes, noise filters and surge protective devices to prevent latch-up phenomenon from electronic circuit boards, finally confirms the effectiveness of the result by experiment.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.265-269
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• 2017

Because of abrupt changes for velocity in water, transient flow is occurred in practical life. To reduce and avoid the high or low pressure of pipe network system, various surge protection facilities are used to prevent the risk in pipe network system. Especially, we focused on study not only preventing positive and negative pressure but also selecting adequate equipment for high pressurized pipelines. Several critical cases were considered by undertaking a steady state hydraulic study and transient dynamic simulation and we suggested that the surge vessel of various surge protection system was recommended to control high and low pressures on pipeline system in perspective.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.5
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• pp.502-509
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• 2010

A test facility which can simultaneously measure turbocharger operating condition variables and vibro-acoustic emission in the situations that are quite similar to real internal combustion engine operating conditions has been introduced. Using this facility, a new method sweeping from full open throttle to deep surge region along constant speed curves can be utilized instead of the stationary method that has been traditionally used to obtain turbocharger compressor maps. Data covering an extensive range of the compressor performance map have been collected and analyzed. An experimental study is performed to define a noise diagram that correlates vibro-acoustic measurements to aerothermodynamic operating conditions. An instrumentation set in the facility allows the automatic definition of the operating point on the turbine and compressor map of the turbocharger. Also, radiated sound pressure and casing vibration data corresponding to the point are obtained by a microphone in the vicinity of the compressor casing and an accelerometer on the casing. The major source(s) of noise at specific operating point on the map can be easily identified with these maps. Also, acoustic characteristics of a given turbocharger at the vicinity of the surge as well as in the surge are also defined. Finally, the possibility to define mild surge region of a turbocharger using vibro-acoustic measurements is studied.

• Journal of the Korean Society of Safety
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• v.30 no.4
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• pp.39-45
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• 2015

This paper deals with development of integrity evaluation instrument for the power line surge protective device. A reliable power supply is an essential element in the developed information and communication society by highly advances in IT technology. However, the lightning incidence also increased with the recent extreme weather events. In Korea, in order to protect the electrical system from lightning surge, SPD(Surge Protective Device) has been used for these past 30 years. However, the method of diagnosing the safety of the SPD in the industry is insufficient. In this paper, SPD integrity evaluation system was composed of a variable DC power source unit, voltage-current sensor and the embedded controller. In order to measure V-I characteristics of MOV, 3 type samples were degraded by impulse current generator. After impulse tests, the varistor voltage of all samples and nonlinearity coefficient were decreased. It confirmed the utility of the developed equipment by this experimental test and the reliability of SPD is expected for surge accident prevention when applied to industrial plant.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.9
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• pp.52-59
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• 2014

The aims of this paper are to characterize the transient overvoltages(TOVs) and to evaluate the risk occurring at 22.9kV consumer's substation. The measurements of lightning- and switching-caused TOVs were made during Mar. 2013 and Feb. 2014. As a consequence, 47 events of TOVs were recorded and 4 of them were higher than the input voltage envelope(IVE) of the information technology industry council(ITI) curve. The measured TOVs are characterized by longer front times and longer durations compared to the $1.2/50{\mu}s$ standard impulse voltage waveform, and some of them represent bipolar waves with lower oscillation frequencies. It suggests that the test of non-standard impulse voltage waveforms is needed for effective risk assessments of power apparatus. Lightning- and switching-caused TOVs exceeding IVE of ITI curve are induced at the secondary of 22.9kV potential transformer(PT). We may, therefore, conclude that the surge protection devices should be applied at the secondary of PT and the surge absorbers should be installed at the primary of VCB or PT. The results presented in this paper could be useful to design the reasonable insulation coordination for 22.9kV consumer's substation.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.4
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• pp.490-494
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• 2009

In this paper, how the temperature of a varistor changes when $10/350{\mu}s$ surge currents and/or DC leakage currents are applied on it, respectively, are investigated. The temperature change in varistor is related with injection energy and leakage current. which is the integration of power in time. By the surge current test, we found that the temperature jump is proportional to the level of surge current with slant 52.535 and has no relation with the ambient temperature. And by the DC leakage current test, the difference in temperatures between varistor and ambient is proportional to the magnitude of leakage current. The slope of measured line(the temperature difference vs. the leakage current) shows alteration around $100{\mu}A$. The varistors can not be used more than $100{\mu}A$ region any more. From the above experimental results, we can conclude that data of the surge current test and also those of DC leakage current test can predict the performance of varistors of which the surge protective devices are made.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.2
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• pp.289-294
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• 2005

This paper deals with the analysis results of surge voltage and current measured on information devices installed in a power substation. The power recorder to measure surge voltage and current was connected to signal lines near power transformers and switches, and the time resolution of the power recorder is 4 MS/s. Peak value of the measured surge voltage and current were ranges of 500~1,300v and 500~3,100k, respectively. During the period of measurement, over 5~10 events per day were recorded. Consequently, information devices installed in around high voltage power facilities should be designed considering the surge voltage and current caused in the condition.

• Journal of Korea Water Resources Association
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• v.42 no.10
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• pp.785-793
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• 2009

Numerical model which can simulate the surge tank for unsteady flow was developed in the present study. Furthermore, reliability model which can calculate the probability of pipe breakage regarding unsteady effect was developed. For the risk estimation of pipe breakage and functional estimation of surge tank, probability of pipe breakage for pipe network with surge tank was calculated regarding unsteady effect. From the results, it was found that unsteady flow significantly increase the probability of pipe breakage and surge tank considerably decrease probability of pipe breakage as damping out the pressure oscillations.