• Proceedings of the KIEE Conference
• /
• 1997.07c
• /
• pp.883-885
• /
• 1997

High impedance fault(HIF) is random in its behavior even in a similar environment. The detection of Ire HIF has focused on the development of algorithms based on harmonic, parameters of the arc currents. However, a fact that proper selection of the harmonic parameters, rather than algorithm selection, is more important is shown in this paper by applying three different performance evaluation methods on two HIF detection algorithms using eight harmonic parameters.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.55 no.9
• /
• pp.384-391
• /
• 2006

The harmonic currents generated along with the operating speed of electrical railroad traction are very difficult to analyze because of its nonlinear characteristics. This paper therefore presents probabilistic approach for the evaluation of harmonic currents about the operating speed of the arbitrary single traction. To use probabilistic method for railroad system, PDF(Probability Density Function) using measuring data based on the realistic h 따 monic currents per operating speed is calculated. Measuring data of harmonic current per operating speed is obtained using the result data of PSCAD/EMTDC dynamic simulation based on an IAT(Intra Airport Transit) in Incheon International Airport. The means(expected values) and variances of harmonic currents of single traction also are obtained by the PDF of the operating traction speed and harmonic currents. The uncertainty of harmonic currents can be calculated through the mean and variance of PDF. The probability of harmonic currents generated with the operating of arbitrary many tractions is calculated by the convolution of functions. The harmonics of different number of tractions are systematically investigated to assess the TDD(Total Demand Distortion) for the railroad system. The calculation of TDD was carried out using Monte-Carlo Simulations(MSCs) and the results of TDD evaluation of the power quality in the IAT power feeding system.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.60 no.4
• /
• pp.733-738
• /
• 2011

As increase of nonlinear loads and renewable energy generators (REGs) being connected to power distribution system via inverters, the concern on harmonic problems have increased. Recently, the harmonics evaluation method considering TDD (Total Demand Distortion) is used to analyze the effect of harmonics from inverters on power distribution quality. Harmonic current sources are typically used for simulation of nonlinear load. Most inverter type for REGs is voltage source inverter (VSI). So, harmonic voltage sources are more suitable to analyze impact of renewable energy generator on harmonics problem in power distribution system. In this paper, we presented the circuit model to analyze interaction between harmonics from nonlinear load and REGs. We verified that the harmonic analysis using the proposed circuit model is more appropriate than the harmonics evaluation method considering TDD through case study using PSCAD/EMTDC.

• Communications of the Korean Mathematical Society
• /
• v.33 no.1
• /
• pp.13-36
• /
• 2018

In this paper, we obtain some formulae for harmonic sums, alternating harmonic sums and Stirling number sums by using the method of integral representations of series. As applications of these formulae, we give explicit formula of several quadratic and cubic Euler sums through zeta values and linear sums. Furthermore, some relationships between harmonic numbers and Stirling numbers of the first kind are established.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.11a
• /
• pp.439-442
• /
• 2005

Generally, noise from a home appliance has been measured by overall sound pressure level or sound power level, dB. Customers evaluation, however, of this noise should be depend on the only overall level but also the sensory feeling, annoyance, unpleasure and so on. Moreover, in this sensory evaluation, irregular, time-varying and uneven sounds which are difficult to describe itself by overall level are more affectable. Unfortunately however the formal evaluation method for this kinds of noise is not determined yet. In this research, the evaluation method for harmonic noise, which is a major noise from home appliance and one of the unmeasurable sounds by overall level, is proposed to evaluate its acceptability based on the consumer's sense of hearing. The proposed approach could be applied to the other sound, which acoustical characteristics are similar to the tonal noise.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.58 no.4
• /
• pp.416-421
• /
• 2009

Recently, the new Korean Tilting Train Express(TTX) which maintains a speed on the curve railway line is developed. Electric railways, including the TTX, have electrical problems that could bring about serious accidents. For such reasons, the electric railway's electrical problems, electrical harmonic and others, have been studied briskly. Thus, TTX's electrical problems also need leading studies because the new Korean TTX will operate earnestly in 2012. The results could be used hereafter diagnosis of it's components and train conditions. In the paper, electrical signals in TTX operation were measured to analyze electrical harmonic. In addition, after the electrical signals were measured to operating mode (coasting mode, acceleration mode and regenerative breaking mode) respectively in test section(Ho-nam line, Chung-buk line, Jung-ang line and Tae-baek line). The electrical harmonics considered operating modes triparted were analysed and evaluated.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.50 no.8
• /
• pp.373-378
• /
• 2001

This paper introduces a new online index to quantify the harmonic distortion. The proposed index based on VI product can represent the harmonic distortion of both voltage and current, and it includes the effect of interharmonic distortion. Also, the new index is suitable to online harmonic distortion evaluation since it only requires the r.m.s. (root mean square) value and fundamental frequency value of the signals. Case studies are presented to show the availability of the proposed index using the comparison with the THD (Total Harmonic Distortion).

• Journal of Biomedical Engineering Research
• /
• v.16 no.3
• /
• pp.359-366
• /
• 1995

The parameter, B/A, quantifies nonlinearity of the pressure-density relationship of propagation medium. This study investigated quantitative evaluation technique for healing fractured bones using this ultrasonic nonlinear parameter, B/A, obtained by the second harmonic amplitude method. A series of fundamental experiments were performed on cylinder phantoms made of aluminium, which demonstrated potential capability of nonlinear parameter B/A in the diagnosis of healing fractured bones using ultrasound.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.33 no.3
• /
• pp.257-263
• /
• 2013

Acoustic nonlinearity of surface waves is an effective method to evaluate the micro damage on the surface of materials. In this method, the $A_1$ (magnitude of the fundamental wave) and $A_2$ (magnitude of the second-order harmonic wave) are measured for evaluation of acoustic nonlinearity. However, if there is another source of second-order harmonic wave other than the material itself, the linear relationship between $A_1{^2}$ and $A_2$ will not be guaranteed. Therefore, the second-order harmonic generation by another source should be fully suppressed. In this paper, we investigated the initial second-order harmonic generation in narrowband surface waves by multi-line laser beams. The spatial profile of laser beam was considered in the cases of Gaussian and square-like. The temporal profile was assumed to be Gaussian. In case of Gaussian spatial profile, the generation of the initial second-order harmonic wave was inevitable. However, when the spatial profile was square-like, the generation of the initial second-order harmonic wave was able to be fully suppressed at specific duty ratio. These results mean that the multi-line laser beams of square-like profile with a proper duty ratio are useful to evaluate the acoustic nonlinearity of the generated surface waves.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.11 no.1
• /
• pp.73-78
• /
• 2010

In this paper, the analysis of the harmonics of distribution power system interconnected with DG(distributed generation) is simulated by using PSCAD/EMTDC and evaluated the harmonics. The modeling system for simulation is similar to the actual distribution system, and solar power system. The simulation analyses are performed at connection points for each sector. Harmonic standards of interconnection with DG (IEEE Std 1547 and IEEE Std 519) are applied to the evaluation algorithm, converted the simulated data through FFT method, evaluated by THD and TDD separately. The harmonic contents in the case of without DG and each sector with DG are evaluated and compared. The results of evaluation showed the effect that the harmonic contents are appropriated at all sector with DG (without DG) in the distribution power systems but the large induction motor(50KW) is increased the harmonic contents.