• Title/Summary/Keyword: Streamer velocity

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The Characteristics of Dust Removal in Flue Gas by the Plasma of Impulse Streamer Corona (충격식 코로나 방전 플라즈마를 이용한 배연가스로부터 먼지제거에 대한 특성)

  • 김은호
    • Journal of Environmental Science International
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    • v.12 no.12
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    • pp.1261-1267
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    • 2003
  • On the basis of the distribution of particle size measured by laser diffraction spectrometers, this research was carried out to investigate the characteristics of mist removal with the change of operating condition in the plasma reactor of impulse streamer corona. The operating parameters in this experiment were power of impulse streamer corona, gas velocity, impulse generation time, gas temperature, and SOx/NOx concentration. The collection efficiency T(d) was estimated by the distribution of particle size in the collection zone through the advanced model.

The Technology of Mist Removal in Flue Gas by the Plasma of Impulse Streamer Corona (저온플라즈마에 의한 배연 가스내의 미스트 처리기술)

  • 하상안;김일배;강신묵
    • Journal of environmental and Sanitary engineering
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    • v.14 no.4
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    • pp.69-76
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    • 1999
  • This research was carried but to investigate the characteristics of mist removal with the change of operating conditions in the plasma reactor of impulse streamer corona based on the distribution of particle size measured by laser diffraction spectrometers. The operating conditions in this experiment were power of impulse streamer corona, gas velocity, collection time, and SOx/NOx concentration. The collection efficiency T(d) was estimated by distribution of particle size in the collection zone through the advanced model.

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Underwater Discharge Phenomena in Inhomogeneous Electric Fields Caused by Impulse Voltages

  • Lee, Bok-Hee;Kim, Dong-Seong;Choi, Jong-Hyuk
    • Journal of Electrical Engineering and Technology
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    • v.5 no.2
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    • pp.329-336
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    • 2010
  • The paper describes the electrical and optical properties of underwater discharges in highly inhomogeneous electric fields caused by 1.2/50 ${\mu}s$ impulse voltages as functions of the polarity and amplitude of the applied voltage, and various water conductivities. The electric fields are formed by a point-to-plane electrode system. The formation of air bubbles is associated with a thermal process of the water located at the tip of the needle electrode, and streamer coronas can be initiated in the air bubbles and propagated through the test gap with stepped leaders. The fastest streamer channel experiences the final jump across the test gap. The negative streamer channels not only have more branches but are also more widely spread out than the positive streamer channels. The propagation velocity of the positive streamer is much faster than that of the negative one and, in fact, both these velocities are independent of the water conductivity; in addition the time-lag to breakdown is insensitive to water conductivity. The higher the water conductivity the larger the pre-breakdown energy, therefore, the ionic currents do not contribute to the initiation and propagation of the underwater discharges in the test conditions considered.

Influence of SF6/N2 Gas Mixture Ratios on the Lightning Streamer Propagation Characteristics of 22 kV MV Circuit Breaker

  • Gandhi, R.;Chandrasekar, S.;Nagarajan, C.
    • Journal of Electrical Engineering and Technology
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    • v.13 no.4
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    • pp.1663-1672
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    • 2018
  • In recent times, gas insulated medium voltage (MV) circuit breakers (CB) form a vital component in power system network, considering its advantages such as reduced size and safety margins. Gas insulation characteristics of circuit breakers are generally measured by lightning impulse (LI) test according to IEC standard 60060-1 as a factory routine test. Considering the environmental issues of $SF_6$ gas, many research works are being carried out towards the mixture of $SF_6$ gases for high voltage insulation applications. However, few reports are only available regarding the LI withstand and streamer propagation characteristics (at both positive and negative polarity of waveform) of $SF_6/N_2$ gas mixture insulated medium voltage circuit breakers. In this paper, positive and negative polarity LI tests are carried out on 22 kV medium voltage circuit breaker filled with $SF_6/N_2$ gas mixture at different gas pressures (1-5 bar) and at different gas mixture ratios. Important LI parameters such as breakdown voltage, streamer velocity, time to breakdown and acceleration voltage are evaluated with IEC standard LI ($1.2/50{\mu}s$) waveform. Weibull distribution analysis of LI breakdown voltage data is carried out and 50% probability breakdown voltage, scale parameter and shape parameter are evaluated. Results illustrate that the $25%SF_6+75%N_2$ gas filled insulation considerably enhances the LI withstand and breakdown strength of MV circuit breakers. LI breakdown voltage of circuit breaker under negative polarity shows higher value when compared with positive polarity. Results show that maintaining the gas pressure at 0.3 MPa (3 bar) with 10% $SF_6$ gas mixed with 90% $N_2$ will give optimum lighting impulse withstand performance of 22 kV MV circuit breaker.

A Spatio-Temporal Density Measurement of NO Molecules in Pulsed Barrier Discharge Using Laser Induced Fluorescence (레이져 유기형광법을 이용한 펄스 배리어 방전 공간에서의 NO분자에 대한 시·공간적 밀도변화 측정)

  • Han, Sang-Bo
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.24 no.5
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    • pp.160-168
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    • 2010
  • This paper tried to find out NO generation and removal mechanisms in the space of the atmospheric pulsed barrier discharge using laser induced fluorescence method, which is a very effective approach to the measurement of spatio-temporal density of specific molecules. The propagation velocity of the primary streamer reaches about $2.7{\times}10^6$[m/s] and the secondary streamer is produced in the vicinity of positive electrode after the primary streamer finished. In this work, pulse Nd:Yag and Dye lasers are used for generating the specific wavelength of 226[nm], which is possible to excite NO molecules into $A^2{\Sigma}^+{\rightarrow}X^2{\prod}$(0,0) and fluorescence signals as the transition of $A^2{\Sigma}^+{\leftarrow}X^2$(0,2) is measured. For the effective removal of NO molecules in the plasma discharge process, the lower oxygen contents are needed and the influence of secondary streamer for the reduction mechanism of NO molecules is important

A Study on the Integrated Seismic Reflection and Refraction for Shallow Marine Site Survey KSEG.KGS Joint Symposium (천해저 조사를 위한 탄성파 반사법 및 굴절법 통합연구)

  • Kim, Chan-Su;Lee, Sang-Chul;Shin, Sung-Ryul;Kim, Hyun-Do;Jo, Chul-Hyun
    • 한국지구물리탐사학회:학술대회논문집
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    • 2007.06a
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    • pp.349-352
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    • 2007
  • Estimating the physical properties of the survey area and mapping the geotechnical basement play an important role in ocean engineering and construction field. In this study, we performed marine seismic reflection and refraction survey as an engineering application at shallow marine. We made use of the dual boomer - single channel streamer as a source-receiver in reflection seismic survey and air-gun source - the manufactured OBC(Ocean Bottom Cable)-type streamer in refraction survey. In the seismic reflection data, we could easily find the geological layers and basement. Moreover, seismic refraction data could present sediment thickness and velocity distribution.

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P-wave velocity analysis around BSR depth using surface and ocean bottom seismic data (탄성파 자료를 이용한 BSR 부근의 속도 분석)

  • Kim, Byoung-Yeop;Koo, Nam-Hyung;Yoo, Dong-Geun
    • 한국지구물리탐사학회:학술대회논문집
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    • 2007.06a
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    • pp.151-156
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    • 2007
  • In December 2006, 2D surface streamer and Ocean Bottom Seismometer (OBS) data were acquired in the Ulleung basin in Korea where strong Bottom Simulating Reflectors (BSR) were shown as a result of 2D and 3D multichannel (MCS) reflection survey. The aim of this study is to provide another reliable source for estimating P wave velocity around BSR depth using OBS data in addition to velocity information from 2D surface seismic data. Four OBSs were deployed and four 20-km shot lines which pass two OBSs respectively were designed. To derive P wave velocity profile, interactive interval velocity analysis using ${\tau}$-p trajectory matching method (Kumar, 2005) was used for OBS data and semblance analysis was used for surface data. The seismic profiles cross the OBS instruments in two different directions yield recordings for four different azimuths. This raised the confidence for the results. All velocity profiles in the vicinity of BSR depth of four OBS sites show almost definite velocity changes which we could consider as upper BSR and free gas layer. Making comparison between velocity from OBS and that from 2D seismic semblance velocity analysis gives consistency in result.

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A Study on the Shallow Marine Site Survey using Seismic Reflection and Refraction Method (탄성파 반사법 및 굴절법을 이용한 천해저 지반조사에 대한 연구)

  • Shin, Sung-Ryul;Kim, Chan-Su;Jo, Churl-Hyun
    • Geophysics and Geophysical Exploration
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    • v.11 no.2
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    • pp.109-115
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    • 2008
  • It is very important to estimate the physical properties of survey area and delineate the geological basement in marine site survey for the design of offshore structures. For the purpose of providing high quality data by means of engineering site survey, it is necessary to apply several survey techniques and carry out the integrated interpretation to each other. In this study, we applied single channel seismic reflection method and OBC (Ocean Bottom Cable) type seismic refraction method at shallow marine. We used a dual boomer-single channel streamer as a source-receiver in seismic reflection survey and airgun source-the developed OBC type streamer in seismic refraction survey. We made 24 channels OBC type streamer which has 4m channel interval and each channel is composed of single hydrophone and preamplifier. We tested the field applicability of the proposed method and applied the typical seismic data processing methods to the obtained reflection data in order to enhance the data quality and image resolution. In order to estimate the geological velocity distribution from refraction data, seismic refraction tomography technique was applied. Therefore, we could successfully perform time-depth conversion using the velocity information as an integrated interpretation. The proposed method could provide reliable geologic information such as sediment layer thickness and 3D basement depth map.

Data Processing using Anisotropic Analysis for the Long-offset Marine Seismic Data of the East Sea, Korea (동해 해역 원거리 해양탄성파 탐사자료의 이방성 분석을 이용한 전산처리)

  • Joo, Yonghwan;Kim, Byoung-yeop
    • Geophysics and Geophysical Exploration
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    • v.23 no.1
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    • pp.13-21
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    • 2020
  • The acquisition and processing of long-offset data are essential for imaging deep geological structures in marine seismic surveys. It is challenging to derive an accurate subsurface image by employing conventional data processing to long-offset data owing to the normal moveout (NMO) stretch and non-hyperbolic moveout phenomena induced by seismic anisotropy. In 2017, the Korea Institute of Geoscience and Mineral Resources conducted a simultaneous two-dimensional multichannel streamer and ocean-bottom seismic survey using a 5.7-km streamer and an ocean-bottom seismometer to identify the deep geological structure of the Ulleung Basin. Herein, the actual geological subsurface structure was obtained via the sequential iterative updating of the velocity and anisotropic parameters of the long-offset data obtained using a multichannel streamer, and anisotropic prestack Kirchhoff migration was performed using the updated velocity and anisotropic parameters as input parameters. As a result, the reflection energy in the long-offset traces, which showed non-hyperbolic moveout owing to seismic anisotropy, was well aligned horizontally and NMO stretches were also reduced. Thus, a more precise and accurate migrated image was obtained, minimizing the distortion of reflectors and mispositioned reflection energy.

A Study on Optimization of the Global-Correlation-Based Objective Function for the Simultaneous-Source Full Waveform Inversion with Streamer-Type Data (스트리머 방식 탐사 자료의 동시 송신원 전파형 역산을 위한 Global correlation 기반 목적함수 최적화 연구)

  • Son, Woo-Hyun;Pyun, Suk-Joon;Jang, Dong-Hyuk;Park, Yun-Hui
    • Geophysics and Geophysical Exploration
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    • v.15 no.3
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    • pp.129-135
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    • 2012
  • The simultaneous-source full waveform inversion improves the applicability of full waveform inversion by reducing the computational cost. Since this technique adopts simultaneous multi-source for forward modeling, unwanted events remain in the residual seismograms when the receiver geometry of field acquisition is different from that of numerical modeling. As a result, these events impede the convergence of the full waveform inversion. In particular, the streamer-type data with limited offsets is the most difficult data to apply the simultaneous-source technique. To overcome this problem, the global-correlation-based objective function was suggested and it was successfully applied to the simultaneous-source full waveform inversion in time domain. However, this method distorts residual wavefields due to the modified objective function and has a negative influence on the inversion result. In addition, this method has not been applied to the frequency-domain simultaneous-source full waveform inversion. In this paper, we apply a timedamping function to the observed and modeled data, which are used to compute global correlation, to minimize the distortion of residual wavefields. Since the damped wavefields optimize the performance of the global correlation, it mitigates the distortion of the residual wavefields and improves the inversion result. Our algorithm incorporates the globalcorrelation-based full waveform inversion into the frequency domain by back-propagating the time-domain residual wavefields in the frequency domain. Through the numerical examples using the streamer-type data, we show that our inversion algorithm better describes the velocity structure than the conventional global correlation approach does.