• Title/Summary/Keyword: PD-spectrum

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Flashover Prediction of Polymeric Insulators Using PD Signal Time-Frequency Analysis and BPA Neural Network Technique

  • Narayanan, V. Jayaprakash;Karthik, B.;Chandrasekar, S.
    • Journal of Electrical Engineering and Technology
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    • v.9 no.4
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    • pp.1375-1384
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    • 2014
  • Flashover of power transmission line insulators is a major threat to the reliable operation of power system. This paper deals with the flashover prediction of polymeric insulators used in power transmission line applications using the novel condition monitoring technique developed by PD signal time-frequency map and neural network technique. Laboratory experiments on polymeric insulators were carried out as per IEC 60507 under AC voltage, at different humidity and contamination levels using NaCl as a contaminant. Partial discharge signals were acquired using advanced ultra wide band detection system. Salient features from the Time-Frequency map and PRPD pattern at different pollution levels were extracted. The flashover prediction of polymeric insulators was automated using artificial neural network (ANN) with back propagation algorithm (BPA). From the results, it can be speculated that PD signal feature extraction along with back propagation classification is a well suited technique to predict flashover of polymeric insulators.

Comparison test for PD measuring about UHF-sensor and HFCT-sensor in cable joint-box of MV grade (MV급 케이블 중간접속부의 PD 측정을 위한 UHF-센서와 HFCT-센서의 비교시험)

  • Shin, Dong-Hoon;Lee, Yong-Sung;Kim, Jung-Yoon;Yang, Jong-Seok;Park, Noh-Joon;Park, Dae-Hee
    • Proceedings of the KIEE Conference
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    • 2006.07c
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    • pp.1511-1512
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    • 2006
  • In this paper, we measured PD signals from artificial surface defects and corona discharges under laboratory circumstances like the fields using both HFCT-sensor and UHF-sensor for MV grade XLPE cable with AMP, spectrum analyzer and oscilloscope. Also, detected signals were analyzed via PRPDA system in this paper. As a result, in this case of HFCT-sensor, the amount of background noise are larger than as compared to UHF-sensor. There is needed some hardware or software or software algorithm removing background noise effectively for diagnosis the underground power transmission cable in the case of HFCT-sensor.

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Characteristics of Radiated Electromagntic Wave With Partial Discharge Progess in the XLPE Solid Dielectric (XLPE 고체절연체내의 부분방전 진전에 따른 방사전자파의 특성)

  • Lee, H.C.;Yoon, D.H.;Jang, H.S.;Park, Ch.K.;Ju, J.H.;Kim, I.K.;Lee, K.S.;Lee, D.I.
    • Proceedings of the KIEE Conference
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    • 2003.07c
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    • pp.1888-1890
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    • 2003
  • 본 논문에서는 XLPE 고체 절연체내의 부분방전(partical discharge:PD)발생 및 진전에 따른 라 방사되는 UHF 대역의 방사전자파를 측정, 분석하고 PD진전에 따른 그 스펙트럼의 특성을 연구 하였다. PD를 모의하기 위해 침을 XLPE 절연체내에 삽입하고 그 사이에 보이드층을 만들었다. 고체절연체의 열화를 고려하여 일정시간 동안 일정 전압을 유지하고 이때 발생되는 방사전자파를 EMI, EMC 안테나(EMCO-3142)와 Spectrum analyzer로 측정, 분석하였다.

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Reduction Characteristics of Triclosan using Zero-valent Iron and Modified Zero-valent Iron (영가철 및 개질 영가철을 이용한 triclosan의 환원분해 특성)

  • Choi, Jeong-Hak;Kim, Young-Hun
    • Journal of Environmental Science International
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    • v.26 no.7
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    • pp.859-868
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    • 2017
  • In this study, the reductive dechlorination of triclosan using zero-valent iron (ZVI, $Fe^0$) and modified zero-valent iron (i.e., acid-washed iron (Aw/Fe) and palladium-coated iron (Pd/Fe)) was experimentally investigated, and the reduction characteristics were evaluated by analyzing the reaction kinetics. Triclosan could be reductively decomposed using zero-valent iron. The degradation rates of triclosan were about 50% and 67% when $Fe^0$ and Aw/Fe were used as reductants, respectively, after 8 h of reaction. For the Pd/Fe system, the degradation rate was about 57% after 1 h of reaction. Thus, Pd/Fe exhibited remarkable performance in the reductive degradation of triclosan. Several dechlorinated intermediates were predicted by GC-MS spectrum, and 2-phenoxyphenol was detected as the by-product of the decomposition reaction of triclosan, indicating that reductive dechlorination occurred continuously. As the reaction proceeded, the pH of the solution increased steadily; the pH increase for the Pd/Fe system was smaller than that for the $Fe^0$ and Aw/Fe system. Further, zero-order, first-order, and second-order kinetic models were used to analyze the reaction kinetics. The first-order kinetic model was found to be the best with good correlation for the $Fe^0$ and Aw/Fe system. However, for the Pd/Fe system, the experimental data were evaluated to be well fitted to the second-order kinetic model. The reaction rate constants (k) were in the order of Pd/Fe > Aw/Fe > $Fe^0$, with the rate constant of Pd/Fe being much higher than that of the other two reductants.

Development and characterization of a ultra-wide bandwidth video detector for the UHF partial discharge monitoring system (UHF 부분방전 감시 장치를 위한 초광대역 검출장치 개발 및 특성조사)

  • Park, Ki-Jun;Goo, Sun-Geun;Yoon, Jin-Yul
    • Proceedings of the KIEE Conference
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    • 2002.07c
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    • pp.1649-1651
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    • 2002
  • Ultra-wide bandwidth (UWB) detection method has been widely used as a front end detection scheme for the ultra-high frequency (UHF) partial discharge (PD) monitoring systems. A broad-band video detector module was developed and characterized for the UHF UWB PD detection systems. The useable bandwidth of the module is more than 2 GHz and it is optimized for 50-ohm systems. The detection sensitivity and dynamic range of the module were characterized by using a known ns-width RF pulses of GHz range. The dynamic range is more than 6-decades and the module can detect pulsed RF signals down to 1 nW. The detector module can eliminate expensive equipment such as high speed oscilloscopes and radio frequency (RF) spectrum analyzers. Therefore, it enables one to use slow speed data acquisition systems for the PD monitoring at the UHF range. The detector module was used to detect real PDs of about <3 pC. The module converts the UWB PD signals into a low-bandwidth video signal with a high signal-to-noise ratio.

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Synthesis and Characterization of Square Planar Mixed-Ligand Complexes (Ⅰ) : Synthesis and Spectroscopic Property of M(S-S)(N-N) Type Complexes with Ni (Ⅱ), Pd (Ⅱ), and Pt (Ⅱ) (평면사각형 혼합 리간드 착물의 합성과 그 특성 (제 1 보) : Ni (Ⅱ), Pd (Ⅱ) 및 Pt (Ⅱ) 의 M(S-S)(N-N) 형 착물의 합성과 분광학적 성질)

  • O, Sang O;Jeong, Deok Yeong
    • Journal of the Korean Chemical Society
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    • v.34 no.6
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    • pp.593-599
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    • 1990
  • A series of new, square planar, and mixed-ligand complexes of Ni(Ⅱ), Pd(Ⅱ), and Pt(Ⅱ) have been prepared. From the observation of electronic spectrum for the variation of the ligand substituents, the very intense absorption band in the visible range is by the electronic transition of dithiolene to diimine ligand, HOMO to LUMO. In the various solvent systems the IT band shows the similar behavior to IT transition of mixed-valence dinuclear complexes followed with Hush theory, happens rto dominently by the inner sphere charge transfer transition. The negative solvatochromism represents that the excited-state electric dipole is reduced or reversed by the electronic transition.

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Electrogeneration of Hypochlorite Ions using a Dimensionally Stable Anode-Type (Ti/PtPd(10%)Ox) Electrode

  • Teresa Zayas;Miriam Vega;Guillermo Soriano-Moro;Anabella Handal;Miguel Morales;Leonardo Salgado
    • Journal of Electrochemical Science and Technology
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    • v.15 no.2
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    • pp.268-275
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    • 2024
  • The study examined the electrogeneration of hypochlorite ions (ClO-) via electrolysis of aqueous NaCl solutions using a dimensionally stable anode-type (DSA-type) electrode based on platinum and palladium oxides supported on titanium mesh (Ti/PtPd(10%)Ox). The electrogenerated ClO- was quantified on the basis of the absorption band at 292 nm (Aλ = 292) of the UV-Vis spectrum. The effect of initial pH, concentration of NaCl, cell potential difference and electrolysis time were investigated in this study. The results showed that the electrolysis of aqueous NaCl solutions increases the solution pH up to high values (≥ 8.0) that favor the formation of ClO- over chlorine or hypochlorous acid. The hypochlorite concentration increases significantly at pH values > 7.0 and shows a linear trend with increasing NaCl concentration and with increasing cell potential difference. When the cell potential and NaCl concentration are held constant, the maximum hypochlorite value during electrolysis depends on both the cell potential and NaCl concentration. The Ti/PtPd(10%)Ox anode favors the production of hypochlorite ions, making this anode a promising material for use in electrochemical oxidation of wastewater via an indirect mechanism.

Digital predistorters for communication systems with dynamic spectrum allocation (가변 스펙트럼 할당을 지원하는 광대역 전력 증폭기를 위한 디지털 전치왜곡기)

  • Choi, Sung-Ho;Seo, Sung-Won;Mah, Bak-Il;Jeong, Eui-Rim
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.15 no.2
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    • pp.307-314
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    • 2011
  • A new predistortion technique for dynamic spectrum allocation systems such as cognitive radio (CR) is proposed. The system model considered in this paper occupies a small band at a time, but the center frequency can be changed in the wide range of frequency. In this scenario. the front-end filter may not eliminate the harmonics of the power amplifier (PA) output. The proposed PD reduces the spectral regrowth of the fundamental signal at the carrier frequency (${\omega}_0$) and removes the harmonics ($2{\omega}_0$, $3{\omega}_0$, ...) at the same time. The proposed PD structure is composed of multiple predistorters (PDs) centered at integer multiples of ${\omega}_0$. The PD at ${\omega}_0$ is for removing spectral regrowth of the fundamental signal, and the others are for harmonic reduction. In the proposed PD structure, parameters of PDs are found jointly. Simulation results show that the spectral regrowth can be reduced by 20dB, and the 2nd and 3rd harmonics can be reduced down to -70dB from the power of the fundamental signal.

Resource Allocation and EE-SE Tradeoff for H-CRAN with NOMA-Based D2D Communications

  • Wang, Jingpu;Song, Xin;Dong, Li
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.14 no.4
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    • pp.1837-1860
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    • 2020
  • We propose a general framework for studying resource allocation problem and the tradeoff between spectral efficiency (SE) and energy efficiency (EE) for downlink traffic in power domain-non-orthogonal multiple access (PD-NOMA) and device to device (D2D) based heterogeneous cloud radio access networks (H-CRANs) under imperfect channel state information (CSI). The aim is jointly optimize radio remote head (RRH) selection, spectrum allocation and power control, which is formulated as a multi-objective optimization (MOO) problem that can be solved with weighted Tchebycheff method. We propose a low-complexity algorithm to solve user association, spectrum allocation and power coordination separately. We first compute the CSI for RRHs. Then we study allocating the cell users (CUs) and D2D groups to different subchannels by constructing a bipartite graph and Hungrarian algorithm. To solve the power control and EE-SE tradeoff problems, we decompose the target function into two subproblems. Then, we utilize successive convex program approach to lower the computational complexity. Moreover, we use Lagrangian method and KKT conditions to find the global optimum with low complexity, and get a fast convergence by subgradient method. Numerical simulation results demonstrate that by using PD-NOMA technique and H-CRAN with D2D communications, the system gets good EE-SE tradeoff performance.

Cutting force regulation of microdrilling using the sliding mode control (슬라이딩 모드 제어를 이용한 마으크로 드릴의 절삭력 제어)

  • 정만실;조동우
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1997.04a
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    • pp.842-846
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    • 1997
  • Micro-hole drilling (holes less than 0.5 mm in diameter with aspect ratios larger than 10) is gaining increased attention in a wide spectrum of precision production industries. Alternative methods such as EDM, laser drilling, etc. can sometimes replace mechanical micro-hole drilling but are not acceptable in PCB manufacture because they yield inferior hole quality and accuracy. The major difficulties in micro-hold drilling are related to wandering motions during the inlet stage, high aspect ratios, high temperature,etc. However, of all the difficulties, the most undesirable one is the increase of drilling force as the drill penetrates deeper into hold. This is caused mainly by chip related effects. Peck-drilling is thus widely used for deep hole drilling despite the fact that it leads to low productivity. Therefore, in this paper, a method of cutting force regulation is proposed to achieve continuous drilling. A proportional plus derivative (PD) and a sliding modecontrol algorithm will be implemented for controlling the spinle rotational frequeency. Experimental results will show that sliding mode control reduces the nominal cutting force and its variation better than the PD control, resulting in a number of advantages such as an increase in drill life, fast stabilization of the wandering motion, and precise positioning of the hole.

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