This article presents a novel phasor domain approach to determine the location of faults in non-homogeneous transmission lines. Best implementation requires synchronized voltage and current phasor ...measurements at all terminals of the transmission line. The overall non-homogeneous transmission line model with fault is established by systematically combining the generalized compact models of all homogeneous line sections. The location of the fault is introduced as an additional state of the overall model. The derivation procedure of the model is without further assumptions, resulting in full consideration of three phase line asymmetry as well as distributed parameters of non-homogeneous transmission lines. Afterwards, the location of the fault is identified using the state estimation algorithm. Extensive numerical experiments in a two-terminal and a multi-terminal non-homogeneous transmission line demonstrate that the method has higher accuracy than existing fault location methods, independent of fault types, locations and impedances.
Line-line (LL) and line-ground (LG) faults may not be detected by common protection devices in Photovoltaic (PV) arrays as these faults are not detectable under high fault impedance and low mismatch ...level. In recent years, many efforts have been devoted to overcome these challenges using intelligent methods. However, these methods could not classify the type of faults and diagnose their severity. In this article, we propose a novel and intelligent fault monitoring method to detect and classify LL and LG faults at the dc side of PV systems. For this purpose, the main features of current-voltage curves under different fault events and normal conditions are extracted. The faults are categorized using the hierarchical classification platform. Later, the LL and LG faults are detected and classified by machine learning methods. The proposed method aims to reduce the amount of dataset, which is required for the learning process, and also obtains a higher accuracy in detecting and classifying the fault events at low mismatch levels and high fault impedance compared with other fault diagnostic methods. The experimental results verify that the proposed method precisely detects and classifies LL and LG faults on PV systems under different conditions and severity with the accuracy of 96.66% and 91.66%, respectively.
Are Power Line Communications (PLC) a good candidate for Smart Grid applications? The objective of this paper is to address this important question. To do so, we provide an overview of what PLC can ...deliver today by surveying its history and describing the most recent technological advances in the area. We then address Smart Grid applications as instances of sensor networking and network control problems and discuss the main conclusions one can draw from the literature on these subjects. The application scenario of PLC within the Smart Grid is then analyzed in detail. Because a necessary ingredient of network planning is modeling, we also discuss two aspects of engineering modeling that relate to our question. The first aspect is modeling the PLC channel through fading models. The second aspect we review is the Smart Grid control and traffic modeling problem which allows us to achieve a better understanding of the communications requirements. Finally, this paper reports recent studies on the electrical and topological properties of a sample power distribution network. Power grid topological studies are very important for PLC networking as the power grid is not only the information source but also the information delivery system-a unique feature when PLC is used for the Smart Grid.
Metabolic reprogramming has been proposed to be a hallmark of cancer, yet a systematic characterization of the metabolic pathways active in transformed cells is currently lacking. Using mass ...spectrometry, we measured the consumption and release (CORE) profiles of 219 metabolites from media across the NCI-60 cancer cell lines, and integrated these data with a preexisting atlas of gene expression. This analysis identified glycine consumption and expression of the mitochondrial glycine biosynthetic pathway as strongly correlated with rates of proliferation across cancer cells. Antagonizing glycine uptake and its mitochondrial biosynthesis preferentially impaired rapidly proliferating cells. Moreover, higher expression of this pathway was associated with greater mortality in breast cancer patients. Increased reliance on glycine may represent a metabolic vulnerability for selectively targeting rapid cancer cell proliferation.
Accurate fault location reduces operating cost and outage time. This paper proposes a time-domain method to accurately locate faults in transmission lines, which only requires a very short data ...window (several milli-seconds) during faults. First, the voltage distribution through the line during faults is accurately obtained by solving the matrix form partial differential equations using the proposed numerical scheme. The proposed numerical scheme is mathematically validated for the transmission line fault location problem, with the optimal selection of time and distance intervals to ensure stability and minimum solution error. Afterwards, the fault location is obtained via the extremum value of the voltage distribution. The method fully considers distributed parameters as well as asymmetry of the line. Extensive numerical experiments validated that (a) the proposed numerical scheme demonstrates advantages towards other numerical schemes; (b) the proposed method presents higher fault location accuracy compared to the existing method, independent of fault types, locations and impedances; and (c) the fault location accuracy is not sensitive towards fault inception angles, loading conditions, measurement errors and parameter errors. The proposed method works with relatively low sampling rates (80 samples per cycle) and is compatible with IEC 61850 standard in present digital substations.
This article presents a class of simultaneous transmitting and reflecting pattern manipulation structures (STAR PMS) using 3-D transmission-line-based elements. First of all, the 3-D element is ...realized by compositing slotlines and microstrip lines together, which obtains a transmitting channel and a reflecting channel. To analyze the operating principle of the proposed element, an equivalent transmission line (TL) model is established, corresponding to the receiving structure and transmitting (or reflecting) structure in each channel. In this way, the transmission and reflection characteristics of our element can be designed with good independence, accuracy, and flexibility through the use of the synthesis method. Then, such elements are quasi-periodically arranged in a transverse plane, where the transmission and reflection phases of each element are adjusted according to the desired performance by virtue of the true-time-delay line. As such, the pattern of transmitted and reflected waves can be simultaneously manipulated. To verify our proposed design concept, a prototype is finally implemented from element synthetic design and simulation to array fabrication and testing. Measured results show a transmitting angle of (<inline-formula> <tex-math notation="LaTeX">\theta _{t} </tex-math></inline-formula> = 150° and <inline-formula> <tex-math notation="LaTeX">\phi _{t} </tex-math></inline-formula> = 90°) and a reflecting angle of (<inline-formula> <tex-math notation="LaTeX">\theta _{r} </tex-math></inline-formula> = 30° and <inline-formula> <tex-math notation="LaTeX">\phi _{r} </tex-math></inline-formula> = 90°) within the operating bandwidth of 74.3% (from 5.5 to 12 GHz), where the highest efficiencies for transmitting and reflecting manipulation are 32.2% and 36.7%, respectively. Therefore, the proposed STAR PMS can be viewed as one of the potential candidates for achieving full space electromagnetic (EM) environment reshaping in future wireless networks.
In this paper, a hybrid time-domain protection scheme for series compensated lines using incremental quantity combined with traveling wave principle is proposed. Each principle is assigned a zone of ...the protected section of the line to achieve fast protection. The incremental quantity-based method is assigned for close-in faults up to 35% and the traveling wave from 33.33% to 66.67% of the line from the relay end. The incremental quantity-based method compares a dynamic restraining quantity obtained from voltage and current to the operating quantity using current for the protection decision. The traveling wave-based method derives a decision by comparing the calculated line length, obtained using the first three arrival times measured at the relay location, to the actual line length. The proposed hybrid approach exploits the advantages of both principles to achieve better reliability and speed of protection for series compensated transmission lines. The proposed scheme is verified for a 400-kV, 300 km series compensated transmission line and results are compared with traditional impedance and incremental quantity-based methods.
We propose a novel method to constrain turbulence and bulk motions in massive galaxies, galaxy groups, and clusters, exploring both simulations and observations. As emerged in the recent picture of ...top-down multiphase condensation, hot gaseous halos are tightly linked to all other phases in terms of cospatiality and thermodynamics. While hot halos (∼107 K) are perturbed by subsonic turbulence, warm (∼104 K) ionized and neutral filaments condense out of the turbulent eddies. The peaks condense into cold molecular clouds (<100 K) raining in the core via chaotic cold accretion (CCA). We show that all phases are tightly linked in terms of the ensemble (wide-aperture) velocity dispersion along the line of sight. The correlation arises in complementary long-term AGN feedback simulations and high-resolution CCA runs, and is corroborated by the combined Hitomi and new Integral Field Unit measurements in the Perseus cluster. The ensemble multiphase gas distributions (from the UV to the radio band) are characterized by substantial spectral line broadening ( v,los 100-200 ) with a mild line shift. On the other hand, pencil-beam detections (as H i absorption against the AGN backlight) sample the small-scale clouds displaying smaller broadening and significant line shifts of up to several 100 (for those falling toward the AGN), with increased scatter due to the turbulence intermittency. We present new ensemble v,los of the warm H +N ii gas in 72 observed cluster/group cores: the constraints are consistent with the simulations and can be used as robust proxies for the turbulent velocities, in particular for the challenging hot plasma (otherwise requiring extremely long X-ray exposures). Finally, we show that the physically motivated criterion C tcool/teddy 1 best traces the condensation extent region and the presence of multiphase gas in observed clusters and groups. The ensemble method can be applied to many available spectroscopic data sets and can substantially advance our understanding of multiphase halos in light of the next-generation multiwavelength missions.
Effective control of both cell survival and cell proliferation is critical to the prevention of oncogenesis and to successful cancer therapy. Using functional expression cloning, we have identified ...GAS5 (growth arrest-specific transcript 5) as critical to the control of mammalian apoptosis and cell population growth. GAS5 transcripts are subject to complex post-transcriptional processing and some, but not all, GAS5 transcripts sensitize mammalian cells to apoptosis inducers. We have found that, in some cell lines, GAS5 expression induces growth arrest and apoptosis independently of other stimuli. GAS5 transcript levels were significantly reduced in breast cancer samples relative to adjacent unaffected normal breast epithelial tissues. The GAS5 gene has no significant protein-coding potential but expression encodes small nucleolar RNAs (snoRNAs) in its introns. Taken together with the recent demonstration of tumor suppressor characteristics in the related snoRNA U50, our observations suggest that such snoRNAs form a novel family of genes controlling oncogenesis and sensitivity to therapy in cancer.
We present a new approach for estimating the parameters of three-phase untransposed electrically short transmission lines using voltage/current synchrophasor measurements obtained from phasor ...measurement units (PMUs). The parameters to be estimated are the entries of the longitudinal impedance matrix and the shunt admittance matrix at the rated system frequency. Conventional approaches relying on the admittance matrix of the line cannot accurately estimate these parameters for short lines, due to their high sensitivity to measurement noise. Our approach differs from conventional ones in the following ways. First, we model the line by the three-phase transmittance matrix that is observed to be less sensitive to measurement noise than the admittance matrix. Second, we compute an accurate noise covariance matrix using the realistic specifications of noise introduced by instrument transformers and PMUs. This noise covariance matrix is then used in least-squares-based estimation methods. Third, we derive different least-squares-based estimation methods based on a statistical model of estimation and show that the weighted least-squares and the maximum likelihood methods, which make use of the noise covariance matrix, produce the best estimates of the line parameters. Finally, we apply the proposed methods to a real data set and show that our approach significantly outperforms existing ones.
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