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Power Lines (power + line)

Distribution by Scientific Domains

Life Sciences	39%
Engineering	30%
Earth and Environmental Science	17%

Selected Abstracts

Removal of DC power-line magnetic-field effects from airborne total magnetic-field measurements

GEOPHYSICAL PROSPECTING, Issue 3 2000
Mehran Gharibi
Power lines carrying DC current can strongly affect total magnetic-field measurements. A simple algorithm using Biot,Savart's law was made to remove magnetic-field components due to a DC power line from airborne total magnetic-field measurements in the Gävle area, Sweden. The power-line location was estimated from observed data and then split into short line segments. The magnetic-field components due to each segment were calculated and summed together to give the total magnetic effect due to the power line at each observation point. The corrected total magnetic field was calculated by subtracting the power-line magnetic-field vector, projected on to the direction of the main field, from the measured total field. The results show a successful removal of the power-line magnetic effect from the total magnetic-field measurements. However, an error in the estimation of the power-line location can result in a magnetic-field residual after correction. A non-linear median filtering was used to remove this residual when needed. [source]

Mitigation of the produced voltages in AC overhead power-lines/pipelines parallelism during power frequency and lightning conditions

EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 4 2005
I. A. Metwally
Abstract This paper presents a theoretical simulation for a pipeline running in parallel to AC overhead power lines using the ,CONCEPT II' package. This package is based on the method of moment combined with a transmission-line model. A 1,km long, 132,kV, three-phase, double-circuit transmission line, and a 2,km long, 40,cm diameter, 1,m high above-ground pipeline are modelled. Extra shielding wires (ESW) under the phase conductors are investigated. Produced voltages in the pipeline are computed under steady-state power frequency (50,Hz) as well as under direct and indirect lightning strikes to the power line. Different current waveforms are simulated to cover the whole range of those of the anticipated lightning. Under lightning strikes, the voltages across line insulators are computed, too. The results reveal that the ESW give many advantages; namely, (1) reducing the power-frequency electric and magnetic fields at the ground level to meet the regularity limits, (2) improving the shielding effectiveness during lightning strikes by reducing the insulator voltages, (3) mitigating the induced voltages in any metallic structure near the power lines, e.g., pipelines, and (4) using them as optical ground wires for telecommunication purposes, where the probability of lightning strikes to such ESW is much lower than that for the normally used grounding wire(s) at the tower top. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Removal of DC power-line magnetic-field effects from airborne total magnetic-field measurements

Safety aspects for public access defibrillation using automated external defibrillators near high-voltage power lines

ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 5 2004
C. J. Schlimp
Background:, Automated external defibrillators (AEDs) must combine easy operability and high-quality diagnosis even under unfavorable conditions. This study determined the influence of electromagnetic interference caused by high-voltage power lines with 16.7-Hz alternating current on the quality of AEDs' rhythm analysis. Methods:, Two AEDs frequently used in Austria were tested near high-voltage power lines (15 kV or 110 kV, alternating current with 16.7 Hz). The defibrillation electrodes were attached either to a proband with true sinus rhythm or to a resuscitation dummy with generated sinus rhythm, ventricular fibrillation, ventricular tachycardia or asystole. Results:, Electromagnetic interference was much more prominent in a human's than in a dummy's electrocardiogram and depended on the position of the electrodes and cables in relation to the power line. Near high-voltage power lines the AEDs showed a significant operational fault. One AED interpreted the interference as a motion artifact, even when underlying rhythms were clearly detectable. The other AED interpreted 16.7-Hz oscillation as ventricular fibrillation with consequent shock advice when no underlying rhythm was detected. Conclusion:, The tested AEDs neither filter nor recognize a technical interference of 16.7 Hz caused by 15-kV power lines above railway tracks or 110-kV overland power lines, as run by railway companies in Austria, Germany, Norway, Sweden and Switzerland. These failures in AEDs' algorithms for rhythm analysis may cause substantial harm to patients undergoing public access defibrillation. The proper function of AEDs needs to be reconsidered to guarantee patients' safety near high-voltage power lines. [source]

Interference of 16.7-Hz electromagnetic fields on measured electrocardiogram

BIOELECTROMAGNETICS, Issue 5 2007
Christoph J. Schlimp
Abstract The extent of electromagnetic interference (EMI) from 16.7-Hz alternate current power lines in the human surface electrocardiogram (ECG) was evaluated. Results showed a direct linear correlation between mean EMI and magnetic induction of 5.8,21 µT on a railroad platform (electric field: 270 V/m). EMI inside a railroad car (10 µT, 0 V/m) was comparable to the electromagnetic field at the platform. Inside a voltage transformer substation (0 µT, 2000 V/m) EMI occurred only when the ECG device was closer to the power line than the test person. Magnetic induction caused 16.7-Hz EMI to a degree that proper diagnosis of ECG-rhythms was rendered impossible. Bioelectromagnetics 28:402,405, 2007. © 2007 Wiley-Liss, Inc. [source]

Mitigation of the produced voltages in AC overhead power-lines/pipelines parallelism during power frequency and lightning conditions

Transmission on indoor power lines: from a stochastic channel model to the optimization and performance evaluation of multicarrier systems

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 5 2003
Virginie Degardin
Abstract This paper deals with optimization and performance evaluation of multicarrier transmissions on indoor power lines, taking the actual channel characteristics into account. From intensive measurements of noise on lines, the most significant parameters of impulsive noise were defined and classified, and then a statistical study was carried out. The other types of noise, i.e. narrow band and coloured noise have also been characterized. In like manner, the transfer functions between two points of a power line network have been measured. From all these data, a stochastic channel model representative of the environment is built and implemented in a software tool simulating the link. Various transmission schemes have been considered to mitigate the effects on one hand of the stationary noise, the channel frequency selectivity and of the change of its state, and on the other, on the impulsive noise. These techniques are optimized for the indoor power line environment and their performances, expressed in terms of bit error rate, are compared. Copyright © 2003 John Wiley & Sons, Ltd. [source]

In-building power lines as high-speed communication channels: channel characterization and a test channel ensemble

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 5 2003
Tooraj Esmailian
Abstract In-building power lines have often been considered as attractive media for high-speed data transmission, particularly for applications like home networking. In this paper, we develop models for power line channels based both on theoretical considerations and practical measurements. We consider power line channel frequency response and noise models in the 1,30 MHz band and propose a number of power line test channels in which to measure the performance of power line modems. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Study of a fuel cell network with water electrolysis for improving partial load efficiency of a residential cogeneration system

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 8 2006
S. Obara
Abstract A fuel cell energy network which connects hydrogen and oxygen gas pipes, electric power lines and exhaust heat output lines of the fuel cell cogeneration for individual houses, respectively, is analysed. As an analysis case, the energy demand patterns of individual houses in Tokyo are used, and the analysis method for minimization of the operational cost using a genetic algorithm is described. The fuel cell network system of an analysis example assumed connecting the fuel cell cogeneration of five houses. If energy is supplied to the five houses using the fuel cell energy network proposed in this paper, 9% of city gas consumption will be reduced by the maximum from the results of analysis. Two per cent included with 9% is an effect of introducing water electrolysis operation of the fuel cells, corresponding to partial load operation of fuel cell cogeneration. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Habitat models of bird species' distribution: an aid to the management of coastal grazing marshes

JOURNAL OF APPLIED ECOLOGY, Issue 5 2000
T. P. Milsom
1.,Coastal grazing marshes comprise an important habitat for wetland biota but are threatened by agricultural intensification and conversion to arable farmland. In Britain, the Environmentally Sensitive Area (ESA) scheme addresses these problems by providing financial incentives to farmers to retain their grazing marshes, and to follow conservation management prescriptions. 2.,A modelling approach was used to aid the development of management prescriptions for ground-nesting birds in the North Kent Marshes ESA. This ESA contains the largest area of coastal grazing marsh remaining in England and Wales (c. 6500 ha) and supports nationally important breeding populations of lapwing Vanellus vanellus and redshank Tringa totanus. 3.,Counts of ground-nesting birds, and assessments of sward structure, surface topography and wetness, landscape structure and sources of human disturbance were made in 1995 and again in 1996, on 19 land-holdings with a combined area of c. 3000 ha. The land-holdings varied from nature reserves at one extreme to an intensive dairy farm at the other. 4.,Models of relationship between the presence or absence of ground-nesting birds and the grazing marsh habitat in each of c. 430 marshes were constructed using a generalized linear mixed modelling (GLMM) method. This is an extension to the conventional logistic regression approach, in which a random term is used to model differences in the proportion of marshes occupied on different land-holdings. 5.,The combined species models predicted that the probability of marshes being occupied by at least one ground-nesting species increased concomitantly with the complexity of the grass sward and surface topography but decreased in the presence of hedgerows, roads and power lines. 6.,Models were also prepared for each of the 10 most widespread species, including lapwing and redshank. Their composition differed between species. Variables describing the sward were included in models for five species: heterogeneity of sward height tended to be more important than mean sward height. Surface topography and wetness were important for waders and wildfowl but not for other species. Effects of boundaries, proximity to roads and power lines were included in some models and were negative in all cases. 7.,Binomial GLMMs are useful for investigating habitat factors that affect the distribution of birds at two nested spatial scales, in this case fields (marshes) grouped within farms. Models of the type presented in this paper provide a framework for targeting of conservation management prescriptions for ground-nesting birds at the field scale on the North Kent Marshes ESA and on lowland wet grassland elsewhere in Europe. [source]

Safety aspects for public access defibrillation using automated external defibrillators near high-voltage power lines

Identification and removal of above-ground spurious signals in GPR archaeological prospecting,

ARCHAEOLOGICAL PROSPECTION, Issue 2 2005
Luigia Nuzzo
Abstract Ground-penetrating radar (GPR) is a shallow geophysical method increasingly used in archaeological prospecting to detect buried remains and to map the stratigraphy of the uppermost earth layers embodying the archaeological features. The GPR sections, however, can be contaminated by spurious correlated signals caused by above-ground obstacles (buildings, trees, fences, power lines) placed either in-line or off-line with respect to the profile (surface scattering). In the case study presented this problem is analysed for a 35,MHz GPR survey carried out for stratigraphical purposes in the archaeological site of the Roman Ships near Pisa (Italy). The investigation inside the archaeological excavation, when the level was about 5,m below the ground surface, produced a severe surface scattering problem caused by the iron sheet-piling protecting the excavation walls and bordering some of the partly excavated boats. An attempt to interpret the profiles was carried out in a zone where the relatively simple geometry of the metallic enclosure allowed understanding of the possible origin of spurious events, also thanks to the high density of profiles acquired along two orthogonal directions. Migration at the air velocity and geometrical considerations helped the identification of hyperbolic and slightly slanted features as surface scattering phenomena from different sides of the iron sheet-piling. A simple but original subtraction procedure was successful for the attenuation of some of the spurious reflections. After this partial removal, other spurious signals could be recognized more easily as well as two weak subhorizontal reflections of probable stratigraphical meaning. Subsequently, filtering procedures based on f-k and Radon transform methods were tried to further reduce the spurious signals, thus enhancing the visibility of the interesting reflections. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Power frequency magnetic fields and risk of childhood leukaemia: Misclassification of exposure from the use of the ,distance from power line' exposure surrogate

BIOELECTROMAGNETICS, Issue 3 2009
Myron Maslanyj
Abstract A recent study examining the relationship between distance to nearby power lines and childhood cancer risk re-opened the debate about which exposure metrics are appropriate for power frequency magnetic field investigations. Using data from two large population-based UK and German studies we demonstrate that distance to power lines is a comparatively poor predictor of measured residential magnetic fields. Even at proximities of 50 m or less, the positive predictive value of having a household measurement over 0.2 µT was only 19.4%. Clearly using distance from power lines, without taking account of other variables such as load, results in a poor proxy of residential magnetic field exposure. We conclude that such high levels of exposure misclassification render the findings from studies that rely on distance alone uninterpretable. Bioelectromagnetics 30:183,188, 2009. © 2008 Wiley-Liss, Inc. [source]

Evaluation of current densities and total contact currents in occupational exposure at 400 kV substations and power lines

BIOELECTROMAGNETICS, Issue 3 2009
Leena H. Korpinen
Abstract This investigation studied the current densities in the neck and total contact currents in occupational exposure at 400 kV substations and power lines. Eight voluntary workers simulated their normal work tasks using the helmet,mask measuring system. In all, 151 work tasks with induced current measurements were made. Work situations were: tasks in 400 kV substations, tasks in 400,110 kV towers and the cutting of vegetation under 400 kV power lines. The average current density in the neck was estimated from the current induced in the helmet. The calculated maximum average current densities in the neck varied from 1.5 to 6.4 mA/m2 and the maximum total contact currents from 66.8 to 458.4 µA. The study shows that the maximum average current densities and the total contact currents (caused by electric field) in occupational exposure at 400 kV substations and power lines does not exceed the limit and action values (10 mA/m2 and 1 mA) of the new EU-directive 2004/40/EC (live-line bare-hand works excluded). Bioelectromagnetics 30:231,240, 2009. © 2009 Wiley-Liss, Inc. [source]

Interference of 16.7-Hz electromagnetic fields on measured electrocardiogram

Importance of addressing National Electrical Code® violations that result in unusual exposure to 60 Hz magnetic fields

BIOELECTROMAGNETICS, Issue 2 2004
Jack Adams
Abstract We evaluated wiring in multifamily developments containing National Electrical Code® (NEC®) violations as a source of unusual exposure to 60 Hz magnetic fields. Two methods were used in this evaluation: measurement and modeling. We measured the building wiring as a source of magnetic fields in six multifamily developments in Michigan. In this small sample, building wiring proved to be an important source of exposure in four of the six cases. In all four cases with exposure from building wiring, one or more NEC violations were involved. To supplement our measurement efforts, we used computer modeling to compare magnetic field exposure due to building wiring with magnetic field exposure from external power lines. Our calculations showed that where the building wiring has a NEC violation leading to net current loops, the exposure due to wiring is likely to be more important than that from external power lines. Our results support the results obtained in a recent study of the exposure of Californian K-12 students to magnetic fields, where building wiring with one or more NEC violation was found to be the single most important exposure source. If 60 Hz magnetic fields are important to avoid, then improved enforcement of the NEC, as required by law, is perhaps the single most important mitigation policy to adopt. Bioelectromagnetics 25:102,106, 2004. © 2004 Wiley-Liss, Inc. [source]