Wavefront Duration Research Articles

Duration of left and right atrial activation wavefront assessed non-invasively is significantly higher in patients with atrial fibrillation than in controls

Abstract Introduction Ablation strategies in atrial fibrillation (AF) are currently a "one-size- fits- all" type of approach. Pulmonary vein isolation as the standard of care is not perfect, especially in the persistent forms, but none of the alternatives has shown better results. The dichotomic paroxysmal versus persistent AF classification in no longer acceptable. Characterization of the atrial substrate before ablation is needed. Electrocardiographic imaging (ECGI) is capable of non-invasively assess atrial activation in a single beat and in a panoramic fashion. The aim of this study was to evaluate the feasibility and accuracy of ECGI to assess the activation speed and identify possible targets for ablation. Methods We studied 18 consecutive patients, 9 referred for ablation of paroxysmal AF and 9 without AF, referred for ablation of premature ventricular contractions (PVCs), that had an ECGI performed before ablation. No patient had structural heart disease and all patients had normal electrocardiographic evaluation in sinus rhythm (SR). The ECGI was performed in SR with the AMYCARD 01 system, based on body surface electrocardiograms of a maximum of 224 electrodes and computed tomography imaging data. Total duration of atrial activation, left atrial (LA), and right atrial (RA) activation duration, and presence of lines of conduction block (LOB) defined as the presence of a jump in the local activation time of 50 ms or more between contiguous points, were assessed. The results were compared in patients with and without AF. Results The results are depicted in the Table. Patients with AF were older. Total atrial activation duration, LA, and RA activation duration were longer in patients with AF and there was a trend towards a higher prevalence of LOB in the LA in patients with AF (Figure). Discussion & Conclusion Total atrial activation duration as well as LA and RA activation duration assessed with the ECGI were significantly prolonged in patients with AF. Presence of LOB in the LA showed a trend towards a higher prevalence in AF patients. These pilot study has proved that this technology is accurate in identifying a pathological substrate in AF patients. We intend to use ECGI in a subsequent study that will include patients with AF both in paroxysmal and persistent forms, in order to identify markers of disease as well as possible targets to perform a customized AF ablation.Comparison between AF and control groupsECGI showing local activation times

Backflashover Performance Evaluation of the Partially Grounded Scheme of Overhead Lines With Fully Composite Pylons

A design of a fully composite pylon has been proposed for new-generation 400 kV transmission towers to save line corridors and to reduce visual impact. Correspondingly, a method of external down-leads is proposed to bring grounding potential to the shield wires, together with a plan that not all pylons are grounded called ‘partially grounded transmission lines’ (PGTLs). This paper investigates backflashover performance of a partial grounding scheme of overhead lines (OHLs) supported by composite pylons. The transient analysis was carried out in PSCAD based on Monte Carlo method. For OHLs with every pylon grounded, reducing footing resistance and soil resistivity can improve backflashover performance effectively, but for PGTLs, these two methods do not have obvious effect and increasing insulation distance has limited effect. When lightning strikes at PGTLs, overvoltage is mainly dependent on the distance to the nearest grounded pylon and a longer distance will cause overvoltage with larger amplitude and longer wave front duration. Therefore, backflashover rate also increases along with the distance to the nearest grounded pylon until reaching a value limited by the inceptive condition of flashover. A coefficient recommended by CIGRE TB 63 to estimate backflashover rate is discussed and modified when using in PGTLs.

高圧配電線多相フラッシオーバに関する検討

This paper discusses multiphase flashover in a Japanese 6.6kV medium voltage line. The multiphase flashover causes a short circuit in the line, and sometimes causes serious damages in power apparatuses and cables. Insulator voltage shows short-tail and stairwise waveform due to traveling waves reflected from neighbor poles and flashovers on the other insulators. A flashover on an insulator is determined using an integration method, which can consider an influence of voltage waveform on the flashover and can be used in the EMTP. Parameters such as grounding resistance, wavefront duration, power-frequency voltage and line configuration are examined to investigate the multiphase flashover in a medium voltage line. The simulation results suggest the insulator waveform significantly affect the multiphase flashover, and the integration method is an important tool for accurate lightning surge analysis with special reference to the multiphase flashover. This paper proposes an unbalanced insulation in power distribution line to reduce the multiphase flashover.

Negative Creeping Discharge along Aerial Insulated Wire in Wet Condition

SUMMARYAerial insulated wires are supported by postinsulators and binding wires on reinforced concrete poles. When a lightning flash strikes near by the wires, an overvoltage due to the indirect lightning surge is induced in the conductive wire core. A creeping discharge can develop along the wire surface from the free end of the binding wire through the postinsulator and reinforced concrete pole if flashover occurs at the postinsulator, and this also leads to wire damage such as melting or snapping. This can occur under either rainy or thunderstorm conditions. In this case, it indicates that the wire surface is stressed by lightning impulses under wet condition. Consequently, it is important to prevent wire damage and to clarify the characteristics of creeping discharges along the wire surface under dry and wet conditions. In previous investigations, we observed the characteristics of creeping discharges along wire surfaces under dry conditions. In this investigation, we examined creeping discharges under both impulse voltages with various wave front durations and wet conditions on the wire surface. These voltages were applied to the conductive wire core as inductive lightning surges. The duration and phenomena of negative creeping discharges developing along the wire surface were measured using a still camera with an image intensifier. We report the characteristics of the development of negative creeping discharges along wire surfaces under wet condition.

Study of the Spread of Potential Rise Between Two Grounding Electrodes

The groundings of the power distribution, signaling, and power systems of a railway system are individually performed to realize fail safe, and the groundings are often installed in close proximity. Thus, when a grounding electrode is invaded by a lightning current, its ground potential rises together with the potential of the adjacent grounding electrodes; hence, there is a possibility of a large overvoltage being applied to the connected devices. In this paper, we have investigated the potential spread between two rod-shaped electrodes widely used in the grounding of the power, signal, and distribution systems of a railway system using the finite-difference time-domain method. The results of this paper are organized in such a way that the extent of the potential spread to the neighboring grounding electrodes can be understood from information such as the grounding resistivity at the installation location of the ground electrode and the wavefront duration of the lightning current, and these findings will be useful for grounding design. We also investigate the effect of the insulator between two neighboring electrodes to prevent the potential spread.

Relationship between Creeping Discharge along Aerial Insulated Cable and Duration of Wave Front of Inductive Lightning Surge

SUMMARYWe report the results obtained on the developing characteristics of creeping discharges along the insulated cable surface under inductive lightning surge voltages with various durations of wave front. The aerial insulated cables, usually, are supported by the post insulator and the binding wire at the reinforced concrete pole. When a lightning strikes near by the aerial insulated cables, the overvoltage due to the inductive lightning surge invades to the central line of the cable. The creeping discharge can develop along the cable surface from the free end of the binding wire just after a flashover of the post insulator at the cable supporting point. This creeping discharge may give rise to the accidents such as a melting or snapping of the cable. An important subject to prevent these accidents is to clarify the characteristics of creeping discharge along the cable surface and the developing mechanism of discharges. In this study, the impulse voltages with various durations of wave front are applied to the central line of the wire as the inductive lightning surge. The length and aspect of positive and negative creeping discharges developing along the cable surface are measured using a still camera with an image intensifier, and the developing mechanisms of creeping discharges are discussed on the basis of the models which are proposed taking into account the obtained results.

A Method for Reducing Grounding Impedance

Summary This paper investigates grounding impedance reduction with various shapes of grounding electrodes in comparison with a conventional vertical rod based on field measurements and FDTD simulations. It is found that a vertical rectangular conducting plate is effective for reducing the transient and steady-state impedance to less than half that of the vertical rod. A circular conducting plate parallel to the earth surface is also effective in reducing the steady-state impedance, but the transient impedance is nearly the same as that of the vertical rod. The rate of reduction is proportional in some way to the surface area of the electrode, but tends to saturate as the area increases. The transient impedance is rather independent of the earth resistivity and permittivity, but tends to be inversely proportional to the wavefront duration of the applied current. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 185(1): 27–35, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22405

Impulsive loading on reinforced concrete wall

This paper deals with the air blast and ground shock parameters for reinforced concrete wall panels. In this investigation peak pressure, pressure wave front arrival time, rising time, decreasing time and duration of the positive pressure phase of air blast time history parameters, and peak particle acceleration, arrival time, shock wave duration and time lag between ground shock and air blast pressure arrival at structures of ground shock owing to air blast were determined experimentally. Empirical relationships have been developed between different parameters. Typical values measured due to various charge weights have been compared with results of previous researchers and Conwep. The SAP2000 was used for stress analysis of wall panels using experimental results. The methodology outlined can be used to estimate the blast response of reinforced concrete walls. It is concluded that an accurate analysis of structure response and damage of structures caused by a nearby surface explosion requires simultaneous consideration of ground shock and air blast pressure.

Relationship between Creeping Discharge along Aerial Insulated Wire and Duration of Wave Front of Inductive Lightning Surge

Relationship between Creeping Discharge along Aerial Insulated Wire and Duration of Wave Front of Inductive Lightning Surge

接地インピーダンス低減手法の検討

This paper investigates grounding impedance reduction with various shapes of grounding electrodes in comparison with a conventional vertical rod based on field measurements and FDTD simulations. It is found that a vertical rectangular conducting plate is effective to reduce the transient and steady-state impedance less than a half of that of the vertical rod. A circular conducting plate parallel to the earth surface is also effective to reduce the steady-state impedance, but the transient impedance is nearly the same as that of the vertical rod. The rate of the reduction is somehow proportional to the surface area of the electrode, but tends to saturate as the area increases. The transient impedance is rather independent of the earth resistivity and permittivity, but tends to inversely proportional to the wavefront duration of an applied current.

Partial discharge signal propagation characteristics inside the winding of gas-filled power transformer - experimental study using winding models in the air

To establish clear control criteria for a partial discharge (PD) test of long duration ac withstand voltage test of a gas-filled power transformer, the authors have conducted a study on the harmful PD level of materials themselves using the insulating material- and structural-models of an actual gas-filled power transformer. In the PD test on an actual transformer, since the PD having occurred inside the transformer is measured from the outside, the measured signal is damped due to various influential factors, such as the position of occurrence, measurement position, and internal structure of the equipment. In particular, in the event of the PD between sections or turns, which might actually occur, significant damping of the signal is anticipated in certain cases due to the influence of the position of occurrence and the internal structure of the equipment, which is a propagation path. Therefore, this damping must be taken into consideration to establish control criteria for the PD. In this paper, to understand the characteristics of this damping, such as its magnitude, two types of winding, interleaved disk and continuous disk, were produced as transformer models to investigate the propagation characteristics of PD signals with the position of occurrence, measurement position, and wavefront duration of the PD as parameters. Consequently, it emerged that, where the PD occurs between sections or turns, the transmission rate at the measurement position was generally low because the PD signal circulates within the PD occurrence parts and does not come outside. Assuming measurement at the bushing test terminal, the lowest transmission rate was 2.8% and 2.0% between sections and turns, respectively. A study was also conducted on the occurrence of the PD against ground, despite the low anticipated potential of actual occurrence, and the lowest transmission rate was 4.0%. Accordingly, the PD having occurred inside the winding of the transformer can be detected with a magnitude of 2% or more; however, from a reverse perspective, the signal is detected as one significantly damped to a level of about 1/50.

Evaluation of overshoot rate of lightning impulse withstand voltage test waveform based on new base curve fitting methods - study on overshoot waveform in an actual test circuit

In a lightning impulse withstand voltage test for large-sized electric power equipment, voltage waveforms sometimes contain overshoot due to the capacitance of the test equipment and the residual inductance of the test circuit including the power source. The authors have been studying fitting methods for extracting a reasonable base curve from this overshoot waveform. In the previous study, each of the fitting methods was applied to the overshoot waveform simulated using a mathematical equation to evaluate the respective merits and demerits. As the test waveform, the present paper used the overshoot waveform actually generated using a large-scale test circuit. This actual waveform was determined as one over which an oscillation waveform of several hundred kHz, which was actually at issue, was superimposed. The correct base curve of the actual waveform was derived through detailed analysis of the equivalent circuit of the test circuit and the overshoot rate was calculated based on this correct value. This correct overshoot rate was compared with that calculated using each of the fitting methods to evaluate which was an optimum fitting method. Consequently, it was found that an overshoot rate close to the correct value could be derived using the new base curve extraction method for the actual waveform. Meanwhile, it should be noted that the kfactor filtering scheme was implemented after the application of various fitting methods, and then the shape parameters of the test voltage waveforms, such as the crest value, wavefront duration, and wavetail duration, were almost identical, which confirmed that fitting methods had only a minor influence on the test voltage waveform.

Evaluation of overshoot rate of lightning impulse withstand voltage test waveform based on new base curve fitting methods - study by assuming waveforms generated in an actual test circuit -

The authors have studied fitting methods to extract a more reasonable base curve from the lightning impulse voltage test waveforms. In this paper, by assuming a test circuit of actual large-sized UHV class equipment, simulated recorded waveforms were created, to which various fitting methods were applied in order to study their merits and demerits. Consequently, it was found that a new base curve extraction method could calculate an overshoot rate close to the correct value for waveforms actually generated. In particular, while the existing method resulted in significant dissociation for waveforms superimposed by oscillation waves of several hundred kHz, which was actually at issue, the new method significantly improved the evaluation results of the overshoot rate. Meanwhile, it should be noted that the k-factor filtering scheme was implemented after the application of various fitting methods, and then the shape parameters of the test voltage waveforms, such as the crest value, wavefront duration, and wavetail duration, were almost identical, which confirmed that fitting methods had only a minor influence on the test voltage waveform.

Evaluation of overshoot rate of lightning impulse withstand voltage test waveform based on new base curve fitting methods

The k-factor, which evaluates an overshoot of the withstand voltage test waveform in a lightning impulse withstand voltage test, is about to be adopted in IEC 60060-1 that specifies high-voltage test techniques for electric power equipment. In its procedure, it is defined that the recorded waveforms are fitted with a double exponential function to derive a base curve. For some waveforms, however, an extracted base curve sometimes deviates upward from the central lines of the recorded waveforms in the wavefront area. In particular, the degree of such dissociation is significant in waveforms with a high overshoot rate and a low frequency, and further it can not be said that the base curve is appropriate in terms of insulating properties. Accordingly, such significant dissociation may result in an irrational calculation of the overshoot rate. To resolve these problems, a numerical equation resulting from a relationship of a solution between an equivalent electric circuit and dominant equation was used, and fitting methods were overviewed in order to extract a more reasonable base curve in previous studies. In this paper, various options from these fitting methods were narrowed down to several options, which were then applied to simulated recorded-waveform; for which the overshoot rate and frequency of superimposed oscillating served as parameters, and a fitting method for extracting a more reasonable base curve was examined. Consequently, the calculation results of the overshoot rate were brought closer to their actual values than with the existing method by using a new base curve extraction method by which the fitting can be performed with removing the oscillatory part from the recorded waveform. While there is significant dissociation in the existing method, especially in the waveform on which a relatively low frequency oscillatory wave is superimposed, evaluation results of the overshoot rate were significantly improved as a result of the use of the new base curve extraction method. In the meantime, it should be noted that the k-factor filtering scheme was implemented after the application of various fitting methods resulted in the shape parameters of the test voltage waveforms, such as crest value, wavefront and wavetail durations, emerging as virtually identical, alongside confirmation of the minor effect of the fitting methods on the test voltage waveform.

Representation of Moving Wavefronts of Whisker Deflection in Rat Somatosensory Cortex

Rats rhythmically sweep their whiskers over object features, generating sequential deflections of whisker arcs. Such moving wavefronts of whisker deflection are likely to be fundamental elements of natural somatosensory input. To determine how moving wavefronts are represented in somatosensory cortex (S1), we measured single- and multiunit neural responses in S1 of anesthetized rats to moving wavefronts applied through a piezoelectric whisker deflector array. Wavefronts consisted of sequential deflections of individual whisker arcs, which moved progressively across the whisker array. Starting position (starting arc), direction, and velocity of wavefronts were varied. Neurons responded strongly only when wavefront starting position included their principal whisker (PW). When wavefronts started at neighboring positions and swept through the PW, responses to the PW arc were suppressed by <or=95%, and responses over the entire wavefront duration were suppressed by <or=60% compared with wavefronts that initiated with the PW. Suppression occurred with interarc deflection delays of >or=5 ms, was maximal at 20 ms, and recovered within 100-200 ms. Suppression of PW arc responses during wavefronts was largely independent of wavefront direction. However, layer 2/3 neurons showed direction selectivity for responses to the entire wavefront (the entire sequence of SW and PW arc deflection). Wavefront direction selectivity was correlated with receptive field somatotopy and reflected differential responses to the specific SWs that were deflected first in a wavefront. These results indicate that suppressive interwhisker interactions shape responses to wavefronts, resulting in increased salience of wavefront starting position, and, in some neurons, preference for wavefront direction.

Characteristics of creeping discharge along aerial insulated wire under impulse voltages with various wave front durations

AbstractWhen lightning occurs in the neighborhood of outdoor high‐voltage distribution lines, creeping discharges propagate along the wire surface from the binding wire tip just after insulator flashover. These discharges give rise to various faults on distribution lines, for instance, disconnection and melting of wire, punch‐through breakdown, and so on. We must clarify the creeping discharge characteristics associated with various inductive lightning surges from the viewpoint of safety in high‐voltage distribution systems. In our previous paper, it was reported that the lengths and aspects of the negative creeping discharges were influenced by the wave front durations of impulse voltages applied to the central line with a grounded binding wire. The present study was performed to obtain more information on such creeping discharges.This paper describes the distinctive characteristics of a creeping discharge along the insulated wire surface when impulse voltages with various wave front durations are applied to the binding wire. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(3): 29–37, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20430

Transient analysis of RC on-chip transmission lines with respect to propagation speed

The effect of finite propagation speed on the total delay through and the transient response of an on-chip transmission line is investigated in the case of an RC line with an open-circuited far end. A model of signal propagation is proposed that enables one to estimate this effect at signal wavefront durations much less than the propagation time. Using analytical formulae derived from the model, the validity range is identified for solutions of telegrapher’s equations as applied to RC interconnections typical of submicrometer technologies.

各種インパルス電圧による架空絶縁電線表面の沿面放電特性

When the lightning occurs at the neighborhood of outdoor high voltage distribution lines, the creeping discharges propagate along the wire surface from the binding wire tip just after the flashover of insulator. These discharges give rise to the various disasters at distribution lines, for instance, disconnection and melting of wire, punch-through breakdown etc. We must clarify the creeping discharge characteristics under various inductive lightning surges from a viewpoint of a safety in high voltage distribution systems. In our previous paper, it was reported that the lengths and aspects of the negative creeping discharges were influenced by the duration of wave front of impulse voltage applied to the central line under the grounded binding wire. The present study was accomplished in order to obtain more information on such creeping discharges.This paper describes the distinctive characteristics of creeping discharge along the insulated wire surface when the impulse voltages with various durations of wave front are applied to the binding wire.

The influence of wave front duration of impulse voltage on creeping discharges along aerial insulated wire

AbstractIn high‐voltage aerial distribution systems, creeping discharges progress along the cable surface from the free end of the binding wire when overvoltages caused by a lightning surge have invaded the central line of an insulated cable. Consequently, various accidents such as punch‐through breakdown, melting, or snapping of a cable, often occur at these systems. In our previous studies, it has been clarified that the lengths and aspects of creeping discharges under a 1.2/50 µ s impulse voltage condition can be markedly affected by changes in the electric field strength on the cable surface. However, lightning impulse surges which may invade the central line of a cable have various wave front durations. This will further complicate creeping discharge phenomena due to lightning.In this paper, we report the influence of the wave front duration on both the lengths and the aspects of the creeping discharges which progress on the cable on application of lightning impulse voltages. It has been shown that the behavior of negative creeping discharges reveals pronounced changes in response to the duration of the wave front of the applied voltage. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 147(2): 30–38, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10263

Influence of Duration of Wave Front of Impulse Voltage on Creeping Discharges along Aerial Insulated Wire.

In high voltage aerial distribution systems, creeping discharges develop along the wire surface from the free end of the binding wire when overvoltages caused by the lightning surge invaded to the central line of an insulated wire. Then, the various disasters such as punch-through breakdown, disconnection and melting of wire, often occur at these systems. In our previous studies, it has been clarified that the lengths and aspects of creeping discharges under a 1.2/50μs impulse voltage condition can be affected remarkably by the change of the electric field intensity on the wire surface. However, the lightning impulse surges which may invade to a central line of wire have various values of duration of wave front. This will more complicate the creeping discharge phenomena due to a lightning.In this paper, we report the influence of the duration of wave front both on the lengths and the aspects of the creeping discharges which develop on the wire under the application of lightning impulse voltages. It has been clarified that the behavior of negative creeping discharges reveals a remarkable change by the duration of wave fronts in the applied voltages.