463 research outputs found
Characterization of vertical electric fields and associated voltages induced on a overhead power line from close artificially initiated lightning
Measurements were characterized of simultaneous vertical electric fields and voltages induced at both ends of a 448 m overhead power line by artificially initiated lightning return strokes. The lightning discharges struck ground about 20 m from one end of the line. The measured line voltages could be grouped into two categories: those in which multiple, similarly shaped, evenly spaced pulses were observed, which are called oscillatory; and those dominated by a principal pulse with subsidiary oscillations of much smaller amplitude, which are called impulsive. Voltage amplitudes range from tens of kilovolts for oscillatory voltages to hundreds of kilovolts for impulsive voltages
Hints of the Quantum Nature of the Universe in Classical Electrodynamics and Their Connection to the Electronic Charge and Dark Energy
The electromagnetic fields of linear radiating systems working without
dispersive and dissipative losses are analyzed both in the time and the
frequency domains. In the case of the time domain radiating system, the
parameter studied is the action, A, associated with the radiation. The action
is defined as the product of the energy and the duration of the radiation. In
the case of the frequency domain radiating system, which produces radiation in
bursts of duration T/2 where T is the period of oscillation, the parameter
studied is the energy, U, dissipated in a single burst of radiation of duration
T/2. In this paper, we have studied how A and U vary as a function of the
charge associated with the current in the radiating system and the ratio of the
length of the radiating system and its radius. We have observed remarkable
results when this ratio is equal to the ratio of the radius of the universe to
the Bohr radius. In the case of the time domain radiating system, we have
observed that when the charge associated with the current propagating along the
radiator reaches the electronic charge, the action associated with the
radiation reduces to h/2*pi where h is the Planck constant. In the case of the
frequency domain radiating system, we have observed that as the magnitude of
the oscillating charge reduces to the electronic charge, the energy dissipated
in a single burst of radiation reduces to h*v, where v is the frequency of
oscillation. Interestingly, all these results are based purely on classical
electrodynamics and general relativity. The importance of the findings is
discussed. In particular, the fact that the minimum free charge that exists in
nature is the electronic charge, is shown for the first time to be a direct
consequence of the photonic nature of the electromagnetic fields. Furthermore,
the presented findings allow to derive for the first time an expression for the
dark energy density of the universe in terms of the other fundamental constants
in nature, the prediction of which is consistent with experimental
observations. This Equation, which combines together the dark energy,
electronic charge and mass, speed of light, gravitational constant and Planck
constant, creates a link between classical field theories (i.e., classical
electrodynamics and general relativity) and quantum mechanics.Comment: 19 pages, 4 figure
Do Wind Turbines Amplify the Effects of Lightning Strikes A Full-Maxwell Modelling Approach
Wind turbines (WTs) can be seriously damaged
by lightning strikes and they can be struck by a significant
number of flashes. This should be taken into account when the
WT lightning protection system is designed. Moreover, WTs
represent a path for the lightning current that can modify
the well-known effects of the lightning discharge in terms of
radiated electromagnetic fields, which are a source of damage
and interference for nearby structures and systems. In this
paper, a WT struck by a lightning discharge is analyzed with
a full-wave modelling approach, taking into account the details
of the WT and its interactions with the lightning channel. The
effects of first and subsequent return strokes are analyzed as
well as that of the rotation angle of the struck blade. Results
show that the lightning current along the WT is mainly affected
by the ground reflection and by the reflection between the struck
blade and the channel. The computed electromagnetic fields
show that, for subsequent return strokes, the presence of a
WT almost doubles their magnitude with respect to a lightning
striking the ground. Such enhancement is emphasized when the
inclined struck blade is considere
Statistical Distributions of Lightning Currents Associated With Upward Negative Flashes Based on the Data Collected at the SĂ€ntis Tower in 2010 and 2011
This paper presents statistical distributions of lightning current parameters based on the lightning current and current-derivative waveforms measured at the SĂ€ntis Tower site in 2010 and 2011. The total number of flashes analyzed in this study was 167, which includes nearly 2000 pulses. The statistical distributions refer to upward negative flashes. It is shown that negative flashes are mainly concentrated in the summer months during the convective season. Statistical data on the salient lightning current parameters, namely, peak current, peak current derivative, risetime, pulse charge, pulse duration, interpulse interval, and flash multiplicity are presented and discussed. The obtained data that constitute the largest dataset available to this date for upward negative flashes are also compared with other available statistical distributions
An Analysis of Current and Electric Field Pulses Associated With Upward Negative Lightning Flashes Initiated from the SĂ€ntis Tower
International audienceWe present a study on the characteristics of current and electric field pulses associated with upward lightning flashes initiated from the instrumented SĂ€ntis Tower in Switzerland. The electric field was measured 15 km from the tower. Upward flashes always begin with the initial stage composed of the upward-leader phase and the initial-continuous-current (ICC) phase. Four types of current pulses are identified and analyzed in the paper: (1) return-stroke pulses, which occur after the extinction of the ICC and are preceded by essentially no-current time intervals; (2) mixed-mode ICC pulses, defined as fast pulses superimposed on the ICC, which have characteristics very similar to those of return strokes and are believed to be associated with the reactivation of a decayed branch or the connection of a newly created channel to the ICC-carrying channel at relatively small junction heights; (3) " classical " M-component pulses superimposed on the continuing current following some return strokes; and (4) M-component-type ICC pulses, presumably associated with the reactivation of a decayed branch or the connection of a newly created channel to the ICC-carrying channel at relatively large junction heights. We consider a data set consisting of 9 return-stroke pulses, 70 mixed-mode ICC pulses, 11 classical M-component pulses, and 19 M-component-type ICC pulses (a total of 109 pulses). The salient characteristics of the current and field waveforms are analyzed. A new criterion is proposed to distinguish between mixed-mode and M-component-type pulses, which is based on the current waveform features. The characteristics of M-component-type pulses during the initial stage are found to be similar to those of classical M-component pulses occurring during the continuing current after some return strokes. It is also found that about 41% of mixed-mode ICC pulses were preceded by microsecond-scale pulses occurring in electric field records some hundreds of microseconds prior to the onset of the current, very similar to microsecond-scale electric field pulses observed for M-component-type ICC pulses and which can be attributed to the junction of an in-cloud leader channel to the current-carrying channel to ground. Classical M-component pulses and M-component-type ICC pulses tend to have larger risetimes ranging from 6.3 to 430 ÎŒs. On the other hand, return-stroke pulses and mixed-mode ICC pulses have current risetimes ranging from 0.5 to 28 ÎŒs. Finally, our data suggest that the 8-ÎŒs criterion for the current risetime proposed by Flache et al. is a reasonable tool to distinguish between return strokes and classical M-components. However, mixed-mode ICC pulses superimposed on the ICC can sometimes have considerably longer risetimes, up to about 28 ÎŒs, as observed in this study
Electromagnetic fields associated with the Mâcomponent mode of charge transfer
In upward flashes, charge transfer to ground largely takes place during the initial continuous current (ICC) and its superimposed pulses (ICC pulses). ICC pulses can be associated with either M-component or leader/returnâstrokeâlike modes of charge transfer to ground. In the latter case, the downward leader/return stroke process is believed to take place in a decayed branch or a newly created channel connected to the ICCâcarrying channel at relatively short distance from the tower top, resulting in the soâcalled mixed mode of charge transfer to ground. In this paper, we study the electromagnetic fields associated with the Mâcomponent charge transfer mode using simultaneous records of electric fields and currents associated with upward flashes initiated from the SĂ€ntis Tower. The effect of the mountainous terrain on the propagation of electromagnetic fields associated with theMâcomponent charge transfer mode (including classical Mâcomponent pulses and Mâcomponentâtype pulses superimposed on the initial continuous current) is analyzed and compared with its effect on the fields associated with the return stroke (occurring after the extinction of the ICC) and mixed charge transfer modes. For the analysis, we use a 2âDimentional FiniteâDifference Time Domain method, in which the Mâcomponent is modeled by the superposition of a downward current wave and an upward current wave resulting from the reflection at the bottom of the lightning channel (Rakov et al., 1995, https://doi.org/10.1029/95JD01924 model) and the return stroke and mixed mode are modeled adopting the MTLE (Modified Transmission Line with Exponential Current Decay with Height) model. The finite ground conductivity and the mountainous propagation terrain between the SĂ€ntis Tower and the field sensor located 15 km away at Herisau are taken into account. The effects of the mountainous path on the electromagnetic fields are examined for classical Mâcomponent and Mâcomponentâtype ICC pulses. Use is made of the propagation factors defined as the ratio of the electric or magnetic field peak evaluated along the mountainous terrain to the field peak evaluated for a flat terrain. The velocity of theMâcomponent pulse is found to have a significant effect on the risetime of the electromagnetic fields. A faster traveling wave speed results in larger peaks for the magnetic field. However, the peak of the electric field appears to be insensitive to the Mâcomponent wave speed. This can be explained by the fact that at 15 km, the electric field is still dominated by the static component, which mainly depends on the overall transferred charge. The contribution of the radiation component to the Mâcomponent fields at 100 km accounts for about 77% of the peak electric field and 81% of the peak magnetic field, considerably lower compared to the contribution of the radiation component to the return stroke fields at the same distance. The simulation results show that neither the electric nor the magnetic field propagation factors are very sensitive to the risetimes of the current pulses. However, the results indicate a high variability of the propagation factors as a function of the branchâtoâchannel junction point height. For junction point heights of about 1 km, the propagation factors reach a value of about 1.6 for the Eâfield and 1.9 for the Hâfield. For a junction height greater than 6 km, the Eâfield factor becomes slightly lower than 1. The obtained results are consistent with the findings of Li, Azadifar, Rachidi, Rubinstein, Paolone, et al. (2016, https://doi.org/10.1109/TEMC.2015.2483018) in which an electric field propagation factor of 1.8 was inferred for return strokes and mixedâmode pulses, considering that junction points lower than 1 km or so would result in a mixed mode of charge transfer, in which a downward leader/returnâstrokeâlike process is believed to take place. It is also found that the field enhancement (propagation factor) for return stroke mode is higher for larger ground conductivities. Furthermore, the enhancement effect tends to decrease with increasing current risetime, except for very short risetimes (less than 2.5 ÎŒs or so) for which the tendency reverses. Finally, modelâpredicted fields associated with different charge transfer modes, namely, return stroke, mixedâmode, classical Mâcomponent, and Mâcomponentâtype ICC pulse are compared with experimental observations at the SĂ€ntis Tower. It is found that the vertical electric field waveforms computed considering the mountainous terrain are in very good agreement with the observed data. The adopted parameters of the models that provide the best match with the measured field waveforms were consistent with observations. The values for the current decay height constant adopted in the return stroke and mixedâmode models (1.0 km for the return stroke and 0.8 km for the mixedâmode pulse) are lower than the value of 2.0 km typically used in the literature
Application to Real Power Networks of a Method to Locate Partial Discharges Based on Electromagnetic Time Reversal
This work was supported by the European Unionâs Horizon 2020 Research and Innovation Programme under the Marie SkĆodowska-Curie Grant under Agreement 838681.The paper presents an experimental validation of a method to locate partial discharges (PDs) on power distribution and transmission networks. The method is based on electromagnetic time reversal (EMTR) theory, and it uses a Transmission Line Matrix (TLM) model to describe the propagation of the PD signals in the reversed time. Since PDs are regarded as a symptom of insulation degradation, on-line PD location is considered an important approach to monitoring the integrity of a power distribution network, with the aim of detecting and preventing faults and improving network reliability. In this paper, the EMTR-based method is described and its effectiveness in PD localization using only one measurement point is demonstrated in three real 33 kV power lines. Its effectiveness is proved with and without an on-line electromagnetically noisy environment, and its accuracy is evaluated with respect to different signal-to-noise ratio (SNR) levels of the networks. The validation shows that the method is able to locate PDs with an error of 0.14% with respect to the total length of the line in the absence of noise, and with an error that is always lower than 0.5% for an SNR down to -7 dB
Location Accuracy Evaluation of ToA-Based Lightning Location Systems over Mountainous Terrain
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