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Source publication
In most of the studies dealing with electromagnetic field
interaction between nearby lightning flashes and electrical
installations, the cloud flashes are assumed to play an insignificant
role. However, our studies show that cloud flashes can generate induced
voltages with amplitudes comparable to those of ground flashes when the
electrical install...
Contexts in source publication
Context 1
... Y-shaped artificial LVPI was built and erected in a meadow close to the Institute of High Voltage Research, Uppsala, Sweden. The cable used in the installation had three isolated wires slightly twisted and enveloped by a PVC insulating jacket (Fig. 1). The length of each turn of the internal wires of the twisted cable was 1 m, alternating the position in a trifilar helix. The voltage measurements were made across a 50-resistor that was connected between the line and protective earth wires (point C in Fig. 2) at one end of the installation. The other two ends of the installation were ...
Context 2
... examples of measured electric fields due to cloud flashes are shown in Figs. 8-11. Even though the first few microseconds of the records were used in the voltage simulation, the total length of the measured fields and voltage records was 10 ms. The features of the recorded waveforms clearly show that these fields are generated by cloud flashes [16]. Note that the electric field pulses generated by cloud flashes are ...
Context 3
... results of our calculations are shown in Figs. 8-11. Note that only in some pulses the amplitude and the shape of the calculated induced voltage agree well with the measured, while in others there are some important differences. The reason for this is that the value of earthing resistance needed to produce a match between the measured and calculated voltage due to a cloud pulse depends ...
Context 4
... voltage was applied in one conductor and the induced voltage was measured in the other conductor, keeping the third one floating. The advantage of the experimental results is that the induced voltage in the receptor circuit contains all the possible modes of coupling (capacitive, inductive, and conductive). The experimental setup is shown in Fig. 12 and the network corresponds to the same circuit used in the original measurements (as indicated by Fig. 4) except for the connection to ground of the protective earth conductor. A Schaffner impulse generator was used to apply the voltage to one conductor through a matching resistor for the impulse generator Rm = 50 and a matching ...
Context 5
... generator Rm = 50 and a matching resistor for the network Rmt = 490 . The terminating resistors R L1 for the generator circuit and R L2 for the receptor circuit were 50 . Due to the fact that the Schaffner generator can generate interference levels in its vicinity, a metallic shielding enclosing the impulse generator was used (dashed line in Fig. 12). The voltage V1 was measured out of the metallic shielding by using a 1002 Tektronix voltage probe of 10 M of input resistance and a bandwidth of 03 dB at 120 MHz. In order to avoid electromagnetic compatibility problems, the voltage V2 was measured by using a Sentinel 1000 fiber-optic link in which the time response lies in the range ...
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Transmission line arresters may be subjected to high energy
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configurations with different degrees of shielding efficiency were used
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The effect of lightning on airborne electronic equipment and powerlines can be severe and a study requires the solution of electromagnetic fields radiated by the lightning flash. We model the return stroke by simple dipolelike line elements with resident charges prior to the return stroke. The resulting computations are from simple closed‐form expr...
Citations
... Voltages induced on an overhead power distribution line by lightning strokes to nearby ground are the most frequent cause of outages on these lines[1]. Further, many instances have been noted and published regarding induced potential from lightning to telecommunication lines[2], data lines[3]and power lines[4][5]. While many research on induced voltages focus on its effect to insulation across the conductor and ground, this work concentrates on the determination of the parameters of the Ground Lightning Return Stroke (GLRS). ...
... A lightning may induce voltage impulses in the conductors in the vicinity due to electromagnetic coupling. The amplitude and the profile of such voltage impulses depends on the Peak and time derivative of the lightning impulse current, proximity to the lightning, ground conductivity (propagation effects), length of the conducting line exposed, its orientation and termination, height of line above the ground, branches of the line between the generation point and the victim etc. [14][15][16][17][18][19][20][21][22] As it was reported by [17], in an isolated small house, the induced voltages in a de-energized power line (which is decoupled from the external supply) exceeded 100 V for a ground flash that struck 24 km away. The rise time of the induced voltage was typically less than a microsecond and the individual pulse width was typically a few microseconds. ...
... Several studies reported in [29] show that in preliminary breakdown pulses (pulse trains that precede return strokes) recorded in Sweden and Denmark the maximum pulse amplitude is several times greater than that of the succeeding return stroke (such observation is not made in the PBPs measured in tropics). As it was observed in several studies [16,17] the induced voltages due to such cloud flashes have amplitudes comparable with that of return stroke generated voltages pertinent to cloud to ground flashes around 10-20 km. However, one could expect the amplitudes of voltages induced by ground flashes will be much greater as the ground strike location becomes closer to the point of observation (as the cloud flashes can not be very close due to the height). ...
A comprehensive review has been done on the types of transients that may affect low voltage electrical systems. The paper discusses various characteristics of lightning, switching, nuclear and intentional microwave impulses giving special attention to their impact on equipment and systems. The analysis shows that transients have a wide range of rise time, half peak width, action integral etc. with respect to both source and coupling mechanism. Hence, transient protection technology should be more specific with regard to the capabilities of the protection devices.
... A lightning may induce voltage impulses in the conductors in the vicinity due to electromagnetic coupling. The amplitude and the profile of such voltage impulses depends on the peak value and peak time derivative of the lightning impulse current, proximity to the lightning, ground conductivity (propagation effects), length of the conducting line exposed, its orientation and termination, height of the line above the ground, branches of the line between the generation point and the victim etc.1314151617. As it was reported by [14], in an isolated small house, the induced voltages in a de-energized power line (which is decoupled from the external supply) exceeded 100 V for a ground flash that struck 24 km away. ...
A comprehensive review has been done on the types of electromagnetic transients that may a®ect low voltage electrical systems. The paper discusses various characteristics of lightning, switching, nuclear and intentional microwave impulses giving special attention to their impact on equipment and systems. The analysis shows that transients have a wide range of rise time, half peak width, action integral etc. with respect to both source and coupling mechanism. Hence, transient protection technology should be more specific with regard to the capabilities of the protection devices. Furthermore, we discuss the components and techniques available for the protection of low voltage systems from lightning generated electrical transients and the adequacy of International Standards in addressing the transient protection issues. The outcome of our analysis questions the suitability of 8/20 μs test current impulse in representing characteristics such as the time derivative and the energy content of lightning impulses. The 10/350 μs test current impulse better represents the integrated e®ects of the energy content of impulse component and long continuing current. A new waveform is required to be specified for testing the ability of protective devices to respond to the fast leading edges of subsequent strokes that may appear 100 s of millisecond after the preceding stroke. The test voltage waveform1.2/50 μs should also be modified to evaluate the response of protective devices for fast leading edges of induced voltage transients. A surge protective device that is tested for lightning transients may not be able to provide defense against other transients.
... Voltages induced on an overhead power distribution line by lightning strokes to nearby ground are the most frequent cause of outages on these lines[1]. Further, many instances have been noted and published regarding induced potential from lightning to telecommunication lines[2], data lines[3]and power lines[4][5]. While many research on induced voltages focus on its effect to insulation across the conductor and ground, this work concentrates on the determination of the parameters of the Ground Lightning Return Stroke (GLRS). ...
... First, the overvoltages are transmitted to the installation through the power-supply network. Second, the overvoltages, which are directly induced in the LV power installations by lightning flashes, directly strike the LPS or indirectly to the proximity of the LPS [7]. It is worth mentioning that for indirect strikes to LPSs, there is a worldwide agreement that the danger radius around a point struck by lightning is about 2 km [8]. ...
This paper presents a numerical electromagnetic analysis of loop-termination voltages inside an outer lightning protection system (LPS) resulting from direct and indirect lightning strikes. The method of moments is combined with the transmission-line model and employed to model the whole structure in three dimensions and the lightning channel, respectively. Three distinct types of class II LPS are modeled with one- and three single-phase parallel vertical loops of the TN-S system inside the LPS. All cases are simulated by using the negative subsequent stroke current with linear-rising front at lightning-protection level II. The connected equipment at the loop terminals is considered in the offstate to simulate the worst condition. The results reveal that for the three-loop configurations, the middle-loop termination voltages of all floors are always higher than those of the outer loops and the frequency of oscillations of the middle loop is roughly twice that of the outer ones. In addition, the midedge strike case gives higher loop-termination voltages for all floors than those of the corner strike case. For the slender LPS, the effect of the strike location dominates in the case of high surge impedance of the feeder only.
There is a general consensus that a transmission line under the ground is less prone to the induction effects caused by a nearby lightning flash. However, the low threshold operation energy levels of modern electronic equipment can be attained in the transmission line due to coupling of electromagnetic fields radiated by the lightning, even if the line is underground. There are numerous references, e.g. [1] – [4], in which the influence of a lightning discharge on above ground power lines and low-voltage installations is investigated. Yet, there is a lack of information on the behaviour of lines under the ground. Therefore a more detailed investigation of induction effects is required for this case.
This paper presents a theoretical investigation on lightning overvoltages on low-voltage (LV) networks installed in urban areas. The combined effect of lightning-induced voltages and transferred lightning surges through distribution transformers is taken into account. It is shown that an accurate estimate of lightning overvoltages on LV networks that have a neutral conductor grounded at the transformer pole require the consideration of the medium voltage line and its electrical connections with the LV line. It is also shown that if the stroke location is relatively close to the evaluated LV line it is possible to neglect the influence of other LV lines in the estimation of peak overvoltages on the connected loads. Finally, it is shown that load overvoltages are strongly dependent on the assumed load model, which suggests that simplified load models must be viewed with caution in studies of lightning overvoltages on LV networks.
