• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.5
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• pp.112-117
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• 2004

In this paper, in order to obtain the detailed information about lightning electromagnetic pulses, the electromagnetic pulses radiated from intracloud discharges were measured, and their characteristics and waveform parameters were analyzed statistically. The electromagnetic pulses produced by intracloud discharges are distinctly different with those by lightning return strokes. The zero-crossing times and the full pulse widths of the large bipolar electromagnetic pulses are gradually decreased as the stroke proceeds. Also, the electromagnetic pulses tend to be bipolar, with narrow and fast leader pulses superimposed on the initial half cycle. The mean numbers of leader pulses superimposed on the initial half cycle were 1.61$\pm$0.74 and 1.75$\pm$0.73 for the positive and negative polarities, respectively.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.1
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• pp.35-41
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• 2003

In this paper statistics on the radiation field waveforms produced by stepped leaders just prior to lightning return strokes were described. As a parameter of stepped leader pulse characteristics, the time interval between the final leader pulse and return stroke peak, the pause time between stepped leaders, the ratio of the final leader peak to the return stroke peak and the stepped leader pulse width at half maximum were examined. The average time intervals between the final leader pulse and return stroke peak were about 16.2 and 14.8$mutextrm{s}$ for the positive and negative polarities, respectively. When the stepped leader approaches closely to ground, the time interval between leader steps was decreased and the mean value was about 17$mutextrm{s}$, and the present results were in reasonable agreement with the data observed in Florida and Japan. The large fraction of the ratios of the final stepped leader pulse to the lightning return stroke peak were distributed over the range from 5 to 35% and in average the ratio of the final leader pulse to the return stroke peak was 17.4$\pm$11.9% for the positive and 18.5$\pm$9.4% for the negative electric field waveforms. In addition, the mean pulse widths at half maximum of the stepped leaders are 1.4Us with a standard deviation of 0.9 for the positive Polarity and 2.2us with a standard deviation of 1.2 for the negative polarity, respectively.

• Journal of Electrical Engineering and Technology
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• v.7 no.3
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• pp.406-410
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• 2012

This paper looks into the field inside the wide rectangular box structure that is excited by the High Power Electromagnetic(HPEM) source as a potential threat to electric grid and communication networks causing malfunction or destruction. The rectangular box is assumed power/ground planes and its internal field is calculated by the cavity model with the lightning strike excitation as an HPEM pulse. The accuracy of the calculation method employed here is validated through a $156mm{\times}106mm{\times}508{\mu}m$ parallel metallic plate case which is manufactured and tested, and is applied to the size of a building. With the help of the cavity model that takes into account loading, the level of the electric field is shown to decrease when a metal pillar is loaded between the power and ground planes.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.6
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• pp.59-66
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• 2005

This paper presents some features and statistics of electromagnetic pulses radiated from intracloud lightning discharges. The LabVIEW based-measurement system of time-dependent electromagnetic fields was constructed. The frequency bandwidth of the measuring system ranged from 300[Hz] to 1[MHz], and the response sensitivity was 2.78(mV/nT). The resolution and the maximum recording length of the data acquisition system were 12(bits) and 100[ms], respectively. In the electromagnetic pulses radiated from intracloud discharges, a pronounced bipolar pulse appeared with one or more fast pulses superimposed on the initial front part of the bipolar pulse. The mean duration of intracloud discharges was $1.05{\pm}0.32[ms]$, and an average of about 8 outburst pulses appeared for a period.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.6
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• pp.330-336
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• 2004

In this work, in order to obtain the detailed information about lightning electromagnetic pulses, the electric fields radiated from multiple lightning return strokes were measured and analyzed statistically. The electric field measuring system consists of a hemisphere antenna of 30cm in diameter, integrator and data acquisition device, and its frequency bandwidth ranges from 200Hz to 1.56MHz, and the sensitivity is 0.96㎷/V/m. The electric field signals are digitized every 200ns with the transient signal analyzer having the resolution of 12-bit and the recording length of 5 kilowords and are registered at personal computer. As a result, the electric fields produced by the first return stroke begin with a slow initial part or front, which starts just after or during the last stepped leader. On the average the rise times of the electric fields for the positive first, second and third strokes are 4.21${\mu}\textrm{s}$, 3.94${\mu}\textrm{s}$ and 2.75${\mu}\textrm{s}$, respectively, and those for the negative first, second and third strokes are 3.46${\mu}\textrm{s}$, 3.15${\mu}\textrm{s}$ and 2.79${\mu}\textrm{s}$, respectively. The zero-crossing times of the electric fields for first return strokes range from about 10 to 80${\mu}\textrm{s}$. The mean zero-crossing times for subsequent return strokes are shorter than those for first lightning return strokes.

• Journal of Sensor Science and Technology
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• v.13 no.5
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• pp.363-368
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• 2004

A reliable voltage measurement system is necessary to monitor status of power facilities in substations, which is easy to set up and is not influenced by electromagnetic interference in and around substation. In this paper, we described a voltage measurement system (VMS) which is composed of a capacitive voltage probe, an impedance converter, and an optical linker. To get a wide-band characteristic of the VMS, a high speed impedance converter was used, and the output impedance of the VMS was set at $50{\Omega}$ to match any types of observing instruments. The frequency bandwidth of the VMS. which was estimated by a step pulse, was ranges from 11.42 Hz to 13.65 MHz, and the VMS showed a good response characteristic in a high frequency domain such as impulse voltages as well as a commercial frequency voltage.

• Journal of the Korea Society for Simulation
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• v.30 no.2
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• pp.33-40
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• 2021

The situation of high-altitude electromagnetic pulses (HEMP) arises from high-altitude nuclear explosions. The HEMP situation can be simulated through the threat level investigation (TLI). In this paper, the induced voltage according to the antenna type of the tactical mobile radio communication system was measured and analyzed by TLI. Under the influence of HEMP, electronic equipment can be paralyzed or damaged. HEMP protection filters are commercially available for power lines and signal lines. However, commercialization of HEMP filters for antennas is insufficient, and even some of them exist for lightning protection. In order to make an appropriate HEMP protection filter according to the frequency and type of the antenna, the induced voltage was measured and the maximum induced voltage was analyzed through extrapolation. It was found that the measured induced voltage decreased as the frequency increased, such as in the HF, VHF and UHF bands of the measurement results.