Observation of Induced Voltage at the Terminal of 10 kV Distribution Line by Nearby Triggered Lightning

et al. 2022

Sci Rep

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A stepped leader propagated along the previous return-stroke channel in triggered lightning. After the stepped leader decayed, the first bidirectional leader went through the process of initiation, propagation and dissipation. Then the second bidirectional leader initiated at the termination of the decayed first bidirectional leader and propagated toward the ground, generating the fourth return-stroke. The observations were synchronously performed through a high-speed camera and electromagnetic field measurements. The first bidirectional leader was characterized by similar average upward and downward velocities of 0.76 × 106 m/s and 0.67 × 106 m/s. The velocity of the upward positive leader of the first bidirectional leader was noticeably fluctuated, ranging 0.39 × 106–1.78 × 106 m/s. The second bidirectional leader was characterized by a sustainable propagating upward end with an average velocity of 1.82 × 106 m/s. The velocity fluctuation trend of the upward end depends on the neutralization amount of the residual negative charge and the positive charge in UPL.

Section: Methodsmentioning

confidence: 99%

Two successive bidirectional leaders propagated in triggered lightning channel

et al. 2022

Sci Rep

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“…The configuration of the experiment equipment at the test site was shown in Figure 1. Our lightning rod installed at the epoxy tower was 12 m high and was connected to a transmission line via a metal wire for transmission characteristics study of direct lightning strikes and induced lightning strikes along transmission lines and protection characteristics of lightning arresters (Wang et al., 2020). The channel‐base current was measured by a coaxial shunt with a resistance of 1 milliohm.…”

Section: Experiments and Equipmentmentioning

confidence: 99%

Optical Progressing and Electric Field Change Characteristics of Altitude—Triggered Lightning Flash With Different Development Paths

et al. 2021

JGR Atmospheres

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The characteristics of optical and electric field waveforms from altitude triggered lightning flash at Guangzhou Field Experiment Site for Lightning Research and Testing (GFESLRT) during the summer of 2019 are presented. The altitude triggered lightning flash had eight return strokes with nine M‐components along four development paths. And the terminal heights of four paths are over 1,626 m above the ground. Our study presented an arithmetic mean of 0.62 kV/m and an arithmetic mean of 0.63 ms of half‐peak width for 16 initial continuous current (ICC) pulses values, as well as an arithmetic mean of 1.24 kV/m and an arithmetic mean of 0.47 ms of half peak width for nine M‐components values. The average 2‐D speed ranged from 3.80°× 105 to 2.94 × 106 m/s for the attempted leaders and from 1.26 × 106 to 6.96 × 106 m/s for the dart leaders. Basically, the greater the downward leader’s 2‐D propagation speed, the larger the electric field change. The electric field waveform in the rising edge of return stroke can be divided into three parts: “SF” indicates the slow front of the return stroke; “FT” indicates the fast transition of the return stroke; “SS” indicates shoulder structure of the return stroke. The arithmetic mean of SF electric field change is 1.45 kV/m and that of SF risetime is 110.6 μs. The arithmetic mean of the first FT electric field change is 4.71 kV/m and that of the first FT risetime is 1.1 μs. The arithmetic mean of the SS electric field change is 3.89 kV/m and that of the SS risetime is 28.1 μs.

“…Since summer of 2018, comprehensive lightning observations and experiments have been conducted by the laboratory of the Lightning Protection and Grounding Technology Center, Wuhan University in Conghua, Guangdong Province (Wang et al., 2020). The lightning was led accurately to the lightning rod by a small rocket launched with the copper wire.…”

Section: Instrumentationmentioning

confidence: 99%

Differences Between Flashes With and Without Return Strokes in Rocket‐Triggered Lightning

Geophysical Research Letters

et al. 2021

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The initial stage of triggered lightning includes the upward positive leader and the following initial continuous current, usually lasting for tens to hundreds of milliseconds, and the current pulse superimposed on the initial continuous current is called ICC pulse (Fisher et al., 1993;Zhou et al., 2015). During the upward positive leader, the initial current variation usually occurs due to wire destruction. After wire destruction, the reconstruction process of the current occurs and plasma channel is reestablished (Biagi et al., 2009), in this way, the triggered lightning is successful. The triggered lightning may or may not contain return strokes, the current cutoff and reestablishment process in the initial stage may affect the formation of return stroke. Olsen et al. (2006) defined Type I and Type II that differ in shape during the initial current variation and found several attempted reconnection pulses prior to the successful current reestablishment with current magnitude of 100 A. Zhang et al. (2017) and Li et al. (2020) observed of the initial stage of a rocket-triggered lightning flash with a high-resolution broadband very high frequency interferometer. However, the current was not recorded via synchronization.Based on simultaneously measured currents and electric field changes, we analyzed the parameter characteristics of the initial stage in rocket-triggered lightning with return strokes and that without return stroke, and obvious differences have been identified between these two kinds of triggered lightning. InstrumentationSince summer of 2018, comprehensive lightning observations and experiments have been conducted by the laboratory of the Lightning Protection and Grounding Technology Center, Wuhan University in Conghua, Guangdong Province (Wang et al., 2020). The lightning was led accurately to the lightning rod by a small rocket launched with the copper wire. The lightning current was measured by the coaxial shunt with a resistance of 1 milliohm and Rogowski coil, and two current measurement ranges are ±50 and ±2 kA,