JPH03216587A - Method and apparatus for discriminating earth thunderbolt - Google Patents

Abstract

PURPOSE:To surely detect thunderbolt by analyzing the frequency of the electromagnetic wave generated by thunder discharge and utilizing the fact that the discharge in a cloud or between clouds, other than thunderbolt striking ground has a frequency band equal to or more than the peak component of the thunderbolt falling to ground in the judgment of the thunderbolt to ground. CONSTITUTION:A level comparing circuit compares the output level of a band- pass filter 3 for judging thunderbolt striking ground with that of a band-pass filter 5 for judging a bipolar vibration waveform and selects '1' output at a terminal 7a when the output level L1 of the band-pass filter 3 is in L1 > L2 relation to the output level L2 of the band-pass filter 5. When the output almost same in level (L1not equal to L2) is inputted from the band-pass filters 3, 5 at the same time, it is judged that a saw-tooth waveform is present to select the '1' output at the terminal 7a. By this method, even thunderbolt falling to ground having a characteristic waveform can be discriminated from discharge in a cloud or between clouds or others and surely be detected.

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to a method and device for determining ground lightning strikes that can reliably detect ground lightning strikes by distinguishing them from intercloud discharges, intracloud discharges, and communication electromagnetic waves. be.

(Prior Art and its Problems to be Solved) Damage caused by lightning strikes is wide-ranging, including damage to power equipment and power outages due to disruption to the system. Therefore, in order to minimize such damage and stabilize the power supply and demand, it is necessary to collect information on past lightning strikes for appropriate lightning-resistant design of power facilities, and for ground lightning strikes to plan the installation of power transmission lines and substations. It is necessary to understand the regional density of At the same time, it is also necessary to obtain lightning information in real time and implement appropriate system operations. Therefore, various studies have been carried out in the past, and for example, in Japan, so-called lightning discharge counters have been developed for a long time. This indicates the strength of lightning activity, including lightning discharges, and issues a warning when lightning activity exceeds a certain level within a certain period of time. It is not possible to distinguish between them and has the drawback of interference with electromagnetic waves of 150 kHz or higher as stipulated by the Radio Law.

For example, in the United States, a magnetic detection method called LLS or LPAT is used to detect ground-based lightning strikes.
A lightning strike detection device called S that utilizes the arrival time difference technology of electromagnetic waves based on lightning has been proposed and has been introduced in Japan. These devices can distinguish between ground-based lightning and discharge between clouds. However, the basic principle of this device for determining lightning strikes was based on the temporal changes in electromagnetic field waveforms that target summer lightning in the United States. For example, the electromagnetic field waveform normally generated from a lightning strike to the ground is a sawtooth waveform, a so-called triangular-shaped waveform, as shown in Figure 1, and this is not only the electromagnetic field waveform, but also its source. The same applies to the actual lightning current waveform. On the other hand, the electromagnetic field waveforms of intercloud discharges that occur between clouds and intracloud discharges that occur inside clouds are waveforms that oscillate across both polarities, as shown in FIG. Therefore, if we distinguish the above two waveforms using the temporal relationship between the level and the peak, we get
It is based on the principle that it is possible to distinguish between ground-based lightning strikes and other intercloud discharges.

However, it is no exaggeration to say that the waveforms of lightning strikes during winter in the Sea of Japan coast region, which currently account for most of the major accidents involving power equipment in Japan, include the waveforms shown in Figure 1 above. Figure 3. As shown in FIG. 4, there are many waveforms that exhibit extremely complex temporal changes across both polarities, ie, waveforms such as sawtooth waveforms that cannot be expressed using several types of temporal parameters. Therefore, the determination device developed in the United States determines this complicated waveform as noise, which makes it difficult to put it into practical use in Japan, especially in the areas along the Sea of Japan.

In addition, the determination of lightning strikes by this device is very complicated and consists of a large number of electronic circuits, so there is a problem that the device is large and expensive.

(Objective of the Invention) The present invention aims to provide a method and apparatus that can reliably distinguish ground-based lightning strikes, which occur in the Japan Sea coast region in winter and have regional characteristics, from cloud-in-cloud discharge, etc. It is something to do.

(Means of the present invention for solving the problem) The present invention is based on a study that revealed, by frequency analysis of waveforms, that there is a clear characteristic difference between ground-based lightning strikes and cloud-in-cloud discharges. This was done based on the results.

FIG. 5(a) is a frequency analysis result of a sawtooth waveform, which is one of the ground lightning waveforms that occur in summer and winter.
This is the amplitude component of the frequency component normalized by the maximum amplitude. FIG. 5(b) shows the original waveform (electromagnetic field waveform). This waveform has a peak at 5kllz and the highest frequency is 300k
Hz, and the amplitude attenuation rate with respect to frequency is 2
It is large at around 0dB/100kHz.

In particular, near the peak, high frequency components above the peak suddenly become smaller, and the area near the peak looks like a sharp peak.

On the other hand, Fig. 6(a) shows the frequency analysis results of the waveform of Fig. 6(b), which corresponds to the bipolar oscillation waveform that occurs during cloud and intercloud discharge shown in Fig. 2, and in this waveform, the frequency is 30kHz.
It has a peak at , and contains frequency components up to 500kllz. Also, the attenuation rate of amplitude with respect to frequency is 10 dB.
/ It has a frequency of about 100kHz and resembles the shape of a gentle mountain.

Figures 7 (a) and 8 (a) are characteristics that occur during winter in coastal areas at the end of the month shown in Figures 3 and 4 (see Figures 7 (b) and 8 (b)). This is the result of frequency analysis of the waveform of a ground-based lightning strike. As is clear from the comparison with FIG. 5, it shows the same tendency as the frequency analysis result of the sawtooth waveform, and the peak frequency is in the low frequency range of 5 k}Iz to 10 kHz.

FIG. 9 is a diagram showing the cumulative frequency distribution of peak frequencies for each waveform. Table 1 summarizes the distribution of peak frequencies for sawtooth waveforms and bipolar vibration waveforms.
Parameters expressing the distribution are expressed as a general 50% value, a standard deviation indicating the spread of the distribution, and an X% value indicating what percentage of the total is present in that region. Note that here, the region in which 90% of the total exists is defined as between the 5% value and the 95% value.

As is clear from Table 1 and Figure 9, bipolar oscillation waveforms are the waveforms of cloud and intercloud discharges, sawtooth waveforms are the waveforms of ground-based lightning strikes, and the peak frequencies of the characteristic lightning waveforms in the Sea of Japan coast region. are clearly different.

Furthermore, as is clear from Table 1, the peak frequency distributions of the sawtooth waveform and the bipolar oscillation waveform are also significantly different, and what is particularly noteworthy is that the ranges in which 90% of the data exists overlap with each other. There is no such thing.

Therefore, if we monitor the peak frequency of the electromagnetic field waveform when lightning occurs, it is possible to detect ground lightning strikes in winter in the Sea of Japan coast region, which have waveforms that are difficult to detect and distinguish in the temporal domain. , it can be reliably detected and distinguished from cloud discharge.

In addition, in implementation, for example, two band-pass filters having a boundary of 13 kHz are used, and the determination can be made based on which of them has a higher output level. Although it is considered to be an even rarer case, if two filters produce outputs of the same level at the same time, it is determined that the output includes a sawtooth wave component. Even lightning strikes with characteristic waveforms, such as ground-level lightning strikes during winter, can be reliably detected without being recognized as noise, unlike the conventional device. Furthermore, since the determination means is simple, an excellent advantage is obtained that the apparatus can be made small and inexpensive.

Next, examples of the present invention will be described.

FIG. 10 is a block circuit of one embodiment of the present invention. In the figure, (1) is an antenna, for example, 1 to 100.
Any antenna can be used as long as it has flat characteristics in the kHz frequency band, and a general antenna that can be treated as a dipole, such as a loop antenna, a parallel plate antenna, or a Rondo antenna, is used. (2) is a narrowband amplifier for detecting ground lightning strikes, and has a frequency of 1 to 13 kHz.
It has flat characteristics in both amplitude and phase over the frequency band. Reference numeral (3) is a band-pass type filter for determining ground lightning strikes, which has a pass band of 1 to 13 kHz and provides large attenuation to low and high frequencies other than this. (4) is a broadband amplifier for determining bipolar vibration waveforms such as in-cloud and inter-cloud discharges, and has flat characteristics in both amplitude and phase over the frequency band of 13 to 77 kHz. (5) is a band-pass filter for bipolar vibration waveform determination;
It has a passband of kHz and provides large attenuation to other low and high frequencies. (6) is a discrimination circuit,
It is formed from the following parts. (7) is a level comparison circuit, which compares the output levels of a bandpass filter (3) for determining ground lightning strikes and a bandpass filter (5) for determining bipolar vibration waveforms caused by snow, intercloud discharge, etc. However, the output level L of the band-pass filter (3) is lower than the output level L2 of the band-pass filter (5). >Lm, a "1" output is sent to the terminal (7a).

Also, being in a LI-L2 relationship means that the terminal (7b) is “1”.
”Sends the output.Also, as mentioned above, at the same time and to the same extent (
When an output with a level of t, +f = t, z) is input from the bandpass filters (3) and (5), it is assumed that a sawtooth waveform exists and a "1" output is sent to the terminal (7a). do. (8) is an output circuit that detects the location of a lightning strike based on the difference in arrival time with the output (9) of a determination device set at a different location, such as a circuit that generates an alarm sound for a ground-based lightning strike, a self-recording recorder for level measurement, or other determination device set at a different location. It consists of arithmetic circuits necessary to obtain lightning information.

(Effects of the Invention) As is clear from the above, according to the present invention, a device with a simple configuration can prevent ground-based lightning strikes with characteristic waveforms that occur in winter in the Japan Sea coast region, where damage is severe, to be detected in and between clouds. It can be detected reliably, distinguishing it from electrical discharges and others, and can provide a variety of information essential for setting up lightning protection for power facilities and planning the installation of power transmission lines and substations.

[Brief explanation of drawings]

Figure 1 is a waveform diagram showing a typical example of ground-based lightning strikes in summer.
Figure 2 is in the clouds. Typical waveform diagrams of intercloud discharge, etc.; Figures 3 and 4 are typical waveform diagrams of land-based lightning strikes that occur in winter in the Sea of Japan coast region; Figures 5 (a) and (b) are typical waveform diagrams of ground lightning strikes that occur in summer and winter. Figures 6 (a) and (b) show the frequency analysis results and original waveform diagrams of ground-to-ground lightning strikes, and Figure 7 (a) (
b), Figures 8 (a) and (b) are frequency analysis results and original waveform diagrams of ground lightning waveforms that occur in winter in the Sea of Japan coast region, Figure 9 is a cumulative frequency distribution diagram of peak frequencies for each waveform, FIG. 10 is a circuit diagram of an embodiment of the present invention. (1)...Antenna, (2)...1~13kli
z narrowband amplifier, (3)...1 to 13kHz bandpass filter, (4) 13 to 77kHz - wideband amplifier, (5) ・13 to 77kHz bandpass filter, (6)... -Discrimination circuit, (7)...Level comparison circuit, (8)...Output circuit. agent

Claims (2)

[Claims] (1) Frequency analysis of electromagnetic waves generated by lightning discharge shows that the peak frequency component of ground-based lightning strikes has a frequency band of 1 to 13 kHz, and that discharges in clouds and between clouds other than ground-based lightning strikes are higher than the peak main component of ground-based lightning strikes. A method for determining a lightning strike to the ground, which is characterized by determining a lightning strike to the ground by utilizing a frequency band. (2) An antenna for receiving electromagnetic waves based on lightning discharge, an amplifier for determining ground lightning strikes, and a 1 to 13 kHz band-pass filter each receiving the output of this antenna as input;
Amplifier for discriminating discharge other than ground lightning strikes and 13 to 77k
Hz band-pass filter and the output level of the 1-13 kHz band-pass filter are compared, and the output level of the band-pass filter is 13-77 kHz.
1. A lightning strike discrimination device for detecting a lightning strike to the ground, comprising a discrimination circuit that determines a lightning strike to the ground when the output level of the band-pass filter of ~13 kHz is high.