JP4171752B2 - Lightning strike electric field amount calculation device and method, program, computer-readable recording medium - Google Patents

Description

  The present invention relates to a lightning strike charge amount calculation device and method for calculating a lightning strike charge amount using measurement results of an electric field and a magnetic field.

  Since lightning strikes can cause enormous damage to various facilities and equipment such as power transmission facilities, conventionally, an apparatus for detecting an approach of lightning and generating an alarm has been proposed (for example, Patent Document 1, (See Patent Document 2).

  By the way, when a lightning strike occurs, it is known that the greater the amount of lightning charge, the greater the damage caused by the lightning strike. Therefore, in order to grasp the degree of damage caused by lightning, it is necessary to correctly calculate the lightning charge amount. However, the device described in Patent Document 1 detects the approach of lightning based on the lightning surge current, and the device described in Patent Document 2 detects lightning due to changes in corona current and electric field. In any case, it is not considered to calculate the amount of lightning strike.

In general, regarding the lightning charge, it is known that the charge amount Q (C) of the lightning is expressed by the following equation (1).

Where π is the circular constant, ε ₀ is the dielectric constant of air, ΔE (V / m) is the change in electric field before and after the lightning strike, and D (m) is observed from the lightning strike point where the lightning strikes the ground. The horizontal distance to the point, H (m), indicates the height of the charge immediately before the occurrence of lightning.

Here, the electric field change amount ΔE can be measured by a known electric field measuring device, and the distance D can be measured by a lightning strike location system (see, for example, Non-Patent Document 1). Conventionally, with respect to the lightning to be evaluated, the electric field change amount ΔE and the distance D are measured at two points, and the measured value at each point is substituted into the equation (1), whereby the charge amount Q and the altitude are measured. A simultaneous equation with H as an unknown is set up, and the charge amount Q and the altitude H are calculated by solving the simultaneous equation.
Japanese Patent No. 3098078 JP 2003-149349 A Yasuo Kishimoto, “Latest Trends in Lightning Observation Systems and Lightning Protection Standards”, [online], NTT Architecture Research Institute, [October 26, 2005 search], Internet <URL: http: //www.ntt-bti .co.jp / pdf / 2005_kish.pdf> Martin A. Uman, “The Lightning Discharge” (USA), 1st edition, Dover Publications, 2001, p. 313-317

  However, the electric field may change due to causes other than lightning such as noise, and it has conventionally been difficult to accurately determine whether the observed change in electric field is due to lightning strikes or causes other than lightning strikes. In particular, when the electric field rises steeply, it can be determined that the electric field change is due to lightning, but when the electric field changes relatively slowly, it is difficult to determine whether it is a change due to the electric field. .

  The present invention has been made in view of the above points, and by using not only an electric field but also a change in a magnetic field, it is possible to accurately determine an electric field change caused by a lightning strike, thereby accurately calculating a lightning charge amount. The purpose is to do so.

In order to achieve the above object, the present invention is a lightning strike evaluation device for calculating the amount of lightning strike,
A data acquisition unit for acquiring electric field data indicating a time change of an electric field at a predetermined measurement target point and magnetic field data indicating a time change of a magnetic field at the predetermined target point;
Based on the acquired electric field data and magnetic field data, a lightning strike charge calculating unit for calculating a lightning strike charge amount,
The lightning strike charge calculation unit
A first determination unit that determines that the electric field change is an electric field change caused by a lightning strike when the acquired electric field data has an electric field change larger than a first predetermined gradient;
When the acquired electric field data has an electric field change that is greater than a second predetermined gradient that is smaller than the first predetermined gradient and less than or equal to the first predetermined gradient, the electric field change occurs. If the change in the magnetic field data is more than a predetermined level during the operation, it is determined that the change in the electric field is an electric field change caused by lightning, and if the change in the magnetic field data is not more than the predetermined degree. A second determination unit that determines that the electric field is not an electric field change caused by lightning,
The electric field value immediately before the first electric field change determined by the first determination unit or the second determination unit as the electric field change due to the lightning strike, and the electric field change due to the lightning strike by the first determination unit or the second determination unit. An electric field change determination unit that determines a difference between the electric field value immediately after the last electric field change determined to be as an electric field change amount by lightning,
A charge calculation unit that calculates a lightning strike charge amount based on the determined electric field change amount.

  According to the present invention, by using not only the electric field but also the change in the magnetic field, the change in the electric field associated with the lightning can be accurately determined, so that the lightning charge amount can also be accurately calculated.

  FIG. 1 is an overall configuration diagram of a system including a lightning charge evaluation device 1 according to an embodiment of the present invention. As shown in the figure, the lightning charge evaluation device 1 of this embodiment is connected to a lightning discharge position locating device 50 and a plurality of measuring slave stations 10.

  The measurement slave station 10 includes an electric field measurement unit 12 and a magnetic field measurement unit 14, and is arranged in a lightning monitoring target area at intervals of, for example, several tens of kilometers. The electric field measurement unit 12 measures the electric field at the installation location of the measurement slave station 10 and generates data indicating the time change of the electric field (hereinafter referred to as electric field data). The magnetic field measurement unit 14 measures the magnetic field at the point where the measurement slave station is arranged, and generates data indicating the temporal change of the magnetic field (hereinafter referred to as magnetic field data). These electric field data and magnetic field data are transmitted to the lightning strike evaluation device 1 together with the identification information of the measurement slave station 10. FIG. 2 shows an example of electric field data and magnetic field data measured by the measuring slave station 10 and transmitted to the lightning charge evaluation device 1.

  The lightning discharge position locating device 50 is a known device having a function of locating a lightning strike position by receiving electromagnetic waves radiated from lightning discharge at a plurality of points and analyzing the received electromagnetic waves. The details are described in Non-Patent Document 1 and the like, for example. Information indicating the lightning strike position determined by the lightning discharge position locating device 50 is transmitted to the lightning strike evaluation device 1.

  As shown in FIG. 1, the lightning strike evaluation apparatus 1 includes a data acquisition unit 20, a lightning strike position acquisition unit 22, a lightning strike detection unit 24, a reader detection unit 26, a reader progress time calculation unit 28, a charge altitude calculation unit 30, and Each function unit of the lightning charge calculation unit 32 and a display device 34 which is a display device such as a CRT or a liquid crystal are provided. The lightning strike evaluation device 1 is configured by, for example, a computer system, and the functional units 22 to 32 are realized by a computer CPU reading and executing a program stored in a storage device such as a hard disk device.

  The data acquisition unit 20 acquires electric field data and magnetic field data transmitted from the measurement slave station 10. In addition, the lightning strike position acquisition unit 22 acquires the lightning strike position information transmitted from the lightning discharge position assessment device 50.

  The lightning strike detection unit 24 detects a lightning strike time based on the electric field data acquired by the data acquisition unit 20. Specifically, in the electric field data, as shown by the symbol A in the electric field waveform shown in FIG. 2, when a peak waveform in which the magnitude of the electric field rapidly changes in a minute time of about several milliseconds appears, The generation time of the peak waveform is determined to be the lightning occurrence time. More specifically, a point in time when a steep electric field change exceeding a predetermined gradient occurs is determined as a lightning strike occurrence point. In FIG. 2, the peak of the electric field waveform is generated a plurality of times as indicated by the symbols A, B, C, D, etc. This is because one lightning strike is divided into a plurality of discharges. The peak A that appears first is determined as a lightning strike point.

  Based on the magnetic field data acquired by the data acquisition unit 20, the reader detection unit 26 detects the generation time of the reader that occurs prior to the occurrence of a lightning strike. Note that the leader is a phenomenon in which lightning charges are discharged in a thundercloud before the occurrence of a lightning strike, and a lightning strike occurs when the leader generated in the thundercloud progresses toward the ground. The reader detection unit 26 refers to the magnetic field data in a predetermined period before the lightning strike detection point detected by the lightning occurrence detection unit 24, and the magnitude of the electric field suddenly changes in the magnetic field waveform within a short period of time. When the peak waveform to appear appears, the generation time of the peak waveform is determined to be the reader generation time. More specifically, as in the case of determining the lightning occurrence time point, the time point when the steep magnetic field change exceeding a predetermined gradient occurs is determined as the reader generation time point. In FIG. 2, it is determined that the time point X is the time when the leader is generated.

  The leader progress time calculation unit 28 calculates the time from the occurrence of the reader detected by the reader detection unit 26 to the occurrence of the lightning strike detected by the lightning occurrence detection unit 24 as the leader progress time.

  The charge height calculation unit 30 calculates the height of the lightning strike based on the leader progress time calculated by the reader progress time calculation unit 28 and the reader progress speed. As mentioned above, a lightning strike occurs when a leader generated in a thundercloud progresses toward the ground and reaches the ground, but when the leader progresses from the thundercloud toward the ground, The speed is the leader progress speed and is generally 0.2 m / μsec. Therefore, the altitude (height from the ground) of the lightning strike can be obtained by multiplying the leader progress time, which is the time from the occurrence of the leader to the time of the lightning strike, by the leader advance speed.

  The lightning charge calculation unit 32 is based on the height of the lightning charge determined by the lightning height calculation unit 30 as described above, the lightning occurrence position acquired by the lightning position acquisition unit 22, and the electric field data acquired by the data acquisition unit 20. To calculate the lightning charge amount.

  The display device 34 displays the lightning strike height calculated by the lightning strike height calculation unit 30 and the lightning strike charge calculated by the lightning charge calculation unit 32, and the data acquired by the data acquisition unit 20 and the lightning strike position acquisition unit as necessary. The position information acquired at 22 is also displayed.

As described in the background section, assuming that the electric field change caused by a lightning strike is ΔE, the distance between the lightning strike point and the observation point is D, and the height of the lightning strike charge is H, the lightning charge amount Q is expressed by the equation (1). Is done.

  Among the parameters necessary for determining the lightning charge amount Q, the lightning charge height H can be calculated by the charge height calculation unit 30 as described above, and the distance D is the transmission source of the electric field data and magnetic field data. It can be calculated from the position information of the measurement slave station and the lightning position information acquired by the lightning position acquisition unit 22. Further, the electric field change ΔE due to lightning can be obtained from the electric field data. The lightning strike charge evaluation apparatus 1 includes a database that holds the correspondence between the identification information of each measurement slave station 10 and the position information, and the charge height calculation unit 30 is sent together with the electric field data and the magnetic field data. Based on the identification information, the position information of the measurement slave station 10 can be acquired by referring to the database.

  Hereinafter, a method for obtaining the electric field change ΔE caused by lightning from the electric field data will be described.

  FIG. 3 is a diagram showing the waveforms of the electric field and the magnetic field when a lightning strike occurs by enlarging the time scale to about 1000 times that of FIG. 2, and the electric field is indicated by a solid line and the magnetic field is indicated by a broken line. In general, lightning strikes often occur when electric charges are divided into a plurality of times and discharged to the ground, and the electric field waveform shown in FIG. 3 also changes a plurality of times corresponding to the plurality of discharges. Among these, the electric field changes ΔE1, ΔE2, ΔE3, ΔE5, ΔE6, and ΔE7 appearing in the electric field waveform of the same figure rise steeply and can be determined to be electric field changes accompanying lightning strikes. On the other hand, the electric field change ΔE4 is caused by the electric field rising with a relatively small gentle gradient. Such a gradual change in the electric field may be caused by noise, and it is difficult to immediately determine from the electric field waveform whether this electric field change ΔE4 is caused by a lightning strike.

  On the other hand, in this embodiment, the lightning charge calculation unit 32 accurately determines whether or not a gentle change such as the electric field change ΔE4 is caused by a lightning strike by referring to the magnetic field data as follows. I can do it.

  According to the investigation and research conducted by the inventors of the present application, while the electric field changes due to lightning, the magnetic field also changes intermittently as indicated by reference numerals S1, S2, S3, S5, S6, S7, etc. in FIG. I know what to do. Accordingly, the lightning charge calculation unit 32 determines whether or not a change exceeding the noise level has occurred in the magnetic field data during the period in which the gentle electric field change occurs, such as the electric field change ΔE4, and the change in the magnetic field has occurred. If so (reference S4 in FIG. 3), it is determined that the electric field change is an electric field change caused by a lightning strike. Then, from the value of the electric field immediately before the first electric field change (ΔE1 in the example of FIG. 3) due to the lightning strike (hereinafter referred to as the electric field initial value E0), the final electric field change (ΔE7 in the example of FIG. 3) is completed. The electric field change amount Etotal (= Ee-E0) up to the electric field value at the time (hereinafter referred to as the electric field value Ee after the lightning strike) is defined as the electric field change ΔE caused by the lightning strike, and this is substituted into the equation (1), Q is calculated. Here, it is assumed that the electric field change due to the lightning strike does not appear even after a certain time after the electric field change ΔE7 shown in FIG. 3, and this ΔE7 is determined to be the last electric field change due to the current lightning strike. Yes.

  FIG. 4 is a functional block diagram of the lightning charge calculation unit 32. As shown in the figure, the lightning charge calculation unit 32 includes a first determination unit 40, a second determination unit 42, an electric field change determination unit 44, and a charge calculation unit 46.

  The first determination unit 40 determines that the electric field change is an electric field change caused by a lightning strike when the electric field data has an electric field change larger than a predetermined gradient K1.

  When the electric field data has an electric field change that is equal to or less than the gradient K1 and greater than a predetermined gradient K2 that is smaller than the gradient K1, the second determination unit 42 is configured to store the magnetic field data while the electric field change is occurring. If a change of a predetermined level or more has occurred, it is determined that the electric field change is an electric field change caused by a lightning strike. On the other hand, if the magnetic field data does not change more than the predetermined level, it is determined that the electric field change is not an electric field change caused by a lightning strike.

  The electric field change determination unit 44 includes an electric field value immediately before the first electric field change determined by the first determination unit 40 or the second determination unit 42 as an electric field change due to a lightning strike (ie, an electric field initial value E0), and an electric field due to a lightning strike. The difference from the electric field value immediately after the last electric field change determined to be a change (that is, the electric field value Ee after the lightning strike) is obtained as the electric field change amount ΔE due to the lightning strike.

  The charge calculation unit 46 includes the electric field change amount ΔE obtained by the electric field change determination unit 44, the electric field height H obtained by the charge height calculation unit 30, the position information of the measuring slave station 10, and the lightning strike position acquisition unit 22 The lightning strike charge amount Q is calculated by substituting the distance D calculated from the obtained lightning strike position information into the equation (1).

  FIG. 5 is a flowchart showing the charge calculation processing by the lightning charge calculation unit 32. First, when a lightning strike is detected by the lightning strike detection unit 24 (S100), the magnitude of the electric field immediately before the lightning strike is stored as the electric field initial value E0 (S102). And the 1st determination part 40 and the 2nd determination part 42 scan the electric field data after the time of a lightning strike in a time-axis direction, and discriminate | determine whether there exists any change exceeding the predetermined gradient K (S104). If there is a change exceeding the gradient K, the first determination unit 40 determines that the electric field change is an electric field change caused by a lightning strike, and sets the electric field value after the change as a post-lightning electric field value Ee (S106). On the other hand, when a gradual electric field change that exceeds a second predetermined gradient K0 smaller than the gradient K occurs (S108), the second determination unit 42 applies a magnetic field to the magnetic field while the gradual change occurs. It is determined whether or not a change exceeding a predetermined gradient K1 has occurred (S110). As a result, if a positive determination is made, it is determined that the gentle electric field change determined in S108 is due to lightning, and the post-lightning electric field value Ee is updated to the electric field value after the gentle electric field change (S112). . If a change in the electric field due to the lightning strike is not detected for a predetermined time or more, the electric field value Ee after the lightning strike is determined (S114), and the electric field change determination unit 44 detects the lightning strike by ΔE = Ee−E0. The accompanying electric field change ΔE is calculated (S116). Then, based on the lightning strike position information acquired from the lightning strike position acquisition unit 22 and the position information of the measurement slave station 10 that is the transmission source of the electric field data and magnetic field data, the distance D from the measurement point to the lightning strike point is calculated ( In step S118, the lightning charge amount Q is calculated by substituting the distance D, the lightning charge height H calculated by the charge height calculation unit 30, and the electric field change ΔE into the equation (1) (S120).

  As described above, according to the present embodiment, when a gradual electric field change occurs, whether or not the electric field change is caused by a lightning strike can be accurately determined based on the magnetic field change during the lightning strike. The electric field change ΔE due to can be obtained accurately. The lightning charge amount Q can be accurately calculated using the electric field change ΔE thus obtained.

1 is an overall configuration diagram of a lightning charge evaluation device according to an embodiment of the present invention. It is the figure which showed the time change of the magnetic field and electric field on the ground at the time of a lightning strike. It is a figure which shows the time change of the magnetic field and electric field which are shown in FIG. 2, expanding the scale of a time axis about 1000 times. It is a functional block diagram of a lightning strike charge calculation part. It is a flowchart which shows the electric charge calculation process of a lightning strike electric charge calculation part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lightning strike evaluation apparatus 10 Measurement slave station 12 Electric field measurement part 14 Magnetic field measurement part 20 Data acquisition part 22 Lightning position acquisition part 24 Lightning strike detection part 26 Reader detection part 28 Reader progress time calculation part 30 Charge height calculation part 32 Lightning charge calculation part 32 Unit 40 First determination unit 42 Second determination unit 44 Electric field change determination unit 46 Charge calculation unit 50 Lightning discharge position locating device

Claims (4)

A lightning strike evaluation device for calculating the amount of lightning strike,
A data acquisition unit for acquiring electric field data indicating a time change of an electric field at a predetermined measurement target point and magnetic field data indicating a time change of a magnetic field at the predetermined target point;
Based on the acquired electric field data and magnetic field data, a lightning strike charge calculating unit for calculating a lightning strike charge amount,
The lightning strike charge calculation unit
A first determination unit that determines that the electric field change is an electric field change caused by a lightning strike when the acquired electric field data has an electric field change larger than a first predetermined gradient;
When the acquired electric field data has an electric field change that is greater than a second predetermined gradient that is smaller than the first predetermined gradient and less than or equal to the first predetermined gradient, the electric field change occurs. If the change in the magnetic field data is more than a predetermined level during the operation, it is determined that the change in the electric field is an electric field change caused by lightning, and if the change in the magnetic field data is not more than the predetermined degree. A second determination unit that determines that the electric field is not an electric field change caused by lightning,
The electric field value immediately before the first electric field change determined by the first determination unit or the second determination unit as the electric field change due to the lightning strike, and the electric field change due to the lightning strike by the first determination unit or the second determination unit. An electric field change determination unit that determines a difference between the electric field value immediately after the last electric field change determined to be as an electric field change amount by lightning,
A lightning strike evaluation apparatus, comprising: a charge calculation unit that calculates a lightning strike charge amount based on the determined electric field change amount. A method for calculating a lightning charge amount for calculating a lightning charge amount by a computer,
A data acquisition step in which the computer acquires electric field data indicating a time change of an electric field at a predetermined measurement target point and magnetic field data indicating a time change of a magnetic field at the predetermined target point;
The computer includes a lightning charge calculation step for calculating a lightning charge amount based on the acquired electric field data and magnetic field data,
The lightning strike charge calculating step includes:
A first determination step of determining that the electric field change is an electric field change caused by a lightning strike when the acquired electric field data has an electric field change larger than a first predetermined gradient;
When the acquired electric field data has an electric field change that is greater than a second predetermined gradient that is smaller than the first predetermined gradient and less than or equal to the first predetermined gradient, the electric field change occurs. If the change in the magnetic field data is more than a predetermined level during the operation, it is determined that the change in the electric field is an electric field change caused by lightning, and if the change in the magnetic field data is not more than the predetermined degree. A second determination step for determining that the electric field is not an electric field change caused by lightning,
The electric field value immediately before the first electric field change determined by the first determination unit or the second determination unit as the electric field change due to the lightning strike, and the electric field change due to the lightning strike by the first determination unit or the second determination unit. An electric field change determination step for determining a difference between the electric field value immediately after the last electric field change determined to be as an electric field change amount by lightning,
A lightning charge evaluation method comprising: a charge calculation step of calculating a lightning charge amount based on the determined electric field change amount.   A program for causing a computer to execute the method according to claim 2. A computer-readable recording medium storing the program according to claim 3.

Images