JP6872192B2 - Lightning charge amount estimation method and system - Google Patents

Description

The present invention relates to a method and system for estimating a lightning charge amount that enables the lightning charge amount to be estimated with high accuracy.

Companies that own infrastructure equipment such as electric power companies and businesses that distribute and manage equipment over a wide area are required to grasp equipment damage caused by lightning strikes as soon as possible.
When a lightning strike occurs, knowing the energy (charge amount) of the lightning strike is very effective in estimating equipment damage.

Since lightning is generated in the process of changing the electric charge in the air such as a thundercloud and neutralizing it with the electric charge on the ground, as described in Patent Document 1 (Japanese Patent No. 42177728), the electric charge in the air at this time As shown in FIG. 11, the change is simulated by the change of the point charge, the horizontal distance D [m] from the lightning strike position (charge center) to the observation point, the electric field change amount ΔE [V / m] before and after the lightning strike, and the charge center. It is known that the amount of electric charge of lightning is estimated from the following (Equation 9) by measuring the altitude L [m] of.
(Equation 9) ΔQ = 2πε ₀ D ³ ΔE {1 + (L / D) ² } ^3/2 / L
(However, ΔQ is the amount of lightning charge [C], π is the pi, and ε ₀ is the permittivity of air.)
In Patent Document 1, D is calculated from the distance between the lightning position defined by the lightning position locating device and the measurement target position, and ΔE is immediately before the first electric field change when it is determined to be a lightning by the magnitude of the gradient of the electric field change. Calculated from the difference between the electric field value of and the electric field value immediately after the last electric field change, L is the leader advance time from the time of occurrence of the lightning strike detected by the electric field sensor and the time of occurrence of the reader preceding the lightning strike detected by the magnetic field sensor. , It is calculated from the progress time and the constant leader progress speed.

Further, in recent years, as described in Non-Patent Document 1 (Electronics B, Vol. 128, No. 5, pp. 785 to 794), the TL model, MTLL model, MTLD model, TCS model, and DU model are used as the return lightning strike model. , MTLD2 model, MDUD model and other various engineering models have come to be used to calculate the current waveform on the return lightning path.
By the way, the amount of electric charge of a lightning strike estimated by assuming a point charge model that simulates a change in charge in the air by a change in point charge is relatively long, about 1 to 20 milliseconds (hereinafter referred to as "ms"). Since the target is the amount of electric charge (stroke charge) over time, most of the estimation of the amount of electric charge is based on electric field observation using a slow antenna to measure ΔE.
However, in the charge amount estimation assuming the feedback lightning strike model that has been used in recent years, the charge amount (impulse charge) in a relatively short time such as up to 1 ms or until the peak value becomes 1 kA or less at the wave tail. Since estimation may be required, electric field observation using the first antenna is also being performed.

Japanese Patent No. 4217728

Yoshihiro Baba, "Engineering Model of Returning Lightning Strike and Application to Lightning Electromagnetic Field Pulse Calculation", Denki B, Vol. 128, No. 5, 2008, pp. 785-794

As described above, various methods have been proposed for estimating the charge amount (stroke charge and impulse charge) of a lightning strike, but the method described in Patent Document 1 has a large leader advance speed depending on the type of lightning strike. Since it changes, it is not possible to obtain the correct calculation result of the altitude of the charge center by using a constant leader advance rate.
Further, in the DU model and the like described in Non-Patent Document 1, since the return lightning current is the source of the electric charge distributed on the lightning path, it is generally described as several tens of microseconds (hereinafter referred to as “μs”). When the feedback lightning current with a specified wave tail length of about) becomes 0, the electric charge at that time reflects the electric charge neutralized on the lightning path.
Therefore, in order to estimate the amount of charge (impulse charge) from the electric field value obtained by the first antenna, it is necessary to obtain the charge distribution accumulated on the lightning path by the reader, but the charge distribution on the reader differs for each lightning strike. Therefore, in order to obtain this, it is necessary to estimate the current by assuming a return lightning strike model.
The first object of the present invention is to use a uniformly distributed charge model assuming that the charges are uniformly distributed in a lightning path perpendicular to the ground as a return lightning strike model, and to use a uniformly distributed charge without using the leader propagation speed. The upper limit of the distributed charge in the model is obtained so that the lightning charge amount (impulse charge) can be estimated easily and accurately.
A second object of the present invention is to make it possible to estimate the lightning strike charge amount (impulse charge) more accurately by adding the lower limit height of the distributed charge in the uniformly distributed charge model.
Further, the third object of the present invention is to make it possible to estimate the lightning charge amount (impulse charge) more accurately by estimating the error rate between the estimated value by the uniformly distributed charge model and the true lightning charge amount. That is.

The invention according to claim 1 is a method for estimating a lightning charge amount by a uniformly distributed charge model for calculating a lightning charge amount.
For each meteorological condition in the observation area and for each range of time difference from the time when the first discharge occurs, the correspondence relationship with the temperature of the air layer where the difference between the estimated charge amount and the measured charge amount becomes small is determined in advance.
The horizontal distance D [m] from the lightning strike position to the observation point and the electric field value before and after the lightning strike at the observation point are measured, and based on the electric field value before and after the lightning strike, the electric field value immediately before the start of the return lightning strike and after the start of the return lightning strike. The amount of change in the electric field ΔE [V / m], which is the difference between the electric field values after the lapse of a predetermined time, is calculated, and the temperature is -5 ° C to -15 ° C from the lightning strike position, the location near the lightning strike occurrence point, and the meteorological observation data at the time point. The range of the above-ground height of the air layer is estimated, and the predetermined response in the observation area including the lightning strike position, the weather conditions at the time of the lightning strike, the time difference range from the time when the first discharge occurs, and the lightning strike position. Based on the relationship, determine the temperature of the air layer where the difference between the estimated charge amount and the measured charge amount becomes small,
The upper limit height H [m] of the distributed charge is determined based on the determined temperature of the air layer and the estimated range of the ground clearance.
Using the horizontal distance D, the electric field change amount ΔE, and the upper limit height H, the lightning charge amount ΔQ [C] is calculated by the following (Equation 1).
(Equation 1) ΔQ = 2πε ₀ HΔE / {1 / D-1 / (D ² + H ² ) ^1/2 }
(However, π represents the pi and ε ₀ represents the permittivity of air.)

In the invention according to claim 2, in the method for estimating the amount of lightning strike according to claim 1, the lower limit height h [m] of the distributed charge is determined based on the estimated range of the above-ground height.
Using the horizontal distance D, the electric field change amount ΔE, the upper limit height H, and the lower limit height h, the lightning charge amount ΔQ is calculated by the following (Equation 2) instead of the above (Equation 1). ..
(Equation 2) ΔQ = 2πε ₀ (H−h) ΔE / {1 / (D ² + h ² ) ^1/2 -1 / (D ² + H ² ) ^1/2 }
(However, π represents the pi and ε ₀ represents the dielectric constant of air, and 0 ≦ h <H.)

The invention according to claim 3 is characterized in that, in the method for estimating the amount of lightning charge according to claim 2, the lower limit height h is determined by calculating the difference between the height of the lightning strike position and the height of the observation point. ..

In the invention according to claim 4, the error rate Er [%] of the lightning strike charge amount ΔQ calculated by the above (Equation 1) is estimated by the lightning strike charge amount estimation method according to claim 1.
Using the horizontal distance D, the electric field change amount ΔE, the upper limit height H, and the error rate Er, the lightning charge amount ΔQ is calculated by the following (Equation 3) instead of the above (Equation 1).
(Equation 3) ΔQ = 2πε ₀ HΔE × 100 / (100 + Er) / {1 / D-1 / (D ² + H ² ) ^1/2 }
(However, π represents the pi and ε ₀ represents the permittivity of air.)

In the invention according to claim 5, in the method for estimating the amount of lightning charge according to claim 4, the wave tail length T [μs] of the electric field waveform before and after the lightning strike is calculated based on the electric field values before and after the lightning strike.
Using the calculated wave tail length T, the error rate Er is estimated by the following (Equation 4).
(Equation 4) Er = αT + β
(However, α and β are constants determined in advance based on the measurement and estimation of the amount of lightning strike charge.)

The invention according to claim 6 is a lightning charge amount estimation system for calculating a lightning charge amount.
A predetermined correspondence with the temperature of the air layer where the difference between the estimated charge amount and the measured charge amount becomes small is recorded for each meteorological condition in the observation area and for each range of time difference from the time when the first discharge occurs. Correspondence relationship recording means and
Return based on the lightning strike position setting means for measuring the horizontal distance D [m] from the lightning strike position to the observation point, the electric field measuring means for measuring the electric field value before and after the lightning strike at the observation point, and the electric field value before and after the lightning strike. At the electric field change amount calculation means for calculating the electric field change amount ΔE [V / m], which is the difference between the electric field value immediately before the start of the lightning strike and the electric field value after a predetermined time has elapsed after the start of the return lightning strike, and at the lightning strike position and the time when the lightning strike occurs. A means for estimating the above-ground height range of the air layer whose temperature is -5 ° C to -15 ° C from meteorological observation data at a nearby location and time point, the above-mentioned lightning strike position, the weather conditions at the time of the lightning strike, and the first An air layer that determines the temperature of the air layer where the difference between the estimated charge amount and the measured charge amount becomes small based on the range of the time difference from the time when the discharge occurs and the predetermined correspondence relationship in the observation area including the lightning strike position. Temperature determination means,
Upper limit height determining means for determining the upper limit height H [m] of the distributed charge based on the temperature of the air layer determined by the air layer temperature determining means and the above- ground height range estimated by the ground clearance estimating means. When,
It is characterized by including a charge amount calculation means for calculating the lightning charge amount ΔQ [C] by performing the following calculation (Equation 1) using the horizontal distance D, the electric field change amount ΔE, and the upper limit height H. And.
(Equation 1) ΔQ = 2πε ₀ HΔE / {1 / D-1 / (D ² + H ² ) ^1/2 }
(However, π represents the pi and ε ₀ represents the permittivity of air.)

In the invention according to claim 7, in the lightning charge amount estimation system according to claim 6, the lower limit height h [m] of the distributed charge is determined based on the range of the above-ground height estimated by the above-ground height range estimation means. Further equipped with a means for determining the lower limit height
The charge amount calculation means uses the horizontal distance D, the electric field change amount ΔE, the upper limit height H, and the lower limit height h to perform the following calculation (Equation 2) instead of the (Equation 1). It is a feature.
(Equation 2) ΔQ = 2πε ₀ (H−h) ΔE / {1 / (D ² + h ² ) ^1/2 -1 / (D ² + H ² ) ^1/2 }
(However, π represents the pi and ε ₀ represents the dielectric constant of air, and 0 ≦ h <H.)

According to the eighth aspect of the present invention, in the lightning charge amount estimation system according to the seventh aspect, the lower limit height determining means includes means for calculating the difference between the height of the lightning strike position and the height of the observation point. It is characterized by that.

The invention according to claim 9 further provides an error rate estimation means for estimating the error rate Er [%] of the lightning strike charge amount ΔQ calculated by the above (Equation 1) in the lightning strike charge amount estimation system according to claim 6. Prepare,
The electric charge amount calculation means uses the horizontal distance D, the electric field change amount ΔE, the upper limit height H, and the error rate Er to perform the following calculation (Equation 3) instead of the (Equation 1). And.
(Equation 3) ΔQ = 2πε ₀ HΔE × 100 / (100 + Er) / {1 / D-1 / (D ² + H ² ) ^1/2 }
(However, π represents the pi and ε ₀ represents the permittivity of air.)

The invention according to claim 10 is a wave tail length calculation for calculating the wave tail length T [μs] of the electric field waveform before and after the lightning strike based on the electric field values before and after the lightning strike in the lightning charge amount estimation system according to claim 9. With more means,
The error rate estimating means is characterized in that the following calculation (Equation 4) is performed using the calculated wave tail length T.
(Equation 4) Er = αT + β
(However, α and β are constants determined in advance based on the measurement and estimation of the amount of lightning strike charge.)

According to the invention according to claim 1 or 6, the upper limit height H [m] of the distributed charge is not calculated from the leader advance time and the predetermined leader advance speed, and the first discharge occurs for each meteorological condition in the observation area. For each range of time difference from the time point, the correspondence relationship with the temperature of the air layer where the difference between the estimated charge amount and the measured charge amount becomes small is determined in advance, and the meteorological observation at the place and time near the lightning position and the time when the lightning occurs. Estimate the range of the above-ground height of the air layer where the temperature is -5 ° C to -15 ° C from the data, and determine the position of the lightning strike, the meteorological conditions at the time of the lightning strike, the range of the time difference from the time when the first discharge occurred, and the position of the lightning strike. Determine the temperature of the air layer where the difference between the estimated charge amount and the measured charge amount becomes small based on the predetermined correspondence relationship in the observation area including, and based on the determined air layer temperature and the estimated ground height range. Since it is determined by selecting one upper limit height H [m], H can be obtained without using the leader propagation speed that greatly changes depending on the magnetic field sensor and the type of lightning strike.
Then, by performing the calculation based on the uniformly distributed charge model (Equation 1) assuming that the charges are uniformly distributed in the lightning path perpendicular to the ground as the return lightning strike model, it is obtained by the first antenna which is an electric field measuring means. A low-cost and accurate lightning strike based on the electric field value after a predetermined time (up to 1 ms or the time selected from the time until the observed peak value of the lightning current becomes 1 kA or less at the crest) from the start of the returned lightning strike. The amount of charge can be estimated.

In the invention according to claim 2 or 7, in addition to the effect of the invention according to claim 1 or 6, the lower limit height h [m] of the distributed charge is determined based on the estimated ground clearance.
Instead of (Equation 1), the lightning strike charge amount ΔQ is calculated by (Equation 2) based on the uniformly distributed charge model assuming that the charge changes and is distributed in the lightning path perpendicular to the ground as a return lightning strike model. , The amount of lightning charge can be estimated more accurately.

In the invention according to claim 3 or 8, in addition to the effect of the invention according to claim 2 or 7, the difference between the height of the lightning strike position and the height of the observation point is calculated to determine the lower limit height h, so that the lower limit height h is determined more accurately. The amount of lightning charge can be estimated.

According to the invention according to claim 4 or 9, the error rate Er [%] of the lightning charge amount ΔQ calculated by (Equation 1) is estimated, and the error rate Er is used instead of (Equation 1) (Equation 1). Since the lightning charge amount ΔQ is calculated by 3), the effect that the lightning charge amount can be estimated more accurately can be obtained.

According to the invention of claim 5 or 10, in addition to the effect of the invention of claim 4 or 9, the wave tail length T [μs] of the electric field waveform before and after the lightning strike is calculated, and the calculated wave tail length T is used. Since the error rate Er is estimated by (Equation 4), the error rate Er is estimated accurately for each lightning strike, and the effect that the amount of lightning strike charge can be estimated more accurately can be obtained.

The figure which shows the uniformly distributed charge model. The conceptual diagram of the lightning charge amount estimation system of Example 1. FIG. The graph which compared the measured charge amount and the estimated charge amount by equation 9. An example of an electric field waveform measurement graph. The conceptual diagram of the lightning charge amount estimation system of Example 3. FIG. An example of an electric field waveform measurement graph after high-frequency cutoff filter processing. A graph showing the relationship between wave tail length and error rate. The conceptual diagram of the lightning charge amount estimation system of Example 4. The figure which shows the change distribution charge model. The figure which shows an example of the lightning charge amount estimation system of this invention. The figure which shows the point charge model.

Hereinafter, embodiments of the present invention will be described with reference to examples.

Since the present invention uses a uniformly distributed charge model assuming that the charges are uniformly distributed in the lightning path perpendicular to the ground shown in FIG. 1 as a return lightning strike model, first, the amount of charges based on the uniformly distributed charge model is used. The estimation method of is described.

In FIG. 1, the peak value of the lightning current observed for a predetermined time (up to 1 ms or observed) from the time when the first electric field change in the discharge in which the charge density on the uniformly distributed lightning path forms a lightning strike occurs (start of the return lightning strike). The amount that changes after the lapse of (the time selected from the time until it becomes 1 kA or less at the wave tail) is Δρ [C / m], the upper limit height of the lightning path is H [m], and the lower limit height of the lightning path is Assuming h [m], the lightning charge amount ΔQ [C], which is the amount of charge change on the lightning path, can be expressed by the following (Equation 5).
(Equation 5) ΔQ = Δρ × (Hh)
Further, for the electric field E [V / m] at a point separated from the lightning path by D [m], if the charge density on the lightning path is ρ [C / m] and r = (D ² + z ² ) ^1/2. The following (Equation 6) is derived.
(Equation 6) E = ∫ (ρ × D / 4πε ₀ r) dz <Integration interval is from h to H>
(However, π represents the pi and ε ₀ represents the dielectric constant of air, and 0 ≦ h <H.)
When this integral is calculated, it becomes the following (Equation 7), and ρ [C / m] can be calculated by the following (Equation 8).
(Equation 7) E = ρ × {1 / (D ² + h ² ) ^1/2 -1 / (D ² + H ² ) ^1/2 } / 2πε ₀
(Equation 8) ρ = 2πε ₀ E / {1 / (D ² + h ² ) ^1/2 -1 / (D ² + H ² ) ^1/2 }
Therefore, if the electric field change amount ΔE [V / m] at a point separated from the lightning path by D [m] is measured, the lightning charge amount ΔQ can be calculated as follows (Equation 2) from the relationship between (Equation 5) and (Equation 8). ) Can be calculated.
(Equation 2) ΔQ = 2πε ₀ (H−h) ΔE / {1 / (D ² + h ² ) ^1/2 -1 / (D ² + H ² ) ^1/2 }

A conceptual diagram of the lightning charge amount estimation system of the first embodiment is shown in FIG.
As shown in FIG. 2, the lightning strike charge amount estimation system of the first embodiment includes the following means.
(1) It is equipped with a Rogowski coil installed at the bottom of the wind power generation facility to directly observe the lightning current and a device to measure the current induced in the Rogowski coil when the wind power generation facility is hit by a lightning strike. A lightning current observing means 1 for recording a trigger time with a GPS clock of about 0.2 μs and recording a current value measured at a sample time interval of 0.1 μs.
The total recording time is about 400 ms, which is about 100 ms before the trigger time and 300 ms after the trigger time.
(2) Equipped with a first antenna that measures changes in the electric field due to a lightning strike, and a GPS watch with an accuracy of about 0.2 μs is time-synchronized with the lightning current observation means 1 of (1) above and measured at a sample time interval of 0.1 μs. An electric field measuring means 2 for recording the generated electric field value.
(3) Data acquisition means 3 for acquiring high-rise meteorological observation data observed at a weather station near the wind power generation facility where the Rogowski coil of (1) above is installed.

(4) A lightning strike position determining means 4 for measuring the horizontal distance D [m] between the wind power generation facility (lightning strike position) where there was a lightning strike and the electric field measuring means 2 (observation point).
The lightning strike position determining means 4 receives electromagnetic waves radiated from a lightning discharge due to a lightning strike at a plurality of points, and receives the received electromagnetic waves by a well-known means (for example, a non-patent document shown in Patent Document 1). Yasuo Kishimoto, "Latest Trends in Lightning Observation Systems and Lightning Protection Standards", see NTT Building Research Institute) to determine the lightning strike position, and the lightning strike position and the horizontal distance D of the electric field measuring means 2. It may be used to measure [m].
(5) The electric field value data before and after the trigger time is extracted from the electric field value data recorded in the electric field measuring means 2 of the above (2), and the specified time (up to 1 ms or the observed lightning current) from the start of the return lightning strike. 5. The electric field change amount calculation means 5 for determining the electric field value after the elapse of (a time selected from the time until the crest value becomes 1 kA or less at the crest) as the electric field change amount ΔE [V / m].
(6) At the weather station closest to the wind power generation facility where there was a lightning strike, the high-rise meteorological observation data observed at the time closest to the time of the lightning strike was extracted, and the temperature above the wind power generation facility where there was a lightning strike was -5 ° C ~-. Ground height range estimating means 6 for estimating the range of the ground height of the air layer at 15 ° C.

(7) The upper limit height determining means 7 that selects one upper limit height H [m] from the range of the ground clearance estimated by the ground clearance estimation means 6 of the above (6) and determines the upper limit height of the distributed charge. ..
The method of selecting one upper limit height H [m] will be described later.
(8) Lower limit height determining means 8 for calculating the difference between the altitude of the wind power generation facility (lightning strike position) where the lightning strike occurred and the altitude of the electric field measuring means 2 (observation point).
(9) The horizontal distance D [m] measured by the lightning position locating means 4 of the above (4), the electric field change amount ΔE [V / m] calculated by the electric field change amount calculating means 5 of the above (5), and the above. Using the upper limit height H [m] determined by the upper limit height determining means 7 of (7) and the lower limit height h [m] determined by the lower limit height determining means 8 of the above (8), the above (formula). The charge amount calculation means 9 for calculating the lightning charge amount ΔQ [C] of the lightning that has fallen on the wind power generation facility and the display means 10 for displaying the calculation result by performing the calculation according to 2).
(10) A display means 11 for displaying the measured charge amount converted from the current value obtained from the lightning current observation means 1 of the above (1).

In establishing the method for determining the upper limit height H [m], the estimated charge amount (stroke) obtained by performing the calculation according to the above (Equation 9) based on the observation by the slow antenna of the electric field associated with lightning in the South Kyushu area. Charge) was compared with the measured charge amount obtained by the measurement.
The lightning charge amount ΔQ [C] in this comparative experiment was observed for the negative electrode lightning strike in which negative charges are accumulated in the thundercloud, but whether it is a negative electrode lightning strike or not is just before the first electric field change in the discharge. It can be determined by the fact that the electric field value is high and the electric field value immediately after the last electric field change is low.

The graph shown in FIG. 3 shows the estimated charge amount based on the amount of electric charge change in the discharge generated less than 1 ms from the time when the first electric field change occurs among the plurality of discharges forming the negative lightning strike, and the same initial electric charge amount. Estimated charge amount based on the amount of electric charge change in the discharge that occurred less than 2 ms from the time when the change occurred, and the estimated amount of charge based on the amount of electric charge change in the discharge that occurred less than 3 ms from the time when the first electric field change occurred. Similarly, it is based on the estimated charge amount based on the amount of electric charge change in the discharge generated less than 4 ms from the time when the first electric field change occurs, and the amount of electric charge change in the discharge generated less than 5 ms from the time when the first electric field change occurs. This is a comparison between the estimated charge amount and the measured charge amount.
The point charge height L [m] used to estimate the lightning charge amount ΔQ [C] was observed at the weather station (Kagoshima Meteorological Observatory) closest to the wind power generation facility where the lightning strike occurred, at the time closest to the time when the lightning strike occurred. 5000m (the above-ground height of the air layer where the temperature is -1.8 ° C), 6000m (the above-ground height of the air layer where the temperature is -6.8 ° C), 6500m (the temperature is-) estimated from the high-level meteorological observation data. Four were selected: the above-ground height of the air layer at 10.0 ° C. and 7,000 m (the above-ground height of the air layer at -12.0 ° C.).

Comparing the estimated charge (stroke charge) based on the point charge model obtained using the four selected heights L [m] with the measured charge, the time from the time when the first electric field change occurred Therefore, it can be seen that the difference between the estimated charge amount and the measured charge amount when the height L [m] is 6500 m (the ground height of the air layer where the temperature is -10.0 ° C) is relatively small. ..
Therefore, when calculating the estimated charge amount (impulse charge) based on the uniformly distributed charge model of this example, it was observed at the weather station (Kagoshima Meteorological Observatory) closest to the wind power generation facility where the lightning struck, at the point closest to the time when the lightning struck. The above-ground height of the air layer whose temperature is -10.0 ° C. estimated from the high-level meteorological observation data was determined as the upper limit height H [m].

Table 1 calculates the amount of electric charge change ΔE based on the electric field value observed using the first antenna at the Kokubu (observation point) in South Kyushu, which is about 18 km away from the wind power generation facility (lightning point) where the lightning struck. This is a comparison between the estimated charge amount obtained by performing the calculation according to (Equation 2) and the measured charge amount obtained by the measurement.
In the example of Table 1, since the elevation difference between the lightning strike point and the observation point was small, h = 0, and ΔE was shown in the graph of FIG. 4 because the charge amount change up to 0.2 ms after the start of the return lightning strike was targeted. As described above, the average value of the electric field values observed from 0.175 ms to 0.225 ms was used (ΔE = 41 V / m in FIG. 4).
Table 1 shows the change in the amount of charge calculated from the time integration of the current waveform (measured value) for the four lightning strikes for which the current waveform could be measured, and the change in the amount of charge estimated from the electric field waveform generated by the target lightning strike (estimated value). The error rate of the estimated value with respect to the measured value is shown.

Data 1 and 2 in Table 1 were observed in association with the first and second lightning strokes that occurred by the downward leader at 10:35 on August 4, 2013, and data 3 and 4 were observed on the same day. It was observed at 10:38 with the first and second lightning strokes also caused by the downward leader.
As shown in Table 1, the error rate was -16.6% to 21.0%, but in deriving the above (Equation 2), (1) the lightning path is perpendicular to the ground (2) on the lightning path. (3) The lightning current is zero 0.2 ms after the start of the return lightning strike. Considering that it was obtained by making many assumptions, it is about this level. The error rate is within the expected range and can be used sufficiently.
Further, the range of the error rate described above is about the same as the error rate of the estimated value based on the electric field value observed using the slow antenna.

In the second embodiment, the lower limit height determining means 8 is omitted from the lightning charge amount estimation system of the first embodiment, and the calculation by the following (Equation 1) is performed instead of the calculation by the above (Equation 2) without using the lower limit height h. The only difference is that the lightning charge amount ΔQ [C] of the lightning that has fallen on the wind power generation facility is calculated, and the other configurations are the same as those of the first embodiment.
(Equation 1) ΔQ = 2πε ₀ HΔE / {1 / D-1 / (D ² + H ² ) ^1/2 }
Therefore, in the conceptual diagram of the lightning charge amount estimation system of the second embodiment, the lower limit height determining means 8 is omitted from FIG. 2, and the upper limit height H is input to the charge amount calculating means 9 only from the upper limit height determining means 7. It becomes.
Then, even in the configuration of the second embodiment, as described in the first embodiment, if the elevation difference between the lightning strike point and the observation point is small, the error rate of the estimated value with respect to the actually measured value is within the assumption even if the lower limit height h is set to 0. Therefore, it can be sufficiently used when estimating the amount of lightning strike charge in the plain area.

In the third embodiment, the lightning charge amount of the stroke charge obtained by performing the calculation by the above (Equation 9) based on the point charge model based on the observation by the slow antenna and the lightning charge amount estimation system of the impulse charge in the first or second embodiment. It is a system integrated with an estimation system, and has a configuration as shown in FIG.
Note that FIG. 5 is an example of a system in which the impulse charge lightning charge amount estimation system and the stroke charge lightning charge amount estimation system are integrated in the first embodiment.

That is, the lightning current observing means 1, the data acquiring means for acquiring high-level meteorological observation data 3, the lightning strike position locating means 4 for measuring the horizontal distance D [m], and the ground of the air layer where the temperature is -5 ° C to -15 ° C. As the ground high range estimation means 6 for estimating the high range, the one of the lightning charge amount estimation system for impulse charge can be used. Therefore, the following means are added to configure the lightning charge amount estimation system for stroke charge. doing.
(1) Equipped with a slow antenna that measures changes in the electric field due to a lightning strike, and a GPS watch with an accuracy of about 0.2 μs is used to synchronize the time with the lightning current observation means 1 and measure the electric field value at a sample time interval of 0.1 μs. Second electric field measuring means 12 for recording.
(2) Second electric field change amount calculation means 13 for calculating the electric field change amount ΔE2 [V / m], which is the difference between the electric field value immediately before the first electric field change and the electric field value immediately after the last electric field change in the discharge forming a lightning strike. ..
(3) the height determining means for ground clearance range estimating means 6 determines one height L [m] from the ground clearance of the range estimated 14.
In Example 3, as in Examples 1 and 2, the ground clearance of the air layer estimated to have a temperature of -10.0 ° C. was defined as the height L [m] of the charge center.
(4) The horizontal distance D [m] measured by the lightning position locating means 4, the second electric field change amount ΔE2 [V / m] calculated by the second electric field change amount calculation means 13 of the above (2), and the above ( The second lightning charge amount ΔQ2 [C] of the lightning that has fallen on the wind power generation facility is calculated by performing the calculation by the equation 9 using the height L [m] determined by the height determining means 14 of 3). The charge amount calculation means 15 and the second display means 16 for displaying the calculation result.

In Example 4, the error rate Er [%] was estimated with respect to the lightning charge amount ΔQ calculated by (Equation 1) of Example 2, the calculation was performed by the following (Equation 3), and the lightning strike fell into the wind power generation facility. The only difference is that the lightning charge amount ΔQ [C] of the lightning strike is calculated, and the other configurations are the same as those in the second embodiment.
(Equation 3) ΔQ = 2πε ₀ HΔE × 100 / (100 + Er) / {1 / D-1 / (D ² + H ² ) ^1/2 }
Here, the error rate Er is positive when the lightning charge amount ΔQ calculated by (Equation 1) is larger than the true value, and negative when it is smaller than the true value, and depends on the terrain, air temperature, wind speed, and the like.
Therefore, if the lightning charge amount ΔQ calculated by (Equation 1) is compared with the measured charge amount in advance under various conditions in each region and the error rate Er in each region and each condition is accumulated, it is possible to accumulate the error rate Er. The error rate Er can be determined according to the target area where the lightning strike occurred and the conditions at the time of the lightning strike.
In addition, as a new finding, it was found that there is a close relationship between the wave tail length T [μs] and the error rate Er in the waveform after high-frequency cutoff filtering of the electric field value measured at the time of a lightning strike. Now, the details will be described.

FIG. 6 is an example of an electric field waveform measurement graph after high-frequency cutoff filter processing in a lightning strike measured at the same South Kyushu / Kokubu (observation point) as the graph of FIG.
As shown in FIG. 6, the point where the electric field value becomes 90% of the peak (hereinafter referred to as “90% point”) and the point where the electric field value becomes 10% of the peak before the peak (46.1685 [V / m]) appears in this graph. (Hereinafter referred to as "10% point") is specified, and the starting point is the point (-0.7467 [μs]) where the straight line connecting the 90% point and the 10% point intersects the time axis.
Next, the point where the electric field value becomes 50% of the peak after the peak appears (hereinafter referred to as "50% point") is defined as the end point (53.1075 [μs]).
Then, the time difference between the start point and the end point (53.8542 [μs]) is defined as the wave tail length.

FIG. 7 shows the wave tail length T and the error rate Er of the lightning charge amount ΔQ calculated by (Equation 1) in multiple lightning strikes observed at the same South Kyushu / Kokubu (observation point) as the graph of FIG. It is a graph which shows the relationship.
As can be seen from this graph, it can be seen that the wave tail length T and the error rate Er have a linear correlation that can be expressed by the following (Equation 4).
(Equation 4) Er = αT + β
Then, in the graph of FIG. 7, it was found that α = -1.5743 and β = 75.919, and the relational expression between the wave tail length T and the error rate Er was Er = -1.5743T + 75.919.
In addition, it is known that there are regional differences in this correlation, but if the relational expressions (values of α and β) are determined in advance in each region, an error will occur without considering other conditions at the time of the lightning strike. The rate Er can be accurately estimated using the wave tail length T specified based on the change in the electric field value measured by the first antenna or the like.

FIG. 8 is a conceptual diagram of a lightning charge amount estimation system that estimates the error rate Er using the wave tail length T and calculates the lightning charge amount ΔQ in the fourth embodiment.
In the fourth embodiment, the wave tail length T is specified based on the change in the measured electric field value, and the error rate Er is estimated using the wave tail length T. , A wave tail length calculation means 17 for specifying the wave tail length T based on the data obtained from the electric field measuring means, and an error rate estimation means 18 for estimating the error rate Er using the wave tail length T are added. It has become.

FIG. 9 is a diagram showing a change distribution charge model assuming that the charges are linearly changed and distributed in a lightning path perpendicular to the ground.
In this change distribution charge model, assuming that the amount of charge that increases with 1 m rise is a [C], the amount of lightning charge ΔQ can be calculated by the following (Equation 10), although the equation in the middle is omitted.
(Equation 10) ΔQ = (2πε ₀ ΔE−aG) × H / {1 / D-1 / (D ² + H ² ) ^1/2 }
(However, G = ln [{(D ² + H ² ) ^1/2 + H} / D] -H / 2D-H / 2 (D ² + H ² ) ^1/2 .)

If (Equation 10) is qualitatively grasped, G is usually a positive value, so when the lightning charge amount ΔQ based on the uniformly distributed charge model is largely estimated (when Er> 0), a is positive. That is, it can be said that the charge is biased to the upper part of the discharge path, and when ΔQ is estimated to be small (when Er <0), a is negative, that is, the charge is biased to the lower part of the discharge path. It can be said that there is.

Further, assuming that ΔQ according to (Equation 3) and (Equation 10) has the same value, the relationship between a and Er can be expressed by the following (Equation 11).
(Equation 11) a = 2πε ₀ ΔE × Er / (100 + Er) × G
Then, by substituting the relationship of (Equation 4) into (Equation 11), the relationship between a and T can be expressed by the following (Equation 12).
(Equation 12) a = 2πε ₀ ΔE × (αT + β) / (100 + αT + β) × G

Modifications of Examples 1 to 4 are listed.
(1) In Examples 1 to 4, the Rogowski coil was installed under the wind power generation facility as the lightning current observation means 1, but it may be installed not only in the wind power generation facility but also in a lightning rod of a tall building or a steel tower. A shunt resistor may be used instead of the logoski coil.
Further, as already described, the lightning strike position can be determined by other means without using the lightning current observation means 1, but in such a case, for example, the lightning strike charge amount estimation system in the first embodiment is as shown in FIG. It will be something like that.
That is, the lightning current observing means 1 and the display means 11 are omitted from the conceptual diagram of FIG.
(2) In Examples 1 to 4, the sample time interval of the lightning current observing means 1 and the electric field measuring means 2 was 0.1 μs, but if there is no problem in specifying the trigger time, the amount of electric field change, and the time difference, The sample time interval may be greater than or less than 0.1 μs.

(3) In Examples 1 to 4, the upper limit height H and the height L were set to the above-ground height of the air layer estimated to have a temperature of -10.0 ° C., but the upper limit height H with a small error rate was used. And the height L changes depending on the area, the temperature of the ground surface, the strength and direction of the wind, so the same observations as in Examples 1 to 4 were performed in advance under various conditions in each area, and the observed high-level meteorological observations. It is necessary to establish a method for determining the upper limit height H and height L for each lightning strike from the data.
Therefore, it is indispensable to accumulate data in order to accurately determine the upper limit height H from the high-level meteorological observation data for each lightning strike, but the height L selected to estimate the stroke charge is usually time. Since it is known that the amount of lightning strikes rises with time, the second lightning charge amount ΔQ2 [C] in the early stage discharge with a time difference of less than a predetermined length (for example, 2 ms) is estimated from the observed high-level meteorological observation data. When calculating the second lightning charge amount ΔQ2 [C] in the late stage discharge where the time difference is equal to or greater than the predetermined length by selecting one of the above-ground heights of the air layer whose temperature is -5 ° C to -10 ° C. It can be said that one of the above-ground heights of the air layer whose temperature estimated from the observed high-level meteorological observation data is -10 ° C to -15 ° C may be selected.

(4) In Examples 1 to 4, the electric field change amount ΔE is the average value of the electric field values observed from 0.175 ms to 0.225 ms, targeting the charge amount change up to 0.2 ms after the start of the return lightning strike. However, it may be possible to appropriately select from the time from the start of the return lightning strike to 1 ms or the time until the peak value of the observed lightning current becomes 1 kA or less at the crest.
Further, the electric field change amount ΔE may be an instantaneous value of the electric field value observed 0.2 ms after the start of the feedback lightning strike, and the average value of the electric field values observed at 0.1 to 50 μs before and after 0.2 ms after the start of the feedback lightning strike. May be.

(5) In Example 4, the error rate Er [%] was estimated with respect to the lightning charge amount ΔQ calculated by (Equation 1) of Example 2, but it was calculated by (Equation 2) of Example 1. The error rate Er [%] may be estimated with respect to the amount of lightning charge ΔQ.

1 Lightning current observation means 2 Electric field measurement means 3 Data acquisition means 4 Lightning position determination means 5 Electric field change amount calculation means 6 Ground height range estimation means 7 Upper limit height determination means 8 Lower limit height determination means 9 Charge amount calculation means 10, 11 Display means 12 Second electric field measurement means 13 Second electric field change amount calculation means 14 Height determination means 15 Second charge amount calculation means 16 Second display means 17 Wave tail length calculation means 18 Error rate estimation means D Horizontal distance ΔE Electric field change amount H Upper limit height h Lower limit height L Charge center height ΔQ Lightning charge amount ΔQ2 Second lightning charge amount Er Error rate T Wave tail length a Charge amount increasing with 1 m rise α, β Based on measurement and estimation of lightning charge amount Predetermined constant

Claims (10)

It is a method of estimating the amount of lightning strike by a uniformly distributed charge model for calculating the amount of lightning strike.
For each meteorological condition in the observation area and for each range of time difference from the time when the first discharge occurs, the correspondence relationship with the temperature of the air layer where the difference between the estimated charge amount and the measured charge amount becomes small is determined in advance.
Measure the horizontal distance D [m] from the lightning strike position to the observation point and the electric field value before and after the lightning strike at the observation point.
Based on the electric field values before and after the lightning strike, the electric field change amount ΔE [V / m], which is the difference between the electric field value immediately before the start of the return lightning strike and the electric field value after the elapse of a predetermined time after the start of the return lightning strike, is calculated.
The range of ground clearance of the air layer where the temperature is -5 ° C to -15 ° C is estimated from the location of the lightning strike and the meteorological observation data at the location and time when the lightning strike occurred.
The estimated charge amount and the measured charge amount based on the lightning strike position, the weather conditions at the time of the lightning strike, the range of the time difference from the time when the first discharge occurs, and the predetermined correspondence relationship in the observation area including the lightning strike position. Determine the temperature of the air layer where the difference is small,
The upper limit height H [m] of the distributed charge is determined based on the determined temperature of the air layer and the estimated range of the ground clearance.
A method for estimating a lightning charge amount, which comprises calculating a lightning charge amount ΔQ [C] by the following (Equation 1) using the horizontal distance D, the electric field change amount ΔE, and the upper limit height H.
(Equation 1) ΔQ = 2πε ₀ HΔE / {1 / D-1 / (D ² + H ² ) ^1/2 }
(However, π represents the pi and ε ₀ represents the permittivity of air.) The lower limit height h [m] of the distributed charge is determined based on the estimated ground clearance.
Using the horizontal distance D, the electric field change amount ΔE, the upper limit height H, and the lower limit height h, the lightning charge amount ΔQ is calculated by the following (Equation 2) instead of the above (Equation 1). The method for estimating the amount of lightning charge according to claim 1.
(Equation 2) ΔQ = 2πε ₀ (H−h) ΔE / {1 / (D ² + h ² ) ^1/2 -1 / (D ² + H ² ) ^1/2 }
(However, π represents the pi and ε ₀ represents the dielectric constant of air, and 0 ≦ h <H.) The method for estimating a lightning charge amount according to claim 2, wherein the lower limit height h is determined by calculating the difference between the height of the lightning strike position and the height of the observation point. The error rate Er [%] of the lightning charge amount ΔQ calculated by the above (Equation 1) is estimated.
A claim characterized in that the lightning charge amount ΔQ is calculated by the following (Equation 3) instead of the above (Equation 1) using the horizontal distance D, the electric field change amount ΔE, the upper limit height H, and the error rate Er. Item 1. The method for estimating the amount of lightning charge according to Item 1.
(Equation 3) ΔQ = 2πε ₀ HΔE × 100 / (100 + Er) / {1 / D-1 / (D ² + H ² ) ^1/2 }
(However, π represents the pi and ε ₀ represents the permittivity of air.) Based on the electric field values before and after the lightning strike, the wave tail length T [μs] of the electric field waveform before and after the lightning strike is calculated.
The lightning strike charge amount estimation method according to claim 4, wherein the error rate Er is estimated by the following (Equation 4) using the calculated wave tail length T.
(Equation 4) Er = αT + β
(However, α and β are constants determined in advance based on the measurement and estimation of the amount of lightning strike charge.) It is a lightning charge amount estimation system for calculating the lightning charge amount.
A predetermined correspondence with the temperature of the air layer where the difference between the estimated charge amount and the measured charge amount becomes small is recorded for each meteorological condition in the observation area and for each range of time difference from the time when the first discharge occurs. Correspondence relationship recording means and
A lightning strike position positioning means that measures the horizontal distance D [m] from the lightning strike position to the observation point,
An electric field measuring means for measuring the electric field value before and after a lightning strike at the observation point,
Based on the electric field values before and after the lightning strike, the electric field change amount ΔE [V / m], which is the difference between the electric field value immediately before the start of the feedback lightning strike and the electric field value after a predetermined time has elapsed after the start of the feedback lightning strike, is calculated. Means and
Ground clearance estimating means for estimating the range of ground clearance of the air layer whose temperature is -5 ° C to -15 ° C from the location of the lightning strike and the meteorological observation data at the location and time when the lightning strike occurred.
The estimated charge amount and the measured charge amount based on the lightning strike position, the weather conditions at the time of the lightning strike, the range of the time difference from the time when the first discharge occurs, and the predetermined correspondence relationship in the observation area including the lightning strike position. An air layer temperature determining means for determining the temperature of the air layer where the difference is small,
Upper limit height determining means for determining the upper limit height H [m] of the distributed charge based on the temperature of the air layer determined by the air layer temperature determining means and the above- ground height range estimated by the ground clearance estimating means. When,
It is characterized in that it is provided with a charge amount calculation means for calculating the lightning charge amount ΔQ [C] by performing the following calculation (Equation 1) using the horizontal distance D, the electric field change amount ΔE, and the upper limit height H. Lightning charge estimation system.
(Equation 1) ΔQ = 2πε ₀ HΔE / {1 / D-1 / (D ² + H ² ) ^1/2 }
(However, π represents the pi and ε ₀ represents the permittivity of air.) Further provided with a lower limit height determining means for determining the lower limit height h [m] of the distributed charge based on the ground clearance estimated by the ground clearance estimating means.
The electric charge amount calculation means uses the horizontal distance D, the electric field change amount ΔE, the upper limit height H, and the lower limit height h to perform the following calculation (Equation 2) instead of the (Equation 1). The lightning charge amount estimation system according to claim 6, wherein the lightning charge amount estimation system is characterized.
(Equation 2) ΔQ = 2πε ₀ (H−h) ΔE / {1 / (D ² + h ² ) ^1/2 -1 / (D ² + H ² ) ^1/2 }
(However, π represents the pi and ε ₀ represents the dielectric constant of air, and 0 ≦ h <H.) The lightning strike charge amount estimation system according to claim 7, wherein the lower limit height determining means includes means for calculating the difference between the height of the lightning strike position and the height of the observation point. An error rate estimating means for estimating the error rate Er [%] of the lightning charge amount ΔQ calculated by the above (Equation 1) is further provided.
The electric charge amount calculation means uses the horizontal distance D, the electric field change amount ΔE, the upper limit height H, and the error rate Er to perform the following calculation (Equation 3) instead of the (Equation 1). The lightning charge amount estimation system according to claim 6.
(Equation 3) ΔQ = 2πε ₀ HΔE × 100 / (100 + Er) / {1 / D-1 / (D ² + H ² ) ^1/2 }
(However, π represents the pi and ε ₀ represents the permittivity of air.) A wave tail length calculation means for calculating the wave tail length T [μs] of the electric field waveform before and after the lightning strike is further provided based on the electric field values before and after the lightning strike.
The lightning strike charge amount estimation method according to claim 9, wherein the error rate estimating means performs the following calculation (Equation 4) using the calculated wave tail length T.
(Equation 4) Er = αT + β
(However, α and β are constants determined in advance based on the measurement and estimation of the amount of lightning strike charge.)

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