JP2011149729A - Lightning current distribution estimating system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To estimate lightning current distribution to a grounding system of a building on a lightning strike by simply and accurately detecting a shunt waveform for an injected current. <P>SOLUTION: The lightning current distribution estimation system includes a current injector 30 for injecting without contact a current composed of a high frequency microcurrent having a predetermined frequency and a predetermined current value from the one point of the grounding system having a plurality of branching routes in the building, a current detector 50 disposed at the other point of the grounding system for detecting without contact the shunt current of the injected current passing through the branching routes in the grounding system, a peak value detecting means 61-70 for detecting a peak value by extracting the current component of a predetermined frequency from the detected shunt current, and a calculation unit 69 for calculating the shunt ratio to the predetermined current value from the peak value and for estimating the lightning current shunt ratio or the lightning current shunt value. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a lightning that estimates the distribution of lightning current that enters a grounding system of a building (for example, an external grounding conductor of a signal line such as a grounding wire, a grounding structure, or an outer tube of a waveguide) during a lightning strike. In particular, it is related to the current distribution estimation system, and in particular, a high-frequency weak current is injected from one point of the grounding system of the building, and the shunting state of the injected current is measured at each other point. The present invention relates to a lightning current distribution estimation system capable of estimating lightning current distribution to buildings in Japan.

  In order to protect equipment from lightning strikes, various lightning countermeasures have been implemented on buildings. For example, in a measure using a lightning rod (protection against a direct lightning strike), a lightning strike is received by a lightning rod, and a lightning current is discharged to a grounded body buried in the ground through a dedicated lightning arrester cable. In addition, when a lightning strike occurs, an induced voltage is generated in a signal line or a power line, and an excessive current may enter the building. Therefore, a surge protection device (hereinafter referred to as “SPD”) is provided in the building as a protection against the induced lightning. ) And a lightning-resistant transformer, and an SPD discharges an excessive current to a grounding body buried in the ground, and a lightning-resistant transformer blocks the entry of the excessive current.

  On the other hand, equipment installed in a building that requires grounding ensures grounding of the equipment by connecting a grounding cable to an earth bar laid in the building or a steel frame of the building.

  In this way, the grounding system is stretched around the building, and lightning protection devices such as SPD and various equipment are connected to this grounding system, and the grounding system is connected to the grounding body buried in the ground. It is connected.

  The lightning rod grounding body may be provided separately from the building grounding body, or may be shared with the building grounding body.

  By the way, as described above, there is a possibility that a lightning current induced during a lightning strike (various from a minute one to an excessive one at which the SPD operates) may flow into the grounding system of the building. It is required to understand the distribution (ratio) of inflow current at each point, and to investigate and analyze the effects on the equipment installed at each point in the grounding system. If such investigation and analysis can be performed satisfactorily, the grounding system can be effectively reviewed (structural review such as ground wire routing changes and facility equipment layout changes). It becomes possible to improve the lightning resistance performance of the entire object. In particular, in recent years, the integration of equipment (hereinafter referred to as “IC”) is progressing, and IC devices generally have low withstand voltage and insulation resistance characteristics, so such investigation and analysis are extremely important. Yes and meaningful.

  Conventionally, when a lightning current intrudes from one point of the grounding system, a lightning current distribution estimation system for grasping the current distribution (ratio) of the lightning current shunting at each point of the grounding system is, for example, the following (1), ( A system such as 2) is known.

(1) System for Applying Impulse Voltage This system, for example, as disclosed in Patent Document 1 below, applies actual lightning to a building (for example, a lightning rod installed on the roof of the building). This is a system that applies a relatively high impulse voltage that simulates the above. A simulated lightning (high voltage waveform) is applied to the building by an impulse generator, and the amount of voltage change is measured by each measuring device (for example, a probe for voltage measurement) installed at a plurality of locations (measurement points) of the building. Based on this test result, the lightning current distribution when the actual lightning current flows is estimated.

(2) System for Injecting Weak Current This system is basically roughly divided into a generator for injecting weak current and a current measuring current transformer (hereinafter referred to as “CT”). This is not a system for applying an impulse voltage as in the above (1), but a system for injecting a weak current.

Japanese Patent No. 4112871

  However, the conventional systems (1) and (2) have the following problems.

(1) Problems of system for applying impulse voltage This system has the following problems.

    (1.1) Since a large impulse voltage of several kV or more is applied to the building during the test, there is a concern about adverse effects on the equipment installed in the building. Moreover, as a countermeasure against lightning, an SPD is usually installed in a building. When such a large impulse voltage is applied, the SPD reacts. If an impulse voltage is applied many times during the test, the SPD may be deteriorated or damaged.

    (1.2) Since the applied voltage is large, it is necessary to give sufficient consideration to safety measures during tests such as electric shock.

    (1 ・ 3) Equipment / preparation will be significant.

    (1 · 4) The implementation cost is high for the reason (1 · 3).

    (1.5) Preparation takes a lot of time.

    (1.6) It is difficult to operate (measure) alone.

    (1.7) In order to determine the shunt distribution from the measurement results, advanced experience and skill are required.

(2) Issues of systems that inject weak currents There are various environments in which buildings can be placed. For example, ordinary houses and commercial buildings are often placed in an environment with little electrical noise. On the other hand, a station building built in a power facility such as a substation / power plant, a building built in a factory site of various industries, or a building built in the vicinity of a railway line inevitably has electrical noise. Will be placed in a big environment.

  Although this system is a method of injecting a weak current, it cannot be satisfactorily tested in a building placed in an environment where electrical noise is large. That is, even if the shunt waveform of the injected current is measured by the measuring instrument, the measurement waveform is greatly affected by noise, and the target measurement waveform cannot be obtained.

  The lightning current distribution estimation system according to claim 1 of the present invention comprises a high-frequency weak current having a predetermined frequency and a predetermined current value from one point of a grounding system having a plurality of branch paths in a building. A current injector that injects an injected current in a contactless manner and a current detector that is installed at another point in the grounding system and detects the shunt current of the injected current via the branch path in the grounding contactlessly A peak value detecting means for detecting a peak value by extracting a current component of the predetermined frequency from the detected shunt current, a lightning current by calculating a shunt ratio with respect to the predetermined current value from the peak value And an arithmetic unit for estimating a shunt ratio or a lightning current shunt value. The predetermined frequency is calculated by setting a partial waveform corresponding to a quarter cycle, which is a rising portion, of the waveform corresponding to one cycle to a waveform that approximates a rising partial waveform of a lightning impulse current waveform. It is a frequency.

  According to a second aspect of the present invention, in the lightning current distribution estimation system according to the first aspect, the current injector includes a current injection probe that injects the injected current into the one point.

  The invention according to claim 3 is the lightning current distribution estimation system according to claim 1 or 2, characterized in that the current detector is constituted by a current transformer that detects the shunt current.

  According to a fourth aspect of the present invention, in the lightning current distribution estimation system according to any one of the first to third aspects, the peak value detecting means is at least based on the predetermined frequency from the detected shunt current. A first filter that cuts off a higher high-frequency component, a signal amplifying unit that amplifies the output signal of the first filter, and a filtering process on the output signal of the signal amplifying unit, and a current component of the predetermined frequency And a filter processing means for extracting and detecting the peak value.

  According to a fifth aspect of the present invention, in the lightning current distribution estimation system according to any one of the first to third aspects, the peak value detection means is at least based on the predetermined frequency from the detected shunt current. A first filter that cuts off high-frequency components, a signal amplification unit that amplifies the output signal of the first filter, a signal generation unit that generates a reference signal having the predetermined frequency, and in synchronization with the reference signal The second system peak value detecting means includes a synchronous detection unit for detecting a frequency component equal to the reference signal from the output signal of the signal amplification unit and detecting the peak value.

  The invention according to claim 6 is the lightning current distribution estimation system according to any one of claims 1 to 3, wherein the peak value detection means includes a peak value detection means of the first system and a peak of the second system. And a value detecting means.

  The peak value detection means of the first system includes at least a first filter that cuts off a high frequency component higher than the predetermined frequency from the detected shunt current, and signal amplification that amplifies an output signal of the first filter And filter processing means for performing a filtering process on the output signal of the signal amplifying unit, extracting a current component of the predetermined frequency, and detecting the peak value. Further, the second system peak value detecting means amplifies at least a first filter that cuts off a high frequency component higher than the predetermined frequency from the detected shunt current and an output signal of the first filter. A signal amplifying unit; a signal generating unit that generates a reference signal having the predetermined frequency; and a frequency component equal to the reference signal is detected from an output signal of the signal amplifying unit in synchronization with the reference signal, and the peak And a synchronous detection unit for detecting a value.

  The invention according to claim 7 is the lightning current distribution estimation system according to claim 4 or 6, wherein the filter processing means is constituted by a digital filter processing unit that performs digital filter processing on an output signal of the signal amplification unit. It is characterized by.

  The invention according to claim 8 is the lightning current distribution estimation system according to any one of claims 1 to 7, wherein the predetermined frequency is a frequency in a range of approximately 10 kHz to 150 kHz, and the predetermined current value is an alternating current. The current value is in the range of about 10 mA to 500 mA.

  The lightning current distribution estimation system of the present invention has the following effects (1) and (2).

(1) The effect of accurately measuring the shunt waveform even if a weak current is used (1.1) The peak value of the amplitude of the shunt waveform at each point (each measurement point) of the grounding system can be detected easily and accurately. . In other words, if the current injected at the time of measurement is weak, if noise (various noises with different frequencies, magnitudes, etc.) is mixed in the weak current, it is usually extremely difficult to measure the shunt waveform of the weak current. Although difficult, according to the inventions according to claims 1 to 8, since the system is configured as described above, even if the current to be injected is weak, noise is effectively processed (removed), and the desired shunting is performed. The peak value of the amplitude of the waveform can be detected easily and accurately.

  In particular, as in the inventions according to claims 6 and 7, the peak value detecting means includes both a first system peak value detecting means for performing digital filter processing and a second system peak value detecting means for performing synchronous detection processing. In this case, since it is possible to detect both systems and compare the detection results of both systems, it is possible to detect the peak value of the amplitude of the shunt waveform at each point of the ground system more accurately. it can.

    (1.2) Since noise can be processed effectively as described above, even in buildings such as substations and power plants (buildings placed in an environment where electrical noise is large) Measurement can be performed without inconvenience.

    (1 ・ 3) In the case of a system that applies a conventional impulse voltage, a large voltage is applied at the time of measurement, so the influence on the building (for example, damage to equipment or SPD in the building or power failure, etc.) ) Is a concern. On the other hand, according to the present invention, since a weak current is used for measurement, the influence on the equipment in the building can be reduced, and the danger of electric shock and the like is low, so that the operator can safely Can work on. Therefore, according to the present invention, conventional concerns can be solved, and measurement can be performed without any problem for a building in operation (in operation).

    (1/4) Since it is a non-contact measurement method, it is not necessary to remove the wire, and the measurement can be performed efficiently. Furthermore, the operability is simple and it is possible to measure by one person. Therefore, compared to a conventional system that applies an impulse voltage, the cost and time required for preparation can be greatly reduced.

    (1.5) When the building to be measured is a high-rise building, etc., because the volume of the building is large (because the layer is multi-layered and the area of each layer is large), the point where you want to measure the shunt waveform may be Dozens of places. In a conventional system that applies an impulse voltage, simultaneous measurement at multiple locations is virtually impossible. In contrast, according to the present invention, since the injection current is not a single lightning impulse waveform but a continuous alternating current (hereinafter referred to as “AC”) waveform, continuous measurement over a long period of time is possible. At the same time, simultaneous measurement at multiple locations is possible.

    (1.6) As described above, the peak value of the amplitude of the shunt waveform at each point of the grounding system can be detected easily and accurately, and multiple points can be simultaneously measured. It is also possible to accurately calculate the ratio (distribution to injection current) of the shunt current (distribution) in.

(2) The effect of accurately estimating the shunt waveform of the lightning current According to the invention according to claim 1, the frequency of the high-frequency weak current to be injected is a quarter cycle that is a rising portion of the waveform for one cycle. Since the partial waveform is a frequency calculated by approximating the rising partial waveform of the lightning impulse current waveform, the shunt ratio at each point of the grounding system and the inflow when the inflow current is high frequency weak current It can be estimated that the shunt ratio when the current is a lightning current is equivalent. Therefore, by measuring the shunt ratio with the high frequency weak current of the present invention, the shunt ratio when the lightning current enters can be estimated with high accuracy.

FIG. 1 is a schematic configuration diagram showing a lightning current distribution estimation system in Embodiment 1 of the present invention. FIG. 2 is a schematic configuration diagram showing the current injector 30 in FIG. FIG. 3 is a schematic configuration diagram showing the current detector 50 in FIG. FIG. 4 is a schematic circuit diagram showing the configuration of the synchronous detection unit 66 in FIG. FIG. 5 is a schematic diagram showing a configuration example of the display unit 71 in FIG. FIG. 6 is a schematic diagram showing a current injection point and a current detection point in the case of a radio tower in a substation. FIG. 7A is a diagram illustrating an injection current waveform as an example of the test result of FIG. FIG. 7-2 is a diagram illustrating an injection current waveform as an example of the test result of FIG. FIG. 7C is a diagram illustrating an injection current waveform as an example of the test result of FIG. FIG. 7-4 is a diagram showing an injection current waveform as an example of the test result of FIG. FIG. 8 is a diagram showing input / output waveforms in the synchronous detector 66 of FIG. FIG. 9A is a signal waveform diagram at the current detection point P1 in FIG. 6 which is an example of a test result. FIG. 9-2 is a diagram illustrating a signal waveform at the current detection point P2 in FIG. 6 which is an example of a test result. FIG. 9C is a diagram illustrating a signal waveform at the current detection point P3 in FIG. 6 which is an example of a test result. FIG. 9-4 is a diagram illustrating a signal waveform at the current detection point P4 in FIG. 6 which is an example of a test result. FIG. 9-5 is a diagram illustrating a signal waveform at the current detection point P5 in FIG. 6 which is an example of a test result. FIG. 9-6 is a diagram illustrating a signal waveform at the current detection point P6 in FIG. 6 which is an example of a test result.

  Modes for carrying out the present invention will become apparent from the following description of the preferred embodiments when read in light of the accompanying drawings. However, the drawings are only for explanation and do not limit the scope of the present invention.

(Configuration of Example 1)
FIG. 1 is a schematic configuration diagram showing a lightning current distribution estimation system in Embodiment 1 of the present invention.

  This lightning current distribution estimation system includes a current injection device 10 that injects an injection current consisting of high-frequency weak current from one point in the grounding system, and a distribution of shunt currents at other points (current detection points) in the grounding system. ) Is measured.

  The current injection device 10 includes a signal generator 20 that generates an injection current, and a current injector 30 connected to the output side. The current injector 30 is composed of a high frequency weak current having a predetermined frequency and a predetermined current value from one point of the grounding system having a plurality of branch paths in the building based on the injected current generated by the signal generator 20. The injection current is injected in a non-contact manner.

  As a current characteristic to be injected into one point of the grounding system as an injection target location, it is desirable that the injection current is a small value so as not to have an adverse effect (malfunction or the like) on the installed equipment. However, on the other hand, if the shunt current to be read by the current detector on the measuring device 40 side is too small, reading is impossible. Therefore, the injection current is a high-frequency weak current having a predetermined frequency and a predetermined current value so as to satisfy both conditions. The predetermined frequency is a frequency calculated by setting a partial waveform corresponding to a quarter of the rising portion of the waveform corresponding to one cycle to a waveform that approximates the rising partial waveform of the lightning impulse current waveform. For example, the frequency is in the range of about 10 to 150 kHz, preferably about 100 kHz. Furthermore, the predetermined current value is desirably a current value in a range of approximately 10 to 500 mA of AC.

  The signal generator 20 for supplying an injection current to the current injector 30 includes, for example, a signal generator 21 such as a crystal oscillator that oscillates at a predetermined frequency, and a signal amplifier connected to the output side of the signal generator 21. A control unit 24 for controlling the signal generation unit 21, the signal amplification unit 22, and the condition setting unit 23.

The signal amplifier 22 is a circuit that amplifies the output signal of the signal generator 21 with a predetermined amplification factor and supplies the amplified signal to the current injector 30. The signal generating unit 21 and the signal amplifying unit 22 are configured to adjust the injection current to be about AC 10 to 500 mA as a result. For example, the signal waveform output from the signal generator 21 is as follows, and the amplification factor of the signal amplifier 22 is as follows. By doing so, the electric current of about AC10-500mA will be inject | poured into the injection | pouring object location.
Voltage: AC1V, Amplification factor: 10 times, Frequency: 100kHz

  The condition setting unit 23 can input various values in order to set the output voltage and frequency of the signal generating unit 21, and can input various values in order to set the amplification factor of the signal amplifying unit 22. It is composed of setting buttons and the like. The control unit 24 controls the signal generation unit 21, the signal amplification unit 22, and the condition setting unit 23 according to the control signals S24a, S24b, and S24c, reads each value input to the condition setting unit 23, and sends it to the signal generation unit 21. On the other hand, it has a function of setting an output voltage and frequency and setting an amplification factor for the signal amplifying unit 22, and is constituted by a central processing unit (hereinafter referred to as "CPU") or the like.

  Note that the value of the current injected into the injection target location varies depending on various conditions (for example, the characteristics of the grounding system, the characteristics of the current injector 30), and is not determined uniformly. Therefore, the original voltage waveform and the amplification factor are set by the signal generation unit 21 and the signal amplification unit 22 so that the value of the injection current is about AC 10 to 500 mA as a result. Each setting is performed by the condition setting unit 23 and the control unit 24.

  The current injector 30 receives the output voltage from the signal amplifying unit 22 and injects a current into one point of the grounding system in a non-contact manner. In the first embodiment, for example, a current injection probe is used. .

  The measuring device 40 includes a current detector 50 that is installed at a current detection point and detects a shunt current in a non-contact manner, and an analysis device 60 that analyzes the detected shunt current and obtains a peak value, a shunt ratio, and the like. I have.

  The current detector 50 is configured by, for example, CT, and an analysis device 60 is connected to the output side.

  The analysis device 60 extracts a current component of a predetermined frequency from the shunt current detected by the current detector 50 and detects a peak value, and calculates a shunt ratio with respect to the predetermined current value from the peak value. And a calculation unit 69 for estimating the lightning current diversion ratio or the lightning current diversion value.

  The peak value detection means includes a first system peak value detection means for performing filter processing (for example, digital filter processing) on the original waveform, and a second system for performing synchronous detection processing by inputting the original waveform and the reference waveform. And a peak value detecting means.

  The peak value detection means of the first system is composed of at least a first filter 61 connected to the output side of the current detector 50, a signal amplification unit 62, and filter processing means (for example, digital filter processing unit 70). Yes. The first system peak value detection means includes a second filter 63 for improving detection accuracy, an analog / digital conversion unit (hereinafter referred to as “A / D conversion unit”) 64 for performing digital processing, and the like. It is desirable to provide.

  The second system peak value detection means includes at least a first filter 61, a signal amplification unit 62, a signal generation unit 65, and a synchronous detection unit 66. The second system peak value detection means includes a second filter 63 and a third filter 67 for improving detection accuracy, and an analog / digital conversion unit (hereinafter referred to as “A / D conversion unit”) for performing digital processing. It is desirable to provide 64 etc.

  In the peak value detection means of the first system, the first filter 61 blocks a high frequency component higher than a predetermined frequency from the shunt current detected by the current detector 50. LPF ”). The shunt waveform follows the grounding system and contains noise (particularly because the shunt waveform in buildings such as substations often contains large noise), the first filter The signal components in a certain frequency band are cut off (cut) by the LPF constituting 61. For example, when the injection current is 100 kHz, the frequency component of 500 kHz or more is cut because the frequency of the shunt waveform to be extracted is also 100 kHz. A signal amplifying unit 62 is connected to the output side of the first filter 61.

  The signal amplifying unit 62 has a weak injection current (for example, about AC 10 to 500 mA) and a shunt current that is a shunt of the injection current becomes weaker. It amplifies with the amplification factor of. Similar to the signal amplification unit 22 on the current injection device 10 side, the amplification factor of the signal amplification unit 62 is variable. A second filter 63 is connected to the output side of the signal amplifier 62. The second filter 63 is for filtering the signal amplified by the signal amplifying unit 62 just in case, and similarly to the first filter 61, for example, a frequency component of 500 kHz or more is cut and this analog is cut. The output signal S63 is applied to the first channel Ch1 of the A / D converter 64.

  In the second system of peak value detection means, the signal generator 65 generates a reference signal S65 composed of a pulse signal having a predetermined frequency, and is constituted by a crystal oscillator or the like. A synchronous detector 66 is connected to the output side of the signal generator 65. The synchronous detection unit 66 is a circuit that detects a frequency component equal to the reference signal S65 from the analog output signal S63 of the second filter 63 in synchronization with the reference signal S65, and outputs a current component of a predetermined frequency. A third filter 67 is connected to the output side. The third filter 67 filters the output signal S66 of the synchronous detection waveform output from the synchronous detection unit 66 just in case, and provides this analog output signal S67 to the second channel Ch2 of the A / D conversion unit 64. It has become.

  The A / D converter 64 converts the analog output signal S63 of the second filter 63 input from the first channel Ch1 into a digital signal, and converts the analog output signal of the third filter 67 input from the second channel Ch2. It has a function of converting into digital signals and supplying these digital signals to the arithmetic unit 69.

  The calculation unit 69 receives the output signal of the A / D conversion unit 64, the output signal of the digital filter processing unit 70, etc., calculates the shunt ratio with respect to a predetermined current value from the detected peak value of the shunt current, and In addition to the function of estimating the current shunt ratio or the lightning current shunt value, the control signal S69a for controlling the signal amplification unit 62, the signal generation unit 65, the condition setting unit 68, and the data output means (for example, the display unit 71). , S69b, S69c, S69d, etc., and a CPU or the like.

  The condition setting unit 68 can input various values for setting the voltage and frequency of the signal generation unit 65 and various values for setting the amplification factor of the signal amplification unit 62. In addition, the display content of the display unit 71 (for example, real-time display, 1-second update display, 5-second update display, etc.) is set, and is configured by setting buttons and the like. The conditions set by the condition setting unit 68 are grasped by the calculation unit 69, and the signal amplification unit 62, the signal generation unit 65, and the condition setting unit are controlled by the control signals S69a, S69b, S69c, and S69d output from the calculation unit 69. 68 and the display unit 71 are configured to perform predetermined operations.

  The digital filter processing unit 70 inputs the analog output signal S63 of the second filter 63 via the A / D conversion unit 64 and the calculation unit 69, and extracts a signal in a target frequency band (for example, a shunt waveform in the 100 kHz band). Thus, the extraction result is provided to the calculation unit 69. The digital filter processing unit 70 extracts a signal component in a target frequency band by performing high-speed calculation (for example, fast Fourier transform or Z conversion) using a mathematical algorithm, and is compared with analog filter processing. The signal-to-noise ratio (SN ratio) is high, and there is an advantage that almost all signals in frequency bands other than the target frequency band can be cut.

Specifically, the calculation unit 69 has the following functions (i) to (iv).
(I) When the output signal of the digital filter processing unit 70 is input, the calculation unit 69 grasps the waveform of the target frequency band extracted by the digital filter processing unit 70 and also grasps the peak value. Thereby, the waveform measurement by the first system is completed. On the other hand, when the output signal of the second channel Ch2 in the A / D conversion unit 64 is input, the calculation unit 69 grasps the synchronous detection waveform that has been A / D converted by the A / D conversion unit 64, and the synchronous detection waveform. Also grasp the peak value of. Note that the frequency of the waveform after the synchronous detection may be modified due to the circuit characteristics of the synchronous detection unit 66, but the peak value of the waveform after the synchronous detection is equal to the peak value of the waveform in the target frequency band. Become. Therefore, the peak value of the waveform after synchronous detection can be regarded as the peak value of the waveform in the target frequency band. Thereby, the waveform measurement by the second system is completed. Then, the calculation unit 69 instructs the display unit 71 to display the peak value of the shunt waveform measured in the first system and / or the peak value of the shunt waveform measured in the second system.

  (Ii) As described above, the calculation unit 69 grasps the peak value of the waveform in the target frequency band and also grasps the injection current value by setting the conditions. Therefore, based on these values, the shunt ratio And the display unit 71 is instructed to display the calculation result.

  (Iii) The computing unit 69 estimates the shunt ratio when the inflow current is a lightning current. The principle of this estimation is that in the first embodiment, the frequency of the high frequency weak current to be injected is the rising waveform of the lightning impulse current waveform. Since it is a frequency calculated by making it a waveform that approximates a partial waveform, the shunt ratio at each point of the grounding system when the inflow current is a high-frequency weak current, and the shunt ratio when the inflow current is a lightning current, It is based on what can be estimated as equivalent. Further, if the current value of a general lightning current is stored in the calculation unit 69 in advance by setting conditions (for example, several types of lightning current values during direct lightning strikes and several types of lightning current values during induced lightning strikes). Based on these general lightning current values and the shunt ratio estimated earlier, the peak value of the lightning shunt current at each point of the grounding system can be estimated. Then, the calculation unit 69 instructs the display unit 71 to display the estimation result.

  (Iv) The calculation unit 69 can output a command to display an alarm on the display unit 71 when the peak value or the diversion ratio of the measured or estimated diversion waveform is equal to or higher than a predetermined level.

  The display unit 71 includes a liquid crystal, a light emitting diode (hereinafter referred to as “LED”), a buzzer component, and the like. In response to a command from the calculation unit 69, the peak value of the shunt waveform measured in the first system, The peak value of the shunt waveform measured in the second system, the shunt ratio, the lightning current shunt ratio (estimation), the peak value (estimation) of the thunder current shunt current, and the like are displayed. Further, when an instruction to display an alarm is received from the calculation unit 69, the LED is turned on or an alarm sound is emitted from a buzzer part. The display unit 71 may have a function of displaying the shunt waveform itself.

FIG. 2 is a schematic configuration diagram showing the current injector 30 in FIG.
The current injector 30 in FIG. 2 is for injecting an injected current from one point of the grounding system (for example, the waveguide 81) in a non-contact manner, and is constituted by, for example, a current injection probe. The current injection probe has a two-part structure that can be attached and detached from the outside of the waveguide 81, and is obtained by winding a conducting wire 32 around a donut-shaped toroidal core 31. When an AC injection current is input to the conducting wire 32, an electromotive force is induced in the waveguide 81 that penetrates the toroidal core 31, and a current corresponding to the injection current is injected into the waveguide 81.

  In the first embodiment, a measurement instrument that can inject an injection current in a non-contact manner, such as a current injection probe, is employed. Therefore, the measurement instrument can be easily and efficiently applied to a target location without requiring work such as wire removal or connection. It becomes possible to set.

FIG. 3 is a schematic configuration diagram showing the current detector 50 in FIG.
The current detector 50 detects a shunt current at another point in the grounding system (for example, the grounding wire 83) in a non-contact manner, is configured by a two-part CT, and a conductor 52 is connected to the donut-shaped toroidal core 51. Is wrapped around. When a shunt current flows through the ground wire 83 penetrating the toroidal core 51, an electromotive force is induced, and a current corresponding to the shunt current is output from the conductor 52.

  In the first embodiment, since a measuring instrument that can extract a shunt current without contact like CT is employed, as in the case of the current injector 30, work such as wire removal and connection is not required, and the target location can be easily obtained. It becomes possible to set a measuring instrument efficiently.

FIG. 4 is a schematic circuit diagram showing the configuration of the synchronous detection unit 66 in FIG.
The synchronous detection unit 66 includes, for example, a multiplication unit 66a and an LPF 66b. The analog output signal S63 of the second filter 63 and the reference signal S65 are multiplied by the multiplication means 66a, and a component equal to the frequency of the reference signal S65 is detected among various signals included in the analog output signal S63 of the second filter 63. And pass through the LPF 66b. As a result, a frequency component equal to the reference signal S65 is detected from the analog output signal S63 of the second filter 63, and this output signal S66 is output to the third filter 67.

  As described above, the frequency of the waveform after the synchronous detection may be deformed due to the circuit characteristics of the synchronous detection unit 66, but the peak value of the waveform after the synchronous detection is the peak value of the waveform in the target frequency band. Is the same value as

FIG. 5 is a schematic diagram showing a configuration example of the display unit 71 in FIG.
The display unit 71 shows a simple structure that displays only the peak value (number) of the extracted shunt waveform. The display content can be freely updated, for example, updated every second.

(Operation of Example 1)
For example, lightning damage has occurred in radio equipment at substations and the like, and optimization of grounding has become an issue. In particular, with lightning strikes on the radio tower, there is a lot of damage to the facilities in the station building near the radio tower. Therefore, the operation when the lightning current distribution estimation system of the first embodiment is used in order to optimally ground the station near the radio tower in the substation will be specifically described with reference to the measurement waveform. Is as follows.

  FIG. 6 is a schematic diagram illustrating a current injection point and a current detection point, taking a radio tower as an example in a substation.

  A station building 90 is installed in the vicinity of the radio tower 75, and a communication line 80 is laid between the radio tower 75 and the station building 90. Here, the communication line 80 is, for example, a waveguide 81, and is drawn into the inside of the office building 90 from the entrance 82 on the first floor of the office building 90. The waveguide 81 is a line with a small transmission loss for transmitting microwave and millimeter wave high frequency power from the transmitter to the transmission antenna and from the reception antenna to the receiver. The part also serves as an external ground conductor. On the other hand, the station 90 is formed of a grounding system (a grounding wire 83, a collective plate 84-1 for collectively connecting a plurality of grounding wires 83, a grounding structure such as a steel frame, an external grounding conductor for signal lines, and the like. The outer tube portion of the waveguide 81 is electrically connected to the grounding system.

  Among the 1st and 2nd floors of the office building 90, on the 1st floor, a plurality of assembly boards 84-1, 84-2, a wiring board 85, a substation facility 86, etc. are installed as equipment, and further on the 2nd floor. A plurality of collective plates 84-3, an observation device 87, a control device 88, and the like are installed as equipment. In the vicinity of the entrance 82 on the first floor, the outer tube portion of the waveguide 81 and the ground wire 83a are connected, and the ground wire 83a is connected to the collecting plate 84-1. In addition, a plurality of wiring boards 85, transformer facilities 86, and the like are electrically connected through a plurality of branch paths formed by ground wires 83 and collecting plates 84-1 and 84-2 provided on the first floor. Yes. Similarly, a plurality of observation devices 87 and a control device 88 are electrically connected through a plurality of branch paths formed by the ground wire 83 and the collecting plate 84-3 provided on the second floor, and these are 1 It is connected to a grounding body 89 buried in the ground via a collective board 84-2 on the floor.

  Here, as shown in FIG. 6, a lightning current flows from one point in the waveguide 81 (a point of the current injection point P0), and an arrow passes from the inlet 82 of the station 90 through the branch path of the internal grounding system. Assuming that a shunt current flows in the direction, (I) the waveform at the current injection point P0, (II) the waveform at the current detection point P1, and (III) the waveforms at the current detection points P2 to P6 will be described.

(I) Waveform at Current Injection Point P0 FIGS. 7-1 to 7-4 are diagrams showing an injection current waveform which is an example of the test result of FIG.

  The current injector 30 shown in FIG. 2 is attached to the current injection point P 0 in the waveguide 81, and the current detection points P 1 to P 6 of the ground wire 83 in the vicinity of each equipment installed in the office building 90 are attached. A current detector 50 shown in FIG. 3 is attached.

  When the power switch (not shown) of the current injection device 10 in FIG. 1 is turned on at the current injection point P0, the control signal S24a of the control unit 24 that reads the voltage, frequency, and amplification factor set by the condition setting unit 23, By S24b and S24c, the voltage (for example, AC1V) and frequency (for example, 100 kHz) of the signal generation unit 21 are set, and the amplification factor (for example, 10 times) of the signal amplification unit 22 is set.

  Then, the signal generator 21 oscillates to output an oscillation signal having a voltage of AC 1 V and a frequency of 100 kHz, which is amplified by the signal amplifying unit 22 at an amplification factor of 10. Therefore, the current injector 30 injects an AC 10 to 500 mA injection current into the current injection point P0.

  The injection waveform diagram on the upper side of FIG. 7-1 shows a voltage waveform V21 (AC1V, 100 kHz) output from the signal generator 21 with one scale on the horizontal axis being 5 μS and one scale on the vertical axis being 200 mV. .

  The injection waveform diagram on the lower side of FIG. 7-1 shows the current waveform I82 in the vicinity of the current injection point P0 (at the inlet 82 side), with one scale on the horizontal axis being 5 μS and one scale on the vertical axis being 20 mA. . This current waveform I82 is a current waveform injected into the grounding system (outer tube portion of the waveguide 81), and is read by the current detector 50 for reference. Since the current waveform I82 is a current waveform that follows the grounding system, it contains a noise component, but it can be generally grasped that the waveform is AC100mA, 100kHz, and therefore the planned injected current waveform is injected into the grounding system. I can grasp that. This current waveform I82 is diverted to various parts of the grounding system (grounding wire 83 and the like).

  Here, the background and reason why the injection current waveform having the above-described frequency is adopted in the first embodiment will be described as the following (a) to (d).

  (A) The injection current waveform may be the same as the lightning impulse waveform, but it is not a single waveform such as a lightning impulse waveform or a square wave (a waveform formed by multiple types of frequency components). There is a problem that it is not easy to detect this shunt waveform (target waveform extracted on the current detector side). That is, it is difficult to extract a waveform such as a lightning impulse formed by a plurality of types of frequency components because signal processing (such as noise removal) becomes complicated. Therefore, it is convenient if the injection current waveform can adopt an AC waveform that is a single wave.

  (B) Due to the characteristics of the synchronization processing, the synchronous detection unit 66 can extract a single-wave AC waveform with extremely high accuracy, while being able to extract a waveform such as a lightning impulse (formed by a plurality of types of frequency components). It is difficult to extract the waveform). Therefore, it is convenient if the injection current waveform can adopt an AC waveform that is a single wave.

  (C) Regarding grounding repair work, if measurement and estimation can be performed in real time (continuous) during a series of work hours before, during, or after grounding repair work, for example, After measuring and estimating after the first ground wire routing change, if the effect of the first ground wire routing change is not sufficient, immediately perform the same work as the second time and so on. Therefore, the grounding system can be optimized in a short time. Thus, in order to be able to measure in real time (continuous), it is desirable that the injected current is not a single waveform such as a lightning impulse waveform but a continuous waveform such as an AC waveform. It is. Therefore, it is convenient if the injected current waveform can adopt an AC waveform that is a continuous waveform.

  (D) Since it is as described in (a) to (c) above, it would be better if the injection current waveform is simply an AC waveform, but naturally the AC waveform is different from the lightning impulse waveform. When an AC waveform is used, a question arises as to whether the lightning current distribution can be accurately estimated. In other words, it is as follows. The AC has a characteristic that when the frequency is high, the inductance is high when propagating through the line, and when the frequency is low, the inductance is low. Therefore, when AC waveforms having different inductances are injected into the grounding system, there is a possibility that the diversion aspect (diversion ratio, attenuation, etc. at each point) is different due to the difference. This raises a concern that the estimation accuracy of the lightning current distribution has a great influence. Therefore, as a result of testing and researching the frequency of an AC wave that exhibits a shunting aspect equivalent to the shunting aspect of the lightning impulse waveform, the present inventor has determined that the frequency of the AC wave is “four rising edges of one waveform. It was found that it is optimal to set the partial waveform for one minute period to a frequency calculated by making the waveform approximate to the rising partial waveform of the lightning impulse current waveform.

  For the above background and reasons, the injection current waveform (in other words, high-frequency weak current) of Example 1 was determined. The approximation of the waveform is illustrated in FIGS. 7-2 to 7-4.

  The lightning impulse current waveform of the present application is a waveform defined by “JEC-0202-1994 Impulse voltage / current test in general” which is a standard of the Japan Electrotechnical Committee (JEC: Electrotechnical Committee). That's it. The lightning impulse current waveform includes a direct lightning waveform and a guided lightning waveform, and the general waveforms are represented as 2/70 μS, 8/20 μS, and 10/350 μS.

  FIG. 7-2 is a diagram illustrating a lightning impulse current waveform having a fast time to reach the maximum value (rise time) and an injection current waveform approximated thereto. One scale on the horizontal axis is 10 μS.

  In FIG. 7-2, the upper waveform is a lightning impulse current waveform, the time to reach the maximum value is 2 μS, and the time to decrease to 50% of the maximum value is 70 μS.

  Here, the frequency of the AC wave is changed to “a partial waveform corresponding to a quarter of the rising portion of the waveform corresponding to one cycle is a rising partial waveform of the lightning impulse current waveform (partial waveform of 2 μS in this figure). When calculated as “frequency calculated by making approximate waveform”, the frequency is approximately 125 kHz, and this AC current waveform is as shown in the lower side of FIG. In this way, the AC injection current waveform corresponding to the lightning impulse current waveform with a fast rise time is calculated.

  FIG. 7-3 is a diagram illustrating a lightning impulse current waveform having a relatively slow time to reach the maximum value (rise time) and an injection current waveform approximated thereto. One scale on the horizontal axis is 5 μS.

  In FIG. 7C, the upper waveform is a lightning impulse current waveform, and the time to reach the maximum value is 8 μS, and the time to decrease to 50% of the maximum value is 20 μS. Here, the frequency of the AC wave is changed to “a partial waveform corresponding to a quarter of the rising portion of the waveform corresponding to one cycle is a rising partial waveform of the lightning impulse current waveform (partial waveform of 8 μS in this figure). When calculated as “frequency calculated by approximating waveform”, the frequency is approximately 31.25 kHz, and this AC current waveform is as shown in the lower side of FIG. In this way, the AC injection current waveform corresponding to the lightning impulse current waveform having a relatively slow rise time is calculated.

  FIG. 7-4 is a diagram illustrating a lightning impulse current waveform with a slow time to reach the maximum value (rise time) and an injection current waveform approximated thereto. One scale on the horizontal axis is 50 μS.

  In FIG. 7-4, the upper waveform is the lightning impulse current waveform, the time to reach the maximum value is 10 μS, and the time to decrease to 50% of the maximum value is 350 μS. Here, the frequency of the AC wave is changed to “a partial waveform corresponding to a quarter of the rising portion of the waveform corresponding to one cycle is a rising partial waveform of the lightning impulse current waveform (partial waveform of 10 μS in this figure). When calculated as “frequency calculated by making approximate waveform”, the frequency is approximately 25 kHz, and this AC current waveform is as shown in the lower side of FIG. 7-4. In this way, the AC injection current waveform corresponding to the lightning impulse current waveform having a slow rise time is calculated.

  As can be seen from FIGS. 7-2 to 7-4, the frequency of the injection current is calculated based on the rise time of the lightning impulse current waveform, and the general lightning impulse current waveform is as described above. The frequency of the injection current is desirably 10 to 150 kHz. Therefore, in the first embodiment, as shown in FIG. 7A, the frequency of the AC voltage waveform V21 output from the signal generating unit 21 is set to 100 kHz, and the AC waveform of the injected current injected into the current injection point P0 is as follows. The frequency is set to 100 kHz.

(II) Waveform at Current Detection Point P1 FIG. 8 is a diagram showing input / output waveforms in the synchronous detection unit 66 of FIG.

  FIGS. 9-1 (a) and (b) are signal waveform diagrams at the current detection point P1 of FIG. 6 which is an example of a test result.

  The upper waveform diagram of FIG. 9-1 (a) shows a current waveform I50 at the current detection point P1, with one scale on the horizontal axis being 5 μS and one scale on the vertical axis being 20 mA. This current waveform I50 is a so-called raw waveform showing what is read by the current detector 50 as a reference. Since the current waveform I50 is a current waveform that has followed the grounding system, it contains a noise component, but it can be generally understood that the peak value is about AC 95 mA and the frequency is 100 kHz. From this, it can be generally understood that the current waveform I50 is a shunt waveform of the injected current waveform (current waveform I82), and the shunt ratio is 95% (= AC 95 mA / AC 100 mA × 100). This current waveform I50 is input to the analysis device 60 and subjected to signal processing by the digital filter processing unit 70 and the synchronous detection unit 66. The reason for grasping the current waveform I50 of the raw waveform as a reference in this way is to confirm accuracy by comparing with the waveform after processing by the analysis device 60. Therefore, it is not actually necessary to display such a raw waveform on the display unit 71.

  The lower waveform diagram of FIG. 9A is a current waveform I70 after the digital filter processing performed by the digital filter processing unit 70, in which one scale on the horizontal axis is 5 μS and one scale on the vertical axis is 20 mA. Is shown. It can be confirmed that the current waveform I70 is an AC waveform (single wave) having no noise component, the peak value is AC95 mA, and the frequency is 100 kHz. That is, it can be seen that the noise was efficiently and reliably cut for the current waveform I50, which is a shunt current including a noise component, and the target shunt current (the shunt current of the injected current waveform I82) was accurately extracted.

  Therefore, the peak value of the shunt waveform at the current detection point P1 is 95 mA, and the shunt ratio is calculated to be 95%. Then, if a lightning current enters similarly, it is estimated that the lightning current shunt ratio is also 95% (the reason is as described above). If the assumed lightning current value (peak value) to be entered is set in advance, the diversion value (peak value) of the incoming lightning current can be estimated based on the estimated lightning current diversion ratio. . For example, based on a general case, assuming that the intruding lightning current value (peak value) is 30 kA, and setting this value in advance, the diversion value (peak value) of the lightning current at the point P1 is 28.5 kA. It will be estimated that. However, when such an excessive current actually flows to the grounding system, there is a high possibility that the equipment will be damaged. Therefore, in practice, it is usual to provide an SPD at an appropriate place in the station building.

  Although the appearance of the upper waveform diagram in FIG. 9-1 (b) differs depending on the scale of the vertical axis, it is the current waveform I50 at the above-described current detection point P1, and therefore the description of the waveform is omitted.

  The middle waveform diagram of FIG. 9-1 (a) shows the reference signal S65 input to the synchronous detector 66, with one scale on the horizontal axis being 5 μS and one scale on the vertical axis being 5V. In order to extract a signal having a frequency of 100 kHz, the reference signal S65 employs a pulse wave that repeats the cycle at 100 kHz. The peak value is a voltage waveform of 5V.

  In the lower waveform diagram of FIG. 9-1 (a), one scale on the horizontal axis is 5 μS, and one scale on the vertical axis is 40 mA. After being processed by the synchronous detector 66, the scale is further processed by the third filter. The subsequent current waveform I67 is shown. It can be confirmed that the current waveform I67 is an AC waveform (single wave) having no noise component, and the peak value is AC95 mA. That is, for the current waveform I50 that is a shunt current including a noise component, the noise was efficiently and reliably cut, and the peak value of the target shunt current (the shunt current of the injected current waveform I82) could be extracted with high accuracy. I understand. As described above, according to the synchronous detection, the frequency of the waveform after the synchronous detection does not necessarily match the frequency of the target waveform due to the characteristics of signal processing, but the peak value of the target waveform is not accurate. This is a well-calculated value, and this point is as shown by the waveform I67 in FIG.

  Therefore, the peak value of the shunt waveform at the current detection point P1 is 95 mA, and the shunt ratio is calculated to be 95%. Then, if a lightning current enters similarly, it is estimated that the lightning current shunt ratio is also 95% (the reason is as described above). If the assumed lightning current value (peak value) to be entered is set in advance, the diversion value (peak value) of the incoming lightning current can be estimated based on the estimated lightning current diversion ratio. . For example, based on a general case, assuming that the intruding lightning current value (peak value) is 30 kA, and setting this value in advance, the diversion value (peak value) of the lightning current at the point P1 is 28.5 kA. It will be estimated that. However, when such an excessive current actually flows to the grounding system, there is a high possibility that the equipment will be damaged. Therefore, in practice, it is usual to provide an SPD at an appropriate place in the station building.

Next, the signal processing operation in the analysis device 60 will be further described as follows.
The current detector 50 of FIG. 3 attached to the current detection point P1 of FIG. 6 detects a shunt current flowing through the current detection point P1. As shown in FIGS. 9-1 (a) and (b), the detected current waveform I50 of the shunt current traces the grounding system and includes noise. The signal component in the frequency band is cut. When the injection current is 100 kHz, a frequency component of, for example, 500 kHz or higher that is larger than the frequency 100 kHz of the shunt waveform to be extracted is cut.

  The injected current is a weak current (AC 100 mA in the first embodiment), and the shunt current shunted from this injected current is even weaker. Therefore, the output signal of the first filter 61 is amplified by the signal amplification unit 62 based on the amplification factor set by the condition setting unit 68 and the calculation unit 69. The amplified signal is filtered by the second filter 63 just in case. In the second filter 63, as in the first filter 61, for example, a frequency component of 500 kHz or higher is cut, and this analog output signal S63 is converted into a first system on the digital filter processing unit 70 side and a first component on the synchronous detection unit 66 side. Branches into two systems.

  On the first system side, the A / D conversion unit 64 inputs the analog output signal S63 of the second filter 63 to the first channel Ch1, converts it to a digital signal, and sends it to the digital filter processing unit 70 via the calculation unit 69. send. The digital filter processing unit 70 is controlled by the calculation unit 69, performs digital filter processing on the converted digital signal, and performs a current waveform I70 (ie, a target frequency band as shown in FIG. 9-1 (a)). 100 kHz band shunt waveform) is extracted, and the shunt waveform (including the peak value) is grasped and transmitted to the calculation unit 69.

  The calculation unit 69 recognizes that the peak value of the current waveform I50 is 95 mA in order to grasp the current waveform I70 extracted by the digital filter processing unit 70. Since the calculation unit 69 recognizes the peak value of the shunt waveform in this way, the shunt waveform has a shunt ratio of 95%, and the shunt current when the shunt current is a lightning current is calculated based on the calculation result. Is also estimated to be 95%. Furthermore, since the calculation unit 69 estimates the shunt ratio when the shunt current is a lightning current as 95%, the lightning current value (peak value) when the shunt current is a lightning current is also estimated. Then, the calculation unit 69 instructs the display unit 71 to display these values in accordance with the signal output from the condition setting unit 68.

  The display unit 71 receives a display command from the calculation unit 69, and receives “a peak value of the shunt waveform (current waveform I70): 95 mA”, “a shunt ratio with respect to the injection waveform (current waveform I82): 95%”, “lightning current It is displayed that the shunt ratio (estimated) is 95% and the peak value of lightning current (estimated) is 28.5 kA.

  On the other hand, on the second system side, the synchronous detector 66 synchronizes with the reference signal S65 output from the signal generator 65 as shown in FIGS. 8 and 9-1 (b). A frequency component equal to the reference signal S65 is detected from the analog output signal S63.

  Here, as shown in FIG. 8, the reference signal S65 input to the synchronous detector 66 is a pulse waveform (square wave) having the same frequency (for example, 100 kHz) as the target shunt waveform. The synchronous detector 66 is a circuit for confirming whether or not the analog output signal S63 of the second filter 63 includes a predetermined frequency signal (= reference signal S65), and the analog output signal S63 of the second filter 63. And the reference signal S65 are multiplied in an analog manner by the multiplication means 66a, the high frequency component is removed by the LPF 66b, and an output signal S66 having a synchronous detection waveform is output. The peak value of the output signal S66 represents the peak value of the reference signal S65 included in the analog output signal S63 of the second filter 63.

  Note that the frequency of the output signal S66 of the synchronous detection waveform does not necessarily match the frequency of the reference signal S65. The peak value of the output signal S66 is a peak value of the frequency of the reference signal S65 included in the analog output signal S63 of the second filter 63. That is, the peak value of the shunt waveform can be grasped from the output signal S66.

  The output signal S66 is filtered by the third filter 67 just in case, and this analog output signal S67 is output to the A / D converter 64. The A / D conversion unit 64 inputs the analog output signal S67 output from the third filter 67 to the second channel Ch2, converts it to a digital signal, and gives it to the calculation unit 69.

  The calculation unit 69 recognizes that the peak value of the current waveform I50 is 95 mA in order to grasp the converted digital signal (synchronous detection waveform: current waveform I67). Since the calculation unit 69 recognizes the peak value of the shunt waveform in this way, the shunt waveform has a shunt ratio of 95%, and the shunt current when the shunt current is a lightning current is calculated based on the calculation result. Is also estimated to be 95%. Furthermore, since the calculation unit 69 estimates the shunt ratio when the shunt current is a lightning current as 95%, the lightning current value (peak value) when the shunt current is a lightning current is also estimated. Then, the calculation unit 69 instructs the display unit 71 to display these values in accordance with the signal output from the condition setting unit 68.

  The display unit 71 receives a display command from the calculation unit 69 and receives “a peak value of the shunt waveform (current waveform I50): 95 mA”, “a shunt ratio with respect to the injection waveform (current waveform I82): 95%”, “lightning current It is displayed that the shunt ratio (estimated) is 95% and the peak value of lightning current (estimated) is 28.5 kA.

  As described above, the calculation unit 69 may display various values calculated and estimated based on the digital filter processing on the display unit 71, and display the various values calculated and estimated based on the synchronous detection processing. 71 may be displayed. However, for example, various values obtained by both processes may be compared, and if there is an error, an average value may be calculated and displayed on the display unit 71. By adding such arithmetic processing, the accuracy can be further improved.

(III) Waveforms at Current Detection Points P2 to P6 FIGS. 9-2 (a) and (b) to FIGS. 9-6 (a) and (b) are current detection points P2 to P6 in FIG. FIG. 9 is a diagram illustrating a signal waveform in FIG. 9, and elements common to elements in FIGS. 9-1 (a) and (b) are denoted by common reference numerals.

  The description of FIGS. 9-2 (a) and (b) to FIGS. 9-6 (a) and (b) is the same as the description of FIGS. 9-1 (a) and (b). A description will be given of the peak value and the diversion ratio of the current waveform detected at each point.

As shown in FIGS. 9-2 (a) and (b), the peak value of the shunt waveform (current waveform I50) at the point P2 is calculated or estimated as follows. However, it is assumed that the lightning current value (peak value) when it is assumed that the lightning current has entered is set to 30 kA.
Peak value of shunt waveform (current waveform I50): 40 mA
* Both digital filter processing and synchronous detection processing are 40 mA.
Shunt ratio to injection waveform (current waveform I82): 40%
Lightning current shunt ratio (estimated): 40%
Lightning current peak value (estimated): 12 kA

As shown in FIGS. 9-3 (a) and (b), the peak value of the shunt waveform (current waveform I50) at the point P3 is calculated or estimated as follows. However, it is assumed that the lightning current value (peak value) when it is assumed that the lightning current has entered is set to 30 kA.
Peak value of shunt waveform (current waveform I50): 30 mA
* 30 mA for both digital filter processing and synchronous detection processing
Shunt ratio to injection waveform (current waveform I82): 30%
Lightning current shunt ratio (estimated): 30%
Lightning current peak value (estimated): 9 kA

As shown in FIGS. 9-4 (a) and (b), the peak value of the shunt waveform (current waveform I50) at the point P4 is calculated or estimated as follows. However, it is assumed that the lightning current value (peak value) when it is assumed that the lightning current has entered is set to 30 kA.
Peak value of shunt waveform (current waveform I50): 10 mA
* 10 mA for both digital filter processing and synchronous detection processing
Shunt ratio to injection waveform (current waveform I82): 10%
Lightning current shunt ratio (estimated): 10%
Lightning current peak value (estimated): 3 kA

As shown in FIGS. 9-5 (a) and (b), the peak value of the shunt waveform (current waveform I50) at the point P5 is calculated or estimated as follows. However, it is assumed that the lightning current value (peak value) when it is assumed that the lightning current has entered is set to 30 kA.
Peak value of shunt waveform (current waveform I50): 10 mA
* 10 mA for both digital filter processing and synchronous detection processing
Shunt ratio to injection waveform (current waveform I82): 10%
Lightning current shunt ratio (estimated): 10%
Lightning current peak value (estimated): 3 kA

As shown in FIGS. 9-6 (a) and (b), the peak value of the shunt waveform (current waveform I50) at the point P6 is calculated or estimated as follows. However, it is assumed that the lightning current value (peak value) when it is assumed that the lightning current has entered is set to 30 kA.
Peak value of shunt waveform (current waveform I50): 90 mA
* Both digital filter processing and synchronous detection processing are 90 mA.
Shunt ratio to injection waveform (current waveform I82): 90%
Lightning current shunt ratio (estimated): 90%
Lightning current peak value (estimated): 27 kA

  As shown in FIGS. 9-1 (a) and (b) to FIGS. 9-6 (a) and (b), the current detection points P1 to P6 set at different points on the ground line 83 are digitally connected. The current waveform I70 after the filter processing and the current waveform I67 after the synchronous detection processing are different, and as a result, the shunt ratio is also different.

  FIGS. 7-1 to 7-4 and FIGS. 9-1 to 9-6 are waveform diagrams showing examples of test results. However, since these images are given priority for illustration, they are slightly actual. There are some differences. That is, in practice, the current waveform output from the current detector 50 is attenuated at the stage of each filter 61, 62, 67, etc. in FIG. Therefore, the peak value of the current waveform output from the current detector 50 and the peak value of the current waveform output from the first channel Ch1 of the A / D converter 64, or the second channel of the A / D converter 64 It does not match the peak value of the current waveform output from Ch2. This is calculated by estimating the current waveform output from the current detector 50 by correcting the calculation unit 69.

(Effect of Example 1)
The effects of the lightning current distribution estimation system according to the first embodiment are summarized as (1) to (5) below.

(1) The effect of accurately measuring the shunt waveform even if a weak current is used (1.1) The peak value of the amplitude of the shunt waveform at each point (each measurement point) of the grounding system can be detected easily and accurately. . In other words, if the current injected at the time of measurement is weak, if noise (various noises with different frequencies, magnitudes, etc.) is mixed in the weak current, it is usually extremely difficult to measure the shunt waveform of the weak current. Although it is difficult, since the system is configured as shown in FIG. 1, noise is effectively processed (removed) even if the injected current is weak, and the peak value of the amplitude of the target shunt waveform can be easily and accurately performed. Can be detected.

  In particular, when the peak value detecting means is constituted by both the first system peak value detecting means for performing digital filter processing and the second system peak value detecting means for performing synchronous detection processing, detection is performed by both systems. In addition, since the detection results of both systems can be compared, the peak value of the amplitude of the shunt waveform at each point of the grounding system can be detected with higher accuracy.

      (1.2) Since noise can be processed effectively as described above, even in buildings such as substations and power plants (buildings placed in an environment where electrical noise is large) Measurement can be performed without inconvenience.

      (1 ・ 3) In the case of a system that applies a conventional impulse voltage, a large voltage is applied at the time of measurement, so the influence on the building (for example, damage to equipment or SPD in the building or power failure, etc.) ) Is a concern. On the other hand, according to the first embodiment, since a weak current is used in the measurement, the influence on the equipment in the building can be reduced, and the risk of electric shock and the like is small. Can work safely. Therefore, according to the present Example 1, the conventional concern can be solved and it can measure without any problem with respect to the building in operation (in operation).

      (1/4) Since it is a non-contact measurement method, it is not necessary to remove the wire, and the measurement can be performed efficiently. Furthermore, the operability is simple and it is possible to measure by one person. Therefore, compared to a conventional system that applies an impulse voltage, the cost and time required for preparation can be greatly reduced.

      (1.5) When the building to be measured is a high-rise building, etc., because the volume of the building is large (because the layer is multi-layered and the area of each layer is large), the point where you want to measure the shunt waveform may be Dozens of places. In a conventional system that applies an impulse voltage, simultaneous measurement at multiple locations is virtually impossible. On the other hand, since the injection current is not a single lightning impulse waveform but a continuous AC waveform, continuous measurement over a long period of time is possible and simultaneous measurement at multiple locations is possible.

      (1.6) As described above, the peak value of the amplitude of the shunt waveform at each point of the grounding system can be detected easily and accurately, and multiple points can be simultaneously measured. It is also possible to accurately calculate the ratio (distribution to injection current) of the shunt current (distribution) in.

(2) The effect of accurate estimation of the lightning current shunt waveform The frequency of the high-frequency weak current to be injected is the lightning impulse current waveform of the waveform for one quarter of the rising waveform. Since the frequency is calculated by making the waveform approximate to the rising partial waveform, the shunt ratio at each point of the grounding system when the inflow current is a high frequency weak current, and the shunt ratio when the inflow current is a lightning current Can be estimated to be equivalent. Therefore, by measuring the diversion ratio with the high-frequency weak current of the first embodiment, the diversion ratio when the lightning current enters can be accurately estimated.

(3) Effects contributing to investigation / analysis As the ratio of shunting at each point of the grounding system when lightning current enters as described above can be accurately estimated, Impact investigation / analysis becomes possible. In other words, since it is possible to accurately estimate the degree of lightning current that can flow into equipment during a lightning strike, by comparing it with the withstand voltage and current withstand characteristics of equipment installed at each point of the grounding system, It is possible to investigate and analyze the impact on equipment (malfunction risk, risk of dielectric breakdown, etc.). In particular, in recent years, as equipment has become increasingly integrated into ICs, IC devices generally have low withstand voltage and insulation resistance characteristics, so such investigation and analysis is extremely important and meaningful. It can meet such needs.

(4) Effects that contribute to the review of the grounding system (4.1) As described above, it is possible to investigate and analyze the effects on the equipment installed at each point of the grounding system. It is possible to effectively take measures such as review (structural review such as ground wire routing change) and facility equipment layout change, and it is possible to improve the lightning resistance of the entire building. Therefore, the system of the first embodiment can also be used as a lightning protection design evaluation device.

      (4.2) Since the measurement and estimation can be performed easily as described above, it is possible to easily verify the effect before the grounding system review (before the grounding repair work) and after the grounding system review (after the grounding repair work). is there. The effects before and after the review can be confirmed directly from the measured and estimated diversion values.

      (4.3) Since measurement and estimation can be performed easily as described above, measurement and estimation are performed as needed or in real time during a series of work hours before, during and after grounding repair work. Is possible. Therefore, for example, if the measurement and estimation are made after the first ground wire routing change, and if the effect of the first ground wire routing change is not sufficient, the same operation as the second time is performed immediately thereafter. The renovation work can be performed efficiently, and the grounding system can be optimized in a short time.

(5) Other effects Conventionally, when equipment is damaged by a lightning strike, the cause is searched and verified by some method, but the search and verification of such a cause is performed in the first embodiment. Can do.

(Modification of Example 1)
The present invention is not limited to the first embodiment, and various usage forms and modifications are possible. For example, the following forms (A) to (D) are available as usage forms and modifications.

  (A) The lightning current distribution estimation system shown in FIG. 1, the current injector 30 shown in FIG. 2, the current detector 50 shown in FIG. 3, and the synchronous detector 66 shown in FIG. good. For example, the A / D unit 64, the calculation unit 69, and the digital filter processing unit 70 are configured by a one-chip microcomputer (hereinafter referred to as “one-chip microcomputer”) in which these functions are integrated to simplify the circuit configuration. Alternatively, it may be configured by a circuit other than the one-chip microcomputer.

  (B) If accuracy is not a concern, a configuration including only one of the first system and the second system in FIG. 1 may be provided, thereby simplifying the circuit configuration. For example, when only the first system is provided, the signal generator 65, the synchronous detector 66, and the third filter 67 may be deleted and the A / D converter 64 may be changed to a one-channel configuration. If only the second system is provided, the digital filter processing unit 70 may be deleted.

  (C) In the first system of FIG. 1, since the digital filter can improve the detection accuracy, the digital filter processing is performed by the arithmetic unit 69 using the digital filter. However, the present invention is not limited to this, Filter processing may be performed using an analog filter.

  (D) On the measurement device 40 side in FIG. 1, a transmission unit controlled by the calculation unit 69 may be added, and the display content displayed on the display unit 71 may be transmitted to the outside by the communication unit. This also enables remote monitoring.

DESCRIPTION OF SYMBOLS 10 Current injection apparatus 20 Signal generator 30 Current injector 40 Measuring apparatus 50 Current detector 60 Analysis apparatus 66 Synchronous detection part 69 Calculation part 70 Digital filter process part

Claims (8)

A current injector that injects an injection current consisting of a high-frequency weak current having a predetermined frequency and a predetermined current value from a single point of a grounding system having a plurality of branch paths in a building; and
A current detector that is installed at another point of the grounding system and detects a shunt current of the injected current via the branch path in the grounding system in a non-contact manner;
Peak value detecting means for detecting a peak value by extracting a current component of the predetermined frequency from the detected shunt current;
A calculation unit for calculating a diversion ratio with respect to the predetermined current value from the peak value and estimating a lightning current diversion ratio or a lightning current diversion value;
The predetermined frequency is a frequency calculated by setting a partial waveform corresponding to a quarter cycle, which is a rising portion, of a waveform corresponding to one cycle to a waveform that approximates a rising partial waveform of a lightning impulse current waveform. A lightning current distribution estimation system characterized by being.   2. The lightning current distribution estimation system according to claim 1, wherein the current injector comprises a current injection probe that injects the injected current into the one point.   The lightning current distribution estimation system according to claim 1, wherein the current detector includes a current transformer that detects the shunt current. The peak value detecting means is at least
A first filter that blocks high frequency components higher than the predetermined frequency from the detected shunt current;
A signal amplifying unit for amplifying the output signal of the first filter;
Filter processing means for performing a filtering process on the output signal of the signal amplifying unit, extracting a current component of the predetermined frequency, and detecting the peak value;
The lightning current distribution estimation system according to any one of claims 1 to 3, wherein the first system peak value detection means has The peak value detecting means is at least
A first filter that blocks high frequency components higher than the predetermined frequency from the detected shunt current;
A signal amplifying unit for amplifying the output signal of the first filter;
A signal generator for generating a reference signal having the predetermined frequency;
Synchronously detecting the frequency component equal to the reference signal from the output signal of the signal amplifier in synchronization with the reference signal, and detecting the peak value,
The lightning current distribution estimation system according to any one of claims 1 to 3, wherein the second system peak value detection means has The peak value detecting means includes
Comprising a first system peak value detection means and a second system peak value detection means;
The peak value detection means of the first system is at least
A first filter that blocks high frequency components higher than the predetermined frequency from the detected shunt current;
A signal amplifying unit for amplifying the output signal of the first filter;
Filter processing means for performing a filtering process on an output signal of the signal amplification unit, extracting a current component of the predetermined frequency, and detecting the peak value;
The peak value detection means of the second system is at least
A first filter that blocks high frequency components higher than the predetermined frequency from the detected shunt current;
A signal amplifying unit for amplifying the output signal of the first filter;
A signal generator for generating a reference signal having the predetermined frequency;
The synchronous detection part which detects the frequency component equal to the said reference signal from the output signal of the said signal amplification part synchronizing with the said reference signal, and detects the said peak value of Claim 1-3 characterized by the above-mentioned. The lightning current distribution estimation system according to any one of the above.   The lightning current distribution estimation system according to claim 4 or 6, wherein the filter processing means includes a digital filter processing unit that performs digital filter processing on an output signal of the signal amplification unit. The predetermined frequency is a frequency in a range of approximately 10 kHz to 150 kHz,
The lightning current distribution estimation system according to any one of claims 1 to 7, wherein the predetermined current value is a current value in a range of approximately 10 mA to 500 mA of alternating current.

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