JP2000028661A - Grounding resistance measurement method and device thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grounding resistance measurement method and device for eliminating the need for measuring a complex amount. SOLUTION: The measurement signal of a frequency, that matches the series resonance frequency of a ground return circuit that is composed of a grounding electrode 11, a metal plate 12, an insulation member 13, and lead wires 14A and 14B, is supplied from a measuring instrument 20. By causing the imaginary part of the impedance of the ground return circuit to be set to zero and utilizing that a complex amount is not related to the measurement of a reflection power, measurement can be made at a real number region, obtaining the absolute value of a reflection coefficient from reflected and incident powers, and the grounding resistance of the grounding electrode 11 is measured. As a result, the need for measurement at a complex region, as in a conventional case, is eliminated, the configuration of a measuring device is simplified, and furthermore a consumption power can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved method and apparatus for measuring ground resistance.

[0002]

2. Description of the Related Art FIG. 1 is a block diagram showing a conventional ground resistance measuring device, in which 1 is a ground electrode, 2 is a metal plate for returning to ground, 3 is an insulating member, 4 and 5 are lead wires. , 6 are impedance measuring instruments.

An impedance measuring device (hereinafter simply referred to as a measuring device) 6 has a coaxial measuring terminal 7 and a measuring terminal 7.
The impedance between the center conductor 7a and the outer conductor 7b can be measured by changing the frequency.

The ground electrode 1 is buried in the ground and connected to the center conductor 7 a of the measuring terminal 7 via the lead wire 4. The metal plate 2 is arranged so that one surface faces the ground surface with the insulating member 3 interposed therebetween.
Is connected to the external conductor 7b of the measuring terminal 7 via the.

Conventionally, a ground electrode 1, a ground, a metal plate 2, an insulating member 3, a lead wire 4,
By measuring the impedance of the loop circuit constituted by 5 with the measuring device 6, both the resistance component and the inductance component in the impedance of the measurement result are evaluated, and the ground resistance is obtained from the real part.

[0006]

However, in the above-mentioned prior art, the impedance of the loop circuit is measured in a complex region, and the inductance portion is not originally required when measuring the ground resistance.

Further, there is a problem that an impedance measuring instrument 6 having a complicated configuration for measuring a complex quantity is required, and power consumption is increased in order to stabilize the frequency of the impedance measuring instrument 6. For this reason, a portable power supply such as a battery cannot be used, so that it is not suitable for outdoor ground resistance measurement.

In view of the above problems, an object of the present invention is to provide a ground resistance measuring method and apparatus which do not need to measure a complex quantity.

[0009]

In order to achieve the above object, according to the present invention, a ground electrode grounded to the ground and a ground electrode having one surface opposed to the surface of the ground in a non-contact state. A ground resistance measuring method using a return conductor, wherein one end of each of two conductor wires is connected to each of the ground electrode and the ground return conductor, and the ground electrode, the ground, the ground return conductor, A measurement signal is supplied with a predetermined transmission power from a measuring instrument connected to the other end of the conductor wire to the ground return circuit formed by the conductor wire, and the frequency of the measurement signal is set to the resonance frequency of the ground return circuit. After setting, the reflection power of the reflected wave signal from the ground return circuit is obtained, and the reflection coefficient of the ground electrode and the ground return conductor is obtained from the value of the ratio of the power of the reflected wave signal to the transmission power. Reflection coefficient and measurement Suggest ground resistance measurement method for obtaining the grounding resistance of the ground electrode against the ground by using the value of the characteristic impedance of the output end of the vessel.

According to the ground resistance measuring method, the ground return circuit formed by the ground electrode, the ground, the ground return conductor, and the conductor wire has a frequency substantially equal to the resonance frequency of the ground return circuit. Since the measurement signal is supplied from the measuring device, the imaginary component of the impedance of the ground return circuit becomes substantially zero, and the impedance becomes a pure resistance. The impedance at this time is a ground resistance between the ground electrode and the ground, a ground resistance between the ground return conductor and the ground, and a combined resistance of a pure resistance component of a parallel circuit including a capacitance and a ground resistance. Become. Furthermore, in the resonance state, the pure resistance component of the parallel circuit including the ground resistance and the capacitance between the ground return conductor and the ground is such that the ground return conductor and the ground are in a non-contact state. The value becomes almost zero.

When the reflection coefficient of the ground electrode and the conductor for the ground return is determined from the ratio of the power of the reflected wave signal from the ground return circuit to the transmission power, the ground resistance of the ground electrode is determined by the reflection resistance. It can be calculated from the coefficient and the characteristic impedance of the measuring instrument, and the measurement of the ground resistance can be performed without measuring the imaginary component.

According to a second aspect of the present invention, in the ground resistance measuring method according to the first aspect, the resonance frequency of the ground return circuit is changed by changing the reactance of the conductor wire, and the frequency matching the resonance frequency is measured. A grounding resistance measuring method for obtaining a frequency characteristic of the grounding resistance by using a signal is proposed.

According to the ground resistance measuring method, the resonance frequency of the ground return circuit is changed by changing the reactance of the conductor wire, and the measurement signal having a frequency matching the resonance frequency is used. Since the imaginary component in the impedance of the ground return circuit becomes zero and the ground resistance can be obtained by measuring the pure resistance at the resonance frequency, if the measurement is performed at a plurality of resonance frequencies by changing the reactance of the series resistance, The frequency characteristic of the ground resistance can be obtained.

According to a third aspect of the present invention, there is provided the ground resistance measuring method according to the second aspect, wherein a ferrite core is attached to the conductor wire to change the reactance of the conductor wire.

According to the ground resistance measuring method, the conductor wire is wound around a ferrite core, or the conductor wire is inserted into a ring-shaped ferrite core, and the ferrite core is attached to the conductor wire. Since the reactance of the conductor wire changes, the reactance of the conductor wire can be changed very easily.

According to a fourth aspect of the present invention, in the ground resistance measuring method according to the first aspect, a directional coupler is provided at the other end of the conductor wire, and the directional coupler supplies the ground supply circuit to the ground return circuit. We propose a ground resistance measurement method that separates signal and reflected wave signal.

According to the ground resistance measuring method, the measurement signal is transmitted from the other end to the one end of the conductor via the directional coupler, and is connected to one end of the conductor. The reflected wave signal from the ground electrode is transmitted from one end to the other end of the conductor wire, and the transmission directions of the measurement signal and the reflected wave signal are opposite to each other. Therefore, the measurement signal is transmitted by the directional coupler. And the reflected wave signal are separated, and only the reflected wave signal can be extracted.

According to a fifth aspect of the present invention, there is provided the ground resistance measuring method according to the first aspect, wherein a capacitance between the ground surface and the ground return conductor is set to be large.

According to the ground resistance measuring method, the impedance of the ground return conductor in the ground return circuit in the resonance state is determined by the ground resistance of the ground return conductor and the electrostatic capacitance between the ground return conductor and ground. Considered as the impedance of a parallel circuit with the capacitance, the imaginary part of the impedance becomes zero due to the resonance frequency, and the real part increases the capacitance between the ground surface and the ground return conductor by setting a large value. The value of the real part becomes substantially zero, and becomes a value that can be ignored compared to the ground resistance of the ground electrode.

According to a sixth aspect of the present invention, in the ground resistance measuring method according to the first aspect, a resistor having a resistance equal to a characteristic impedance of the measuring device is connected in series between the ground electrode and the conductor wire. We propose a method for measuring the grounding resistance in which the measurement is performed in a state where the measurement is performed.

According to the ground resistance measuring method, the reflection coefficient can usually take a value of -1 to +1. However, since the reflection coefficient is obtained from the power ratio, the reflection coefficient is an absolute value thereof. At this time, two values may be considered as the ground resistance to be measured with the characteristic impedance as a boundary. This is because the ground resistance is obtained by using the reflection coefficient and the characteristic impedance of the measuring instrument, and the measurement is performed in an area where it is unknown whether the ground resistance is larger or smaller than the characteristic impedance. However, by providing the resistor, including the resistance value of the resistor in the ground resistance, and finally subtracting the resistance value, the reflection coefficient obtained from the power ratio may be used as a positive value. Thus, only one value is obtained as the value of the ground resistance.

According to a seventh aspect of the present invention, a ground electrode grounded to the ground, a ground return conductor having one surface opposed to the ground surface in a non-contact state, and one end connected to the ground electrode. A first conductor wire, a second conductor wire having one end connected to the ground return conductor, and a first port connected to the other end of each of the first conductor wire and the second conductor wire; A directional coupler having: a ground electrode, a ground, a ground return conductor, and a resonance frequency detecting means for detecting a resonance frequency of a ground return circuit formed by the conductor wire; and a second port of the directional coupler. A transmitter that outputs a measurement signal having a frequency substantially equal to the resonance frequency of the ground return circuit, and a first power detection unit that detects a transmission power of the transmitter; direction A second power detecting means connected to a third port of the coupler in a state where the impedance is matched, and extracting a frequency component of the output signal of the transmitter and detecting the power of the frequency component; The device outputs the input signal to the second port to the first port without outputting the signal to the third port, and outputs the input signal to the first port to the third port without outputting the signal to the second port. We propose a ground resistance measuring device that has directivity to output to a port.

According to the ground resistance measuring apparatus, the resonance frequency of the ground return circuit formed by the ground electrode, the ground, the ground return conductor, and the conductor wire is detected by the resonance frequency detecting means. Further, the ground electrode from the transmitter,
A measurement signal having a frequency substantially coincident with the resonance frequency of the ground return circuit is supplied to the ground, the ground return circuit, and the ground return circuit formed by the conductor wire.

As a result, the imaginary component of the impedance of the ground return circuit in the resonance state becomes substantially zero, and the impedance becomes a pure resistance. Further, the impedance at this time is a combination of a ground resistance between the ground electrode and the ground, and a pure resistance component of a parallel circuit including a ground resistance and a capacitance between the ground return conductor and the ground. It becomes resistance.

Further, the measurement signal is supplied from the transmitter via the directional coupler to the other ends of the first and second conductor wires, and is transmitted from the other end to one end of the conductor wires. The reflected wave signal from the ground electrode connected to one end of the conductor wire is transmitted from one end of the conductor wire to the other end,
Since the transmission directions of the measurement signal and the reflected wave signal are opposite to each other, the measurement signal and the reflected wave signal are separated by the directional coupler, and only the reflected wave signal can be extracted.

Further, the power of the measurement signal output from the transmitter is measured by the first power detection means, and the ground return path separated from the measurement signal by the directional coupler by the second power detection means. The power of the frequency component of the measurement signal in the reflected wave signal from the circuit is detected.
Thereby, the reflection coefficient of the ground electrode and the conductor for the ground return can be obtained from the value of the ratio between the output power of the transmitter and the power of the reflected wave signal. Further, since the ground resistance of the ground electrode can be calculated from the reflection coefficient and the characteristic impedance, without measuring the imaginary component,
Measurement of ground resistance can be performed.

According to an eighth aspect of the present invention, there is provided a ground resistance measuring apparatus according to the seventh aspect, further comprising an insulating member provided between the ground surface and the ground return conductor.

According to the grounding resistance measuring device, an insulating member is provided between the ground surface and the ground return conductor,
Since the ground surface and the ground return conductor are insulated from each other, the ground return conductor can be easily installed without contacting the ground surface.

According to a ninth aspect of the present invention, there is provided the grounding resistance measuring device according to the eighth aspect, wherein the insulating member is made of a high dielectric constant insulator.

According to the grounding resistance measuring device, since the insulating member having a high dielectric constant is provided between the ground surface and the ground return conductor, the area of the surface of the ground return conductor facing the ground surface is reduced. By reducing the capacitance, the capacitance between the ground surface and the ground return conductor can be set large.

According to a tenth aspect of the present invention, in the grounding resistance measuring apparatus according to the seventh aspect, a reactance variable means for changing a reactance of the ground return circuit is provided, and a frequency for changing the frequency of the measurement signal to the transmitter is provided. A ground resistance measuring device with variable means is proposed.

According to the grounding resistance measuring device, the reactance of the conductor wire can be changed by the reactance varying means, whereby the resonance frequency of the ground return circuit can be changed, and the frequency matching the resonance frequency can be changed. Can be generated from the transmitter. Thereby, at the resonance frequency, the imaginary component in the impedance of the ground return circuit becomes zero, and the ground resistance at the resonance frequency can be obtained by measuring the pure resistance. Therefore, a plurality of resonance frequencies can be obtained by changing the reactance of the series resistance. , The frequency characteristic of the ground resistance can be obtained.

According to the eleventh aspect, in the ground resistance measuring apparatus according to the seventh aspect, a resistance is connected in series between the ground electrode and the first conductor line and is equal to a characteristic impedance value of the directional coupler. We propose a ground resistance measuring device provided with a resistor having a value.

According to the grounding resistance measuring device, the reflection coefficient can usually take a value of -1 to +1. However, since the reflection coefficient is obtained from the power ratio, the reflection coefficient is an absolute value. At this time, two values may be considered as the ground resistance to be measured with the characteristic impedance as a boundary. This is because the ground resistance is obtained by using the reflection coefficient and the characteristic impedance of the measuring instrument, and the measurement is performed in an area where it is unknown whether the ground resistance is larger or smaller than the characteristic impedance. However, by providing the resistor, including the resistance value of the resistor in the ground resistance, and finally subtracting the resistance value, the reflection coefficient obtained from the power ratio may be used as a positive value. Thus, only one value is obtained as the value of the ground resistance.

According to a twelfth aspect of the present invention, in the grounding resistance measuring apparatus according to the seventh aspect, a square root of a ratio between the transmitted power and the reflected wave power is determined based on a detection result of the first and second power detection means. A grounding resistance measuring device provided with a reflection coefficient display means for obtaining and displaying the same is proposed.

According to the grounding resistance measuring device, the square root of the ratio between the transmitted power and the reflected wave power is automatically obtained by the reflection coefficient display means based on the detection results of the first and second power detection means. Displayed.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a configuration diagram showing a ground resistance measuring apparatus according to the first embodiment of the present invention. In the figure, 1
1 is a ground electrode, 12 is a metal plate, 13 is an insulating member for preventing direct contact between the metal plate and the ground E, 14A, 14B
Is a first and a second lead wire, and 20 is a measuring device, and these components constitute a ground resistance measuring device.

The ground electrode 11 is buried in the ground E and connected to a measuring instrument 20 via a lead wire 14A.
A metal plate 12 is disposed on the surface of the ground E at a predetermined distance from the ground electrode so that one surface of the metal plate 12 is opposed to the ground E with the insulating member 13 interposed therebetween. ing.

The measuring device 20 includes a transmitter 21, a receiver 22,
It comprises a directional coupler 23, an arithmetic processing unit 24, a display 25, and a battery 26 for supplying power thereto, and these components are housed in a portable case (not shown).

The oscillator 21 includes an oscillation circuit 211 and a power detection circuit 212. The oscillation circuit 211 directionally couples a sine wave signal having a frequency based on a control signal from the arithmetic processing unit 24 via the power detection circuit 212. Output to the device 23. The power detection circuit 212 detects the output power of the oscillation circuit 211 and outputs the value to the arithmetic processing unit 24.

The receiver 22 includes a filter circuit 221 and a power detection circuit 222. The filter circuit 221 is
It is connected between the directional coupler 23 and the power detection circuit 222, and sets a signal passing frequency band based on a control signal from the arithmetic processing unit 24. The power detection circuit 222 detects the power of the signal output from the filter circuit 221 and outputs the value to the arithmetic processing unit 24.

The directional coupler 23 has first to third ports 231, 232, 233, and the entire circuit has a specific characteristic impedance Z ₀ (for example, 50Ω). 1st port 2
Reference numeral 31 denotes a coaxial connector mounted on the case of the measuring instrument 20, the center conductor of which is connected to the ground electrode 11 via the lead wire 14A, and the outer conductor is connected to the metal plate 12 via the lead wire 14B. I have. The second port 232 is connected to the output terminal of the transmitter 21 with impedance matching, and the third port 233 is connected to the input terminal of the receiver 22 (input terminal of the filter circuit 221) with impedance matching. Have been.

Further, the directional coupler 23 has a second port
Directionality in which the input signal to 232 is output to the first port 231 without being output to the third port 233, and the input signal to the first port 231 is output to the third port 233 without being output to the second port 232 have. That is, the measurement signal output from the transmitter 21 is converted by the directional coupler 23 into the leads 14A, 14A.
B, and the reflected wave signal from the lead wires 14A and 14B, and the ground return circuit composed of the ground electrode 11, the ground E, and the metal plate 12, is separated from the measurement signal by the directional coupler 23, and is separated from the receiver signal. 22 only.

The arithmetic processing unit 24 is composed of a keyboard and a well-known one-chip microcomputer, etc., and outputs a control signal for instructing the oscillation frequency to the oscillation circuit 211 based on the frequency value input from the keyboard, and also includes a filter circuit.
A control signal indicating a pass frequency band is output to 221. Further, the arithmetic processing unit 24 calculates the square root of these ratios (the absolute value of the reflection coefficient γ described later) based on the power values input from the power detection circuits 212 and 222 of the transmitter 21 and the receiver 22, respectively. While storing the value in the memory corresponding to the frequency, based on an input command from the keyboard, the absolute value of the reflection coefficient γ stored in the memory,
Alternatively, the frequency characteristic curve of this value is displayed on the display 25.

Next, a description will be given of a method of measuring the ground resistance using the measuring device having the above-described configuration.

The ground return circuit 30 including the ground electrode 11, the ground E, the metal plate 12, the insulating member 13, and the lead wires 14A and 14B can be represented by an equivalent circuit shown in FIG.

In FIG. 3, Rg is the ground resistance of the ground electrode 11, R is the ground resistance of the metal plate 12, C is the capacitance of the metal plate 12, r is the combined resistance of the lead wires 14A and 14B, and L is the lead wire. This is a combined reactance of 14A and 14B, and it is considered that the ground resistance R and the capacitance C of the metal plate 12 are connected in parallel.

When the measurement signal generated by the transmitter 21 is supplied to the leads 14A and 14B via the directional coupler 23, the combined impedance Z of the ground return circuit 30
Is represented by the following equation (1).

[0050]

(Equation 1) The second term on the right side of the above equation (1) is the impedance of the metal plate 12, and the third and fourth terms are the combined impedance of the lead wires 14A and 14B.

When the real part and the imaginary part of the second term on the right side of the above equation (1) are represented by separated complex numbers, the following equation (2) is obtained.

[0052]

(Equation 2) At this time, the resistance r of the lead wires 14A and 14B is so small as to be negligible, and furthermore, a measurement signal having a frequency equal to the resonance frequency f ₀ of the ground return circuit 30 is transmitted by the
And the series return is generated in the ground return circuit 30, the values of the third and fifth terms on the right side of the above equation (2) become zero.

Therefore, the resonance frequency f of the ground return circuit 30
_{When the} transmitter 21 generates a measurement signal having a frequency equal to ₀ , the impedance Z of the ground return circuit 30 becomes a pure resistance and is expressed by the following equation (3).

[0054]

(Equation 3) The second term on the right side of the above equation (3) is the pure resistance component of the parallel circuit composed of the ground resistance R and the capacitance C between the metal plate 12 and the ground E when the ground return circuit 30 is in a resonance state. It is. Normally, the ground resistance R of the metal plate 12 insulated from the ground E is considered to be infinite.
When it is considered that the ground resistance R of the second is infinite, the second term on the right side of the equation (3) becomes zero.

Here, since the impedance represented by the equation (3) is a pure resistance, the power reflected by the ground electrode 11 (reflected wave power) does not include reactive power. Therefore, oscillator 21, the characteristic impedance Z ₀ of the first port 231 of the receiver 22 and the characteristic impedance Z ₀ at the output of the measuring device 20 composed of a directional coupler 23, i.e. the directional coupler 23, ground return Using the absolute value of the reflection coefficient γ of the circuit 30, the ground resistance Rg of the ground electrode 11 is expressed by the following equation (4).

[0056]

(Equation 4) Here, the reflection coefficient γ is expressed by the following equation (5).

[0057]

(Equation 5) Here, Pi is the transmission power of the transmitter 21, and Pr is the reception power obtained by measuring the reflected wave separated by the directional coupler at the receiver. These powers Pi and Pr are detected by a power detection circuit.
Detected by 212,222.

By using the above equations (4) and (5), the ground resistance Rg of the ground electrode 11 can be easily obtained.

Also, two possible values of the ground resistance Rg in the above equation (3) are that the ground resistance Rg matches the characteristic impedance Z ₀ of the measuring instrument 20 (here, Z ₀ = 50Ω). If in the boundary, and the reflected wave power when grounding resistor Rg is the characteristic impedance Z ₀ is less than, ground resistance Rg
Is greater than the characteristic impedance Z _0, the reflected wave power becomes symmetric.

Here, if the characteristic impedance Z ₀ of the measuring instrument 20 is set to a value that is significantly different from the value that the ground resistance Rg can take, one value can be easily determined as the value of the ground resistance Rg. it can.

However, a value generally used as a characteristic impedance of an electronic circuit is 50Ω or 75Ω.
Is the most. Thus, the measuring instrument 2 having the characteristic impedance Z ₀ close to the possible value of the ground resistance Rg.
0, the ground resistance Rg is calculated by the following method.
One value can be easily determined as the value of.

That is, as shown in FIG. 4, a resistor 3 having a value (= Rz) equal to the characteristic impedance Z ₀ (for example, 50Ω) of the measuring instrument 20 is provided between the ground electrode 11 and the lead wire 14A.
1 may be connected in series in advance.

By connecting the resistor 31 in this manner, the value obtained by adding the resistance value Rz of the resistor 31 to the value of the ground resistance Rg is defined as the ground resistance Rg ′ (= Rg + Rz), and the above equation (4) is used. Similarly, it is obtained by the following equation (6).

[0064]

(Equation 6) However, the reflection coefficient γ here indicates the reflection coefficient when the resistor 31 (for example, the resistance value Rz = Z ₀ = 50Ω) is inserted.

When the above equation (6) is solved for the ground resistance Rg to be measured, the ground resistance Rg is expressed by the following equation (7).

[0066]

(Equation 7) As described above, the ground resistance Rg can be obtained using the above equation (7).

When the above-described measuring device is used, the value of the characteristic impedance Z ₀ of the measuring device 20 is known, and the absolute value of the reflection coefficient γ is obtained by the measuring device. Can be calculated. This calculation process can also be easily performed automatically by the arithmetic processing unit 24.

Further, the resonance frequency of the ground return circuit 30 can be determined by the frequency at which the reflection coefficient γ has the minimum value by looking at the above-mentioned frequency characteristic curve of the absolute value of the reflection coefficient γ. That is, when a resonance state occurs in the ground return circuit 30, the imaginary part of the impedance Z of the ground return circuit 30 becomes zero, and this impedance Z shows the minimum value, and the reflection coefficient γ at this time also shows the minimum value. .

On the other hand, the value of the grounding resistance R of the metal plate 12 is usually considered to be infinite, but shows a finite value depending on the environmental state or the state of the land at the measurement site. The term cannot be ignored and a measurement error may occur.

In such a case, the occurrence of a measurement error can be prevented by the following method.

That is, in the above equation (3), the capacitance C or the ground resistance R of the metal plate 12 may be set such that the second term on the right side can be ignored.

For example, the capacitance C and the ground resistance R of the metal plate 12 may be selected so as to satisfy the following equation (8).

[0073]

(Equation 8) If the capacitance C and the ground resistance R of the metal plate 12 are selected so as to satisfy the following equation (9) obtained by modifying the above equation (8), it is possible to prevent the occurrence of measurement error.

[0074]

(Equation 9) As a simple method for satisfying the condition of the above expression (9), a method of increasing the area of the metal plate 12 or a material having a large dielectric constant is used as the insulating member 13 between the metal plate 12 and the ground E. Although there are methods and the like, it is effective to increase the area of the metal plate 12.

As described above, according to the present embodiment, a measurement signal having a frequency substantially coincident with the resonance frequency of the ground return circuit 30 is supplied to the ground return circuit 30, and the imaginary number in the impedance Z of the ground return circuit 30 is supplied. Since the ground resistance Rg of the ground electrode 11 can be obtained by measuring the pure resistance so that the component becomes zero, the conventional measurement in the complex region is unnecessary, and the configuration of the measuring device is simplified. be able to.

As a result, the measurement accuracy can be improved, and the power consumption can be reduced as compared with the conventional case, so that the battery can be driven and the ground resistance can be measured at an arbitrary place. .

Further, by using a battery as a drive power source of the measuring device, the ground resistance Rg can be measured more favorably than in the prior art, because it is not affected by the stray capacitance generated in the power supply line or the like.

Next, a second embodiment of the present invention will be described.

FIG. 5 is a block diagram showing a grounding resistance measuring device according to the second embodiment. In the figure, the first
The same components as those of the embodiment are denoted by the same reference numerals, and description thereof will be omitted. Further, the difference between the first embodiment and the second embodiment is that the combined reactance L of the lead wires 14A and 14B is changed to change the ground resistance R at a plurality of frequencies.
g is able to be measured.

Here, the reactance of the lead wire 14A is increased by mounting the ferrite core 32 in the middle of the lead wire 14A connected to the ground electrode 11.

Thus, the ground resistance Rg can be measured at a plurality of frequencies by changing the resonance frequency of the ground return circuit 30, so that the frequency characteristics of the ground resistance Rg can be obtained.

A plurality of ferrite cores 32 are attached to the lead wire 14A, or different types of ferrite cores 32 are attached.
The resonance frequency can be changed by including the above.

Further, in order to simplify the switching of the reactance of the lead wire 14A, a plurality of types of inductor elements may be interposed in the lead wire 14A via a switch or the like.

The first and second embodiments are specific examples of the present invention, and it goes without saying that the present invention is not limited to these.

For example, a measuring device for measuring only the ground resistance at a specific frequency may be configured. In the above-described embodiment, the absolute value of the reflection coefficient γ is automatically calculated by the arithmetic processing unit 24.However, a measuring apparatus including power detection circuits 212 and 222 having only a function of displaying a measured value is configured. The operator may read the power and calculate the reflection coefficient γ and the ground resistance Rg.

[0086]

As described above, according to the ground resistance measuring method of the first aspect of the present invention, the ground return circuit formed by the ground electrode, the ground, the ground return conductor, and the conductor wire is provided. A measurement signal having a frequency substantially equal to the resonance frequency of the ground return circuit is supplied, and the imaginary component in the impedance of the ground return circuit becomes substantially zero, and the ground resistance of the ground electrode is obtained by measuring the pure resistance. This eliminates the need for conventional measurements in the complex domain,
The configuration of the measuring device can be simplified. As a result, the measurement accuracy can be improved, and the power consumption can be reduced as compared with the related art. Therefore, the portable power supply such as a battery can be driven, and the ground resistance can be measured at an arbitrary place. be able to. Further, when a battery is used, the resistance to stray capacitance generated in a power supply line or the like is not affected, so that the ground resistance can be measured better than before.

According to the ground resistance measuring method of the second aspect, in addition to the effect of the first aspect, the ground resistance can be obtained by measuring the pure resistance using the resonance frequency of the ground return circuit. In addition, since the measurement can be performed at a plurality of resonance frequencies by changing the reactance of the series resistance, the frequency characteristic of the ground resistance can be obtained very easily.

According to the ground resistance measuring method of the third aspect, in addition to the effect of the second aspect, a conductor wire is wound around a ferrite core, or a conductor wire is inserted through a ring-shaped ferrite core. By attaching a ferrite core to the conductor wire, the reactance of the conductor wire can be easily changed, so that the resonance frequency of the ground return circuit can be changed very easily.

According to the ground resistance measuring method of the fourth aspect, in addition to the effect of the first aspect, the measurement signal and the reflected wave signal can be easily separated by the directional coupler. Only the reflected wave signal can be easily extracted.

According to the ground resistance measuring method of the fifth aspect, in addition to the effect of the first aspect, in addition to the effect of the ground resistance of the ground return conductor and the capacitance between the ground return conductor and the ground. The imaginary part of the impedance in the parallel circuit becomes zero due to the resonance frequency, and the value of the real part approaches zero by setting the capacitance between the ground surface and the ground return conductor large, so that the grounding is performed. The value is negligible compared to the ground resistance of the electrode, and the impedance of the ground return circuit is substantially equal to the ground resistance between the ground electrode and the ground. Therefore, the ground resistance can be measured very easily without including an error due to the ground resistance component of the ground return conductor.

According to the ground resistance measuring method of the sixth aspect, in addition to the effect of the first aspect, it is unclear whether the ground resistance of the ground electrode is larger or smaller than the characteristic impedance of the measuring instrument. Even in the local measurement, one value can be obtained as the value of the ground resistance.

According to the ground resistance measuring apparatus of the present invention, the ground return circuit formed by the ground electrode, the ground, the ground return conductor, and the conductor wire is substantially equal to the resonance frequency of the ground return circuit. A ground signal of the ground electrode can be obtained by measuring a pure resistance by supplying a measurement signal having a coincident frequency so that an imaginary component in the impedance of the ground return circuit becomes substantially zero. Measurement is unnecessary, and the configuration of the measuring device can be simplified. As a result, the measurement accuracy can be improved, and the power consumption can be reduced as compared with the conventional case. Therefore, the device can be driven by a portable power source such as a battery, and the ground resistance can be measured at an arbitrary place. Can be. Further, when a battery is used, the resistance to stray capacitance generated in a power supply line or the like is not affected, so that the ground resistance can be measured better than before.

According to the grounding resistance measuring device of the eighth aspect, in addition to the effect of the seventh aspect, the ground surface and the ground return conductor are insulated by the insulating member. The ground return conductor can be easily installed without making contact with the ground surface, and can be easily installed at any measurement location.

According to the grounding resistance measuring device of the ninth aspect, in addition to the effect of the eighth aspect, since the insulating member having a high dielectric constant is used, the surface of the ground return conductor facing the ground surface is used. Since the capacitance between the ground surface and the ground return path conductor can be set to be large, the pure resistance component of the ground return path conductor in the impedance of the ground return path circuit can be set as This value can be made almost negligible compared to the ground resistance of the ground electrode with respect to the ground, and the ground resistance of the ground electrode can be measured more easily.

According to the ground resistance measuring apparatus of the tenth aspect, in addition to the effect of the seventh aspect, the ground resistance can be obtained by measuring the pure resistance using the resonance frequency of the ground return circuit. In addition, since the reactance of the series resistance can be changed by the reactance variable means to measure at a plurality of resonance frequencies, the frequency characteristic of the ground resistance can be obtained very easily.

According to the grounding resistance measuring device of the present invention, in addition to the effect of the above-mentioned claim, it is possible to determine whether the grounding resistance of the grounding electrode is larger or smaller than the characteristic impedance. In measurement, one value can be obtained as the value of the ground resistance.

According to the ground resistance measuring apparatus of the twelfth aspect, in addition to the effect of the seventh aspect, the ratio of the reflection coefficient is automatically determined and displayed by the reflection coefficient display means. Work can be simplified.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a conventional ground resistance measuring device.

FIG. 2 is a configuration diagram showing a ground resistance measuring device according to the first embodiment of the present invention.

FIG. 3 is a diagram showing an equivalent circuit of the ground return circuit according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating connection positions of resistors according to the first embodiment of the present invention.

FIG. 5 is a configuration diagram showing a ground resistance measuring apparatus according to a second embodiment of the present invention.

[Explanation of symbols]

11 ground electrode, 12 metal plate, 13 insulating member, 14
A, 14B: lead wire, 20: measuring instrument, 21: transmitter,
211: oscillation circuit, 212: power detection circuit, 22: receiver, 22
1 filter circuit, 222 power detection circuit, 23 directional coupler, 231 first port, 232 second port, 233 third
Port, 24 arithmetic processing unit, 25 display, 26 battery, 30 ground return circuit, 31 resistor, 32 ferrite core, E ground, Rg ground resistance of ground electrode, R ground of metal plate Resistance, C: capacitance of metal plate, r: combined resistance of lead wire 14, L: combined reactance of lead wire.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hidefumi Ohashi 3-19-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo F-term in Nippon Telegraph and Telephone Corporation (reference) 2G028 AA01 AA03 AA04 BC06 BE08 CG05 CG08 CG13 CG15 CG20 DH05 DH11 EJ01 FK01 FK02 FK09 HN02 HN09 HN14 LR02

Claims (12)

[Claims] 1. A ground resistance measuring method using a ground electrode grounded to the ground, and a ground return conductor having one surface opposed to the surface of the ground in a non-contact state, wherein the ground electrode and the ground are One end of each of the two conductor wires is connected to each of the return conductors, and the ground electrode, the ground, the other end of the conductor wire with respect to the ground return circuit formed by the ground return conductor and the conductor wire. After supplying the measurement signal with a predetermined transmission power from the connected measuring instrument and setting the frequency of the measurement signal to the resonance frequency of the ground return circuit, the reflection power of the reflected wave signal from the ground return circuit is obtained. From the value of the ratio between the power of the reflected wave signal and the transmitted power, the reflection coefficient of the ground electrode and the ground return conductor is determined. Said Ground resistance measurement method characterized by obtaining the grounding resistance of the earth electrode. 2. The method according to claim 1, wherein a resonance characteristic of the ground return circuit is changed by changing a reactance of the conductor wire, and a frequency characteristic of the ground resistance is obtained by using a measurement signal having a frequency corresponding to the resonance frequency. The method for measuring a ground resistance according to claim 1, wherein 3. The ground resistance measuring method according to claim 2, wherein a reactance of the conductor wire is changed by attaching a ferrite core to the conductor wire. 4. The measuring device has a directional coupler connected to the other end of the conductor line, and separates a measurement signal and a reflected wave signal supplied to the ground return circuit by the directional coupler. 2. The method according to claim 1, wherein the ground resistance is measured. 5. The ground resistance measuring method according to claim 1, wherein the capacitance between the ground surface and the ground return conductor is set large. 6. The measurement according to claim 1, wherein the measurement is performed in a state in which a resistor having a resistance equal to the characteristic impedance of the measuring device is connected in series between the ground electrode and the conductor wire. Ground resistance measurement method. 7. A ground electrode grounded to the ground, a ground return conductor having one surface opposed to the ground surface in a non-contact state, and a first conductor wire having one end connected to the ground electrode. A second conductor wire having one end connected to the ground return conductor, and a first conductor wire connected to the other end of each of the first conductor wire and the second conductor wire.
A directional coupler having a port connected thereto and having a predetermined characteristic impedance; anda ground frequency electrode, a ground, a resonance frequency detecting means for detecting a resonance frequency of a ground return circuit formed by the ground return conductor and the conductor wire, A transmitter connected to the second port of the directional coupler in a state where the impedance is matched, and outputting a measurement signal having a frequency substantially equal to the resonance frequency of the ground return circuit; and detecting a transmission power of the transmitter. A first power detecting means connected to a third port of the directional coupler in a state where impedance is matched, and a second power detecting means for extracting a frequency component of an output signal of the oscillator and detecting a power of the frequency component Power detection means, wherein the directional coupler outputs an input signal to the second port to the first port without outputting to the third port, and Ground resistance measuring device, characterized in that the input signal to the port and has a directionality to be output to the third port without outputting to said second port. 8. The grounding resistance measuring device according to claim 7, wherein an insulating member is provided between the ground surface and the ground return conductor. 9. The ground resistance measuring apparatus according to claim 8, wherein the insulating member is made of a high dielectric constant insulator. 10. The ground according to claim 7, further comprising: a reactance varying means for varying a reactance of the ground return circuit, and a frequency varying means for varying a frequency of the measurement signal in the transmitter. Resistance measuring device. 11. A resistor connected in series between the ground electrode and the first conductor line, the resistor having a resistance equal to a value of a characteristic impedance of the directional coupler is provided. The ground resistance measuring device according to the above. 12. A reflection coefficient display means for obtaining and displaying a square root of a ratio between the transmitted power and the reflected power based on the detection results of the first and second power detection means. The ground resistance measuring device according to claim 7.