JP2002131347A - Ground resistance measuring device and ground resistance measuring method - Google Patents

Abstract

(57) [Summary] To measure the ground resistance stably and accurately without being affected by environmental factors such as the state of the ground when measuring the ground resistance. A high-frequency signal generated from a signal generation source is transmitted to a signal generator.
By sequentially outputting to the measurement line through various kinds of inductances, it is sequentially injected into the ground. At this time, the frequency between the first connection terminal connecting the measurement line and the second connection terminal connecting the ground electrode to be measured is changed for each of the three types of inductance by changing the frequency of the high-frequency signal. Is measured, and a resonance frequency is obtained based on the measured voltage,
The ground resistance of the measured ground electrode is obtained using the obtained three kinds of resonance frequencies. As a result, calculation elements affected by environmental factors such as the state of the ground can be eliminated, and the ground resistance can be measured stably and accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground resistance measuring device and a ground resistance measuring method for measuring the ground resistance of a ground rod (same as a ground electrode) embedded in the ground.

[0002]

2. Description of the Related Art Conventionally, a three-electrode method has been used as a method for measuring the grounding resistance of a grounding rod. However, this method requires an auxiliary grounding rod and requires that the auxiliary grounding rod be driven into the ground. Since the measurement is troublesome, a ground resistance measuring device as shown in FIG. 5 which does not use an auxiliary grounding rod which avoids this problem has been proposed (JP-A-11-248767).

FIG. 5 is a configuration diagram showing a conventional example of a ground resistance measuring device which does not use an auxiliary electrode. The grounding resistance measuring device includes a variable frequency signal generator 1 for generating a sinusoidal high frequency signal, an output resistor (Rout) 2 for outputting the high frequency signal generated by the signal generator 1, and an output resistor 2. A voltage measuring unit 3 for measuring the voltage on the output side of the device, a resonance frequency is obtained by changing the oscillation frequency of the signal generator for measurement 1 based on the measured voltage of the voltage measuring unit 3, and the ground resistance Rg is calculated from the resonance frequency. And a terminal 6 for connecting a line 8 connected to the ground rod 7 to be measured.

Here, Rg is the ground resistance of the ground rod 7 to be measured, L is the inductor component of the line 8 connected to the ground rod 7 to be measured, C is the coupling capacitance component between the measurement line 5 and the ground and G Is the resistance value of the coating of the measurement line 5 (that is, the insulation resistance value), Rc
Is the ground resistance in the vicinity of the measurement line 5 and Cc is the capacitance in the vicinity of the measurement line 5, an equivalent model (measurement equivalent model without using the auxiliary electrode) of the measurement system using the ground resistance measurement device is as shown in FIG. .

A description will be given of a method of measuring a ground resistance by a conventional apparatus for measuring a ground resistance as described above. 1)
The measurement lines 5 and 8 are connected to the terminals 6 and 9 of the earth resistance measuring device, and the ground rod 7 to be measured is connected to the line 8. 2) The signal generator 1 for measurement generates a high-frequency signal for measuring the ground resistance of the ground rod 7 and outputs it to the measurement line 5 via the output resistor 2. The high-frequency signal is injected into the ground via the ground-to-ground coupling capacitance of the measurement line 5 and returns to the device via the ground rod 7 and the line 8. The CPU 4 causes the signal generator 1 to change the frequency f of the high-frequency signal so that a series resonance of the coupling capacitance C between the ground of the measurement line 5 and the inductance component L of the line 8 occurs. 4) The voltage measuring unit 3 measures the voltage at the point P of the output resistor 2, that is, the voltage between the terminals 6 and 9. Here, the voltage measurement unit 3 includes a synchronous detection circuit and an LPF (low-pass filter) unit, and measures the voltage at the point P of the output resistor 2 as a DC voltage value. 5) The frequency f of the high-frequency signal is changed by the CPU 4 to measure the voltage value Vm (the voltage value at the resonance point) at which the voltage value becomes the smallest. As a result, the ground resistance Rg of the ground rod 7 is given by the voltage dividing ratio with the output resistance 2.
That is, assuming that the injection voltage is Vc and the measured voltage is Vm, the ground resistance Rg = Rout · Vm / (Vc−Vm).

The following is a description of the above measurement operation applied to the equivalent model shown in FIG. Measurement signal generator 1
The high frequency signal generated from the
And output as test current and injected into the ground. The test current injected from the measurement line 5 passes through a parallel circuit of the coupling capacitance C, the ground resistance Rc and the coupling capacitance Cc near the measurement line 5, and is connected to the line 8 connected to the ground resistance Rg of the ground rod 7 to be measured. Then, the signal is fed back to the signal generator 1 via the inductance component L of the measurement line 5 and the series resistance r to form a loop circuit as a whole. However, in the measurement apparatus of FIG. 5, the insulation resistance G of the measurement line 5 is generally very large,
5 is a simple equivalent model as shown in FIG.

In the equivalent model shown in FIG. 6, the method of calculating the ground resistance Rg is described in Japanese Patent Laid-Open No. 11-2487.
It is as follows when quoted from 67 "ground resistance measuring apparatus and ground resistance measuring method using the same".

The complex impedance Z seen from the signal generator 1 is

[0009]

(Equation 1)

At this time, in a state where the series resonance frequency fR composed of L, C, and Cc → ωR = 2πfR, Z becomes only a real part,

[0011]

(Equation 2)

Equation (2) is expressed as Rc · Cc >> L and ωR
Under sufficiently large conditions,

[0013]

(Equation 3)

## EQU1 ##

[0015]

However, in the above-described conventional measuring apparatus and measuring method, the above-mentioned conditions may not be satisfied. This is mainly due to the fact that Rc and Cc change depending on the state of the earth (geology, water content, weather, etc.), and that Rc becomes relatively small depending on the shape and length of the measurement line 5. This is because it becomes difficult to satisfy the condition of Rc · Cc >> L. Also, in order to obtain the result of equation (3), ωR must be extremely large.
To this end, the impedance of the measurement system as viewed from the signal generator 1 must be increased, that is, the measurement line 5 needs to be sufficiently long. However, if the measurement line 5 is long, it is necessary to route this long line at the time of measurement, and the convenience deteriorates, which is not preferable from the viewpoint of practical use. When ωR is set large, the electromagnetic field emission from the measurement line 5 becomes remarkable,
There is also a risk that this will have an undesired effect around the measurement site.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and its object is to be performed without being influenced by environmental factors such as the state of the ground when measuring the grounding resistance.
Another object of the present invention is to provide a ground resistance measuring device and a ground resistance measuring method capable of measuring ground resistance stably and accurately without using a long measuring line.

[0017]

To achieve the above object, the present invention is characterized in that a frequency-variable signal generator for generating a high-frequency signal and a high-frequency signal output side of the signal generator are provided. A variable inductance circuit unit that connects one terminal and connects the other terminal to a first measurement terminal, and measures a voltage between a second measurement terminal that connects the first measurement terminal and the ground electrode to be measured. A voltage measuring unit, and one end connected to the first measuring terminal, a measuring wire having a predetermined length or more arranged in an insulated state on the ground, and a grounding target to be measured connected to the second measuring terminal. After connecting the electrodes, the inductance of the variable inductance circuit section is changed in three ways, and the frequency of the high-frequency signal generated by the signal generation section is changed for each of them to obtain a resonance frequency, and the resonance frequency is obtained based on these resonance frequencies. In determining the grounding resistance of the constant ground electrode.

A second feature of the present invention is that a frequency-variable signal generator for generating a high-frequency signal, one terminal is connected to the output side of the high-frequency signal of the signal generator, and the other terminal is connected to the first terminal. A variable inductance circuit unit connected to the measurement terminal; a voltage measurement unit measuring a voltage between the first measurement terminal and the second measurement terminal connecting the ground electrode to be measured; Resonance frequency obtaining means for changing the frequency of the high-frequency signal generated by the signal generation unit for each of them, and obtaining a resonance frequency based on the measurement voltage of the voltage measurement unit at that time, and the resonance frequency acquisition means Calculating means for determining the ground resistance of the ground electrode to be measured using the three types of resonance frequencies obtained by the method, and connecting one end to the first measurement terminal, Comprising a predetermined length or more measuring lines disposed in an insulated state, after connecting the measured ground electrode to the second measurement terminal is to determine the ground resistance of the measured ground electrode.

A feature of the invention according to claim 3 is that it comprises a display unit for displaying the ground resistance of the ground electrode to be measured calculated by the calculating means.

According to a fourth aspect of the present invention, the resonance frequency obtaining means and the arithmetic means are constituted by a microcomputer.

According to a fifth aspect of the present invention, there is provided a ground resistance measuring method for determining a ground resistance of a ground electrode to be measured by injecting a high frequency signal into the ground from a measurement line arranged on the ground. Injecting the high-frequency signal into the ground through the inductance in order from the measurement line, and changing the frequency of the high-frequency signal while injecting the high-frequency signal into the ground through the inductance. And a step of obtaining a ground resistance of the ground electrode to be measured using the obtained three types of resonance frequencies.

A feature of the invention according to claim 6 is that a voltage between a first connection terminal for connecting the measurement line and a second connection terminal for connecting the ground electrode to be measured is measured. The three types of resonance frequencies are sequentially obtained based on the magnitude.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing a configuration according to a first embodiment of a ground resistance measuring device of the present invention.
However, the same components as those in the conventional example will be described with the same reference numerals. The grounding resistance measuring device includes a variable frequency measurement signal generator 1 for generating a high frequency sinusoidal high frequency signal, an output resistor (Rout) 2 for outputting the high frequency signal generated by the measurement signal generator 1, and an output. A voltage measuring unit 3 for measuring a voltage at a point P on the output side of the resistor 2, a resonance frequency is obtained by changing an oscillation frequency of the measurement signal generating unit 1 based on a measurement voltage of the voltage measuring unit 3, and grounding is performed from the resonance frequency. CPU 4 for calculating resistance Rg, terminal 6 for connecting measurement line 5, terminal 9 for connecting line 8 connected to ground bar 7 to be measured, changeover switch 10 for changing inductance, inductance for changing over operation of changeover switch 10 A switching unit 11, an operation unit 12 for inputting instructions and setting information of a measurer to the CPU 4, and a display unit 13 for displaying measurement results and the like
And inductances L1 and L2.

The voltage measuring section 3 measures the voltage at the point P, which means that the voltage between the changeover switch 10 and the terminal 9 is measured.

Here, Rg is the ground resistance of the ground rod 7 to be measured, L is the inductor component of the line 8 connected to the ground rod 7 to be measured, C is the coupling capacitance component between the measurement line 5 and the ground, and G is Is the resistance value (= insulation resistance value) of the coating of the measurement line 5, the equivalent model (measurement equivalent model not using the auxiliary electrode) of the measurement circuit by the above-described ground resistance measurement device is generally the insulation resistance G of the measurement line 5. Is very large and the series resistance r of the measurement line 5 is very small, so that a simple equivalent model as shown in FIG. 2 is obtained.

Next, a method of measuring the ground resistance by the above-described ground resistance measuring apparatus will be described with reference to the flowchart of FIG. The measurement lines 5 and 8 are connected to the terminals 6 and 9 of the earth resistance measuring device, and the ground rod 7 to be measured is connected to the line 8 (step 301). The measurement signal generator 1 includes a ground rod 7
A high-frequency signal for measuring the grounding resistance is generated (step 302). At the same time, the CPU 4 controls the inductance switching unit 11 to switch the changeover switch 10 to the terminal a (step 303). Output to the measurement line 5 via the resistor 2. The high-frequency signal is injected into the ground via the ground-to-ground coupling capacitance C of the measurement line 5,
It returns to the line 8 via the ground rod 7. The CPU 4 causes the signal generator 1 to change the frequency f of the high-frequency signal so as to cause series resonance of the coupling capacitance C between the ground of the measurement line 5 and the inductance component L of the line 8 (step 304). The voltage measuring section 8 measures the voltage at the point P of the output resistor 2. Here, the voltage measurement unit 8 includes a synchronous detection circuit and an LPF (low-pass filter) unit, and measures the voltage at point P as a DC voltage value. The measurement frequency f is changed by the CPU 4 to measure the voltage value Vm (voltage value at the resonance point) at which the voltage value becomes the smallest, and the CPU 4 records the resonance angular frequency ω1 corresponding to the measurement frequency f1 at that time (step). 305).

Next, the CPU 4 controls the inductance switching unit 1.
The changeover switch 10 is switched to the terminal b side by 1 (step 303). As a result, the high-frequency sine wave is output to the measurement line 5 via the output resistor 2 and the inductance L1. Thereafter, the same measurement operation is performed, and the CPU 4 determines the resonance angular frequency corresponding to the resonance frequency f2 of the high-frequency signal at that time. ω2 is recorded (step 305).

Finally, the CPU 4 switches the changeover switch 10 to the terminal c side by the inductance switching section 11 (step 303). As a result, the high-frequency signal is output to the measurement line 5 via the output resistor 2 and the inductance L2, and the same measurement operation is performed thereafter. The CPU 4 determines the resonance angular frequency ω3 corresponding to the resonance frequency f3 of the high-frequency signal at that time. Is recorded (step 305).

The CPU 4 uses three different types of inductances L, L + L1 and L + L2 to determine the resonance angular frequencies ω1 and ω
2. When ω3 is obtained, the following calculation is performed to calculate the ground resistance Rg (step 307).

Here, in the method of calculating the ground resistance Rg in this embodiment, correction is made by eliminating Rc and Cc from the measurement results of the three types of inductances at the respective resonance frequencies. In equation (2), there are three unknowns (Rg, Rc, Cc), so three different inductances (L, L + L1, L
+ L2) can be corrected. Here, usually, three measurements are instantaneously performed by the CPU 4, and therefore, it is assumed that the Rc and Cc parameters being measured are considered to be stationary. The state (length / laying state) does not change.

Assuming that the resonance angular frequencies due to the three different inductances are ω1, ω2, and ω3, the complex impedances Z1, Z2, and Z3 at these resonance frequencies as viewed from the signal generator 1 in FIG. 2 are as follows. .

[0032]

(Equation 4)

[0033]

(Equation 5)

[0034]

(Equation 6)

By solving the equations (4) to (6) for (Cc, Rc),

[0036]

(Equation 7)

[0037]

(Equation 8)

Solving equations (7) and (8) for Rc gives:

[0039]

(Equation 9)

By solving equation (9) for Rg, the following equation is finally obtained.

[0041]

(Equation 10)

The expression (10) is expressed by the following expression when expressed in frequency.

[0043]

[Equation 11]

Accordingly, the CPU 4 executes step 305 in FIG.
After obtaining the resonance angular frequencies ω1, ω2, and ω3, the impedances Z1, Z2, and Z3 are calculated using Expression (2). Next, the impedances Z1, Z
2, Z3 and the resonance angular frequencies ω1, ω2, ω3 are substituted to calculate the ground resistance Rg (step 30).
7). Thereafter, the CPU 4 displays the calculated ground resistance Rg on the display unit 13 and ends the processing.

According to the present embodiment, the impedance of the measurement loop is changed three times so that each of the resonance angular frequencies ω1,
By calculating ω2 and ω3 to calculate the ground resistance Rg, it is possible to eliminate Rc and Cc that are affected by the environment, the installation state of the measurement line 5, and the like in the calculation process, and to obtain a highly accurate ground resistance. Rg can be easily measured.

FIG. 4 shows a second embodiment of the earth resistance measuring apparatus according to the present invention.
FIG. 3 is a configuration diagram illustrating a configuration according to the exemplary embodiment. However, the same components as those of the first embodiment are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

The configuration and the measuring method of the ground resistance measuring apparatus of this example are the same as the configuration of the first embodiment shown in FIG. The difference lies in that by inserting Lx as an inductance for changing the impedance of the measurement loop, the inductance when the changeover switch 10 is switched to the terminal a is L + Lx. Thereby, the impedances L + Lx, L + L1, L + L2 of the measurement loop
Can be adjusted by the values of the inductances Lx, L1, and L2, and the impedance of all the measurement loops when the inductance is switched three times can be set large.

By the way, the above inductance is represented by L
Since the resonance frequency obtained when x, L1, and L2 are switched three times is not a large value, the expression (2) is not satisfied. Therefore, the impedance of the measurement loop is naturally L + Lx, L.
+ L1 and L + L2 are both set to be large values. At this time, in this example, even if L is small, that is, even if the measurement line 5 is short, the setting satisfying the above conditions can be performed by setting the inductances Lx, L1, and L2 to be large.

Therefore, according to the present embodiment, even if the measurement line 5 is short, the resonance angular frequencies ω1, ω2, and ω3 can all be increased by appropriately setting the inductances Lx, L1, and L2. In addition, highly accurate measurement of the ground resistance Rg can be easily performed. Other effects are the same as in the first embodiment described above, and the measurement of the ground resistance Rg with high accuracy can always be easily performed without being affected by the environment, the installation state of the measurement line 5, and the like.

The present invention is not limited to the above-described embodiment, but may be embodied in various other forms in terms of specific structure, function, operation, and effect without departing from the gist of the invention. .

[0051]

As described above in detail, according to the present invention, stable measurement can be performed without being affected by environmental factors such as the earth condition at the time of measuring the ground resistance, and without using a long measurement line. In addition, the ground resistance can be accurately measured.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a configuration according to a first embodiment of a ground resistance measuring device of the present invention.

FIG. 2 is a circuit diagram showing an equivalent model of a measurement system using the device shown in FIG.

FIG. 3 is a flowchart showing a procedure of a measuring method using the device shown in FIG.

FIG. 4 is a configuration diagram showing a configuration according to a second embodiment of the grounding resistance measuring device of the present invention.

FIG. 5 is a configuration diagram showing a conventional example of a ground resistance measuring device that does not use an auxiliary electrode.

FIG. 6 is a circuit diagram showing an equivalent model of a measurement system using a conventional ground resistance measuring device.

FIG. 7 is a circuit diagram showing a simplified equivalent model of a measurement system using a conventional ground resistance measuring device.

[Explanation of symbols]

 Reference Signs List 1 signal generating unit 2 output resistance 3 voltage measuring unit 4 CPU 5 measuring line 8 line 6, 9 terminal 7 ground bar to be measured 10 switch 11 inductance switching unit 12 operation unit 13 display unit L1, L2, Lx inductance

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hidefumi Ohashi 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo East Japan Nippon Telegraph and Telephone Corporation (72) Inventor Mitsuo Hattori 3-19 Nishishinjuku, Shinjuku-ku, Tokyo No. 2 Tonichi Nippon Telegraph and Telephone Co., Ltd. (72) Inventor Masanobu Machida 81 Sakuracho, Oizumi, Ueda-shi, Nagano F-term in Hioki Electric Co., Ltd. 2G028 AA01 AA02 AA05 BE08 CG05 DH11 DH14 EJ01 FK01 GL20

Claims (6)

[Claims] 1. A variable frequency signal generating unit for generating a high frequency signal, and a variable inductance connecting one terminal to an output side of the high frequency signal of the signal generating unit and connecting the other terminal to a first measuring terminal. A circuit unit, a voltage measurement unit that measures a voltage between a second measurement terminal that connects the first measurement terminal and the ground electrode to be measured, and one end connected to the first measurement terminal, A measurement line having a predetermined length or more arranged in an insulated state on the ground, and after connecting a measured ground electrode to the second measurement terminal, changing the inductance of the variable inductance circuit unit into three types, A ground resistance measuring device for obtaining a resonance frequency by changing a frequency of a high-frequency signal generated by the signal generation unit for each of them, and obtaining a ground resistance of the ground electrode to be measured based on the resonance frequencies. . 2. A variable-frequency signal generating section for generating a high-frequency signal, and a variable inductance for connecting one terminal to an output side of the high-frequency signal of the signal generating section and connecting the other terminal to a first measuring terminal. A circuit unit; a voltage measuring unit that measures a voltage between a second measuring terminal connecting the first measuring terminal and the ground electrode to be measured; and an inductance of the variable inductance circuit unit, which is changed in three ways. Changing the frequency of the high-frequency signal generated by the signal generation unit, and obtaining a resonance frequency based on the measured voltage of the voltage measurement unit at that time; three types of resonance frequency acquisition units obtained by the resonance frequency acquisition unit Calculating means for determining the ground resistance of the ground electrode to be measured using the resonance frequency; and one end connected to the first measurement terminal, which is arranged in an insulated state on the ground. Comprising a predetermined length or more measuring line, and after connecting the measured ground electrode to the second measurement terminal, the ground resistance measurement device and obtaining the grounding resistance of the measured ground electrode. 3. The ground resistance measuring apparatus according to claim 2, further comprising a display unit for displaying a ground resistance of the ground electrode to be measured calculated by the calculating means. 4. The ground resistance measuring apparatus according to claim 2, wherein said resonance frequency obtaining means and said calculating means are constituted by a microcomputer. 5. A grounding resistance measuring method for determining a grounding resistance of a ground electrode to be measured by injecting a high-frequency signal from a measurement line arranged on the ground to the ground, wherein the high-frequency signal is transmitted through three types of inductances. Sequentially injecting the ground from the measurement line, and when injecting the high-frequency signal into the ground via the inductance, changing the frequency of the high-frequency signal and changing the resonance frequency for each of the three types of inductances Determining the ground resistance of the ground electrode to be measured using the obtained three types of resonance frequencies. 6. A voltage between a first connection terminal for connecting the measurement line and a second connection terminal for connecting the ground electrode to be measured, and the voltage is measured based on the magnitude of the measured voltage.
6. The ground resistance measuring method according to claim 5, wherein types of resonance frequencies are sequentially obtained.