JP2000206162A - Ground resistance measuring method and ground resistance measuring system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure a ground resistance without removing a ground wire of a ground electrode to be measured and a wire for connecting the ground electrode to be measured to another ground electrode, and a measuring system suitable for the method. I will provide a. In a method for measuring a ground resistance according to the present invention, a first signal voltage V1 is injected into a ground electrode to be measured 101, and one or both are connected to the ground electrode to be measured and disconnected from a ground line, or are connected to each other. Two or more of the ground poles are used as current auxiliary poles 102, and a second signal voltage V 2 having the same frequency as the first signal voltage V 1 is adjusted between this and the measured ground pole 101 to adjust the amplitude and phase. And inject. As a result, the signal current I1 generated at V1 and V2 flows only between the measured ground electrode 101 and the current auxiliary electrode 102,
Also, current is prevented from flowing through the other ground pole 103, and the ground resistance R of the measured ground pole 101 is set to R = V1
/ I1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system and a method for measuring a ground resistance of a ground electrode in a building or the like.

[0002]

2. Description of the Related Art Conventionally, a method of measuring ground resistance includes:
There are a three-electrode method and a two-electrode method. In the three-electrode method, as shown in FIG. 4, for measurement, a ground wire and an electric wire connected to another ground electrode are previously removed from the measured ground electrode 41, and a current auxiliary electrode 42 is provided. 41 and current auxiliary pole 4
This is a method in which a potential auxiliary pole 43 is provided in the middle between the two for measurement. The ground resistance R of the measured ground electrode 41 is
1 and the current auxiliary electrode 42, an AC signal voltage 44 is injected, a current I flows, the current I is measured by an AC ammeter 45, and the distance between the measured ground electrode 41 and the current auxiliary electrode 42 is made sufficiently large. Then, the potential difference V between the potential auxiliary electrode 43 and the measured ground electrode 41 in which the potential fluctuation due to the installation position is suppressed is measured by the AC voltmeter 46, and is obtained from the relationship of R = V / I.

The ground line is disconnected from the ground line to be measured because the ground line is connected to one having electrical continuity with the ground regardless of intention. This is to prevent the current I from shunting to the above.

In the two-electrode method, as shown in FIG. 5, a part of a building that can serve as a ground electrode, such as an existing water pipe or a structure such as a steel frame, a reinforcing bar, or a concrete structure of a building, or an auxiliary electrode provided separately is used. An AC signal voltage 53 is injected between the measured ground electrode 51 and the current auxiliary electrode 52 as an auxiliary electrode 52, and the value of an injection voltage source or a voltage injection portion between the measured electrode 51 and the current auxiliary electrode 52 is used. , An AC voltmeter 54 is connected in parallel to measure the injection voltage V, and the injection current I is measured by an AC ammeter 55 connected in series to the voltage injection portion, and the injection voltage V is divided by the injection current I. In this manner, the total resistance value of the circuit including the measured ground electrode 51 and the current auxiliary electrode 52 is obtained. Therefore, in the present method, the resistance value includes the ground resistance value of the current auxiliary pole 52,
2 is obtained by another means or the measured ground electrode 51
The ground resistance of the ground electrode 51 to be measured is determined by assuming that the ground resistance is sufficiently smaller than the ground resistance of the ground electrode 51 to be measured.

[0005]

As apparent from the above description, in the case of the ground resistance measuring method by the three-electrode method,
A ground wire connected to the measured ground electrode 41 so that a current injected between the measured ground electrode 41 and the current auxiliary electrode 42 does not flow except between the measured ground electrode 41 and the current auxiliary electrode 42. And other wires connected to the ground electrode must be removed in advance,
In addition, since it is necessary to provide the current auxiliary electrode 42 and the potential auxiliary electrode 43 for measurement, if any one of these cannot be performed, the measurement method cannot be applied to measure the ground resistance.

On the other hand, in a building where the grounding poles are connected to each other in order to make the grounding poles in the building equal potential when a lightning surge enters, it is difficult to remove the grounding wire and the electric wire between the grounding poles. In some parts, the non-paved part around the building is decreasing and it is becoming difficult to provide auxiliary poles. Therefore, there is a problem that the ground resistance measurement cannot be performed by the three-electrode method in these buildings. .

In the case of the two-electrode method, it is not always necessary to disconnect the ground line connected to the ground electrode to be measured. However, the ground resistance of the current auxiliary electrode 52 can be obtained by another means or the ground electrode 51 to be measured can be obtained. It is necessary to assume that the ground resistance value is sufficiently smaller than the ground resistance value, and the problem is that the ground resistance of the ground electrode 52 to be measured cannot be known only from the measurement by this method.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a grounding system in which a plurality of grounding poles are connected to each other, such that the grounding wire of the grounding electrode to be measured, the grounding electrode to be measured, and the like. It is an object of the present invention to provide a method for measuring the ground resistance of a ground electrode to be measured without disconnecting an electric wire for connection to a ground electrode, and a measuring system suitable for the method.

[0009]

The present invention employs the following means in order to solve the above-mentioned problems. That is, in the grounding resistance measuring method according to claim 1, in a grounding system in which a plurality of grounding poles are electrically connected to each other, a first signal voltage is injected to the grounding pole to be measured and connected to the grounding pole to be measured. One or two or more of the ground poles connected to each other and having a ground line removed are used as current auxiliary poles at the same frequency as the first signal voltage between the current auxiliary pole and the ground electrode to be measured. A certain second signal voltage is injected with its amplitude and phase adjusted, and a signal current generated by these signal voltages flows only between the measured ground electrode and the current auxiliary electrode, and the other ground electrodes To measure the signal current generated by the first signal voltage and the first signal voltage and the second signal voltage at the ground electrode to be measured, the first signal voltage Dividing the value of the signal by the value of the signal current to obtain the quotient It is characterized in that for obtaining a more ground resistance.

First, generally, in a grounding system in which a plurality of grounding poles are connected to each other, the grounding resistance of each grounding pole is generally regarded as the connection resistance of a parallel circuit connected to this ground plane. Can be. Therefore, even if the connection line of the measured ground electrode cannot be disconnected, an AC voltage (the first signal voltage) is applied to the measured ground electrode by inductive coupling using a clamp-type probe or the like, and A signal voltage (the second signal voltage) having the same frequency as the AC voltage between the pole and a current auxiliary pole using one or more grounded poles disconnected from the ground wire. The current is circulated only between the ground electrode to be measured and the current auxiliary electrode by adjusting the amplitude and phase, and the current flowing to the other ground electrode of the grounding system is suppressed to zero. It is possible to do.

That is, the first signal voltage (effective value)
V1, the ground impedance of the measured ground electrode is Z, the ground resistance, which is the real part of Z, is R, and the signal current (effective value) is I.
If it is set to 1, a commercially available grounding resistance meter using the three-pole method is 300
Since the frequency is as low as about 1 Hz to 1 kHz, the self-inductance and the like of the electric wire laid between the ground electrode to be measured and the current auxiliary electrode for measurement are ignored, and the absolute value of the reactance component of the ground impedance Z is determined by the ground resistance. If it is assumed that the distance is sufficiently small, V1 =
Since | Z | × I1 ≒ R × I1 holds, V1 and I1 are measured, and the value of V1 is divided by the value of I1 to obtain the ground resistance R.
Can be requested. At this time, if the ground resistance of the current auxiliary electrode is Rc, as long as the self-inductance of the wire laid between the measured ground electrode and the current auxiliary electrode is sufficiently smaller than Rc, V2ＶRc Since × I1 holds, Rc can be obtained by measuring V2 and I1. Further, as the current auxiliary electrode, a current auxiliary electrode may be provided separately from the ground electrode in the grounding system without being applied thereto (claim 2).

In the grounding resistance measuring method according to the present invention, as is apparent from the above description of the measuring method, the grounding electrode to be measured and the current auxiliary electrode as in a commercially available three-pole grounding resistance meter are used. The self-inductance of the wire between them has little effect on the ground resistance. Further, the absolute value of the reactance in the electric wire between the measured ground electrode and the current auxiliary electrode in the measurement using a commercially available three-electrode grounding resistance meter is represented by f, the signal frequency, and the self-inductance per unit length of the wiring. Is L and the length of the wiring is s, 2π ×
Although it can be expressed as f × L × s, the self-inductance of the wiring is about 1 μH regardless of the wire diameter, the length of the wiring is usually about 100 m at most, and the signal frequency f is at most 1 kHz. From that, 2π × f × L × s
<1Ω holds. That is, the impedance of the circuit with respect to the signal current circulating through the measured ground electrode and the current auxiliary electrode is usually large, since the auxiliary electrode has a large ground resistance of 100Ω or more.
As described above, it can be determined that it can be regarded as pure resistance.

According to a third aspect of the present invention, there is provided a method for measuring a ground resistance, comprising: a synchronizing signal for a signal measuring device for measuring the signal current from a two-phase signal generator for generating the first signal voltage and the second signal voltage; And has a function of a lock-in amplifier using the same.

According to this, in the detection of the current and the voltage, the detection sensitivity can be improved by applying the lock-in amplifier, so that the levels of the first signal voltage V1 and the second signal voltage V2 are weakened. It becomes possible to.

The ground resistance measuring system according to the fourth to eighth aspects is a system having the most suitable configuration for realizing the ground resistance measuring method according to the first to third aspects. I can say that.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram showing a configuration of a ground electrode and the like in a first embodiment of the present invention, and relates to an individual measurement of a ground resistance of a ground electrode in a ground system in which a plurality of ground electrodes are connected to each other. It is.
By the way, in addition to the normal ground electrode,
In general, those which cause electrical continuity with the ground, that is, metal pipes buried in the ground, steel frames of buildings, reinforcing bars, concrete, and the like are also included in the concept.

The ground electrode 101 to be measured is connected to a current auxiliary pole 102 using one or more ground electrodes connected to each other, which is previously disconnected from the ground terminal box in the ground terminal box, or a current auxiliary pole 102 provided separately. It is connected by an electric wire 104 and connected to one or more other ground poles 103 by an electric wire 105.

In this grounding system, the two-phase signal generator 1
The first signal generated from 06 is the clamp type probe 1
07, and is injected into the measured ground electrode 101 as a first signal voltage V1. Then, the two-phase signal generator 106
A second signal having the same frequency as the first signal voltage V1 generated from the above is adjusted to an amplitude and a phase and applied to a clamp-type probe (inductive coupling element) 108 so that a ground electrode 101 to be measured and a current auxiliary electrode 102 and the second signal voltage V2
Inject. The application of these signal voltages V1 and V2 is performed from the two-phase signal generator 106 via the application cable 113 as shown in FIG.

Here, in general, in a grounding system in which a plurality of grounding poles are connected to each other, as shown in the schematic diagram of FIG. It can be regarded as a connection resistance of the connected parallel circuit. That is, in FIG.
04, ..., 20n are the first, second,
.. Represents the ground resistance at the n-th ground pole,
The ground resistor 206 related to the measured ground pole and the ground resistor 209 related to the current auxiliary pole can be regarded as being in parallel with these.

In the ground resistance measurement according to the present invention, the amplitude and phase of the second signal voltage injected between the ground electrode to be measured and the current auxiliary electrode are finely adjusted to adjust the ground voltage to be measured. Since the current flowing through the ground pole other than the current pole and the current auxiliary pole is suppressed, the reactance associated with each of the ground poles cannot be ignored in the adjustment. In FIG. Instead, it is described as the ground impedance. For the same purpose, the current auxiliary electrode is described as an impedance including the impedance of the wiring between the current auxiliary electrode and the ground electrode to be measured, in addition to the ground impedance.

In the case of FIG. 2, even if the connection line of the ground electrode to be measured cannot be disconnected, an AC voltage (in the above case, the first voltage) is applied to the ground electrode to be measured by inductive coupling using a clamp-type probe or the like. The signal voltage V1) 207 is applied, and the AC voltage and the above-mentioned AC voltage are applied between the ground electrode to be measured and a current auxiliary electrode using one or more ground electrodes connected to each other with one or more ground wires disconnected from each other. A signal voltage having the same frequency (the second signal voltage V
2) By injecting 210 with its amplitude and phase adjusted, the signal current 208 is circulated only between the ground electrode to be measured and the current auxiliary electrode, and flows to another ground electrode of the grounding system here. The current 211 can be suppressed to zero.

In FIG. 2, reference numeral 211 denotes an alternating current flowing through the point, and reference numeral 201 denotes an impedance network connecting the ground electrodes to each other.

Returning to FIG. 1 based on the above principle, the first signal voltage V1 and the second signal
The specific aspect of the second embodiment is defined as follows.

The measured value of the ground resistance is the electric conductivity of the earth,
Since it depends on the polarization resistance at the ground pole, etc., it depends on whether the signal applied to the measurement is direct current or alternating current, and in the case of alternating current the frequency is different.Therefore, the ground resistance value is defined in this distinction. There must be. In the Japanese Industrial Standard (JIS C-1304) that defines the grounding resistance meter using the three-pole method, there is no definition regarding the frequency and waveform of the signal for measurement. Although it is not constant, since a sine wave or a square wave is used for a signal having a repetition frequency of about 300 Hz to 1 kHz, a value close to the ground resistance value obtained by an existing commercially available ground resistance meter using a three-pole method is used. For the purpose of obtaining, an AC signal of about 300 Hz to 1 kHz should be used as a signal for measurement, and the S / N due to the interference of the commercial power supply should be used.
In order to avoid a decrease in the ratio, it is desirable to select a frequency having a value as far as possible from the frequency of the commercial power supply and its harmonics.

The amplitude and phase of the first signal voltage and the second signal voltage are set as follows. That is, using a complex number representation, the first signal voltage is V1 ^* exp (2πf · jt), the second signal voltage is V2 ^* exp (2πf · jt), and the current flowing through the measured ground electrode is I1 ^*. exp (2πf · jt), the ground impedance of the ground electrode to be measured is Z1, and the ground impedance of the current auxiliary electrode is Z2, by adjusting the phase and amplitude of the second signal voltage with respect to the first signal voltage. The current is circulated only between the measured ground electrode 101 and the current auxiliary electrode 102, and the current flowing to another ground electrode of the ground system is suppressed to zero. In this state, V1 ^* =
Since I1 ^* .Z1 and V2 ^* = I1 ^* .Z2 hold, V2 ^*
/ V1 ^* = Z2 / Z1. Further, V1 = | V1 ^* | / √ with respect to the first signal voltage (effective value) V1 and the current (effective value) I1 flowing through the measured ground electrode 101.
2. Using the relationship of I1 = | I1 ^* | / √2 and the relationship of Z1 ≒ R based on the above consideration, V1 ≒ I1 × R holds, and the first signal voltage (effective value) V1 and the measured By measuring the current (effective value) I1 flowing through the ground pole 101,
The ground resistance R of the measured ground electrode 101 is obtained.
Therefore, the second signal voltage has an amplitude of | Z2 / Z1 | ≒ | Z2 | / R times the first signal voltage and a phase angle of arg (Z2 / Z1) ≒ arg (Z2).
[Rad] is set as the advance phase.

The amplitude of the first signal voltage and the amplitude of the second signal voltage are preferably as small as possible to reduce the possibility of affecting communication equipment connected to the ground line. In this case, environmental noise mixed in a current probe, a voltage probe, or the like, or noise of the signal detector itself becomes an obstacle to a favorable signal-to-noise ratio, and the lower limit of the amplitude is limited.

As described above, the signal current I1 is circulated only between the measured ground electrode 101 and the current auxiliary electrode 102, and the electric wire 105 and the electric wire 105 connecting the measured ground electrode 101 and the other ground electrode of the ground system are connected. The current I2 flowing through the ground line 115 can be suppressed to zero.

Based on the above circumstances, the ground resistance R at the measured ground electrode 101 can be obtained as follows. That is, using the signal measuring device 109 in which conversion coefficients of the voltage measuring probe 112 and the clamp type probe 110 for current detection are stored in advance, the injection voltage V1 is obtained from each output of the voltage measuring probe 112 and the clamp type probe 110. And the signal current I1 flowing through the non-grounded pole is measured, and the value of V1 is divided by the value of I1 to display this quotient as the ground resistance.
Can be obtained. Here, the signal measuring device 109 is, as apparent from these descriptions,
It has functions related to voltage detection, storage, calculation, and display of probe conversion coefficients.

In the first embodiment, the electric wire 10 connecting the measured ground electrode 101 and the current auxiliary electrode 102 is used.
4 can be removed, the second signal generated from the two-phase signal generator 106 is directly transmitted between the electric wire 104 and the measured ground electrode 101 or the current auxiliary electrode 102 without using a clamp-type probe. To increase the signal voltage injection efficiency.

Hereinafter, a second embodiment of the present invention will be described. FIG. 3 is an explanatory view showing an individual measurement of a ground resistance of a ground electrode in a ground system in which a plurality of ground electrodes are connected to each other according to the second embodiment. In FIG. 2, components having the same functions or functions as those in FIG. 1 are denoted by the same reference numerals.

In FIG. 3, when compared with FIG. 1 according to the first embodiment, a cable 315 for a synchronization signal is newly provided between the two-phase signal generator 106 and the signal measuring device 109. Is different. In other respects, as apparent from comparison between FIG. 3 and FIG. 1, the configuration is the same, and the ground resistance measurement similar to the method described with reference to FIG. 1 is performed.

In the second embodiment, in addition to the provision of the cable 315, a lock-in amplifier for detecting current and voltage with high sensitivity using a synchronization signal from the two-phase signal generator 106 is used. Function of signal measuring instrument 109
To improve the signal detection sensitivity and miniaturize the signal voltages V1 and V2. As a result, the measurement accuracy is improved, and the voltage applied to the grounding system is reduced, so that the risk of affecting electronic devices such as a communication system installed around the device due to the measurement can be reduced. .

Finally, Table 1 shows an actual measurement example of the ground resistance in the second embodiment. In this case, since the lock-in amplifier is used as described above, the sensitivity of the signal detection system is increased, and the amplitude of the first signal voltage and the amplitude of the second signal voltage are increased. This suppresses the amplitude, and satisfies the requirement that the amplitude is smaller, as described in the first embodiment. However, this does not mean, of course, that the request is not satisfied in the first embodiment.

[0034]

[Table 1]

As shown in Table 1, in the present configuration using the lock-in amplifier, the signal current I1 is approximately 1 m
By adjusting the amplitude to about A, by adjusting the amplitude and phase of the injection voltage V2 between the measured ground electrode 101 and the current auxiliary electrode 102, the current flowing through the ground electrode other than the measured ground electrode 101 and the current auxiliary electrode 102 can be reduced. It can be said that the signal current I1 can be set to a minute noise level of several tenths or less and a minimum value. Under these conditions, the ground resistance R is a value obtained by dividing the injection voltage V1 of the measured ground electrode 101 by the signal current I1, and if the upper limit of the ground resistance measurement range is set to 1 kΩ which is considered to be practically sufficient, The voltage V1 becomes 1 V or less. The ground resistance of the current auxiliary pole 102 is also 1 k.
Ω, the measured ground electrode 101 and the current auxiliary electrode 1
Also, the injection voltage V2 during 02 becomes 1 V or less. However, the above numerical values show one index for the set value of the grounding resistance measuring system according to the present invention, and it is natural that the numerical values are appropriately changed depending on the situation of the measurement target.

[0036]

As described above, according to the grounding resistance measuring method according to the first or second aspect, even in a building having no non-paved portion in the periphery, such as an urban area, if there is a grounding pole from which the grounding line can be removed. Using this as a current auxiliary electrode, it is possible to measure the ground resistance of the target ground electrode to be measured. Further, there is an advantage that the measurement can be performed without disconnecting the connection wire even when the current auxiliary electrode is connected to the ground electrode to be measured. Further, this measuring method has an advantage that the ground resistance of the current auxiliary electrode can be known at the same time. Note that, even when the ground electrode from which the ground wire cannot be removed is used as the current auxiliary electrode, the signal current for measurement is connected to the current auxiliary electrode or the current auxiliary electrode among the electric wires connected to the ground electrode to be measured. It is clear from the above description that the ground resistance can be known by the present measuring method if it can be prevented from flowing through wires other than the ground wire.

According to the third aspect of the present invention, the detection sensitivity of the signal can be improved by using the lock-in amplifier in the detection system of the measurement signal, so that the measurement accuracy can be improved. By weakening the voltage injected into the grounding system, it is possible to obtain an advantage that the risk of the present measurement affecting peripheral electronic devices such as a communication system can be reduced.

Further, the ground resistance measuring system according to claims 4 to 8 can be said to have the most appropriate configuration in realizing the above-described ground resistance measuring method according to claims 1 to 3. Of course, the above-mentioned effects can be similarly enjoyed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a first embodiment according to the present invention.

FIG. 2 is a schematic diagram illustrating the principle of the ground resistance measuring method according to the present invention.

FIG. 3 is an explanatory view showing a second embodiment according to the present invention.

FIG. 4 is an explanatory view showing a conventional method of measuring a ground resistance by a three-electrode method.

FIG. 5 is an explanatory diagram showing a conventional method of measuring a ground resistance by a two-electrode method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 101 Ground pole to be measured 102 Current auxiliary pole 103 Ground pole 104, 105 Electric wire 106 Two-phase signal generator 107 Clamp type probe (for injection) 108 Clamp type probe (for injection) (inductive coupling element) 109 Signal measuring instrument 110, 111 Clamp type probe (for current detection) 112 Voltage measurement probe 113 Cable (for application) 114 Cable (for detection) 115 Ground wire connected to the ground electrode to be measured 201 Impedance network 202 Ground 203, 204,..., 20n Ground impedance 206 Ground impedance of the ground electrode to be measured 207 AC voltage 208 Signal current 209 Sum of the ground impedance of the current auxiliary electrode and the impedance of the wiring 210 Signal voltage 211 having the same frequency as AC voltage 207 211 AC current 315 Cable (synchronous signal) 41) Ground electrode to be measured 42 Current auxiliary electrode 43 Potential auxiliary electrode 44 AC signal voltage 45 AC ammeter 46 AC voltmeter 47 Measurement lead 51 Measurement ground electrode 52 Current auxiliary electrode 53 AC signal voltage 54 AC voltmeter 55 AC ammeter 56 Conductor for measurement

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[Procedure amendment]

[Submission date] November 12, 1999 (1999.11.
12)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claim 4

[Correction method] Change

[Correction contents]

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

[0009]

The present invention employs the following means in order to solve the above-mentioned problems. That is, the ground resistance measurement method according to claim 1 is embedded in the ground metal
A building that creates electrical continuity with the body or the earth
Is a grounding electrode, and in a grounding system in which the grounding electrodes are electrically connected to each other , a first signal voltage is injected into a grounding electrode to be measured to which a grounding line is connected, and is connected to the grounding electrode to be measured. One or two or more of the ground poles connected to each other and having a ground line removed are used as current auxiliary poles at the same frequency as the first signal voltage between the current auxiliary pole and the ground electrode to be measured. A certain second signal voltage is injected with its amplitude and phase adjusted, and a signal current generated by these signal voltages flows only between the measured ground electrode and the current auxiliary electrode, and the other ground electrodes To measure the signal current generated by the first signal voltage and the first signal voltage and the second signal voltage at the ground electrode to be measured, the first signal voltage Is divided by the value of the signal current to obtain the quotient, It is characterized in that for obtaining the anti.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Naoto Izumo 3-4-1 Shibaura, Minato-ku, Tokyo Inside NTT Facilities Co., Ltd. (72) Seiichi Muroyama 3-4-1 Shibaura, Minato-ku, Tokyo No. 1 F-term in NTT Facilities (reference) 2G014 AA13 AA32 AB55 AB62 AC19 2G028 AA01 AA03 BC06 BE08 CG05 DH05 FK01 FK02 GL03 HN02 HN10 HN15 MS05

Claims (8)

[Claims] In a grounding system in which a plurality of grounding electrodes are electrically connected to each other, a first signal voltage is injected into a grounding electrode to be measured, and a first signal voltage is connected to the grounding electrode to be measured and a ground wire is disconnected. Two or more ground electrodes connected to each other as a current auxiliary electrode, and a second signal voltage having the same frequency as the first signal voltage between the current auxiliary electrode and the ground electrode to be measured. The amplitude and phase are adjusted and injected, so that the signal current generated by these signal voltages flows only between the ground electrode to be measured and the current auxiliary electrode, and does not flow to the other ground electrodes. Measuring the first signal voltage and the signal current at the ground electrode to be measured, and calculating the ground resistance by dividing the value of the first signal voltage by the value of the signal current to obtain a quotient thereof. A ground resistance measuring method characterized by the above-mentioned. 2. The ground resistance measuring method according to claim 1, wherein a separate current auxiliary pole is provided instead of using the ground pole in the ground system as a current auxiliary pole. 3. A function of a lock-in amplifier using a synchronizing signal from a two-phase signal generator for generating the first signal voltage and the second signal voltage to a signal measuring device for measuring the signal current. The method for measuring a ground resistance according to claim 1 or 2, wherein: 4. A grounding system in which a plurality of grounding electrodes are connected to each other, wherein a grounding electrode to be measured to which a first signal voltage is injected is connected to the grounding electrode to be measured and a grounding wire is disconnected. One or more current auxiliary poles selected from the grounding system or two or more current auxiliary poles, and the same frequency as the first signal voltage between the ground electrode to be measured and the current auxiliary pole, and the amplitude thereof. An inductive coupling element for injecting a second signal voltage whose phase has been adjusted, a two-phase signal generator for generating the first signal voltage and the second signal voltage, and the first signal A function of measuring a voltage and a signal current flowing between the ground electrode to be measured and the current auxiliary electrode and a current flowing to the ground electrode other than the ground electrode to be measured and the current auxiliary electrode; and Reduces the number of functions for performing division by signal current Ground resistance measurement system comprising: a signal measuring device comprising also. 5. The method according to claim 1, wherein the measured ground electrode and the current auxiliary electrode are dissociated without providing the inductive coupling element, and the second signal voltage is directly applied between the two terminals. Item 6. The ground resistance measuring system according to Item 4. 6. The ground resistance measuring system according to claim 4, wherein the current auxiliary pole is separately provided without being selected from the grounding system. 7. A cable for connecting the two-phase signal generator and the signal measuring device and transmitting a synchronization signal from the former to the latter, and a lock-in amplifier in the signal measuring device. The ground resistance measuring system according to claim 4. 8. The ground resistance measuring system according to claim 4, wherein the two-phase signal generator and the signal generator are integrated.