JP3167016B2 - Ground resistance measuring device and measuring method thereof - Google Patents

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 measuring method thereof, and more particularly to a ground resistance measuring device capable of accurately measuring a ground resistance without being affected by noise or induced voltage.
The present invention relates to a ground resistance measuring device capable of measuring a ground resistance without removing a communication device and the like, and a measuring method thereof.

[0002]

2. Description of the Related Art Grounding plays an important role in safely protecting communication devices and electronic devices from lightning strikes on buildings or leakage of electric devices attached to the buildings. Generally, grounding is performed by driving a metal ground rod into the ground.
For this reason, the grounding resistance increases or decreases depending on the state of the soil or the surface of the grounding rod. In order to maintain the initial grounding effect, it is necessary to measure and control the grounding resistance at all times, and to maintain the resistance at such a low level that it does not hinder the arrival of lightning or a leakage accident.

As a method of reducing the electromagnetic induction voltage, an induction shielded cable using a metal as a part of a coating is used. This shielded cable also needs to be grounded, and both ends of the cable jacket are connected to a ground electrode. The ground resistance of this ground electrode is also measured periodically to confirm that it falls within the required ground resistance range. If the ground electrode falls outside the range, measures are taken to reduce the resistance value.

Conventionally, when measuring the ground resistance, FIG.
As shown in (1), the communication device, the electronic device, and the cable connected to the ground electrode 1 for which the ground resistance is to be measured are once removed, and the potential auxiliary electrode 2 and the current auxiliary are connected to the ground at a predetermined distance from the ground electrode 1. The electrode 3 is driven, an AC signal 4 is applied between the ground electrode 1 and the current auxiliary electrode 3 to flow a current, and an amplitude value of the current I flowing at this time and a difference between the ground electrode 1 and the potential auxiliary electrode 2 The voltage (potential difference) V was measured for the amplitude value, and the ground resistance was determined from the ratio of the voltage V to the current I.

[0005]

However, according to the conventional measuring method, in the case of large-scale grounding in which the conductor connecting the potential auxiliary electrode 2, the current auxiliary electrode 3, and the voltmeter 5 is long, and the measurement frequency is low. When the potential is high, an induced voltage is generated in the conductor connected to the potential auxiliary electrode 2 under the influence of the magnetic field generated by the current flowing through the conductor connected to the current auxiliary electrode 3, thereby causing the ground electrode 1 and the potential There is a problem in that an error occurs in a measurement voltage between the auxiliary electrode 2 and an accurate value cannot be measured.

Further, in the conventional measuring method, if the ground resistance of the ground electrode 1 is measured while the operating communication device is connected, the current leaks to a portion other than the ground electrode 1 so that the ground resistance is accurately measured. There was a problem that can not be.

Further, in order to reduce the influence of noise generated from the communication device, a large current is applied to the ground electrode to cope with the problem. However, the communication device may malfunction due to the large current. There is a problem that it is necessary to temporarily disconnect the communication device 1 and the communication device, and to connect to a newly provided ground electrode or an existing ground electrode for ground measurement.

On the other hand, in the case of measuring the ground resistance of the ground electrode of the induction shielded cable, the conventional measurement method has been performed with the ground wire removed from the ground electrode. In this case, a high voltage may be induced in the sheath of the induction shielded cable, and when disconnecting the ground wire, there is a fear that a power accident such as an electric shock of the worker may occur. Therefore, there is a problem that the worker needs to take safety measures such as wearing gloves.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art, and an object of the present invention is to reduce a measurement error of a ground resistance in a ground resistance measuring apparatus and a ground resistance measuring method. It is another object of the present invention to provide a technology capable of reducing the influence of electromagnetic noise.

Another object of the present invention is to provide a grounding resistance measuring device and a grounding resistance measuring method without removing a device in operation or an induction shielding cable, not deteriorating device operation or shielding performance, and reducing noise. It is an object of the present invention to provide a technique capable of accurately measuring a ground resistance even when a current is large.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0012]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

That is, according to the present invention, in a grounding resistance measuring device, a signal generator for generating an AC signal, a grounding electrode for measuring a grounding resistance, and a current feedback device installed at a predetermined distance from the grounding electrode. A current injection unit that applies an AC signal from the signal generation unit between a ground electrode and a current to inject a current into the ground electrode, a current detection unit that detects a current flowing through the ground electrode, and the ground electrode. A potential difference detecting means for detecting a potential difference between the ground electrode and a potential auxiliary electrode provided at a predetermined distance, and an AC signal from the signal generator as a reference phase signal, which is detected by the current detecting means. the amplitude of the potential difference between the amplitude (Ia) and the phase difference of the current flowing to the ground electrode and (.phi.i), wherein a ground electrode that is detected by the potential difference detection means and the potential auxiliary electrode
(Va) and the phase difference (.phi.v) and the synchronous detection measurement unit for measuring the amplitude (Ia) and the phase difference of the current flowing to the ground electrode as measured by the synchronous detector measuring unit and (.phi.i), wherein
Potential amplitude (Va) and the phase difference between the measured synchronous detection measurement portion a and the ground electrode and the potential auxiliary electrode (phi
v) , the function of R = {Va * cos (φv−φi)} / Ia
And an arithmetic unit for calculating a ground resistance (R) by a relational expression . Also, the present invention provides a grounding resistance measuring device.
, A signal generator for generating an AC signal, and a ground resistor
A ground electrode to be measured, and a predetermined distance from the ground electrode
The signal is placed between the ground electrode and the current feedback
Apply an AC signal from the signal generator and apply a current to the ground electrode.
Current injecting means for injecting a current,
Current detecting means for detecting the ground, the ground electrode, and the ground
Between the electrode and the potential auxiliary electrode installed at a predetermined distance
A potential difference detecting means for detecting a potential difference;
The AC signal as a reference phase signal,
Phase base in the current flowing through the ground electrode detected at
A component (I0) having the same phase difference as that of the reference signal, and a phase reference
A component (I90) having a phase difference of 90 degrees from the signal and the potential difference detection
The ground electrode and the potential auxiliary electrode detected by the output means
The phase difference between the phase reference signal and the phase difference at the potential difference between
Minute (V0) and a phase difference of 90 degrees from the phase reference signal.
And a synchronous detection measurement section for measuring the minute (V90).
Current flowing through the ground electrode measured by the wave measurement unit
(I0) having the same phase difference as the phase reference signal, and
A component (I90) having a phase difference of 90 degrees and the synchronous detection measurement unit
Between the ground electrode and the potential auxiliary electrode measured at
A component having the same phase difference as the phase reference signal (V
0) and the component (V90) having a phase difference of 90 degrees,
= Of (V0 * I0 + V90 * I90 ) / (I0 2 + I90 2)
An arithmetic unit for calculating a ground resistance (R) by a relational expression
It is characterized by that.

According to the present invention, in a method for measuring a ground resistance, an AC signal is applied between a ground electrode to be measured for a ground resistance and a current feedback ground electrode provided at a predetermined distance from the ground electrode. A first step of injecting a current into the ground electrode, detecting a current flowing through the ground electrode, and a potential difference between the potential auxiliary electrode provided at a predetermined distance from the ground electrode and the ground electrode. A second step of performing synchronous detection using the AC signal as a reference phase signal, and detecting the amplitude (Ia) and phase difference (φi) of the detected current flowing through the ground electrode and the detected ground electrode potential difference in amplitude between the potential auxiliary electrode and (V
a) measuring the phase difference (φv) , and measuring the amplitude of the current flowing through the ground electrode.
(Ia) and the phase difference between (.phi.i), the potential difference between said measured the ground electrode and the potential auxiliary electrode amplitude (V
a) and the phase difference (φv), R = ｛Va * cos
(Φv−φi)｝ / Ia, the ground resistance
And a fourth step of obtaining (R) . The present invention also relates to a method for measuring a ground resistance,
A ground electrode whose earth resistance is to be measured;
Between the ground electrode for current feedback and a fixed distance
A first signal for applying a current signal and injecting a current into the ground electrode.
And a current flowing through the ground electrode, and
Potential auxiliary electrode installed at a predetermined distance from ground electrode and front
A second step of detecting a potential difference between the ground electrode and the ground electrode
And synchronous detection using the AC signal as a reference phase signal.
In the detected current flowing through the ground electrode,
A component (I0) having the same phase difference as the phase reference signal, and
A component (I90) having a phase difference of 90 degrees from the phase reference signal;
Potential between the output ground electrode and the potential auxiliary electrode
The component having the same phase difference as the phase reference signal (V
0) and a component having a phase difference of 90 degrees from the phase reference signal (V9
0) and before the measured
Phase reference signal and phase difference in the current flowing through the ground electrode
Are in-phase components (I0) and components having a phase difference of 90 degrees
(I90), the measured ground electrode and the potential compensator.
The phase reference signal and the phase difference in the potential difference between the auxiliary electrode
The in-phase component (V0) and the component having a phase difference of 90 degrees (V9
0) from a, R = (V0 * I0 + V90 * I90) / (I0 2 +
I90 ² ) The fourth equation for obtaining the ground resistance (R) by the relational expression
And the step of:

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings.

In all the drawings for describing the embodiments, those having the same functions are denoted by the same reference numerals, and their repeated description will be omitted.

[First Embodiment] FIG. 1 is a diagram for explaining a ground resistance measuring method according to an embodiment of the present invention.

As shown in FIG. 1, in this embodiment, the ground electrode 1 whose ground resistance is to be measured is the same as in the conventional example.
The potential auxiliary electrode 2 and the current auxiliary electrode 3 serving as a current feedback ground electrode are placed in the ground at a predetermined distance. Then, an AC signal is applied between the ground electrode 1 and the current auxiliary electrode 3 to cause a current to flow from the signal generator 4 ′ in the ground resistance measuring device 6, and the current flowing to the ground electrode 1 is detected by the current probe 7. The ground electrode 1 detected by the current probe 7
And the potential difference between the potential auxiliary electrode 2 and the ground electrode 1 are input to the ground resistance measuring device 6 to measure the ground resistance.

FIG. 2 is a block diagram showing a schematic configuration of a grounding resistance measuring device according to an embodiment of the present invention.

As shown in FIG.
Includes a signal generation unit 4 ', a synchronous detection measurement unit (lock-in amplifier unit) 6', a calculation unit 15, and a display unit 16. Also, connected to the ground electrode 1 and the current auxiliary electrode 3,
A current output terminal 4 for applying an AC signal between the ground electrode 1 and the current auxiliary electrode 3 from the signal generator 4 'to flow a current.
a ′, an injection current measurement terminal 6 b connected to the current probe 7, and an inter-electrode potential difference measurement terminal 6 c connected to the potential auxiliary electrode 2 and the ground electrode 1. Here, an amplifier 6d for obtaining a high input impedance is connected to the inter-electrode potential difference measuring terminal 6c.

The synchronous detection measuring section 6 'performs synchronous detection using the AC signal from the signal transmitting section 4' input through the signal line 6a 'as a phase reference signal, and grounds input from the injection current measuring terminal 6b. The amplitude and phase difference of the current flowing through the electrode 1 and the amplitude and phase difference of the potential difference between the ground electrode 1 and the potential auxiliary electrode 2 input from the inter-electrode potential difference measuring terminal 6c are measured.

In this case, a signal switching section is provided between the injection current measuring terminal 6b and the interelectrode potential difference measuring terminal 6c, and the synchronous detection measuring section 6 '. The amplitude and the phase difference of the current flowing through the ground electrode 1 and the amplitude and the phase difference of the potential difference between the ground electrode 1 and the potential auxiliary electrode 2 inputted from the inter-electrode potential difference measuring terminal 6c are sequentially synchronized with one another. The detection and measurement may be performed by the detection and measurement unit 6 ′. Further, dedicated synchronous detection and measurement units 6 ′ are provided for the current and the potential difference, respectively. The phase difference and the amplitude and phase difference of the potential difference between the ground electrode 1 and the potential auxiliary electrode 2 input from the inter-electrode potential difference measurement terminal 6c may be measured simultaneously.

The arithmetic unit 15 obtains the ratio between the current flowing through the ground electrode 1 measured by the synchronous detection measurement unit 6 'and the potential difference between the ground electrode 1 and the potential auxiliary electrode 2 as a vector quantity. The real part of the value is output as ground resistance. The display unit 16 displays the calculation result of the calculation unit 15.

Next, the method of measuring the ground resistance according to the present embodiment will be described in more detail.

In the first step, the potential auxiliary electrode 2 and the current auxiliary electrode 3 are placed at a predetermined distance in the ground.
In the second step, an AC signal is applied between the ground electrode 1 and the current auxiliary electrode 3 from the signal generator 4 'to flow a current.
In a third step, a current flowing through the ground electrode 1 is detected by a current probe 7 and input to a synchronous detection measurement unit 6 '.

In the fourth step, at the time of measurement, electromagnetic waves generated by nearby electric appliances and power transmission lines become interference waves, so that the effect of the interference waves is minimized.
The AC signal from the signal generator 4 'is input to the synchronous detector 6', and the synchronous detector 6 'outputs the signal to the signal generator 4'.
And performs synchronous detection using the AC signal from
The amplitude and phase difference of the current flowing through the ground electrode 1 input in the third step are measured.

In the fifth step, the potential difference between the potential auxiliary electrode 2 and the ground electrode 1 input from the inter-electrode potential difference measuring terminal 6c is determined by the synchronous detection measurement unit 6 'in the same manner as in the fourth step. Synchronous detection is performed using the AC signal from the signal generator 4 'as a phase reference signal, and the amplitude and phase difference of the potential difference between the potential auxiliary electrode 2 and the ground electrode 1 are measured.

In the sixth step, the ratio of the current flowing through the ground electrode 1 measured in the fourth step to the potential difference between the potential auxiliary electrode 2 and the ground electrode 1 measured in the fifth step is calculated as a vector quantity. And the real part of the obtained value is calculated as the ground resistance of the ground electrode 1.

In a seventh step, the ground resistance obtained in the sixth step is displayed on a display unit (display or printer) 16.

Next, a method of calculating the ground resistance will be described.

FIG. 3 is a diagram schematically showing the potential on the ground surface.

As shown in the figure, the potential of the ground electrode 1
The potential difference of the potential auxiliary electrode 2 where the potential is almost zero is
The potential of the ground electrode 1 rises. The ratio of the potential rise to the current flowing through the ground electrode 1 (or the injected current injected into the ground electrode 1) represents the ground resistance. However, at this time, the current flowing in the conductor between the ground electrode 1 and the current auxiliary electrode 3 causes the conductor between the potential auxiliary electrode 2 and the synchronous detection and measurement unit 6 'and the conductor between the ground electrode 1 and the synchronous detection and measurement unit 6'. Since the induced voltage is generated, the measured value of the potential difference includes the induced voltage.

Since the induced voltage has a phase difference of 90 degrees from the current flowing through the ground electrode 1, the ratio of the potential difference between the current flowing through the ground electrode 1 and the in-phase component is obtained, that is, the vector amount is obtained. The influence of the induction can be eliminated by taking the part.

Here, as a method of obtaining the ratio of the potential difference between the potential auxiliary electrode 2 and the ground electrode 1 to the current flowing through the ground electrode 1 as a vector quantity, the synchronous detection measurement section 6 'includes a signal generation section. the AC signal from the 4 'performs synchronous detection as a phase reference signal, measuring the amplitude I _a and the phase difference phi _i of the current flowing to the ground electrode 1. Further, 'in the signal generator 4' synchronous detector measuring unit 6 performs synchronous detection AC signal from the phase reference signal, the amplitude V _a and the phase difference of the potential difference between the ground electrode 1 and the potential auxiliary electrode 2 phi Measure _v .

The ground resistance R is obtained by the following equation (1).

[0036]

R = {V _a * cos (φ _v −φ _i )} / I _a (1) FIG. 4 is used for the synchronous detection measurement unit 6 ′ of the present embodiment. 1 is a block diagram showing a schematic configuration of a typical example of a lock-in amplifier to be used.

The lock-in amplifier is an AC voltmeter that accurately selects and detects only a component having a fixed phase relationship with the reference signal among the signals buried in noise, and includes a main amplifier 21 for amplifying an input signal, a reference signal Reference amplifier 2 that amplifies
2. Synchronous rectifier circuit 23 which forms the center of the device, phase circuit 24 for adjusting the phase of the reference signal, and low-pass filter 2
And 5.

FIG. 5 is a principle diagram showing a double-wave gate type synchronous rectifier circuit as an example of the synchronous rectifier circuit 23 shown in FIG.

In the figure, reference numeral 26 denotes an inverting amplifier, and the double-wave gate type synchronous rectifier circuit shown in the same figure performs double-wave rectification by alternately switching the switches SW1 and SW2 according to the polarity of the reference signal. is there.

Now, when the input signal e _i is a signal as shown in the following equation (2), an output e _o as shown in the following equation (3) is output from the double-wave gate synchronous rectifier circuit shown in FIG. Is obtained.

[0041]

E _i = e ₀ sin (ωt−φ) (2) e _o = Ae ₀ cos φ (3) Here, φ is a phase difference between the reference signal and the input signal, and A is a constant.

Therefore, in the phase circuit 24 shown in FIG.
By adjusting the phase of the reference signal, the output e when cos φ is 1
_{By obtaining o} , the amplitude of the input signal can be obtained, and, by obtaining a component of the input signal having the same phase as the reference signal and a component having a phase difference of 90 ° from the reference signal,
The phase difference φ between the reference signal and the input signal can be determined.

Next, another example of the method of calculating the ground resistance will be described.

In the method of calculating the ground resistance, the ratio of the potential difference between the potential auxiliary electrode 2 and the ground electrode 1 to the current flowing through the ground electrode 1 is determined as a vector quantity. For each of the potential differences between the potential auxiliary electrode 2 and the ground electrode 1, a component having the same phase as the AC signal from the signal generation section 4 'as a phase reference signal and a component having a phase difference of 90 degrees from the AC signal are measured. I do. From these, the ratio of the current flowing through the ground electrode 1 to the potential difference between the potential auxiliary electrode 2 and the ground electrode 1 is determined as a vector quantity, and the ground resistance is determined from its real part.

Here, a component of the potential difference between the potential auxiliary electrode 2 and the ground electrode 1 which is in phase with the AC signal from the signal generator 4 'is V ₀ , and a component having a phase difference of 90 degrees with the AC signal is V V. and _90, the current flowing to the ground electrode 1, the component of the AC signal in phase from the signal generator 4 'I _0, AC signal and the phase difference is 90
When the degree component is I ₉₀ , the ground resistance value R is obtained as the following equation (4).

[0046]

R = Re {(V ₀ + jV ₉₀ ) / (I ₀ + jI ₉₀ )} = (V ₀ * I ₀ + V ₉₀ * I ₉₀ ) / (I ₀ ² ) + I ₉₀ ² (4) As described above, according to the present embodiment, the potential detection electrode 2 and the ground electrode are controlled by the synchronous detection measurement unit 6 '. 1 and the current flowing through the ground electrode 1 are measured, and the ratio between the potential difference between the potential auxiliary electrode 2 and the ground electrode 1 and the current flowing through the ground electrode 1 is calculated as a vector quantity. Is determined as the ground resistance, the ground resistance measuring device 6
And the effect of the dielectric voltage caused by electromagnetic induction on the conductor connecting the ground electrode 1 or the potential auxiliary electrode 2 is removed,
It is possible to accurately measure the ground resistance.

Further, according to the present embodiment, the synchronous detection and measurement section 6 ′ synchronously detects the AC signal from the signal generation section 4 ′ as a phase reference signal, thereby obtaining the AC signal from the signal generation section 4 ′. Since the voltage having the same frequency as that of the above can be selectively detected, the external noise component can be efficiently reduced.

[Embodiment 2] FIG. 6 is a diagram for explaining a ground resistance measuring method according to another embodiment of the present invention.

In this embodiment, the electronic device 1 is connected to the ground electrode 1.
3 is connected by the ground wire 10, the electronic device 13
This is an embodiment in which the ground resistance of the ground electrode 1 is measured without removing the ground electrode.

Here, the electronic device 13 is connected to the power supply line 11, and between the ground line 10 and the power supply line 11 is alternately connected by a power supply filter of the electronic device 13 or a capacitance such as a stray capacitance of a transformer. ing. Also, this power supply line 11
Is connected to the second type ground 12 by the power distribution transformer 9. The second type ground 12 forms a current feedback ground electrode.

As shown in FIG. 6, in the present embodiment, the current injection probe 8 is connected to the ground line 10 connected to the ground electrode 1.
And apply an AC signal from the signal generator 4 '
A minute current is injected into the ground electrode 1. Next, similarly to the first embodiment, the current flowing through the ground electrode 1 is detected by the current probe 7 and guided to the injection current measuring terminal 6b of the ground resistance measuring device 6, and the synchronous detection measuring unit 6 'generates a signal. Synchronous detection is performed using the AC signal from the unit 4 ′ as a phase reference signal, and the amplitude and phase difference of the current flowing through the ground electrode 1 are measured.

Further, a potential auxiliary electrode 2 is provided between the ground electrode 1 and the second type ground 12 at a place where the current injected from the current injection probe 8 is sufficiently diffused to the ground. The potential difference between the ground electrode 1 is led to the inter-electrode potential difference measuring terminal 6c of the ground resistance measuring device 6, and the synchronous detection measuring section 6 'performs synchronous detection using the AC signal from the signal generating section 4' as a phase reference signal. Then, the amplitude and the phase difference of the potential difference between the potential auxiliary electrode 2 and the ground electrode 1 are measured.

Finally, as a vector quantity, the potential auxiliary electrode 2
The ground resistance of the ground electrode 1 is calculated by dividing the potential difference between the ground electrode 1 and the current flowing through the ground electrode 1 to obtain the real part.

In the present embodiment, similarly to the above-described embodiment, accurate grounding resistance can be measured by eliminating the influence of noise and induction, and minute current is applied to the ground electrode 1 using the current injection probe 8. Since the current flows, the measurement can be performed without removing the ground wire 10 to which the electronic device 13 is connected from the electronic device 13. This makes it possible to simplify the maintenance work of the communication ground.

[Embodiment 3] FIG. 7 is a diagram for explaining a ground resistance measuring method according to another embodiment of the present invention.

This embodiment is an embodiment in the case where the ground resistance of the ground electrode 1 connected to the shielding sheath of the induction shielding cable 14 is measured.

The induction shielded cable 14 is applied to a cable that generates a high induced voltage that poses a problem in human safety. For example, two or more cables are grounded like the ground electrode 1 and the ground electrode 17 shown in FIG. It is necessary to check its grounding resistance regularly. At the time of this inspection, if the ground electrode 1 is removed from the cable sheath, the required shielding effect cannot be obtained. If the operator swings on the shielding sheath, there is a risk of electric shock or the like. Therefore, when measuring the ground resistance, the ground electrode 1 for which the ground resistance is to be measured is placed on the shielding sheath.
It is desirable to perform measurement with the device connected.

In the present embodiment, as in the second embodiment, a minute current is injected into the ground electrode 1 using the current injection clamp 8, but since the ground electrode 17 becomes a current feedback ground electrode, The current flowing through the ground electrode 1 is
Is returned to the ground electrode 1. For others,
The ground resistance is measured in the same manner as in the second embodiment.

According to the present embodiment, the shielded cable 14
It is possible to safely measure the ground resistance while the ground electrode 1 to be measured is connected.

As described above, the invention made by the present inventor is:
Although a specific description has been given based on the above-described embodiment, the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the invention.

[0061]

The effects obtained by typical ones of the inventions disclosed in the present application will be briefly described as follows.

(1) According to the present invention, the potential difference between the potential auxiliary electrode and the ground electrode and the current flowing through the ground electrode are measured by the synchronous detection measurement unit, and the potential difference between the potential auxiliary electrode and the ground electrode is measured. The ratio of the potential difference between the current and the current flowing through the ground electrode is calculated as a vector quantity, and the real part thereof is obtained as the ground resistance, so that the induction generated in the conductor connecting the ground resistance measuring device and the ground electrode or the potential auxiliary electrode. The ground resistance can be accurately measured without being affected by the voltage.

(2) According to the present invention, a voltage having the same frequency as the AC signal from the signal generator is selected by the synchronous detection and measurement unit performing synchronous detection using the AC signal from the signal generator as the phase reference signal. Can be detected
External noise components can be efficiently reduced.

(3) According to the present invention, the ground resistance can be measured by injecting a small current into the ground electrode, so that the ground resistance can be measured without removing the ground electrode from the sheath of the electronic device or the induction shielded cable. Therefore, the maintenance work of the communication ground can be simplified.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a ground resistance measuring method according to an embodiment of the present invention.

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

FIG. 3 is a diagram schematically showing a potential on the ground surface.

FIG. 4 is a block diagram illustrating a schematic configuration of a typical example of a lock-in amplifier used in a synchronous detection measurement unit according to the present embodiment.

FIG. 5 is a principle diagram showing a double-wave gate synchronous rectifier circuit as an example of the synchronous rectifier circuit shown in FIG. 4;

FIG. 6 is a diagram for explaining a ground resistance measuring method according to another embodiment of the present invention.

FIG. 7 is a diagram for explaining a ground resistance measuring method according to another embodiment of the present invention.

FIG. 8 is a diagram for explaining a conventional ground resistance measuring method.

[Explanation of symbols]

Reference numerals 1, 17: ground electrode, 2: electric potential auxiliary electrode, 3: current auxiliary electrode, 4: AC signal, 4 ': signal generator, 4a': current output terminal, 5: voltmeter, 6: ground resistance measuring device, 6 '...
Synchronous detection measurement section, 6a ': signal line, 6b: injection current measurement terminal, 6c: electrode potential difference measurement terminal, 6d: amplifier, 7
... current probe, 8 ... current injection probe, 9 ... power distribution transformer, 10 ... ground wire, 11 ... power supply line, 12 ... second-class ground, 13 ... electronic equipment, 14 ... induction shielded cable, 15 ...
Arithmetic operation unit, 16 display unit, 21, 22 amplifier, 23 synchronous rectifier circuit, 24 phase circuit, 25 low-pass filter, 26
... inverting amplifier.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01R 27/20

Claims (5)

(57) [Claims] A signal generator for generating an AC signal; a ground electrode for measuring a ground resistance; and a current feedback ground electrode provided at a predetermined distance from the ground electrode. A current injection unit that applies an AC signal from a unit and injects a current into the ground electrode; a current detection unit that detects a current flowing through the ground electrode; a ground electrode; and a predetermined distance from the ground electrode. Potential difference detection means for detecting a potential difference between the potential auxiliary electrode to be performed, and an AC signal from the signal generation unit as a reference phase signal,
The amplitude of the potential difference between the amplitude (Ia) and the phase difference of the current flowing to the ground electrode detected by said current detecting means and (.phi.i), wherein a ground electrode that is detected by the potential difference detection means and the potential auxiliary electrode (Va) and a phase difference (φv) , a synchronous detection measurement unit, an amplitude (Ia) and a phase difference (φi) of a current flowing through the ground electrode measured by the synchronous detection measurement unit, and the synchronous detection
Potential amplitude (Va) and the phase difference between the ground electrode as measured by the wave measuring unit and the potential auxiliary electrode from (φv), R = {Va * cos (φv-φi)} / Ia relationship
And a calculation unit for calculating the ground resistance (R) . 2. A signal generator for generating an AC signal, and a ground electrode to be measured of the ground resistance, between the ground electrode and the predetermined distance is disposed apart current feedback ground electrode, the signal generator A current injecting unit that applies an AC signal from a unit and injects a current into the ground electrode; a current detecting unit that detects a current flowing through the ground electrode; the ground electrode; and a predetermined distance from the ground electrode. Sa
Potential difference detection to detect the potential difference between the potential auxiliary electrode
Means, the AC signal from the signal generator as a reference phase signal,
The electric current flowing to the ground electrode detected by the current detecting means
Of the phase reference signal and the phase difference (I
0) and a component having a phase difference of 90 degrees from the phase reference signal (I9
0) and the ground electrode detected by the potential difference detecting means
Reference signal at the potential difference between
Signal (V0) with the same phase difference as the signal, and the phase reference signal
And synchronous detection for measuring the 90 ° phase difference component (V90)
Measuring part , flowing to the ground electrode measured by the synchronous detection measuring part
A component having the same phase difference as the phase reference signal (I
0) and a component (I90) having a phase difference of 90 degrees,
The ground electrode and the potential auxiliary measured by the period detection measurement unit
The phase difference between the phase reference signal and the
The phase component (V0) and the component having a phase difference of 90 degrees (V9
0) from a, R = (V0 * I0 + V90 * I90) / (I0 2 +
The relationship of I90 ^2), calculation for obtaining the grounding resistance (R)
And a grounding resistance measuring device. 3. A ground electrode whose ground resistance is to be measured,
A current feedback contact installed at a predetermined distance from the ground electrode
An AC signal is applied between the ground electrode and a current
A first step of injecting, a current flowing through the ground electrode,
A potential auxiliary electrode installed at a fixed distance and the ground electrode
A second step of detecting a potential difference between the signals; and performing synchronous detection using the AC signal as a reference phase signal.
The detected amplitude of the current flowing through the ground electrode (Ia)
And the phase difference (φi) and the detected ground electrode
The amplitude (Va) of the potential difference between
A third step of measuring the fine phase difference (.phi.v), the amplitude of the current flowing to the ground electrode, which is the measured (I
a) and the phase difference (φi),
The amplitude (Va) of the potential difference between the pole and the potential auxiliary electrode and
And the phase difference (φv), R = ｛Va * cos (φv−
φi) Using the relational expression of に よ り / Ia, find the ground resistance (R)
And a fourth step of measuring the ground resistance. 4. A ground electrode whose ground resistance is to be measured,
A current feedback contact installed at a predetermined distance from the ground electrode
An AC signal is applied between the ground electrode and a current
A first step of injecting, a current flowing through the ground electrode,
A potential auxiliary electrode installed at a fixed distance and the ground electrode
A second step of detecting a potential difference between the signals; and performing synchronous detection using the AC signal as a reference phase signal.
Phase base in the detected current flowing through the ground electrode
A component (I0) having the same phase difference as that of the reference signal, and a phase reference
A component (I90) having a phase difference of 90 degrees from the signal,
The potential difference between the ground electrode and the potential auxiliary electrode.
(V0) having the same phase difference as the phase reference signal
And a component (V90) having a phase difference of 90 degrees from the phase reference signal.
A third step of determining the phase in the measured current flowing through the ground electrode.
A component (I0) having the same phase difference as the reference signal, and the phase difference
Is a 90 degree component (I90) and the measured ground
Phase reference for the potential difference between a pole and said potential auxiliary electrode
A component having the same phase difference as the signal (V0) and a phase difference of 9
From the 0-degree component (V90), R = (V0 * I0 + V90 * I
The relationship of the ^{90) / (I0 2 + I90} 2), ground resistance
(R) is obtained.
Ground resistance measurement method to. Wherein said first step comprises the steps of using a current injection probe, injecting current into said ground electrode
The ground resistance measuring method according to claim 3 or 4 , wherein