JPH0712866A - Grounding resistance measuring apparatus - Google Patents

Abstract

PURPOSE:To allow highly precise measurement of the grounding resistance of a grounding pole while connecting the grounding pole with that of a base for installing an electric machine. CONSTITUTION:AC current I is fed from an AC power supply 50 to a grounding pole 30 to be measured Without disconnecting the grounding pole 30 from that 40 of the base for installing an electric machine. The current I and the voltage V between the grounding pole 30 and the earth are then measured individually and the grounding resistance of the grounding pole is operated 58.

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 for measuring a ground resistance existing between a ground electrode to be measured and ground by using a plurality of auxiliary ground electrodes in combination.

[0002]

2. Description of the Related Art As widely known in the art, as a safety standard for equipment, household electrical equipment, etc., it is possible to attach a grounding electrode to prevent lightning and electric shock according to "Technical Standards for Electrical Equipment". Mandatory. Then, it is necessary to regularly measure whether or not the ground resistance value of the ground electrode is in conformity with the standard.

As a method of measuring the ground resistance of the ground electrode, a potential drop method has been conventionally known. Therefore, this measuring method will be described below with reference to FIG.

In FIG. 2, reference numeral 1 is a ground electrode to be measured, and 2 and 3 are auxiliary ground electrodes. T ₁ , T ₂ , and T ₃ are terminals for connecting the ground electrodes ₁ , ₂ , and ₃ . Therefore, each of the illustrated ground electrodes 1, 2, and 3 is actually connected to each of the terminals T ₁ and T 2.
₂ , including a lead wire (not shown) connected to T ₃ and a ground electrode connected to the lead wire and buried in the ground.

Reference numeral 4 denotes a constant current power source, which has terminals T ₁ and T
Connected between _two . 5 is a high input impedance type voltmeter connected between terminals T ₁ and T ₃ .

Since the ground electrode to be measured 1 is usually connected to the ground electrode (not shown) of the electric equipment mounting base, when measuring the ground resistance of the ground electrode to be measured 1, first the ground electrode to be measured 1 is to be measured. And the ground pole of the electrical equipment mounting base must be disconnected. The reason is that the measured ground electrode 1
This is because, if the ground resistance is measured in a state in which is connected to the grounding electrode of the electrical equipment mounting base, the resistance of the grounding electrode of the electrical equipment mounting base is also added, and the grounding resistance of the measured grounding electrode itself cannot be measured.

Therefore, when measuring the ground resistance, the constant current I is supplied from the constant current power source 4 to the ground electrode to be measured, which is separated from the ground electrode of the electric equipment mounting base. Then, the ground resistance of the measured ground electrode 1 is measured by measuring the voltage with high accuracy by the high input impedance type voltmeter 5 connected between the auxiliary ground electrode 3 and the measured ground electrode 1. That is, by measuring the voltage V, Ohm's law R = V
The ground resistance R can be obtained from / I.

[0008]

However, in the above-mentioned conventional measuring method, there is a troublesome work such that the connection between the grounding electrode 1 to be measured and the grounding electrode of the electric equipment mounting base must be released every time measurement is performed. Along with this, it was necessary to secure the constant current power source 4 again.

Therefore, in view of the above points, the object of the present invention is to measure the ground resistance of the measured grounding electrode with high accuracy in a state where the measured grounding electrode is connected to the grounding electrode of the electric equipment mounting base. An object of the present invention is to provide a ground resistance measuring device that can perform

[0010]

In order to achieve the above object, a ground resistance measuring apparatus according to the present invention applies an AC voltage between a first auxiliary ground electrode and a ground electrode to be measured, and 1
An alternating current power source for flowing a current through the auxiliary grounding electrode and the circuit to the grounding electrode to be measured, a current detecting means for detecting the value of the current flowing to the grounding electrode to be measured, and a second auxiliary grounding electrode. A high input impedance type voltage detecting means for detecting a difference between the ground potential detected via the ground potential and the potential generated in the ground electrode under measurement, and based on the detection output from the voltage detecting means and the current detecting means. And arithmetic means for calculating the value of the ground resistance of the measured ground electrode.

Here, it is preferable that the current detecting means has an AC device or a clip-on meter magnetically coupled to the ground electrode to be measured. Further, in addition to the above configuration, it is possible to include means for displaying and / or recording the output of the arithmetic means.

[0012]

According to the present invention, an AC current is passed from the AC power supply to the ground electrode under test without disconnecting the ground electrode under test from the ground electrode of the mounting base for electrical equipment, and the current I and the ground electrode under test are measured. The ground resistance value of the ground electrode to be measured is calculated by separately measuring the voltage V between the ground and the ground.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below.

FIG. 1 is a block diagram showing an entire embodiment of the present invention. In this figure, 10 is a first auxiliary ground electrode, 20 is a second auxiliary ground electrode, and 30 is a measured ground electrode. Further, R _A , R _B , and R _C are the ground electrodes 10, 20,
It is a ground resistance existing between 30 and the ground.

T _A , T _B and T _C are the ground electrodes 10 and 2
These are terminals for connecting 0 and 30, respectively. Therefore, the illustrated ground electrodes 10, 20, 30 are connected to the terminals T _A , T _B , T _C via lead wires (not shown).

Reference numeral 40 is a grounding electrode of the mounting base for electric equipment, T _D
Is a terminal for connecting the grounding electrode via a lead wire (not shown), and R _D is a grounding resistance of the electric equipment mounting base.

The interior surrounded by the broken line in FIG. 1 shows the ground resistance measuring apparatus according to this embodiment.

Here, reference numeral 50 is an AC power source, which has a terminal T.
_An AC voltage is applied between _A and T _C. Therefore, the first auxiliary ground electrode 10 → ground resistance R _A → ground → ground resistance R _C →
An AC current I flows from the AC power supply 50 to the circuit reaching the measured ground electrode 30. The output voltage and output current of the AC power supply 50 need not be controlled to constant values.

Reference numeral 52 is a current transformer, which detects the alternating current I flowing through the measured ground electrode 30 in a non-contact manner. Therefore, the AC current I can be measured by using a commercially available clip-on meter instead of the current transformer 52 or by inputting the calibrated output voltage of the pickup coil to an oscilloscope. Is.

Reference numeral 54 is a current converter, which converts the output from the current transformer 52 into digital data and sends it out.

Reference numeral 56 is a high input impedance type voltage converter having two input terminals. Here, one input end is connected to the ground via the terminal T _B and the second auxiliary ground electrode 20. The other input end is connected to the terminal T _C.

Therefore, since no current flows through the second auxiliary ground electrode 20, the potential difference between the terminals T _B and T _C is
It corresponds to the voltage drop V at the ground resistance R _C of the measured ground electrode 30.

From the voltage converter 56, the voltage drop V
The digitized data is output.

Reference numeral 58 denotes an arithmetic unit which inputs the current data I output from the current converter 54 and the voltage data V output from the voltage converter 56 and performs an operation of R = V / I. Therefore, this R is the ground resistance R of the ground electrode 30 to be measured.
Represents _C.

Reference numeral 60 is a recording device, and 62 is a display, which records and displays the ground resistance data output from the calculator 58, respectively.

As described in the section of the prior art, the ground electrode 30 to be measured is generally always connected to the ground electrode 40 of the electric equipment mounting base, but in this embodiment, the connection is released. It is possible to easily and accurately measure the ground resistance R _C of the measured ground electrode 30 itself, and since it has a recording function, it is possible to record and compare the results of periodic measurement in time series. The work of measuring the resistance of the measuring ground electrode becomes very simple and contributes greatly to safety prevention.

[0027]

As described above, according to the present invention, it is possible to directly and non-contactly detect an alternating current flowing through a ground electrode under test and measure a voltage drop caused by a ground resistance of the ground electrode under test. The above-mentioned ground resistance can be calculated immediately by using, so that it is possible to measure the ground resistance of the measured ground electrode with high accuracy while the measured ground electrode remains connected to the ground electrode of the electrical equipment mounting base. It will be possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing a ground resistance measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a conventionally known ground resistance measuring method.

[Explanation of symbols]

10 first auxiliary ground electrode 20 and the second auxiliary ground electrode 30 to be measured earth electrode R _A, R _B, R _C earth resistance T _A, T _B, T _C connection terminal 50 AC power supply 52 current transformer 54 current converter 56 voltage converter 58 arithmetic unit 60 recording device 62 indicator

Claims (3)

[Claims] 1. An AC voltage is applied between a first auxiliary ground electrode and a ground electrode to be measured, and a current is passed through a circuit reaching the ground electrode to be measured via the first auxiliary ground electrode and ground. An alternating current power supply; a current detecting means for detecting a value of a current flowing through the ground electrode under test; a ground potential detected through a second auxiliary ground electrode; and a potential generated at the ground electrode under test. A high input impedance type voltage detecting means for detecting a difference; and an arithmetic means for calculating the value of the ground resistance of the ground electrode to be measured based on the detection outputs from the voltage detecting means and the current detecting means. An earth resistance measuring device characterized by. 2. The ground resistance measuring device according to claim 1, wherein the current detecting means has an AC device or a clip-on meter magnetically coupled to the ground electrode to be measured. 3. The ground resistance measuring apparatus according to claim 1, further comprising means for displaying and / or recording the output of the computing means.