JP2006275623A - Ground resistance measurement method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ground resistance measurement method for making measurement rapid and easy even if a buried pipe is buried below a place, such as a basement, making ground resistance measurement difficult. <P>SOLUTION: This ground resistance measurement method is for measuring ground resistance of a first buried object 1 which is a measuring object between the buried object 1 partly coming out of a medium and a second buried object 2. This method includes: a process for deriving series resistance of the buried objects 1 and 2 through the medium 10; a process for providing a power source electrode 6 grounded through the medium 10 to place a potential difference across the source electrode 6 and a contact 7, with the contact 7 provided between the buried objects 1 and 2; a process for severally measuring a first electric current flowing through the buried object 1 and contact 7, and a second electric current flowing through the buried object 2 and contact 7; and a process for proportionally dividing the series resistance at a ratio between the first and second electric currents. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for measuring the ground resistance of an embedded object to be measured among a plurality of embedded objects embedded in a medium. More specifically, the present invention relates to a method for measuring a ground resistance used for diagnosis of a corrosion state in an embedded object such as an embedded pipe to be measured.

  Various types of pipes are buried in the ground to supply utilities such as water and gas into buildings where consumers live. Such piping is drawn into the site of each building as an inner pipe via a main branch pipe (outer pipe) buried under the road or the like, and reaches the inside of the building.

  When corrosion occurs in such a buried pipe, problems such as water leakage and gas leakage may occur from the corroded portion. In order to avoid this problem, various anticorrosion methods for pipes and corrosion state inspection methods for pipes have been proposed. In addition, when piping is buried underground such as under a road, underground in a building, concrete in a building or underground in a building, the piping is dug out. It is required to inspect pipes for corrosion without any problems.

  As one of the conventional methods for diagnosing buried piping, there is a method for determining the corrosion state of the buried piping by measuring the ground resistance (impedance) of the buried piping as a measurement target (for example, Patent Document 1). reference). In the method of Patent Document 1, it is determined that damage (corrosion) has occurred in the buried piping when the measured value of the ground resistance falls below a predetermined threshold value.

Japanese Patent Laying-Open No. 2003-232764 (FIG. 1)

  However, in the method of Patent Document 1, it is necessary to install at least two electrodes in order to measure the ground resistance of the buried piping that is the measurement target. For this reason, the measurement site of the buried piping, for example, on the outside of the concrete wall of the basement, under the asphalt-paved road surface, or under a hard ground, takes time to install the electrode, This places a heavy burden on the worker.

  Moreover, the buried piping as a measurement target may exist at a position far from a place where the electrode can be installed. In such a case, it is difficult to route the lead wire connected to the electrode.

  Further, when the buried piping and the electrode are separated from each other, the work of setting the electrode and the lead wire every measurement is very troublesome for the operator and the work efficiency is poor.

  The present invention has been made in view of the above-described problems, and the purpose thereof is when the buried pipe as the measurement object is buried in a place where it is difficult to measure the normal grounding resistance, such as the outside of the basement. Even so, an object of the present invention is to provide a ground resistance measurement method capable of measuring the ground resistance quickly and easily.

  The characteristic configuration of the ground resistance measuring method according to the present invention is that a ground resistance for measuring the ground resistance of the first embedded object to be measured among the first embedded object and the second embedded object partially exposed from the medium. A measuring method, wherein a step of deriving a series resistance through the medium in the first embedded object and the second embedded object, and a power supply electrode grounded to the medium are provided, the power supply electrode and the first embedded object A step of applying a potential difference between an object and a contact provided between the second embedded object, a first current flowing between the first embedded object and the contact, and the second embedded object and the The method includes a step of measuring each second current flowing between the contacts and a step of dividing the series resistance by a ratio of the first current and the second current.

  With the ground resistance measurement method of this configuration, for example, using a part of the buried object exposed from a medium (for example, a concrete wall or soil) in a basement or the like, the ground resistance in the buried part of the buried object is used. Can be measured. Therefore, it is not necessary to install an electrode on the medium in order to measure the ground resistance as in the prior art, and quick and easy measurement is possible. This also reduces the burden on the operator and improves the work efficiency.

  In the ground resistance measuring method of the present invention, the step of calculating the series resistance includes the step of applying a potential difference between the first embedded object and the second embedded object, and the first embedded object and the second embedded object. And measuring the total current flowing through the object, and the series resistance can be derived from the potential difference and the total current.

  With the ground resistance measurement method of this configuration, series resistance can be easily achieved by applying a potential difference between the first embedded object and the second embedded object and measuring the current flowing at that time. Can be measured.

  In the ground resistance measurement method of the present invention, the first embedded object and the second embedded object may be electrically connected to each other through a conductor at the exposed portion.

  In the ground resistance measurement method of this configuration, when the first embedded object to be measured is in conduction with the second embedded object to be measured and the conductor, at least a part of these embedded objects is a medium. If it is in an exposed state, it is not necessary to install an electrode for measuring the ground resistance on the medium, as described above, and quick and easy measurement is possible. Therefore, the burden on the worker is reduced and the work efficiency is improved.

  In the ground resistance measuring method of the present invention, the power supply electrode can be an existing power ground wire.

  With the ground resistance measurement method of this configuration, since the existing power ground wire can be used as the power electrode for measuring the ground resistance of the buried object, there is no need to bother installing the power electrode for ground resistance measurement. Further work efficiency can be improved. In addition, the measurement cost can be reduced by the amount that the power supply electrode is not required.

<Measurement principle>
First, the measurement principle of the ground resistance measurement method of the present invention will be described with reference to FIGS. FIG. 1 shows a measurement model (hereinafter referred to as a non-conductive buried object measurement model) when the first embedded object 1 as a measurement object and the second embedded object 2 as a non-measurement object are not conductive. Is a measurement model when the first embedded object 1 and the second embedded object 2 are conductive (hereinafter referred to as a conductive embedded object measurement model). In addition, as the 1st buried object 1 and the 2nd buried object 2 demonstrated in this embodiment, the metal buried piping etc. which were coat | covered with resin etc. are mentioned, for example.

[1] Non-conductive buried object measurement model In the non-conductive buried object measurement model shown in FIG. 1, the ground resistance of the first embedded object 1 to be measured among a plurality of embedded objects partially exposed from the medium 10. A case of measuring the will be described. As shown in FIG. 1A, the first embedded object 1 and the second embedded object 2 are partially exposed from a medium 10 such as concrete. A state of being electrically connected to the first embedded object 1 and the second embedded object 2 using the lead wire 3 or the like as shown in FIG. 1B is formed. In this electrical connection state, the power supply device 4 is connected to the first embedded object 1 and the second embedded object 2 to apply a potential difference (referred to as an overall voltage E). In the present invention, an AC power supply is used as the power supply device 4, but a DC power supply can also be used.

Next, an ammeter 5 measures a current (referred to as a total current I) flowing through the entire first embedded object 1 and the second embedded object 2. Then, the series resistance R through the medium in the first embedded object and the second embedded object is calculated from the overall voltage E and the overall current I. That is, the following formula (1):
Series resistance R = total voltage E / total current I (1)
As a result, a series resistance R is obtained.

Next, as shown in FIG. 1C, a power supply electrode 6 is provided on the medium 10, and a power supply device is provided between the power supply electrode 6 and the contact 7 provided between the first embedded object 1 and the second embedded object 2. A potential difference is applied by 4 '. The power supply device 4 ′ may be the same as the previously used power supply device 4 or may be separate. When the potential difference is applied, the first current I ₁ flows between the first embedded object 1 and the contact 7, and the second current I ₂ flows between the second embedded object 2 and the contact 7. It measures with the ammeters 11 and 12, respectively. When the series resistance R is apportioned by the ratio of the first current I ₁ and the second current C, the ground resistance R ₁ of the first embedded object ₁ is expressed by the following formula (2):
R ₁ = I ₂ / (I ₁ + I ₂ ) × R (2)
As required.

[2] Conductive buried object measurement model A case where the ground resistance of the first buried object 1 is measured using the conductive buried object measurement model shown in FIG. 2 will be described. As shown in FIG. 2A, the first embedded object 1 and the second embedded object 2 are partially exposed from the medium 10 such as concrete, and in this model, the first embedded object 1 and the second embedded object 2 are also exposed. The object 2 is in a conductive state via a conductor 20 such as a metal tube, thereby forming an electrically connected state.

A clamp ground resistance meter 30 is attached to the conductor 20 as shown in FIG. The clamp ground resistance meter 30 flows through the conductive body 20 by the annular magnetic field, an external magnetic coil unit 31 that generates an annular magnetic field around the conductive body 20, a power supply means 32 that applies a set voltage Es to the external magnetic coil unit 31. Current measuring means 33 for measuring the current, that is, the total current I flowing through the entire first embedded object 1 and the second embedded object 2 is provided. From the measurement result by the clamp ground resistance meter 30, the series resistance R through the medium in the first embedded object and the second embedded object can be calculated. That is, the following formula (3):
Series resistance R = total voltage E / total current I (3)
It becomes. Here, the total voltage E is
E = a × Es + b (4)
a: Constant determined by ambient temperature b: Defined by a constant determined by noise caused by ambient electromagnetic waves. For example, a correlation map indicating a relationship with the set voltage Es may be created in advance for the entire voltage E, and the whole voltage E may be derived therefrom.

Next, determine the ground resistance R ₁ in FIG. 2 (c), the for this step can be performed in the same manner as the steps described with reference to FIG. 1 (c) in the non-conductive buried objects measurement model. That is, the first current I ₁ and the second current I ₂ flowing on both sides of the contact 7 are obtained by the clamp ammeters 11 ′ and 12 ′, respectively, and from these current values and the series resistance R, the first embedded object 1 it can be determined grounding resistance R _1.

In the non-conductive buried measurement model described in [1] above, when obtaining the series resistance R, as shown in FIG. 1B, the power supply device 4 for applying the entire voltage E and the first buried object The ammeter 5 for measuring the total current I flowing through the first and second buried objects 2 is used, but it is obtained by the clamp ground resistance meter 30 as in the conductive buried object measuring model described in [2]. Is also possible. That is, after the first embedded object 1 and the second embedded object 2 are electrically connected with a lead wire or the like, the clamp ground resistance meter 30 is attached to the lead wire, and the ground resistance R ₁ is obtained in the same manner as described above. You may do it.

<Example>
An embodiment of the ground resistance measuring method of the present invention will be described with reference to FIG. FIG. 3 schematically shows the utility pipe 50 embedded in the basement 60 with a part thereof exposed. The utility pipe 50 includes a main pipe 51 and a plurality of branch pipes 52 (for example, branch pipes 52 a, 52 b, 52 c). The main pipe 51 and the branch pipe 52 are connected by an insulating joint 53. The upstream side of the main pipe 51 and the downstream side of the branch pipe 52 are in a state where they pass through the wall portion 61 of the basement 60 and are buried in the soil. Furthermore, the downstream of the branch pipe 52 is in contact with the building rebar 70 in the soil to form a conductive state. In this context, measurement of the ground resistance R ₁ of the main pipe 51 is performed by the following procedure

  First, as shown in FIG. 3A, the main pipe 51 and the branch pipe 52 (for example, the branch pipe 52a) are connected by the lead wire 3, and the external magnetic coil unit 31 and the current of the clamp ground resistance meter 30 are connected to the lead wire 3. A measuring means 33 is attached. Then, in accordance with the measurement principle described above, the series resistance R between the main pipe 51 and the branch pipe 52 is obtained from the total voltage E and the total current I. In this example, the external magnetic coil unit 31 was electromagnetically induced by the power source means 32 (1 kHz AC power source) built in the clamp ground resistance meter 30, and the ground resistance was obtained from the current flowing in the lead wire 3. As a result, the ground resistance value was 2980Ω.

Next, the clamp ground resistance meter 30 is removed, and as shown in FIG. 3B, the contact 7 provided on the lead wire 3 and the power ground wire 6 that can be used as the power supply electrode are connected by another lead wire 3 ′. Here, a power supply device 4 ′ (for example, an AC voltage of 500 Hz) is provided to apply a potential difference (for example, 29 V). At this time, the first current I ₁ flowing between the main pipe 51 and the contact 7 and the 21st current I ₂ flowing between the branch pipe 52 and the contact 7 were measured by the clamp ammeters 11 and 12, respectively. As a result, I ₁ = 0.1 mA and I ₂ = 11.5 mA.

Therefore, when the above equation (2) is applied, the ground resistance R ₁ of the main pipe 51 is
Ground resistance R ₁ = 2980Ω × 11.5 mA / (0.1 mA + 11.5 mA)
= 2954Ω
As required. Thus, in this embodiment, grounding resistance R ₁ of the main pipe 51 becomes a large value. From this result, it can be determined that the main pipe 51 is a cladding pipe.

  Thus, in the grounding resistance measuring method of the present invention, the grounding resistance in the buried portion of the utility pipe 50 is utilized by using a part of the utility pipe 50 exposed from the medium (for example, concrete wall or soil) in the basement. Can be easily measured. Therefore, it is not necessary to install an electrode on the medium in order to measure the ground resistance as in the prior art, and quick and easy measurement is possible. This also reduces the burden on the operator and improves the work efficiency. In order to obtain the ground resistance, it is necessary to obtain the series resistance of the utility tube 50. However, in the ground resistance measurement method of the present invention, a potential difference is applied to the utility tube 50 and the current flows at that time. The series resistance can be easily measured by a relatively simple operation of measuring the current.

  In the present invention, if a part of the utility pipe 50 composed of the main pipe 51 and the branch pipe 52 is exposed from the medium, the ground resistance can be measured regardless of whether or not both are conductive. Is possible.

  Furthermore, if the existing power ground wire 6 is used as a power supply electrode for measuring the ground resistance of the utility tube 50 as in the above embodiment, it is not necessary to install a power supply electrode for ground resistance measurement. Further work efficiency can be improved. Furthermore, it is also effective in that the cost for measurement can be reduced because the installation of the power supply electrode is unnecessary.

  The ground resistance measuring method of the present invention can be used for measuring ground resistance in various utility tubes. For example, it can be used to measure the ground resistance of gas pipes buried in the ground, water and sewage pipes, various cable pipes, etc., or various pipes concealed on the wall of a building.

The figure which shows the non-conductive buried object measurement model in case the 1st buried object and the 2nd buried object are not connected. The figure which shows the conduction | electrical_connection buried object measurement model in case the 1st buried object and the 2nd buried object are conducting. Schematic of a utility pipe that is buried with a part exposed in the basement

Explanation of symbols

1 First buried object 2 Second buried object 6 Power supply electrode (electric power ground wire)
7 Contact 10 Medium 20 Conductor

Claims (4)

A ground resistance measurement method for measuring a ground resistance of a first embedded object to be measured among a first embedded object and a second embedded object partially exposed from a medium,
Deriving a series resistance through the medium in the first embedded object and the second embedded object;
Providing a grounded power supply electrode to the medium, and applying a potential difference between the power supply electrode and a contact provided between the first embedded object and the second embedded object;
Measuring a first current flowing between the first embedded object and the contact and a second current flowing between the second embedded object and the contact;
And a step of dividing the series resistance by a ratio of the first current and the second current.   The step of calculating the series resistance includes a step of applying a potential difference between the first embedded object and the second embedded object, and a step of measuring an entire current flowing through the first embedded object and the second embedded object. The ground resistance measurement method according to claim 1, wherein the series resistance is derived from the potential difference and the total current.   The ground resistance measuring method according to claim 1 or 2, wherein the first embedded object and the second embedded object are electrically connected to each other through a conductor at an exposed portion.   The grounding resistance measuring method according to any one of claims 1 to 3, wherein the power supply electrode is an existing power ground wire.

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