JP5242455B2 - Electromagnetic induction voltage prediction method - Google Patents

Description

  The present invention relates to electromagnetic waves generated in a buried metal conductor or an overhead metal conductor laid adjacent to the AC overhead power transmission line or the AC electric railway due to magnetic flux density of the AC overhead power transmission line or the AC electric railway. The present invention relates to an induced voltage prediction method.

  As a means of transporting or supplying gas, water, oil, etc., it is common to embed a metal pipeline and use it. In order to prevent corrosion in the soil, the buried metal pipeline is usually coated with insulation. However, defects in the coating may occur and the surface of the metal pipeline may come into contact with the soil, and there is a concern about the progress of corrosion in such coating defects.

  Here, when a metal pipeline is buried close to an AC overhead power transmission line or an AC electric railway, the AC current being transmitted is affected by the magnetic field formed around it, An electromagnetic induction voltage is generated in the tube axis direction. Due to the generated electromagnetic induction voltage, a potential difference, that is, a ground AC potential is generated between the metal pipeline and the ground. As a result, an alternating current flows through the coating defect portion. When the alternating current in the coating defect is high, corrosion due to alternating current, that is, alternating stray current corrosion occurs. In addition, when the ground AC potential generated in the metal pipeline rises to a certain level, there is a possibility that an operator may be electrocuted by touching the metal pipeline during field work.

  One example of measures against such AC stray current corrosion and electric shock is a low grounding measure. Specifically, it is possible to disperse the ground by dispersing magnesium electrodes or the like and connecting them to a metal pipeline. As a result, the alternating current flows through the magnesium electrode, reduces the alternating current flowing through the coating defects, prevents alternating stray current corrosion, reduces the ground AC potential of the metal pipeline, Prevent electric shock.

  When a communication cable or a telephone line is laid close to an AC overhead power transmission line or an AC electric railway, noise is generated due to the influence of electromagnetic induction caused by the AC current transmitted in the same manner. Therefore, measures are taken such as securing a sufficient separation or applying a shielded cable.

  On the other hand, before burying a metal pipeline, theoretical formulas and computer simulation methods used for prediction have been proposed in order to predict the electromagnetic induction voltage that will occur in the metal pipeline, as well as the ground AC potential. (For example, refer nonpatent literature 1.).

  In addition, it has been proposed to predict an electromagnetic induction voltage generated in a metal pipeline and further a ground AC potential using a simple approximate expression (see, for example, Non-Patent Document 2).

  It has also been proposed to measure the magnetic flux density in the vicinity of the ground surface of the planned route for laying the metal pipeline to predict the electromagnetic induction voltage generated in the metal pipeline, and further to the ground AC potential (for example, (Refer nonpatent literature 3.).

Hiroshi Isogai, Akihiro Ameya, Yuji Hosokawa, IEEJ Transaction B, Vol. 126, No. 1, pp. 43-50, 2006 Yuji Hosokawa, Ryuji Koga, Hiroshi Isogai, Akihiro Ameya, AC induction evaluation of buried pipelines kept in high contact state, 53rd Materials and Environmental Discussion, B-306, pp. 241-244 (2006) Yuji Hosokawa, Ryuji Koga, Akihiro Amaya, Prediction of electromagnetic induction level of buried pipeline using magnetic sensor, 28th Rust and corrosion prevention technology presentation convention, 209, pp. 117-120 (2008)

  However, as described in Non-Patent Document 1, when the electromagnetic induction voltage is predicted using a theoretical formula, there are a large number of AC overhead power transmission lines, metal pipelines, communication cables, and AC overhead power transmission lines. If the positional relationship is not constant, there is a problem that the calculation becomes complicated. Furthermore, calculation is extremely difficult in a special environment where the periphery of a metal pipeline or the like laid in a steel shield is covered with a magnetic material. Even if the electromagnetic induction voltage generated in a metal pipeline or communication cable is predicted using a theoretical formula, if the electromagnetic induction voltage actually generated after laying the metal pipeline or communication cable is measured, the prediction There are many cases in which the values differ greatly.

  In addition, in the method using a simple approximate expression as described in Non-Patent Document 2, the apparent transmission current that contributes to electromagnetic induction must be estimated and set, and the actual transmission current becomes the apparent transmission current. If they are different, there is a problem that the error becomes large.

  Further, as described in Non-Patent Document 3, in the method of measuring the magnetic flux density in the vicinity of the planned installation route and predicting the electromagnetic induction voltage, the magnetic flux density is measured, the measured magnetic flux density is calculated, The electromagnetic induction voltage has to be evaluated through many processes such as measuring the positional relationship, and there has been a problem that advanced measurement techniques and calculation techniques are required.

  Therefore, for places where the occurrence of electromagnetic induction voltage is predicted in metal pipelines and communication cables, measures to reduce electromagnetic induction such as the installation of low grounded objects and the use of shielded cables when laying metal pipelines and communication cables in advance. It is common to implement. However, as described above, there are many problems in predicting the electromagnetic induction voltage generated in metal pipelines and communication cables. Therefore, it is not possible to place the grounding object with the proper ground resistance value or grounding object, and there are cases where the design is on the safe side or the grounding object is added due to insufficient measures. There was a problem that the cost of reducing electromagnetic induction was higher than necessary.

  In view of the above background, there has been a demand for a method that can easily and easily predict electromagnetic induction voltages generated in metal pipelines and communication cables, as well as ground AC potential, with high accuracy.

  Therefore, the present invention has been made in view of such problems, and its purpose is to predict the electromagnetic induction voltage generated in buried metal conductors or overhead metal conductors such as metal pipelines and communication cables with extremely high accuracy. An object of the present invention is to provide a new and improved electromagnetic induction voltage prediction method capable of predicting an electromagnetic induction voltage even in an environment where a conventional theoretical formula cannot be applied.

  In order to solve the above-mentioned problems, the inventors of the present application have conducted intensive research. Easily predict the electromagnetic induction voltage generated in buried metal conductors or overhead metal conductors after installation of buried metal conductors or overhead metal conductors by laying continuous conductors and measuring the potential difference between the ground at the ends. I realized that it was possible.

  The present invention has been completed based on such findings, and the gist of the present invention is as follows.

(1) Electromagnetic induction generated in a buried metal conductor or an overhead metal conductor laid adjacent to the AC overhead power transmission line or the AC electric railway due to the magnetic flux density of the AC overhead power transmission line or the AC electric railway An electromagnetic induction voltage prediction method for predicting a voltage before laying the buried metal conductor or the overhead metal conductor, wherein the voltage is electrically continuous with the ground surface of the planned route for the buried metal conductor or the overhead metal conductor. A continuous conductor that is a conductive conductor is measured, a potential difference between an arbitrary point of the continuous conductor laid on the ground surface and the ground is measured, and the buried metal conductor or the aerial metal conductor based on the obtained measurement value A method for predicting electromagnetic induction voltage, characterized by evaluating electromagnetic induction voltage of a route planned for installation.
(2) The laying planned route is divided into a plurality of sections, the continuous conductors are laid for each of the sections, and the continuous conductors laid in the sections adjacent to each other are laid in one section. Measuring the amplitude and phase difference of the potential difference generated between the end of the conductor and the end of the continuous conductor laid in the other section located on the side of the continuous conductor laid in the one section. The electromagnetic induction voltage prediction method according to (1), characterized in that it is characterized.
(3) The laying route is divided into a plurality of sections, the continuous conductors are laid for each of the sections, and the potential difference between one end of the continuous conductor laid in the section and the ground The amplitude and phase difference are measured, and the amplitude and phase difference of the potential difference between the ends of the continuous conductors laid in the sections adjacent to each other and the opposite ends of the continuous conductor are measured. The method for predicting electromagnetic induction voltage according to (1).
(4) The electromagnetic induction voltage prediction method according to any one of (1) to (3), wherein an end portion of the continuous conductor located at one end portion of the planned laying route is grounded. .
(5) A reference signal measuring means is fixed in the vicinity of the AC overhead power transmission line or the AC electric railway, and a phase difference between a potential difference measured by the potential difference measuring means and a signal measured by the reference signal measuring means The electromagnetic induction voltage prediction method according to any one of (2) to (4), characterized in that measurement is performed together.
(6) The electromagnetic induction voltage prediction method according to any one of (1) to (4), wherein a potential difference between the continuous conductor and the ground is continuously measured using a wheel electrode.
(7) Electromagnetic induction generated in the buried metal conductor or the overhead metal conductor laid adjacent to the AC overhead power transmission line or the AC electric railway due to the magnetic flux density of the AC overhead power transmission line or the AC electric railway An electromagnetic induction voltage prediction method for predicting a voltage before laying the buried metal conductor or the overhead metal conductor, wherein the voltage is electrically continuous with a ground surface of the planned route for laying the buried metal conductor or the overhead metal conductor. Laying a continuous conductor as a conductor, and measuring a potential difference between the continuous conductor laid on the ground surface and the ground in a state where a low-grounded object is connected to an arbitrary point of the continuous conductor; An electromagnetic induction voltage generated in a buried metal conductor or an overhead metal conductor, wherein the degree of reduction by the low grounding object of the ground AC potential generated in the metal conductor or the overhead metal conductor is predicted. Prediction method.

  According to the present invention, it is possible to predict an electromagnetic induction voltage generated in a buried metal conductor or an aerial metal conductor such as a metal pipeline or a communication cable without performing a complicated calculation, and apply a conventional theoretical formula. It is possible to predict the electromagnetic induction voltage with extremely high accuracy even in an environment where it was not possible.

It is explanatory drawing for demonstrating the electromagnetic induction voltage prediction method which concerns on the 1st Embodiment of this invention. It is explanatory drawing for demonstrating the electromagnetic induction voltage prediction method which concerns on the 2nd Embodiment of this invention. It is explanatory drawing for demonstrating the phenomenon of one end grounding. It is explanatory drawing for demonstrating the phenomenon of one end grounding. It is explanatory drawing for demonstrating the electromagnetic induction voltage prediction method which concerns on the 3rd Embodiment of this invention. It is explanatory drawing for demonstrating the electromagnetic induction voltage prediction method which concerns on the 4th Embodiment of this invention. It is explanatory drawing for demonstrating the example which uses a magnetic sensor as a reference signal of an alternating current voltmeter. It is explanatory drawing for demonstrating addition of the ground alternating current potential at the time of vector description. It is explanatory drawing for demonstrating addition of the ground alternating current potential at the time of vector description. It is explanatory drawing for demonstrating the electromagnetic induction voltage prediction method which concerns on the 5th Embodiment of this invention. It is explanatory drawing for demonstrating the electromagnetic induction voltage prediction method which concerns on the 6th Embodiment of this invention. It is explanatory drawing for demonstrating the electromagnetic induction voltage prediction method which concerns on the 7th Embodiment of this invention. It is explanatory drawing for demonstrating the positional relationship of a high voltage | pressure overhead power transmission line and a metal pipeline.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  In each of the embodiments of the present invention described below, the case where the buried metal pipeline is affected by electromagnetic induction from the AC overhead power transmission line will be described. It goes without saying that the same applies to cases where buried or aerial metal pipelines are affected by AC electric railways, and when communication cables that are buried or aerial are affected by AC overhead power transmission lines or AC electric railways. Yes.

(About the outline | summary of the electromagnetic induction voltage prediction method which concerns on each embodiment of this invention)
First, a case where a single-phase AC type AC overhead transmission line is provided in the transmission tower will be described with reference to FIG. 11, and an outline of the electromagnetic induction voltage prediction method according to each embodiment of the present invention will be described in detail. To do. FIG. 11 is an explanatory diagram for explaining the positional relationship between the AC overhead power transmission line and the metal pipeline.

  As shown in FIG. 11, the positional relationship between the AC overhead power transmission line A (white triangles in the figure) and the planned pipeline P for metal pipelines (white circles in the figure) is defined. . Further, a planned route for laying a metal pipeline (that is, an axial direction of the metal pipeline) is an x direction, a horizontal direction is a y direction, and a vertical method is a z direction.

Here, in FIG.
h _a : Height from the ground surface of the AC overhead power transmission line A h _p : Depth of the planned route P of the metal pipeline _yp : Horizontal from the AC overhead power transmission line A of the planned route P of the metal pipeline Separation distance a: A linear distance between the AC overhead power transmission line A and the planned route P of the metal pipeline.

  Further, in the calculation for predicting the electromagnetic induction voltage, it is necessary to consider the mirror image of the AC overhead transmission line A and the planned route P of the metal pipeline. When considering a mirror image, the ground surface is not a mirror surface, but a position below the ground surface by a depth called the ground penetration depth is a mirror surface. With this mirror plane as the symmetry plane, consider the mirror image A ′ of the AC overhead power transmission line A and the mirror image P ′ of the planned route P of the metal pipeline, and parameters for the mirror image A ′ of the AC overhead power transmission line A are as follows: Define.

h _e : Earth penetration depth b: Linear distance between AC overhead power transmission line A and mirror image P ′ of planned route P of metal pipeline

  Similarly, considering the continuous conductor Q laid on the ground surface and the mirror image Q ′ of the continuous conductor Q, the positional relationship with the AC overhead power transmission line A is defined as follows.

a ′: Linear distance between AC overhead power transmission line A and continuous conductor Q laid on the ground surface b ′: Linear distance between AC overhead power transmission line A and mirror image Q ′ of continuous conductor Q laid on the ground surface

As described above, the positional relationship between the AC overhead power transmission line A and the planned route P of the metal pipeline is defined, and the transmission current flowing through the AC overhead power transmission line A is _Ia. The electromagnetic induction voltage V _m is expressed by the following formula 101 using the transmission current I _a and the ground return mutual impedance Z _m between the metal pipeline and the AC overhead transmission line.

・・・（式１０１）

... (Formula 101)

Here, above the earth return mutual impedance Z _m, although exact solutions are given by Pollaczek, in the method according to the present embodiment, Ametani et al approximate expression obtained by modifying the approximate expression between overhead conductor according Deri et al ( Equation 102) is used.

・・・（式１０２）

... (Formula 102)

Here, in the above formula 102, j is the imaginary unit, omega power transmission current _{I a} of the angular frequency (= 2 [pi] f, a f = 50 Hz in the Kanto area, in Kansai is f = 60 Hz.) A, μ ₀ is the vacuum permeability (= 4π × 10 ⁻⁷ ). In addition, a is a linear distance between the AC overhead power transmission line A and the metal pipeline P as described above, and b is a linear distance between the AC overhead power transmission line A and the mirror image P ′ of the metal pipeline P. is there. The a and b are represented by the following formula 103 and formula 104, respectively.

・・・（式１０３）

・・・（式１０４）

... (Formula 103)

... (Formula 104)

In the above formula 104, _{h e} is a ground penetration depth as described above, the _{h e} is expressed by equation 105 below.

・・・（式１０５）

... (Formula 105)

Here, [rho _e is earth resistivity, for example, when 50Ωm the earth resistivity ρ _e, 356 (m) is obtained as an absolute value of _{h e.} Incidentally, h _e may use either of the complex or the absolute value thereof. In the following, a description will be given using an example in which absolute values are used.

Here, from Expression 101 and Expression 102, the following Expression 106 is obtained as an expression representing the electromagnetic induction voltage V _m .

・・・（式１０６）

... (Formula 106)

Here, in the formula _{106, a, b, h a} , h p , using the equation 103 and Formula 104, is a constant determined from the geometrical positional relationship between the metal pipeline, _{h e} is the earth resistance It is a value that can be calculated from the rate and the magnetic permeability of the vacuum.

Further, by accumulating the electromagnetic induction voltage V _m calculated using Expression 106 in the extension direction of the metal pipeline, the ground AC potential E _AC can be calculated as shown in Expression 107 below.

・・・（式１０７）

... (Formula 107)

The electromagnetic induction voltage V′m induced by the continuous conductor Q laid on the ground surface can be obtained in the same way, but here, the straight line between the AC overhead transmission line A and the planned route P of the metal pipeline The distances a and b, and the linear distances a ′ and b ′ between the AC overhead power transmission line A and the continuous conductor Q are larger than the depth hp of the planned pipeline P to be laid on the metal pipeline, and a≈a ′ and b≈ Considering b ′, the equation 108 is derived. That is, the electromagnetic induction voltage V′m induced in the continuous conductor Q laid on the ground surface on the laying route P of the metal pipeline can be approximated to the electromagnetic induction voltage V _m induced in the metal pipeline. it can. Further, by accumulating the electromagnetic induction voltage V ′ _m calculated by using the formula 108 in the extending direction of the continuous conductor Q, the ground AC potential E ′ _AC can be calculated by the following formula 109. .

・・・（式１０８）

・・・（式１０９）

... (Formula 108)

... (Formula 109)

As described above, to contribute to the induction voltage V _m to the metal pipe lines, geometrical positional relation, frequency, and are earth resistivity, the positional relationship between the AC overhead line is approximately the same If this is the case, even if it is a metal pipeline buried in the ground or a continuous conductor laid on the ground surface, an electromagnetic induction voltage of the same magnitude as shown in Equation 106 and Equation 107 is generated. To do. Accordingly, a continuous conductor such as a cable is laid on the ground surface in the vicinity of the planned installation route of the metal pipeline, and the electromagnetic induction voltage V ′ _m generated in the continuous conductor, that is, the ground AC potential E ′ _AC is measured. Thus, it is possible to predict the electromagnetic induction voltage V _m generated in the metal pipeline after laying, and further the ground AC potential E _AC .

  In addition, electrostatic induction can also be mentioned as an influence from AC overhead power transmission lines on metal pipelines and communication cables. However, when metal pipelines and communication cables are buried, the ground is covered with the earth. Therefore, it is not affected by electrostatic induction, and when it is laid on the ground surface, the influence of electrostatic induction is at a negligible level.

In the above description, the electromagnetic induction voltage V _m and the ground AC potential E _AC in the metal pipeline adjacent to the single-phase AC overhead transmission line have been described. Most of the actual AC overhead power transmission lines are multiphase, specifically, the three-phase AC system, but the handling is basically the same as the single phase.

  Based on the outline of the electromagnetic induction voltage prediction method as described above, specific examples of the electromagnetic induction voltage prediction method according to each embodiment of the present invention will be described in detail below.

(First embodiment)
First, the electromagnetic induction voltage prediction method according to the first embodiment of the present invention will be described in detail with reference to FIG. FIG. 1 is an explanatory diagram for explaining an electromagnetic induction voltage prediction method according to the present embodiment.

  The metal pipeline is generally electrically insulated from the surrounding soil by a highly insulating coating, and this metal pipeline is buried close to the AC overhead transmission line as shown in FIG. The case where this is done will be described below.

  In the electromagnetic induction voltage prediction method according to the present embodiment, a planned route 14 for laying a metal pipeline is set in the vicinity of the AC overhead power transmission line 12 stretched between the adjacent transmission tower 10 and the transmission tower 11. In this case, the electromagnetic induction voltage generated in the metal pipeline after laying, and also the ground AC potential are predicted before laying the metal pipeline.

  In the electromagnetic induction voltage prediction method according to the present embodiment, as shown in FIG. 1, using the continuous conductor 101 and the AC voltmeter 102 laid on the ground surface S, the AC potential difference between the continuous conductor 101 and the ground, that is, The AC potential to ground of the continuous conductor 101 is measured, and the electromagnetic induction voltage is predicted.

  The continuous conductor 101 is a continuous conductor made of a metal or a material having a high electrical conductivity. Specific examples thereof include a cable made of copper or aluminum. As the continuous conductor 101, for example, a belt-like member such as an iron plate can be used. However, in consideration of ease of handling, a metallic cable is preferable as the continuous conductor.

  Moreover, it is desirable to cover the continuous conductor 101 with a highly insulating coating so as not to be in electrical contact with the ground.

  In the electromagnetic induction voltage predicting method according to the present embodiment, the continuous conductor 101 as described above is laid along the planned laying route 14 of the metal pipeline, as shown in FIG.

  The AC voltmeter 102 is a voltmeter that measures a potential difference between the continuous conductor 101 and the ground, that is, an AC potential to the ground of the continuous conductor 101. The internal resistance of AC voltmeter 102 is preferably as large as possible. For example, it may be 1 MΩ or more.

  The verification electrode 103 is an electrode that is installed on the ground and measures the potential of the ground. Examples of such verification electrode 103 include, for example, a saturated copper sulfate verification electrode and a steel ground rod.

  As shown in FIG. 1, in the electromagnetic induction voltage predicting method according to the present embodiment, an AC voltmeter 102 is inserted between the end of the continuous conductor 101 and the verification electrode 103 installed on the ground. By installing the AC voltmeter 102 and the verification electrode 103 in this manner, the AC voltmeter 102 measures the potential difference between the end of the continuous conductor 101 and the verification electrode 103, that is, the ground AC potential of the continuous conductor 101. can do.

  As described above, in the electromagnetic induction voltage prediction method according to the present embodiment, the conductor 101 that is electrically continuous on the ground surface S is laid along the planned laying route 14 of the metal pipeline. A potential difference from the ground, that is, an AC potential to ground of the continuous conductor 101 is measured by an AC voltmeter 102. Thereby, it is possible to predict the electromagnetic induction voltage generated in the metal pipeline after laying, and further the ground AC potential before laying the metal pipeline.

  As a result, for metal pipelines and communication cables, laying of metal pipelines and communication cables by evaluating the necessity of electromagnetic induction countermeasures and designing appropriate measures when countermeasures are required. At the same time, appropriate electromagnetic induction reduction measures can be taken, and the costs for electromagnetic induction measures can be greatly reduced.

(Second Embodiment)
Next, an electromagnetic induction voltage prediction method according to the second embodiment of the present invention will be described in detail below with reference to FIGS. 2, 3A, and 3B. FIG. 2 is an explanatory diagram for explaining an electromagnetic induction voltage prediction method according to the present embodiment, and FIGS. 3A and 3B are explanatory diagrams for explaining a phenomenon of one-end grounding.

  The electromagnetic induction voltage prediction method according to the present embodiment is an AC overhead transmission stretched between adjacent power transmission towers 10 and 11 like the electromagnetic induction voltage prediction method according to the first embodiment of the present invention. When the planned route 14 of the metal pipeline is set in the vicinity of the electric wire 12, the electromagnetic induction voltage generated in the metal pipeline after installation, and further the AC potential to the ground, are set before the installation of the metal pipeline. It is a method to predict.

  In the electromagnetic induction voltage prediction method according to the present embodiment, for example, as shown in FIG. 2, one end of the continuous conductor 101 laid on the ground surface S is grounded (hereinafter referred to as “one-end grounding”). Thus, the ground AC potential generated in the metal pipeline after laying is predicted. 2 illustrates the case where the left end of the continuous conductor 101 is grounded, the end to be grounded is not limited to the example illustrated in FIG.

  When the continuous conductor 101 is grounded at one end, the AC potential to ground at the end on the side grounded at one end is zero. Therefore, the electromagnetic induction voltage generated in the entire length of the continuous conductor 101 and further the ground AC potential can be evaluated only by measuring the ground AC potential at the other end of the continuous conductor 101 that is not grounded.

  In the electromagnetic induction voltage prediction method according to the present embodiment, it is desirable that the grounding resistance of the ground object used for grounding one end of the continuous conductor 101 is smaller than the internal resistance of the AC voltmeter 102. For example, when the internal resistance of the AC voltmeter 102 is 1 MΩ, the ground resistance of the grounded object is preferably 1 kΩ or less. The smaller the ratio of the grounding resistance of the grounded object to the AC voltmeter 102, the more accurate the measurement of the ground AC potential.

Next, refer to FIG. 3A and FIG. 3B.
A continuous conductor 101 is laid for a length L [m] in parallel with the AC overhead power transmission line 12 stretched between the power transmission tower 10 and the power transmission tower 11, and the AC overhead power transmission line 12 and the continuous conductor 101 are connected to each other. If the separation is constant at all points in this section, the electromagnetic induction voltage generated at an arbitrary point of the continuous conductor 101 is also a constant value. If the electromagnetic induction voltage per unit length at this time is V _m , the electromagnetic induction voltage generated across the entire length of the continuous conductor 101 is V _m L.

At this time, as shown in FIG. 3A, when the continuous conductor 101 is insulated from the ground without being grounded, the AC potential to ground of the continuous conductor 101 is 0 at the center (that is, the position of L / 2 in FIG. 3A). Thus, the distribution increases as it goes to the end portion of the continuous conductor 101, and V _m L / 2 [V] is obtained at both end portions of the continuous conductor 101. The distribution shown in FIG. 3A corresponds to the distribution of measurement results in the electromagnetic induction voltage prediction method according to the first embodiment of the present invention.

On the other hand, as shown in FIG. 3B, when the continuous conductor 101 is grounded at one end, the ground AC potential of the continuous conductor 101 is 0 at the point where the one end is grounded, and monotonically as it goes to the other end. The distribution increases so that V _m L [V] is obtained at the other end.

Actually, the following is a comparison of measured and compared ground AC potential of a metal pipeline buried near an AC overhead transmission line and ground AC potential of a cable laid on the ground surface. For metallic pipeline measured the ground ac potential in terminal box T ₁ and T ₂ of the two locations provided in the metal pipe line. Here, the terminal box is a place where the lead wire connected to the metal pipeline rises up to the ground surface, and the ground AC potential can be measured. As for the cable, the cable from the terminal box T ₁ of the metal pipeline near the ground surface laid until T _2, further the end portion of the T ₁ near while one end grounded, T ₂ near the The edge AC potential was measured. Here, the distance between the terminal boxes T ₁ and T ₂ is 484 m.

The measurement results are shown in Table 1 and Table 2 below. From Table 1, the difference in ground alternating potential at terminal box T ₁ and T ₂ of the two portions of the metal pipeline was 3.8 V. On the other hand, ground alternating potential end of the T ₂ near the cable with one end grounded end of T ₁ near was 3.6V. As is apparent from this result, ground exchanges and the difference in potential, ground AC cable and one end grounded and laid on a metallic pipeline ground surface in the vicinity of the terminal box T ₁ and T ₂ of the two portions of the metal pipeline It can be seen that the potential is almost the same.

  Thus, it can be seen that the ground AC potential of the cable laid on the ground surface in the vicinity of the metal pipeline shows a good agreement with the ground AC potential actually generated in the metal pipeline.

(Third embodiment)
Next, an electromagnetic induction voltage prediction method according to the third embodiment of the present invention will be described in detail below with reference to FIG. FIG. 4 is an explanatory diagram for explaining an electromagnetic induction voltage prediction method according to the present embodiment.

In the electromagnetic induction voltage predicting method according to the present embodiment, a lead wire is attached to a point in the middle of the continuous conductor 101, and a voltage between the continuous conductor 101 and the ground at the point where the lead wire is attached, that is, a ground AC potential is measured. Is the method. More specifically, for example, as shown in FIG. 4, one end of the continuous conductor 101 laid on the ground surface S is grounded, and an arbitrary point (P _i , 1 in FIG. ≦ i ≦ n), a lead wire is attached, and the lead wire is connected to the AC voltmeter 102. Further, a collation electrode 103 is installed near the point where the lead wire is attached and connected to the AC voltmeter 102.

In this way, not only the end of the continuous conductor 101, can be measured to ground AC voltage of an arbitrary point P _i of the continuous conductor 101, knowing the details of the distribution of ground alternating potential at any point of the continuous conductor 101 it can.

(Fourth embodiment)
Next, an electromagnetic induction voltage prediction method according to the fourth embodiment of the present invention will be described in detail below with reference to FIGS. 5, 6, 7A, and 7B. FIG. 5 is an explanatory diagram for explaining an electromagnetic induction voltage prediction method according to the present embodiment, and FIG. 6 is an explanatory diagram for explaining an example in which a magnetic sensor is used as a reference signal for an AC voltmeter. 7A and 7B are explanatory diagrams for explaining the addition of the ground AC potential in the vector notation.

  In the electromagnetic induction voltage prediction method according to the present embodiment, a plurality of continuous conductors 101 are used, or the continuous conductor 101 is used a plurality of times, and the ground AC potential of the continuous conductor 101 is measured.

  When the extension of the planned route of the metal pipeline is long, if the total extension of the planned route of the metal pipeline is to be measured with one continuous conductor 101, a large amount of the continuous conductor 101 is required or installed. Problems such as difficulty in managing the continuous conductor 101 occur. Therefore, by dividing the planned route for laying the metal pipeline into a plurality of short sections and using the plurality of continuous conductors 101 or the plurality of continuous conductors 101 multiple times, it is possible to easily measure the ground AC potential of the continuous conductor 101. It becomes possible.

FIG. 5 shows an electromagnetic induction voltage generated in a metal pipeline by dividing a planned route for laying a metal pipeline into n short sections and laying n continuous conductors 101 on the ground surface of each section. Furthermore, it shows about the case where prediction of ground AC potential is performed. On the planned installation route of the metal pipeline, one continuous conductor 101 is installed in each section, and a total of n continuous conductors 101 are installed. For section 1, the end of point P _{0 of} continuous conductor 101 is grounded, the other end of point P ₁ of continuous conductor 101 is connected to AC voltmeter 102 with a lead wire, and AC voltmeter 102 is connected to the ground. The installed verification electrode 103 is connected with a lead wire.

For the section 2 adjacent to the section 1, the end of the point P ₁ on the side of the continuous conductor 101 facing the continuous conductor 101 in the section 1 is directly connected to the verification electrode 103. The verification electrode 103 is used for the purpose of grounding the continuous conductor 101. In FIG. 5, the end of the continuous conductor 101 at the point P ₁ in the section 2 is connected to the reference electrode 103 connected to the AC ammeter 102 connected to the continuous conductor 101 in the section 1. Another verification electrode 103 or a low grounding object may be installed. Furthermore, the end of the other P ₂ points of the continuous conductors 101 of the section 2 is connected to the AC voltmeter 102 at leads, furthermore, connected to the reference electrode 103 is installed on the ground. Similarly, a circuit is formed for the continuous conductor 101 from the section 3 to the section n.

First, measure the ground alternating potential E _AC1 continuous conductor 101 of P ₁ point in the case relative to the P ₀ point using a continuous conductor 101 laid in sections 1. Next, measure the ground alternating potential E _AC2 continuous conductor 101 of P ₂ points when the reference _point P using a continuous conductor 101 laid in sections 2. The same measurement is repeated up to the section n, and the ground AC potential E _ACi of the continuous conductor 101 in each divided section is sequentially measured. By adding the ground AC potential E _ACi of the continuous conductor 101 in each section obtained by such measurement, the ground AC potential E _AC generated for the entire extension of the metal pipeline after laying is predicted.

Furthermore, for example, for the period 1 to period 3, by adding the ground alternating potential E _ACi of continuous conductor 101 of each section, ground alternating potential of the continuous conductor 101 of P ₃ points when based on the P ₀ points As described above, the ground AC potential of the metal pipeline generated at any other point can be obtained using any point of the metal pipeline as a reference point.

  The AC voltmeter 102 used at this time has a synchronous detection function. Here, synchronous detection refers to a method of detecting a correlation by multiplying a received signal by a signal (synchronous signal) that matches the period of a signal to be detected. The synchronization signal is also referred to as a reference signal and may be generated from a crystal resonator or the like inside the AC voltmeter 102 or may be used by inputting a signal from the outside of the AC voltmeter 102. By using the AC voltmeter 102 having the synchronous detection function, in addition to the amplitude of the ground AC potential of the continuous conductor 101, the phase is also measured.

  FIG. 6 shows an example in which the magnetic flux density generated from the AC overhead power transmission line 12 is used as a reference signal input from the outside to the AC voltmeter 102 having the synchronous detection function. In the AC voltmeter 102, an AC voltage from a reference magnetic sensor 106, which is an example of a reference signal measuring means installed near the AC overhead power transmission line 12, is input as a reference signal. In the AC voltmeter 102, the component synchronized with the waveform of the AC voltage input from the reference magnetic sensor 106 in the ground AC potential of the continuous conductor 101 is measured by synchronous detection, and the ground AC potential of the continuous conductor 101 is measured. The amplitude and the phase difference from the AC voltage from the reference magnetic sensor 106 are obtained. Thereby, it becomes possible to measure the phase based on the magnetic flux density generated from the AC overhead power transmission line 12.

  Here, the AC voltage from the reference magnetic sensor 106 is an example of a reference signal. The reference signal that can be used in the present embodiment is not limited to the AC voltage from the reference magnetic sensor 106, but is output along with an output signal from an ammeter installed in the AC overhead power transmission line or the AC overhead power transmission line. Any signal can be used as long as it is a signal generated due to an alternating current flowing through the AC overhead power transmission line, such as a ground AC potential induced in a cable laid on the ground surface.

When the phases of the ground AC potentials E _{AC1 to} E _ACn of the continuous conductor 101 in each section are the same, the amplitude of the ground AC potential | E _ACi | is sequentially added to make the metal from the point P ₀ as a reference. The AC potential E _ACn to the ground of the continuous conductor 101 at the terminal point P _{n of the} pipeline laying planned route can be obtained. That is, it is possible to predict the ground AC potential generated in the metal pipeline at the terminal point P _{n of the} planned route for laying the metal pipeline when the point P ₀ is used as a reference.

On the other hand, when the phase of the ground AC potentials E _{AC1 to} E _ACn of the continuous conductor 101 in each section is different, a vector is obtained from the amplitude and phase of the ground AC potential E _ACi , and the respective vectors are added to obtain P ₀ point. The E _ACn of the continuous conductor 101 at the end point P _{n of the} planned route for laying the metal pipeline when used as a reference can be obtained. That is, it is possible to predict the ground AC potential generated in the metal pipeline at the terminal point P _{n of the} planned route for laying the metal pipeline when the point P ₀ is used as a reference.

As an example, the ground AC potential E _AC1 of the continuous conductor 101 obtained in the section ₁ and the ground AC potential E _AC2 of the continuous conductor 101 obtained in the section 2 are added to obtain the ground AC potential E of the continuous conductor 101. _respect, the influence of the phase difference between _{E AC1} and _{E AC2} give, will be described with reference to FIGS. 7A and 7B.

7A _is when the phase difference of the phase theta ₂ phase theta ₁ and _{E AC2} of _{E AC1} is _small, shows a ground alternating potential E derived by adding the _{E AC1} and _{E AC2.} Here, the phases θ ₁ and θ ₂ are angles formed by the vector and the real axis Re. As shown in FIG. _7A, when the phase difference of the phase theta ₂ phase theta ₁ and _{E AC2} of _{E AC1} is small, the amplitude of E will be close to the value obtained by adding the amplitudes of the _{E AC2 E-AC1.} That is, | E | ≈ | E _AC1 | + | E _AC2 |

On the other hand, FIG. 7B, E in the case of a large phase difference between the _two 'phases θ of _{AC2' 1} and E 'phase θ of _AC1', E _'AC1 and E' _AC2 and ground AC potential E derived by adding the ' Is shown. Here, the amplitude and phase of E ′ _AC1 are equal to E _AC1 shown in FIG. 7A (ie, | E ′ _AC1 | = | E _AC1 |, θ ′ ₁ = θ ₁ ), and the amplitude of E ′ _AC2 Is equal to E _AC2 shown in FIG. 7A (that is, | E ′ _AC2 | = | E _AC2 |). As shown in FIG. 7B, when the phase difference between _two 'phases θ of _{AC2' 1} and E 'phase θ of _AC1' E is large, E 'amplitude of E' smaller than the amplitude of _AC1 and amplitude and E _'AC2 May be.

Thus, when the phase difference of the ground AC potential of the continuous conductor 101 in each section is small, the ground AC potential E _AC of the continuous conductor 101 tends to monotonously increase toward the end of the planned route for laying the metal pipeline. . That is, the ground AC potential generated in the metal pipeline toward the end of the planned route for laying the metal pipeline tends to increase monotonously. On the other hand, when the phase difference of the ground AC potential of the continuous conductor 101 in each section is large, the ground AC potential E _AC of the continuous conductor 101 does not increase but decreases toward the end of the planned route for laying the metal pipeline. There is also. That is, the ground AC potential generated in the metal pipeline toward the end of the planned route for laying the metal pipeline does not increase but may decrease.

  In the present embodiment, the collation electrode 103 serves as both a collation electrode for measuring the ground AC potential of the continuous conductor 101 and a ground electrode for one-end grounding. Therefore, it is desirable that the ground resistance of the verification electrode 103 is smaller than the internal resistance of the AC voltmeter 102. For example, when the internal resistance of the AC voltmeter 102 is 1 MΩ, the ground resistance of the verification electrode 103 is preferably 1 kΩ or less. The smaller the ratio of the ground resistance of the verification electrode 103 to the AC voltmeter 102 is, the more accurate the measurement of the alternating current potential to the ground of the continuous conductor 101 is, and it also serves as a grounded object with one end grounded.

  Thus, by measuring the phase together with the amplitude of the ground AC potential of the continuous conductor 101, it is possible to accurately predict the distribution of the ground AC potential generated in the metal pipeline.

(Fifth embodiment)
Next, an electromagnetic induction voltage prediction method according to the fifth embodiment of the present invention will be described in detail below with reference to FIG. FIG. 8 is an explanatory diagram for explaining an electromagnetic induction voltage prediction method according to the present embodiment.

  Instead of grounding one of the continuous conductors 101 as in the second embodiment of the present invention, as shown in FIG. 8, the planned route for laying the metal pipeline is divided into a plurality of short sections, and a plurality of continuous conductors are divided. By laying the conductor 101 and measuring the ground AC potential at both ends of each continuous conductor 101, it is possible to predict the electromagnetic induction voltage generated in the metal pipeline and further the ground AC potential.

  In this case, as shown in FIG. 8, AC voltmeters 102 are installed at both ends of each continuous conductor 101, and verification is performed between the AC voltmeters 102 provided at the ends of continuous conductors 101 adjacent to each other. The electrode 103 is installed.

  Here, when the ground AC potential of the continuous conductor 101 is measured by the method shown in FIG. 8, the ground AC potential of the continuous conductor 101 becomes high at both ends of the continuous conductor 101 as shown in FIG. 3A. Show the distribution. Therefore, the ground AC potential of the continuous conductor 101 in all sections is obtained by adding all the ground AC potentials at both ends of the continuous conductor 101 in each section.

(Sixth embodiment)
Next, an electromagnetic induction voltage prediction method according to the sixth embodiment of the present invention will be described in detail below with reference to FIG. FIG. 9 is an explanatory diagram for explaining an electromagnetic induction voltage prediction method according to the present embodiment.

  Wheel electrodes 104 as shown in FIG. 9 can be used instead of inserting the verification electrode 103 into the ground and installing it as in the electromagnetic induction voltage prediction method according to each embodiment of the present invention described above. Hereinafter, a method of using the wheel electrode 104 instead of the verification electrode 103 will be described.

  In the electromagnetic induction voltage prediction method according to the present embodiment, for example, as shown in FIG. 9, one end of the continuous conductor 101 is grounded, and the other end of the continuous conductor 101 is connected to the wheel electrode 104. An AC voltmeter 102 is disposed between the continuous conductor 101 and the wheel electrode 104. Thereafter, the continuous conductor 101 is laid along with the movement of the wheel electrode 104. Thereby, it becomes possible to continuously measure the ground AC potential of the continuous conductor 101 at an arbitrary point. Also, by using this method, the ground AC potential distribution of the continuous conductor 101 can be grasped in detail.

  Here, for the wheel electrode 104, for example, conductive rubber or the like is used. Moreover, it is possible to improve the measurement accuracy of the alternating current ground potential of the continuous conductor 101 by spraying water on the ground and reducing the contact resistance between the wheel electrode 104 and the ground.

  Moreover, the continuous conductor 101 can be easily laid on the ground surface S by moving the continuous conductor 101 while being wound around a cable reel or the like. When the cable reel is used, if the end of the continuous conductor 101 and the wheel electrode 104 are connected by a cable, the cable may be twisted. In order to prevent this, for example, when a slip ring or the like is used, the continuous conductor 101 and the wheel electrode 104 can be easily electrically connected without causing twisting of the cable.

(Seventh embodiment)
Next, an electromagnetic induction voltage prediction method according to the seventh embodiment of the present invention will be described in detail below with reference to FIG. FIG. 10 is an explanatory diagram for explaining an electromagnetic induction voltage prediction method according to the present embodiment.

  When a large ground AC potential is observed in the continuous conductor 101 by the electromagnetic induction voltage prediction method according to each of the embodiments described above, a low-grounded object is connected to the metal pipeline to be laid as a countermeasure for reducing electromagnetic induction. Measures need to be taken.

  For example, when an electromagnetic induction reduction measure is applied to a steel pipeline as an example of a metal pipeline, an Mg anode is buried in the vicinity of the steel pipeline as a low grounded object, and the Mg anode is connected to the steel pipeline. In general, a connection method using lead wires is used. The Mg anode is originally intended to be connected to a steel pipeline as a sacrificial anode for applying anticorrosion to a steel pipeline, but it can also be used as a low grounding material to reduce electromagnetic induction at the same time. . For example, when terminal boxes are installed at intervals of several hundred meters in steel pipelines, Mg anodes are embedded in the vicinity of a plurality of terminal boxes, and each is connected to the steel pipelines in a distributed manner. Grounding is ensured and the ground AC potential of the steel pipeline can be effectively reduced.

  However, even if the Mg anode is grounded, the ground AC potential of the steel pipeline does not decrease sufficiently, or even if the ground AC potential of the steel pipeline decreases at the terminal near the Mg anode grounded, A phenomenon may occur where the AC potential of the terminal steel pipeline increases. This is because the resistivity of the soil in which the steel pipeline is embedded differs depending on the location, so even if the same Mg anode is used, the ground resistance of the Mg anode varies, and the AC overhead power transmission line and the steel pipeline There is a possibility that the magnitude of the influence of electromagnetic induction varies depending on the location because the distance between them is not constant. For this reason, it is difficult to quantitatively predict the low grounding conditions necessary for electromagnetic induction reduction measures before laying a metal pipeline, including a steel pipeline.

  Therefore, an arbitrary point of the continuous conductor 101 laid on the ground surface on the planned route for laying the metal pipeline is connected to a low-grounded object, and the ground AC potential of the continuous conductor 101 with the low-grounded object connected is measured. By doing so, the ground AC potential of the metal pipeline when the low-grounded object is connected to the metal pipeline after laying is predicted.

More specifically, for example, as shown in FIG. 10, a lead wire is attached to an arbitrary point (P _Ri , 1 ≦ i ≦ n in FIG. 10) of the continuous conductor 101 laid on the ground surface S, and the resistance value r Connect a low grounded object with _i . Furthermore, a lead wire is attached to an arbitrary point (P _{Vj in} FIG. 10, 1 ≦ j ≦ m) of the continuous conductor 101, and an AC voltage between the reference electrode 103 installed in the vicinity of the point where the lead wire is attached. A total 102 is connected, and the AC potential of the continuous conductor 101 to ground is measured. In this state, the measured AC potential to the ground of the continuous conductor 101 is a value obtained when the low-grounded object 105 installed at the same place with the same resistance value is connected to the metal pipeline after laying the metal pipeline. Corresponds to pipeline AC potential. That is, it is possible to predict the reduction effect of the ground AC potential of the metal pipeline when the low grounding object 105 is connected to the metal pipeline before laying the metal pipeline.

By using this method, the measurement of the AC potential to ground of the continuous conductor 101 is repeated while changing the connection position of the low grounding object 105 and the resistance value r _i when the low grounding object 105 is connected. The optimum grounding condition of the low grounding object 105 is found so that the AC ground potential distribution of the ground becomes the smallest. That is, it can be said that the grounding condition at this time is the optimum grounding condition in the metal pipeline to be laid. By such a method, it is possible to predict an optimum grounding condition for the metal pipeline before laying the metal pipeline.

(Summary)
As described above, according to the method for predicting electromagnetic induction voltage according to the present invention, there are a plurality of AC overhead power transmission lines, and the positional relationship between the AC overhead power transmission lines and the metal pipeline is complex, Without complicated calculations, it is possible to predict the electromagnetic induction voltage generated in the metal pipeline, and further to the ground AC potential with high accuracy.

  In addition, it has been extremely difficult to predict the electromagnetic induction voltage generated in a metal pipeline laid in a special environment such as a steel shield in a deep underground, but the electromagnetic prediction according to the present invention is difficult. By using the method of predicting the induced voltage, it is possible to predict the electromagnetic induced voltage generated in the metal pipeline laid in the special environment, and further the ground AC potential.

  The method for predicting electromagnetic induction voltage according to the present invention is mainly intended for AC overhead transmission lines with commercial frequencies of 50 Hz and 60 Hz in Japan, but the present invention is limited to commercial frequencies. Needless to say, the present invention can also be applied to AC frequencies other than commercial frequencies.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this example. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  For example, in the above-described embodiment, the case of a metal pipeline has been described. However, even in the case of a communication cable that is aerial or buried, a communication cable that is provided in a deep underground shield, etc., electromagnetic induction voltage, Furthermore, it is possible to calculate a predicted value of the ground AC potential.

10, 11 Transmission tower 12 AC overhead power transmission line 14 Metal pipeline planned route 101 Continuous conductor 102 AC voltmeter 103 Reference electrode 104 Wheel electrode 105 Low-grounded object 106 Magnetic sensor S Ground surface

Claims (7)

Due to the magnetic flux density of the AC overhead power transmission line or AC electric railway, electromagnetic induction voltage generated in the buried metal conductor or the overhead metal conductor laid adjacent to the AC overhead power transmission line or the AC electric railway, A method for predicting electromagnetic induction voltage to be predicted before laying the buried metal conductor or the aerial metal conductor,
Laying a continuous conductor that is an electrically continuous conductor on the ground surface of the planned route for laying the buried metal conductor or the aerial metal conductor,
Measure the potential difference between any point of the continuous conductor laid on the ground surface and the ground,
An electromagnetic induction voltage prediction method characterized by evaluating an electromagnetic induction voltage of a route planned to lay the buried metal conductor or the overhead metal conductor based on the obtained measurement value. Dividing the planned laying route into a plurality of sections, laying the continuous conductor for each division,
For the continuous conductors laid in the sections adjacent to each other, the end of the continuous conductor laid in one section and the continuous conductors laid in the one section of the continuous conductor laid in the other section The electromagnetic induction voltage prediction method according to claim 1, wherein an amplitude and a phase difference of a potential difference generated between the end portion located on the side are measured. Dividing the planned laying route into a plurality of sections, laying the continuous conductor for each division,
Measure the amplitude and phase difference of the potential difference between the end of one of the continuous conductors laid in the section and the ground, and on the opposite sides of the continuous conductors laid in the sections adjacent to each other The electromagnetic induction voltage prediction method according to claim 1, wherein the amplitude and phase difference of the potential difference between the end and the ground are measured. The electromagnetic induction voltage prediction method according to claim 1, wherein an end portion of the continuous conductor located at one end portion of the planned laying route is grounded. A reference signal measuring means is fixed in the vicinity of the AC overhead power transmission line or the AC electric railway,
5. The electromagnetic induction voltage according to claim 2, wherein a phase difference between a potential difference measured by the potential difference measuring unit and a signal measured by the reference signal measuring unit is measured together. Prediction method. The electromagnetic induction voltage prediction method according to claim 1, wherein a potential difference between the continuous conductor and the ground is continuously measured using a wheel electrode. Due to the magnetic flux density of the AC overhead power transmission line or AC electric railway, electromagnetic induction voltage generated in the buried metal conductor or the overhead metal conductor laid adjacent to the AC overhead power transmission line or the AC electric railway, An electromagnetic induction voltage prediction method for predicting before laying the buried metal conductor or the aerial metal conductor,
In the state where a continuous conductor which is an electrically continuous conductor is laid on the ground surface of the planned installation route of the buried metal conductor or the aerial metal conductor, and a low grounding object is connected to an arbitrary point of the continuous conductor, A potential difference between the continuous conductor laid on the ground surface and the ground is measured, and a degree of reduction by the low grounding object of the ground AC potential generated in the buried metal conductor or the overhead metal conductor after laying is predicted. An electromagnetic induction voltage prediction method.

Images