JP2010281234A - Method and device for suppressing rise in potential of steel tower leg - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost method and a device for suppressing a rise in potential, surely suppressing the rise in the potential of a tower leg by a simple structure such that a loop conductor or a tabular conductor is connected to the periphery of the anchor portion or base portion of the steel tower leg. <P>SOLUTION: In a structure including the base portion 20 buried in the ground and the anchor portion 11 fixed to the base portion 20, the loop conductor 30 or the tabular conductor is connected to the surface of the anchor portion 11 or the surface of the base portion 20, and induced current in a direction canceling lightning current flowing onto the ground from the steel tower leg through the anchor portion 11 or the base portion 20 is conducted to the loop conductor 30 or tabular conductor. Thereby, it is possible to suppress a steep rise in the potential of the steel tower leg 10. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a suppression method and a suppression device for suppressing an increase in potential of a steel tower base (hereinafter also simply referred to as a tower base) such as a wind power generation system.

In a wind power generation system, if a lightning current that sharply increases the wave front part flows from the tower base to the ground due to a lightning strike to a steel tower to which the wind power generator is grounded, the potential due to the wave head part of the lightning current is caused by the inductance component of the ground point. The rising value may be significantly larger than the wave tail.
Here, FIG. 13 (a) is a waveform diagram showing an example of a lightning current flowing from the tower base of the wind power generation system to the ground, and FIG. 13 (b) is a waveform diagram showing the potential of the grounding point due to the lightning current. It can be seen that a steep increase in potential corresponding to the wavefront portion of the lightning current occurs due to the inductance component of the anchor portion for fixing the leg and the foundation portion in the ground.

  Due to the above potential increase, an overvoltage is applied between the power, communication and control equipment installed in or near the tower base of the wind power generation system and the conductor drawn from the outside. It is described in Non-Patent Documents 1 and 2 that damage occurs.

  On the other hand, in Patent Document 1, in order to suppress an increase in ground potential at the time of a lightning strike in a wind power generation system, a reinforcing bar provided at a base portion of a steel tower is grounded and separated sufficiently beyond an equivalent radius of the base portion. It is described that the composite grounding resistance is reduced by embedding a plurality of grounding electrodes at a predetermined position.

JP 2004-225660 A (paragraphs [0027] to [0031], [0076] to [0082], FIG. 9, FIG. 10, etc.)

Kazuo Yamamoto et al., "Experimental study on lightning overvoltage of wind power generation system using reduced model" (The Institute of Electrical Engineers of Japan B, vol. 126, No. 1, pp. 65-72, January 2006) Kazuo Yamamoto et al., “Experimental study on lightning overvoltage of wind power generation system-Reduction model experiment in actual soil” (The Institute of Electrical Engineers of Japan B, vol. 126, No. 12, pp. 1230-1238, December 2006)

In the prior art described in Patent Document 1, there is a problem that a lot of labor and cost are required for the connection work between the bar arrangement and the plurality of grounding electrodes and the work for burying the grounding electrodes.
Therefore, the problem to be solved by the present invention is that the potential increase of the tower pedestal is reliably suppressed and reduced by a simple structure in which a loop or flat conductor is connected to the surface of the anchor part or the base part for fixing the tower pedestal. An object of the present invention is to provide a potential rise suppression method and a suppression device that can be realized at a low cost.

In order to solve the above-described problem, a method for suppressing the potential increase of a tower pier according to claim 1 is embedded in the ground in order to fix the foundation tower buried in the ground and the tower tower base. In a structure provided with an anchor part,
When a conductor is connected to the surface of the anchor part or the surface of the foundation part, when a lightning current flows from the tower tower base to the ground through the anchor part or the foundation part, the lightning current is generated by electromagnetic induction. An induced current in a direction to cancel is passed through the conductor to suppress an increase in the potential of the tower tower base.

The tower tower pedestal potential rise suppressing device according to claim 2 includes a foundation part buried in the ground and an anchor part buried in the ground to fix the tower tower base to the foundation part. In structure
A conductor is connected to the surface of the anchor part or the surface of the foundation part, and an induced current is passed through the conductor in a direction to cancel lightning current flowing from the tower tower base through the anchor part or the foundation part to the ground. , It suppresses the potential rise of the tower pedestal.

The apparatus for suppressing an increase in potential of a tower pedestal according to claim 3 is the apparatus for suppressing an increase in potential according to claim 2,
The conductor is connected to the surface of the anchor portion or the surface of the base portion, and forms a closed circuit together with the surface of the anchor portion or the surface of the base portion, and magnetic flux generated by lightning current is chained to the internal space. It is a linear loop conductor that intersects.

The apparatus for suppressing an increase in potential of a steel tower base according to claim 4 is the apparatus for suppressing an increase in potential according to claim 2,
The conductor is a flat conductor that is connected to the surface of the anchor portion or the surface of the base portion and in which magnetic flux generated by lightning current is linked.

The apparatus for suppressing an increase in potential of a steel tower base according to claim 5 is the apparatus for suppressing an increase in potential according to claim 3,
The anchor portion is constituted by a rod-shaped member, and a plurality of the loop conductors are connected radially to the outer peripheral surface thereof at equal intervals.

The apparatus for suppressing an increase in potential of a steel tower base according to claim 6 is the apparatus for suppressing an increase in potential according to claim 4,
The anchor portion is composed of a rod-shaped member, and a plurality of the flat plate conductors are connected radially to the outer peripheral surface at equal intervals.

According to the present invention, the direction of canceling the lightning current flowing from the tower base to the anchor part or the base part by connecting the loop conductor or the flat plate conductor to the surface of the anchor part or the base part in the ground for fixing the tower tower base. Inductive current can be flowed, and a steep potential rise of the tower base due to the inductance component of the anchor portion or the base portion can be suppressed.
Further, the present invention is useful for reducing the steady ground resistance value of the tower base, in addition to the suppression of the steep potential increase due to the lightning current described above.

It is a figure which shows the schematic structure of this invention. It is a figure for demonstrating the suppression principle of the electric potential rise by this invention. It is the figure which showed the analysis space of the FDTD method with the analysis model. It is explanatory drawing of the dimension of a loop conductor and a flat conductor. It is a wave form chart of injection current used for analysis. It is explanatory drawing of the connection position of the loop conductor or flat plate conductor used for the analysis. It is a graph which shows the electric potential rise value about each case from which the connection position of a conductor differs. It is a graph which shows the electric potential rise value about each case from which the kind of conductor differs. It is a graph which shows the maximum value of an electric potential rise value when changing the length of one side about a loop conductor. It is a graph which shows the maximum value of the electric potential rise value when changing the length of one side about a flat conductor. It is a graph which shows the maximum value of the electric potential rise value when changing the length of one side about a loop conductor. It is a graph which shows the maximum value of the electric potential rise value when changing the length of one side about a flat conductor. It is a wave form diagram (Drawing 13 (a)) which shows an example of the lightning current which flows into the ground from the tower base of a wind power generation system, and a wave form diagram (Drawing 13 (b)) which shows the potential of the grounding point by the above-mentioned lightning current.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, FIG. 1 is a schematic diagram showing the configuration of the present invention. In this invention, as shown in FIG. 1, the anchor part 11 embed | buried in the ground is being fixed to the tower base 10 of the steel tower which comprises a wind power generation system, The surface of this anchor part 11, or the foundation part 20 A loop conductor 30 or a flat conductor (not shown) for supplying an induced current that cancels the lightning current is connected to the surface of the substrate. Here, strictly speaking, the loop conductor 30 is not formed in a loop shape (annular shape) but is formed in, for example, a U-shape, and forms a closed circuit in combination with the surface of the anchor portion 11 or the like to which the loop conductor 30 is connected. In this specification, as long as such a function is achieved, it is referred to as a loop conductor. In this case, the anchor part 11 and the foundation part 20 connected to the loop conductor 30 or the flat conductor are made of, for example, reinforced concrete.
In FIG. 1, a and b indicate the length of each side of the loop conductor 30, and X, Y, and Z indicate three-dimensional directions.

FIG. 2 is a diagram for explaining the principle of suppressing the rise in potential according to the present invention.
Now, it is assumed that a lightning current flows through the tower pedestal 10 and a current I ₁ flows through the anchor portion 11 electrically connected to the tower pedestal 10 as illustrated. Note that the current I ₁ has a waveform in which the wave front portion sharply increases as described above.
When the magnetic flux Φ is generated in the internal space of the loop conductor 30 by the current I ₁ , an electromotive force is generated in the loop conductor 30 so as to generate the magnetic flux Φ ′ in the direction to cancel the magnetic flux Φ according to Lenz's law, and the induced current I ₂ Flows.

As a result, a current (I ₁ -I ₂ ) flows on the surface of the anchor portion 11 to which the loop conductor 30 is connected, and the anchor portion 11 and the foundation are compared with the case where the loop conductor 30 is not connected. The transient potential increase due to the inductance component of the unit 20 is suppressed.
Here, as shown in FIG. 1, the loop conductors 30 may be arranged radially at equal intervals from each other at a plurality of locations (for example, 4 locations, 8 locations, etc.) on the outer peripheral surface around the axis of the anchor portion 11. desirable.

The effect of suppressing the potential increase described above depends on the magnitude of the induced current I ₂ , in other words, depends on the type, connection position, size, etc. of the loop conductor 30 or the flat conductor.
For this reason, the inventor analyzed the effect of suppressing the potential increase in various cases by the following method.

As an analysis method, an FDTD (Finite Difference Time Domain) method which is one of numerical electromagnetic field analysis methods was used. This FDTD method is described in, for example, “Understanding electromagnetic field and antenna analysis by FDTD method” by Koyo Uno (Corona, 1986).
FIG. 3 is a view showing an analysis space of the FDTD method together with an analysis model (consisting of a tower base 10, an anchor portion 11, a base portion 20, a loop conductor 30 or a flat conductor). As for the size of the analysis space 50, the length in each direction of X, Y, and Z was 50 [m], and the step size of the space was 0.5 [m] in all directions. The six faces surrounding the analysis space 50, which is a cube, simulate an open space using a secondary Liao absorption boundary condition. The earth is expressed by filling a substance having a resistivity ρ = 100 [Ω · m] up to a height of Z = 20 [m]. Reference numeral 60 denotes a current injection line connected to the tower base 10.

As loop conductor 30, Y.Baba, N.Nagaoka, A.Ametani, “Modeling of the wires in a lossy medium for FDTD simulation”, IEEE Transaction on Electromagnetic Compatibility, Vol.47, Issue 1, pp. 54-60 The thin wire conductor model described in (February 2005) was used.
FIG. 4 is a diagram in which the dimensions of the loop conductor 30 or the flat conductor used in the analysis are defined. The length in the Z direction (longitudinal direction of the anchor portion 11) is a [m], and the width direction ( The length in the Y direction was b [m].

In order to verify the effect of suppressing the potential increase when using various loop conductors 30 and flat plate conductors, the injection current I to the current injection line 60 and the potential increase value V of the base portion 20 (from the periphery of the base portion 20 to the loop) The direction toward the central axis of the conductor 30 is positive).
FIG. 5 is a waveform diagram of the injection current I, simulating a wavefront portion of a lightning current that rises relatively steeply as a steep rising waveform having a peak value of 1 [A] and a wavefront length of 0.1 [μs].

FIG. 6 is a diagram illustrating the connection position of the loop conductor 30 or the flat conductor. For convenience, only the loop conductor 30 is shown in FIG. 6, but the flat conductor is also connected to the same position.
FIG. 6A shows a loop conductor 30 or a flat conductor on the outer peripheral surface (side surface) of the anchor portion 11 so as to be located in a plane including the central axis of the anchor portion 11 (along the radial direction of the anchor portion 11). Are connected to each other, and these are referred to as Case 2 and Cases 6-18. FIG. 6B shows an example in which the loop conductor 30 or the flat plate conductor is connected so as to be located in a plane orthogonal to the upper surface of the base portion 20.
FIG. 6C shows an example in which the loop conductor 30 or the flat plate conductor is connected to the side surface of the base portion 20 so as to be located in a plane including the central axis of the anchor portion 11 (along the radial direction of the base portion 20). This is referred to as Case 4. FIG. 6D shows an example in which the loop conductor 30 or the flat plate conductor is connected so as to be located in a plane orthogonal to the lower surface of the base portion 20.
An example in which the loop conductor 30 or the flat conductor is not connected is referred to as case 1.

In the arrangement examples of FIGS. 6A to 6D described above, the direction of the loop conductor 30 or the flat plate conductor is such that the magnetic flux generated by the lightning current flowing through the anchor portion 11 is linked in accordance with the principle of the present invention. It is necessary to. For example, with respect to the loop conductor 30, the magnetic flux is arranged in such a direction that it penetrates the internal space of the loop conductor 30.
When the loop conductor 30 or the flat conductor is connected to a plurality of locations (for example, 4 locations, 8 locations, etc.), it is desirable to arrange them radially at equal intervals as described above.

Specific conditions of the above cases 1 to 18 are shown in Table 1 as a list. For example, the case 2 shows a case where four loop conductors having a dimension of 3 [m] × 5 [m] and a cross-sectional area of 100 [mm ² ] are connected to the side surface of the anchor portion 11.

FIG. 7 shows the potential increase value V of the base portion 20 for cases 1-5. It was confirmed that in each of cases 2 to 5 in which the loop conductors 30 were connected to different positions compared to the case 1 in which the loop conductors 30 and the like were not connected, the potential increase value V decreased.
Incidentally, the ratio of the maximum value of the potential increase value V in cases 2 to 18 with respect to case 1 is summarized in Table 2. According to Table 2, even if the loop conductor 30 or the like is connected to the upper surface, side surface, or lower surface of the base portion 20, the effect of suppressing the potential increase is low, and the effect of suppressing the potential increase is better when connected to the side surface of the anchor portion 11. Clearly high.

The above results show that, for example, most of the inductive characteristics of the ground of the wind power generation system are due to the inductance component of the anchor portion 11.
In an actual wind power generation system, in order to obtain a low ground resistance value, various ground wires are connected to the base portion. Therefore, in such a case, instead of connecting the ground wire to the base portion, as shown in FIG. 6 (a), connecting the side surface of the anchor portion 11 reduces the steady ground resistance value. In addition, it is possible to suppress a steep potential rise when a lightning current whose wave head sharply increases enters the ground side, which can be said to be more effective.
For the reason described above, in the following, the case where the loop conductor 30 or the flat conductor is connected to the side surface of the anchor portion 11 will be studied.

First, the relationship between the type of conductor and the effect of suppressing potential rise will be considered.
The effect of suppressing the potential increase when the cross-sectional area of the linear conductor constituting the loop conductor 30 is changed or a flat conductor is used instead of the loop conductor 30 will be examined.
FIG. 8 shows the potential increase value V of the base portion 20 for cases 1, 2, 6-9. According to the figure, the effect of suppressing the potential increase is larger when the loop conductor 30 has a larger cross-sectional area, but the difference in potential increase value V due to the difference in cross-sectional area is as small as 1% or less, and the loop conductor 30 is used. In some cases, it has been found that the conductors currently used as ground wires are sufficient.
In addition, in the case 6 using a flat conductor having the same size as the loop conductor 30 (a and b are equal to each other), it has been clarified that the effect of suppressing the potential increase is larger than when the loop conductor 30 is used. .

Next, the relationship between the size of the conductor (the length of a and b) and the potential increase suppressing effect will be considered.
Here, regarding the loop conductor 30 and the flat conductor, the effect of suppressing the potential increase when the lengths a and b shown in FIG. 4 are changed will be examined.

FIG. 9 shows the maximum value V _max of the potential increase value V when the width b of the loop conductor 30 is fixed to 5 [m] and the height a is changed. Moreover, FIG. 10 is a thing at the time of measuring similarly about a flat conductor.
From these figures, it can be seen that in any case, the effect of suppressing the increase in potential increases as the height a is increased.

Further, FIG. 11 shows the maximum value V _max of the potential increase value V when the height a of the loop conductor 30 is fixed to 3 [m] and the width b is changed. Moreover, FIG. 12 is a thing at the time of measuring similarly about a flat conductor.
In any case, the longer the width b, the greater the effect of suppressing the potential increase. However, it has been found that the effect of suppressing the unit conductor length is greater when the height a is increased. This is because the magnetic field due to the current flowing through the tower pedestal decreases as the distance from the tower pier (anchor part) decreases. Therefore, the longer a is, the more magnetic flux is linked to the loop conductor than b is longer. This is because the induced current corresponding to the magnetic flux also increases.
However, in places where the earth resistivity is large, it is possible to lower the steady grounding resistance value by increasing b, and when it is desired to reduce the transient grounding resistance during lightning strikes in combination with such effects, It can be said that it is effective to lengthen b.

As described above, according to this embodiment, the loop conductor 30 or the flat plate conductor is connected to the surface of the anchor portion 11 or the surface of the base portion 20, so that It is possible to suppress the potential from rising rapidly.
Further, since the necessary parts are the loop conductor 30 or the flat conductor, and the connection work to the side surface of the anchor portion 11 and the like can be easily realized, the cost of materials and construction can be reduced, and the cost can be reduced. it can.

  The present invention is not limited to a wind power generation system, and can also be applied to tower legs such as a power transmission tower.

10: Tower base 11: Anchor part 20: Foundation part
30: Loop conductor 50: Analysis space 60: Current injection line

Claims (6)

In a structure comprising a foundation part buried in the ground, and an anchor part buried in the ground in order to fix the tower pedestal to the foundation part,
When a conductor is connected to the surface of the anchor part or the surface of the foundation part, when a lightning current flows from the tower tower base to the ground through the anchor part or the foundation part, the lightning current is generated by electromagnetic induction. A method of suppressing an increase in the potential of a tower tower pedestal, wherein an induced current in a direction to cancel is passed through the conductor to suppress an increase in potential of the tower tower pedestal. In a structure comprising a foundation part buried in the ground, and an anchor part buried in the ground to fix the tower pedestal to the foundation part,
A conductor is connected to the surface of the anchor part or the surface of the base part, and an induced current is passed through the conductor in a direction to cancel lightning current flowing from the tower tower base to the ground through the anchor part or the base part. An apparatus for suppressing an increase in potential of a steel tower column, which suppresses an increase in potential of the steel tower column. In the tower tower pedestal potential rise suppression device according to claim 2,
The conductor is connected to the surface of the anchor portion or the surface of the base portion, and forms a closed circuit together with the surface of the anchor portion or the surface of the base portion, and magnetic flux generated by lightning current is chained to the internal space. An apparatus for suppressing an increase in potential of a tower pedestal, which is a linear loop conductor that intersects. In the tower tower pedestal potential rise suppression device according to claim 2,
The electric conductor is a flat plate conductor connected to the surface of the anchor portion or the surface of the base portion, and a magnetic flux generated by a lightning current is interlinked, and the apparatus for suppressing an increase in potential of tower towers. In the tower tower potential increase control device according to claim 3,
An apparatus for suppressing an increase in potential of a tower tower, wherein the anchor portion is composed of a rod-like member, and a plurality of the loop conductors are radially connected to the outer peripheral surface thereof at equal intervals. In the tower tower pedestal potential rise suppression device according to claim 4,
The tower tower base potential rise suppression device characterized in that the anchor portion is constituted by a rod-like member, and a plurality of the flat conductors are radially connected to the outer peripheral surface thereof at equal intervals.

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