JP6519790B2 - Grounding device - Google Patents

Description

  BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a grounding device for independently grounding equipment and equipment.

In general, grounding is for the purpose of preventing electric shock to people etc., preventing fire due to leakage, preventing high voltage from entering the low voltage side due to a mixed accident inside the transformer, grounding the neutral point of the low voltage side of the transformer etc. The types of construction include Class A grounding construction, Class B grounding construction, Class C grounding construction and Class D grounding construction. The Class A grounding work is applied to a metal outer box for high-pressure equipment and a lightning arrester, and the Class B grounding work is applied to the low pressure side of a transformer that transforms high pressure and low pressure. Class C grounding work is applied to the metal outer box or metal tube of low voltage electric machine equipment exceeding 300 V, and Class D grounding work is applied to the low voltage electric machine equipment of 300 V or less, metal outer box and metal pipe etc. Applied. Grounding methods include an independent grounding method in which grounding works are performed independently for each facility or device , and a common grounding method in which a plurality of grounding works are connected to one grounding electrode and shared. In the independent grounding method, it is necessary to secure a sufficient separation distance to eliminate the mutual influence of the grounding electrodes, but there is actually a limitation on the site, so A grounding and C grounding are other than B grounding. As for D-type grounding, common grounding may be made by connecting to a steel frame or reinforcing bar of a structure (see, for example, Patent Document 1).

  On the other hand, if the B type grounding is common to the A type grounding, the C type grounding, and the D type grounding, a large current equivalent to a short circuit current flows in the circuit at the time of grounding, and protection coordination with other circuits can not be obtained. Therefore, it is required to set a desired grounding resistance so that a weak ground fault current can be reliably detected at the time of a ground fault accident by setting the independent grounding system. Therefore, the number, shape and length of the ground rods of the independent ground pole are adjusted to obtain a desired ground resistance. There is also a system in which a ground conductor is spirally wound around a ground rod to obtain a desired ground resistance (see Patent Document 2).

Unexamined-Japanese-Patent No. 2002-271964 JP 2008-152927 A

  However, the grounding resistance is determined from the preliminary study to secure the desired value, because the resistivity in the soil is unknown, the ground resistance is not uniform, and so on, because it is affected by the nearby structure. It can not be secured by the number, shape or length, and adjustment at the construction site is often required. In particular, when the resistivity in the soil is high, it is an operation that requires a great deal of effort to secure a desired resistance value.

  FIG. 4 is a block diagram of a conventional example showing an example of a grounding device of a structure. The structure 11 is, for example, a building, and in FIG. 4, the structure 11 is a three-story building, and a part of the steel frame of the structure 11 and rebar (hereinafter referred to as rebar 12) is in the soil below the ground 13 The embedded reinforcing bar 12 is used as a common ground electrode, and a ground rod is embedded outside the structure 11 as an independent ground electrode 14.

  The neutral point of the transformer 15 installed inside the structure 11 is grounded to a B type and connected to the independent ground pole 14 outside the structure 11 by the ground wire 16x. Further, the outer box of the transformer 15 is A-type grounded and connected to the reinforcing bar 12y by the ground wire 16y. The outer box of the loads 17a, 17b, 17c is D-type grounded and connected to the reinforcing bars 12a, 12b, 12c by the ground wires 16a, 16b, 16c.

  Now, assuming that a ground fault has occurred at F1 in FIG. 4, the ground fault current is, as shown by the arrows, from the ground fault point F1 → the outer box of the load 17c (class D ground) → ground wire 16c → structure 11 Rebar 12c → soil 18 → independent ground pole 14 → ground wire 16x → neutral point of transformer 15 (B-type ground) → low voltage winding of transformer 15 → power supply lines 19c1 and 19c2 → route of ground junction F1 It flows with. Therefore, when the independent ground electrode 14 has to be provided outside the structure, the resistance changes due to the ground resistivity 18 of the soil 18 outside the structure 11 and the positional relationship between the structure 11 and the independent ground electrode 14 Therefore, adjustment of the ground resistance is also complicated.

  An object of the present invention is to provide a grounding device capable of easily obtaining a desired grounding resistance.

Grounding device of the present invention, the internal grounding electrode is independently grounded outside of the structure for the equipment installed inside the structure, connected by a connecting line to steel or rebar structure used in common grounding the device An external ground pole surrounding the periphery of the internal ground pole, a length between the external ground pole and the internal ground pole, and a length of the external ground pole filled between the internal ground pole and the external ground pole It is characterized by including a filler for adjusting a resistivity to make a grounding resistance capable of reliably detecting a ground fault current flowing to the ground pole corresponding to a radius .

  According to the present invention, the ground resistance of the device is provided with an external ground pole surrounding the periphery of the internal ground pole, and the external ground pole constitutes a structure having a sufficiently low resistance value to the required ground resistance value. The connection resistance from the infinite distance to the external ground pole can be ignored because the connecting wire from the steel frame or rebar is connected. The size of the grounding resistance of the grounding device should be determined by adjusting the resistivity of the filler filled between the internal grounding pole and the external grounding pole, and the radius and length of the internal grounding pole and the external grounding pole. Can. As a result, the magnitude of the ground resistance value and the shape of the ground pole can be planned in advance, and a desired ground resistance can be easily obtained. Further, when it is necessary to adjust the grounding resistance after the grounding device is attached, it can be easily performed by adjusting the resistivity of the filler.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram which shows an example of the earthing | grounding apparatus which concerns on embodiment of this invention. BRIEF DESCRIPTION OF THE DRAWINGS The block diagram of an example of the ground pole part of the earthing | grounding apparatus which concerns on embodiment of this invention. Explanatory drawing of a grounding electrode part in the case of considering resistance of a grounding device concerning an embodiment of the present invention in consideration of influence of a structure by electromagnetic field analysis. The block diagram of the prior art example which shows an example of the earthing | grounding apparatus of a structure.

  Hereinafter, embodiments of the present invention will be described. FIG. 1 is a block diagram showing an example of a grounding device according to an embodiment of the present invention. According to the embodiment of the present invention, in contrast to the conventional example shown in FIG. 4, instead of the ground bar of the independent ground pole 14, the internally grounded internal body having a dimension previously set to a desired resistance value. Ground electrode 20 and external ground electrode 21 surrounding the periphery of internal ground electrode 20, external ground electrode 21 is connected to common ground by connecting wire 22, and between internal ground electrode 20 and external ground electrode 21 And the filler 23. The other configuration is the same as that of FIG. 4, so the same reference numerals are given to the same elements, and duplicate explanations are omitted.

  In FIG. 1, the internal ground electrode 20 is a ground electrode for independently grounding a device installed inside the structure 11, and is provided outside the structure 11. In FIG. 1, the internal ground pole 20 is formed in a rod shape, and the device installed inside the structure 11 is the transformer 15, and the neutral point of the B-type grounded transformer 15 is a structure by the ground wire 16x. 11 shows one connected to the 11 external internal ground poles 20.

  The external ground electrode 21 is provided surrounding the periphery of the internal ground electrode 20. In FIG. 1, the external ground electrode 21 is formed in a cylindrical shape, and a rod-like internal ground electrode 20 is accommodated in the cylinder to surround the side surface of the internal ground electrode 20. Further, the external ground electrode 21 is connected to the reinforcing bar 12 of the structure 11 in which the device installed inside the structure 11 is shared and grounded by a connecting line 22. As a result, the external ground electrode 21 is maintained at the same potential as the rebar 12 of the structure 11 commonly grounded.

  Furthermore, between the inner ground electrode 20 and the outer ground electrode 21, ie, in the cylinder of the outer ground electrode 21, a filling material 23 having a resistivity set to a desired resistance value is filled in advance. There is.

  Now, assuming that a ground fault has occurred at F1 in FIG. 1, the ground fault current is, as shown by the arrows, from ground fault point F1 → outer box of load 17c (class D ground) → ground line 16c → structure 11 Rebar 12c → connecting line 22 → external ground pole 21 → filler 23 → internal ground pole 20 → ground line 16x → neutral point of transformer 15 (class B grounding) → low voltage winding of transformer 15 → power line 19c1 , 19c2 → flows on the route of the ground fault point F1. Although earth fault current flows from the reinforcing bar 12c of the structure 11 to the external ground pole 21 through the earth 18 in addition to the joint line 22, the resistance of the joint line 22 is smaller than the resistance of the earth 18 Most ground current flows in the connecting line 22.

  The external ground pole 21 is connected to the rebar 12c of the structure 11 with common ground by the connecting line 22, so the external ground pole 21 is maintained at the same potential as the rebar 12c of the structure 11 with common earth. Therefore, there is no need to consider the resistance of the ground 18 without being affected by the nearby structure, so the internal ground pole with the dimensions set to the desired resistance value in advance, the external ground The desired grounding resistance can be easily obtained simply by attaching a grounding device consisting of a pole and a filler. Further, even if it is necessary to change the ground resistance value after the grounding device is attached, it is possible to easily obtain a desired ground resistance simply by adjusting the resistivity of the filler.

  In the above description, the case where the internal grounding electrode 20 independently grounds the apparatus to which the B-class grounding is performed has been described, but instead of the B-type grounding, the apparatus to which the A-class grounding, the C-class grounding, and the D-class grounding are independent It may be the case of grounding. In addition, although the case where the grounding device configured by the internal grounding electrode 20 and the external grounding electrode 21 is provided outside the structure 11 is shown, it may be provided inside the structure 11.

  Next, the grounding resistance of the grounding device according to the embodiment of the present invention will be described. FIG. 2 is a configuration diagram of an example of a ground pole portion of the grounding device according to the embodiment of the present invention. As shown in FIG. 2, the lengths of the internal ground electrode 20 and the external ground electrode 21 are l, and the internal ground electrode 20 and the external ground electrode 21 are embedded at a position of the embedded depth t from the ground 13. Further, it is assumed that the radius of the rod-like inner ground electrode 20 is a, and the radius of the outer ground electrode 21 is b. The resistivity of the filler 23 is ρ.

  Now, four types of grounding devices shown in Table 1 are prepared. That is, grounding devices of condition 1, condition 2, condition 3 and condition 4 were prepared. The ground resistivity ee at a location where the internal ground pole 20 and the external ground pole 21 of the grounding device of the condition 1, the condition 2, the condition 3 and the condition 4 are set to 100 Ωm. The resistivity ρ of the filler in conditions 1 and 2 is 100 Ωm, which is the same as the ground resistivity ee, and in conditions 3 and 4, the resistivity ρ of the filler is 50 Ωm and 80 Ωm in order to compare with 100 Ωm in conditions 1 and 2. And

条件１、条件２、条件３及び条件４の接地装置の内部接地極２０と外部接地極２１との間の抵抗は（１）式で示す算出式から求められる。

The resistance between the internal ground pole 20 and the external ground pole 21 of the grounding device of the condition 1, the condition 2, the condition 3 and the condition 4 can be obtained from the calculation equation shown by the equation (1).

R = (ρ / 2πl) · ln (b / a) (1)
The equation (1) represents the resistance value when the single grounding device in which the external ground pole 21 surrounding the internal ground pole 20 is formed in a cylindrical shape is used as an independent ground pole without considering the influence of the nearby structure 11. It is a formula.

  On the other hand, in the embodiment of the present invention, since the external ground pole 21 of the grounding device and the reinforcing bar 12c of the structure 11 are connected by the connecting wire 22, and the internal ground pole 20 and the ground wire 16x are connected, Of the electromagnetic field analysis, the FDTD (Finite-difference time-domain method) method (electromagnetic field analysis by the finite difference time domain method (hereinafter It is simply obtained by electromagnetic field analysis).

  FIG. 3 is an explanatory view of the ground electrode portion in the case where the resistance of the grounding device is determined in consideration of the influence of the structure 11 by electromagnetic field analysis, and FIG. Explanatory drawing in the case of calculating | requiring the resistance value of a grounding device by calculating | requiring the voltage between the ground pole 20 and the structure 11 by electromagnetic field analysis, FIG. 3 (b) considers the structure 11 and the internal ground pole 20 and infinite distance Is obtained by electromagnetic field analysis to determine the ground resistance value of the grounding device.

  In FIG. 3A, in a circuit in which the injection line 24 is connected to the internal ground pole 20 and the external ground pole 21 and the reinforcing bar 12c of the structure 11 are connected by the connecting line 22, grounding in consideration of the influence of the structure 11 It is to find the resistance value of the device. The simulated current which flows at the time of a ground fault from the injection line 24 of Fig.3 (a) is flowed, and the voltage between the injection line 24 (internal ground pole 20) and the structure 11 (rebar 12c) is calculated by electromagnetic field analysis. The resistance value of the grounding device was determined. Thus, the resistance value of the grounding device can be calculated on the assumption that the B-type grounding is performed in consideration of the influence of the structure 11.

  Similarly, in FIG. 3 (b), in the same circuit as FIG. 3 (a), a simulated current is caused to flow from injection line 24 when a ground fault occurs, and injection line 24 (internal ground pole 20) is infinitely distant The voltage between the reference point 25 and the reference point 25 was calculated by electromagnetic field analysis to determine the grounding resistance value of the grounding device. Thereby, the grounding resistance value of the grounding device can be calculated on the assumption that the B type grounding is in consideration of the influence of the structure 11 viewed from an infinite distance.

  Table 2 shows the resistance values obtained from the calculation formula of equation (1) and the resistance values obtained from the electromagnetic field analysis of FIGS. 3 (a) and 3 (b).

表２において、条件１、条件２、条件３、条件４の（１）式の算出式から求めた抵抗値と、電磁界解析から求めた抵抗値とは、それぞれの条件において近い値になっていることがわかる。（１）式の算出式と図３の電磁界解析から求めた抵抗値の差は、外部接地極２１が構造物１１の鉄筋１２ｃに接続されているためと考えられるが、接地装置の抵抗値は（１）式で近似できることが分かる。

In Table 2, the resistance values obtained from the calculation formulas (1) of Condition 1, Condition 2, Condition 3 and Condition 4 and the resistance values obtained from electromagnetic field analysis are close values under the respective conditions. I understand that Although the difference between the resistance value obtained from the calculation formula of equation (1) and the electromagnetic field analysis of FIG. 3 is considered to be because the external ground electrode 21 is connected to the reinforcing bar 12c of the structure 11, the resistance value of the grounding device It can be seen that can be approximated by equation (1).

  In Table 2, based on conditions 1 and 2 in which the radius b of the external ground pole 21 and the length l of the ground pole are changed, any resistance value can be obtained by changing the radius b of the external ground pole and the length l of the ground pole. It can be seen that it is possible to secure

In Table 2, conditions 1 resistivity change the [rho filler 23 (condition 2), condition 3, that can be secured to any resistance value by changing the resistivity of the filler 23 [rho than condition 4 Recognize.

  In addition, the ground resistance value as an independent ground pole determined by electromagnetic analysis under condition 1, condition 2, condition 3 and condition 4 is also the resistance value determined from the ground resistance value or electromagnetic field analysis determined from the formula of equation (1) The fact that the values are close to each other means that using the grounding device of the embodiment of the present invention connected to the connecting wire 22 from the steel frame or rebar of the structure 11 makes the value as an independent grounding pole. It will be secured.

  As described above, according to the embodiment of the present invention, the external ground pole 21 surrounding the periphery of the internal ground pole 20 which is independently grounded is provided outside the structure 11, and the external ground pole 20 is commonly grounded. The voltage V between the internal ground pole 20 of the grounding device and the structure 11 by the ground fault current can be reduced because it is connected to the connecting line 22 from the steel frame or the reinforcing bar and held at the common ground potential. The ground resistance can be adjusted simply by adjusting the resistivity ρ of the filler 23 filled between the inner ground pole 20 and the outer ground pole 21. This makes it possible to easily obtain a desired ground resistance capable of reliably detecting the ground fault current.

  While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and the gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 11 ... Structure, 12 ... Rebar, 13 ... Ground, 14 ... Independent ground pole, 15 ... Transformer, 16 ... Ground wire, 17 ... Load, 18 ... In the ground, 19 ... Power wire, 20 ... Internal ground pole, 21 ... external ground pole, 22 ... connection line, 23 ... filling material, 24 ... injection line, 25 ... reference point at infinite distance

Claims (1)

An internal ground pole that is independently grounded to the outside of the structure for equipment installed inside the structure;
An external ground pole connected to the steel frame or rebar of the structure having the common ground and connected to the equipment with a connecting line and surrounding the inner ground pole;
It is filled between the internal ground pole and the external ground pole, and ensures a ground fault current flowing to the ground pole according to the lengths of the external ground pole and the ground pole of the internal ground pole and the radius of the external ground pole. A filler that adjusts the resistivity to provide a ground resistance that can be detected
The grounding device characterized by having.

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