Ground resistance reduction material and grounding device

Abstract

To provide a ground resistance reduction material that can contribute to reducing carbon dioxide emissions and can be used in the same way as a ground resistance reduction material using fossil fuel coke, and a grounding device using the ground resistance reduction material, and to provide a ground resistance reduction material that can be further reduced in weight.SOLUTION: A ground resistance reduction material 14 is to be placed between a ground electrode 11 buried in the soil 12 and the soil 12, and contains carbide powder obtained by incomplete combustion of biomass.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a ground resistance reducing material and a grounding device using the ground resistance reducing material. [Background technology]

[0002] When burying a ground electrode such as a bare copper wire in the soil, a technique is known in which a ground resistance reducing material is placed between the ground electrode and the soil to reduce the ground resistance. For example, Patent Document 1 proposes that a ground resistance reducing material made of a mixture of carbon powder such as coke produced from coal or petroleum as an electrically conductive material and cement powder as an alkaline solidifying agent is spread into a groove in the earth to bury the ground electrode. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 165975 / 1983 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the powders such as coke used in the earth resistance reduction materials are refined from fossil fuels, so a large amount of carbon dioxide is generated during the manufacturing process, which does not contribute to the realization of carbon neutrality, and since the price of coke powder has been rising in recent years, alternatives are desired. In addition, since conventional earth resistance reduction materials are heavy, there is a demand for lighter materials that contribute to reducing the burden of manually transporting earth resistance reduction materials in the work of burying earth electrodes in mountainous areas where transportation vehicles cannot be used.

[0005] Therefore, the present invention aims to provide a ground resistance reducing material that can contribute to reducing carbon dioxide emissions and can be used in the same way as ground resistance reducing materials that use fossil fuel coke, and another aim is to make such ground resistance reducing material lighter. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention provides a ground resistance reducing material to be placed between a ground electrode buried in the soil and the soil, and this ground resistance reducing material is characterized in that it contains carbonized powder obtained by incomplete combustion of biomass. According to the present invention, the carbonized powder is obtained by incomplete combustion of biomass, so that the amount of carbon dioxide emitted during the manufacturing process can be reduced compared to coke made from fossil fuels. Furthermore, since the biomass is carbonized and placed in the soil, it can be prevented from decaying or decomposing and can be stably retained in the soil for a long period of time. Therefore, it can contribute to reducing carbon dioxide emissions for a long period of time. Moreover, even when biomass-derived carbonized powder is used, the resistivity as a ground resistance reducing material can be kept as low as that of coke made from fossil fuels, so that a sufficient effect of reducing ground resistance can be obtained. Therefore, according to the present invention, it is possible to provide a ground resistance reducing material that can contribute to CO2 reduction for a long period of time and can be used in the same way as ground resistance reducing materials that use coke.

[0007] The ground resistance reducing material of the present invention preferably has a resistivity of 430 Ω·cm or less for the carbide powder particles, making it easy to keep the resistivity low and ensure the effect of reducing ground resistance. In addition, in the ground resistance reducing material of the present invention, the bulk density of the carbide powder is 0.40 g / cm 3 It is better to have the following: The carbonized powder obtained by incomplete combustion of biomass has a smaller bulk density than coke, a fossil fuel, so the ground resistance reduction material can be made lighter.Before construction, the ground resistance reduction material is easy to transport and handle.During construction, the work effort is reduced and the ground electrodes can be easily buried and fixed, simplifying the construction effort.

[0008] In the ground resistance reducing material of the present invention, the mass fraction of moisture contained in the carbide powder is preferably 7.5 wt % or less. In this way, the hardening of the hydraulic components can be suppressed before the ground resistance reducing material is used. In addition, when the carbide powder has a high mass fraction of moisture, lumps tend to form when the ground resistance reducing material is mixed with water. However, by setting the mass fraction of moisture in the above range, the mixing process can be made easier.

[0009] It is preferable that the ground resistance reducing material of the present invention contains a mixture of the above-mentioned carbide powder and hydraulic powder, and is capable of integrating the ground electrode by hardening. In this way, the carbon powder can be held in a fixed position by hardening, and the ground electrode can be integrated with the ground resistance reduction material to increase the area of ​​the ground electrode that comes into contact with the soil, thereby improving the effect of reducing ground resistance.

[0010] In this case, it is preferable that the carbide powder and the hydraulic powder are mixed in a weight ratio of 10:90 to 50:50. If the carbide powder and hydraulic powder are mixed in this ratio to make a ground resistance reducing material, the strength of the ground resistance reducing material can be ensured when it is hardened in soil, and a sufficient effect of reducing ground resistance can be ensured. In addition, since the ground electrode is embedded in the ground resistance reducing material and is easily maintained in a fixed state, the resistivity can be kept low, improving the effect of reducing ground resistance.

[0011] The earthing device of the present invention is a device in which the earth resistance reducing material as described above is hardened and buried in the soil, and a grounding electrode is integrated into the earth resistance reducing material. Effect of the Invention

[0012] According to the present invention, it is possible to provide a grounding resistance reducing material that can significantly contribute to reducing carbon dioxide emissions and can be used with performance equivalent to that of a grounding resistance reducing material using fossil fuel coke, and a grounding device that uses this grounding resistance reducing material. [Brief description of the drawings]

[0013] [Figure 1]1 is a longitudinal cross-sectional view showing a grounding device formed using a ground resistance reduction material according to an embodiment of the present invention. [Diagram 2] 3A and 3B are diagrams illustrating a ground electrode of a grounding device according to an embodiment of the present invention. [Diagram 3] 5A to 5C are diagrams illustrating a method for manufacturing a grounding device according to an embodiment of the present invention. [Figure 4] FIG. 11 is a vertical cross-sectional view showing a grounding device according to a modified example of the embodiment of the present invention. [Diagram 5] 13A and 13B are diagrams illustrating the arrangement of ground electrodes according to another modified example of the embodiment of the present invention. [Figure 6] 10A and 10B are diagrams illustrating a ground electrode of a grounding device according to another embodiment of the present invention. [Figure 7] 1 is a graph showing the change in resistivity versus the mixing ratio of carbide powder particles and cement in Example 1. [Figure 8] 1 is a graph showing the results of measuring changes in ground resistance over time in Example 1 and Comparative Example 1. [Figure 9] 1 is a graph showing the results of measuring the change over time in ground resistance in Examples 2 and 3 and Comparative Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The ground resistance reduction material of this embodiment is a material that is placed between the ground electrode and the soil to reduce ground resistance when the ground electrode of various electrical equipment, lightning protection equipment, etc. is buried in the soil, and in this embodiment, the ground electrode is fixed and integrated in a buried state inside the ground resistance reduction material.

[0015] This ground resistance reducing material contains a mixture of carbide powder particles obtained by incomplete combustion of biomass and hydraulic powder. When placed in the soil, it may be in a powdered or granular state, or may be in a slurry state mixed with an aqueous liquid, but it is necessary that it hardens over time after being placed in the soil.

[0016] The carbide powder is a powder produced in advance by incomplete combustion of biomass. However, it was found that various properties vary depending on the raw biomass. Therefore, the inventors used various biomasses to investigate electrical conductivity, particle size, etc., and confirmed that it is preferable to use carbide powder made of wood biomass such as cedar and cypress as the carbide powder, as described in this embodiment.

[0017] The incomplete combustion during the production of carbonized powder or granules may be any heat treatment capable of carbonizing at least a portion of the biomass, and may be, for example, a treatment in which the biomass is heated while the amount of oxygen supply is appropriately regulated to cause incomplete combustion.

[0018] It is preferable to use such carbide powder with a resistivity of 430 Ω·cm or less. If the resistivity of the carbide powder is excessively high, it becomes difficult to obtain a sufficient effect of reducing the ground resistance. The resistivity of the carbide powder can be measured, for example, by the four-electrode method while the carbide powder is absorbed with water.

[0019] The carbide powder particles are preferably those having a resistivity of 100 Ω·cm or less when mixed with hydraulic powder. As long as the resistivity is 100 Ω·cm or less when mixed with hydraulic powder, the carbide powder may be made of biochar powder such as charcoal, bamboo charcoal, rice husk, or livestock waste.

[0020] The carbide powder may have a particle size in the range of 998 μm to 0.291 μm (16 mesh pass or less). The particle size may be measured by, for example, classification using a sieve or laser diffraction (for example, a laser diffraction measuring device "SALD-3100" manufactured by Shimadzu Corporation). Such carbide powder particles have good affinity with water, and when mixed with hydraulic powder, unevenness in the agitation properties during addition of water is unlikely to occur.

[0021] The bulk density of the carbide powder is 0.40 g / cm 3 It is preferred that: If the specific gravity of the carbide powder is small like this, the earth resistance reduction material can be made much lighter than fossil fuel coke, making it easier to handle and install. Furthermore, if the volume of the earth resistance reduction material can be secured, the contact area with the soil can be secured when it is hardened in the soil, which makes it possible to obtain a sufficient earth resistance reduction effect.

[0022] Furthermore, the mass fraction of moisture contained in the carbide powder is preferably 7.5 wt% or less. The mass fraction of moisture contained in the carbide powder can be measured, for example, by a measurement method in accordance with JIS M 8812:2004. If the mass fraction of moisture is within this range, the hardening of the hydraulic component due to the moisture contained in the carbide powder and granules can be suppressed before the ground resistance reduction material is used. Furthermore, when carbonized powder has a high mass fraction of moisture, lumps tend to form easily when the ground resistance reduction material is mixed with water and then placed in the soil in the form of a slurry. Therefore, by setting the mass fraction of moisture to 7.5 wt% or less, the formation of lumps can be suppressed, making the mixing process easier.

[0023] On the other hand, hydraulic powder is a material that can harden over time by adding water and mixing it, or by receiving moisture from the surroundings in the soil. By hardening the hydraulic powder in a mixed state with carbide powder, the hydraulic powder can fix the carbide powder in a fixed position in the soil and also fix the buried earth electrode in a fixed position. Any suitable material that can be hardened by water can be used as the hydraulic powder, and examples of such materials include Portland cement, mixed cement such as blast furnace cement and fly ash cement, and various types of cement such as ecocement.

[0024] The ground resistance reducing material is a powder containing a mixture of these carbide powder and hydraulic powder. It may also contain other materials, such as bentonite and inorganic salts.

[0025] The mixing ratio of the carbide powder particles and the hydraulic powder may be 10:90 to 50:50 by weight. When the ratio of carbide powder is increased, the effect of reducing ground resistance increases, but the amount of hydraulic powder is decreased relative to the amount of carbide powder, and the strength of the hardened ground resistance reducing material may be insufficient when placed in the soil and hardened. Also, the strength required to bury and fix the ground electrode in the ground resistance reducing material may be insufficient, for example, cracks or breakage may occur after hardening, or a gap may form between the ground electrode and the material, allowing moisture or humidity from the soil to penetrate and causing corrosion of the ground electrode. On the other hand, when the ratio of hydraulic powder is increased, the strength increases, but the amount of hydraulic powder is increased relative to the amount of carbide powder, and the resistivity is likely to increase, making it difficult to obtain the effect of reducing ground resistance.

[0026] Next, a grounding device according to this embodiment using such a ground resistance reducing material will be described with reference to FIGS. The grounding device 10 is a device in which a grounding electrode 11 connected to an earthed body is buried in soil 12. As shown in Fig. 1, in this grounding device 10, the grounding electrode 11 is arranged along a groove-shaped recess 13 provided in the soil 12, and a grounding resistance reducing material 14 is laid in the recess 13 to bury the grounding electrode 11, and this grounding resistance reducing material 14 is buried in the soil 12'.

[0027] In this grounding device 10, a covered wire 15 connected to an electrical facility, a lightning protection facility, etc. (not shown) is extended and a grounding electrode 11 is connected to the tip side of the covered wire 15. As shown in Fig. 2, the grounding electrode 11 is made of a bare copper stranded wire connected at the end to the covered wire 15 by a connecting metal fitting 16, and the entire length of the bare copper stranded wire is buried in a ground resistance reducing material 14 in the soil. The ground resistance reducing material 14 hardens over time in the soil 12 due to the hydraulic powder mixed in. When completely hardened, it becomes a continuous band-shaped hardened material, and fixes the ground electrode 11 to the soil 12 as a whole.

[0028] To prepare such a grounding device 10, as shown in Fig. 3, a groove-shaped recess 13 is excavated in soil 12, a grounding electrode 11 connected to a covered wire 15 is arranged along the recess 13, and a grounding resistance reducing material 14 is laid in the recess 13 so as to bury the grounding electrode 11. At this time, the grounding resistance reducing material 14 may be laid in the recess 13 as it is in the form of powder or may be laid in the recess 13 in the form of a slurry that has been previously mixed with water. Thereafter, soil 12' is backfilled and compacted, and further soil 12' is added to completely backfill the groove-shaped recess 13. Then, the grounding device 10 is completed as the ground resistance reducing material 14 completely hardens over time.

[0029] According to the grounding device 10 of the present invention, electricity flows from the grounding electrode 11 to the soil 12 through the grounding resistance reducing material 14. At that time, the grounding resistance reducing material 14, which has a low specific resistance, is arranged in a hardened state surrounding the grounding electrode 11, and the wide surface of the grounding resistance reducing material 14 is in contact with the soil, so that a sufficient effect of reducing the grounding resistance can be obtained.

[0030] According to the above-described ground resistance reducing material 14 and grounding device 10 of the present embodiment, the carbonized powder is obtained by incomplete combustion of biomass, so that the amount of carbon dioxide emitted during the manufacturing process can be reduced compared to coke made from fossil fuels. In addition, since the biomass is carbonized and placed in the soil 12, it is prevented from decaying or decomposing, and can be stably retained in the soil 12 for a long period of time. Therefore, it can contribute to reducing carbon dioxide emissions for a long period of time, and contribute to the realization of carbon neutrality. Moreover, even if biomass-derived carbonized powder is used, the resistivity of the ground resistance reducing material 14 can be kept as low as that of coke made from fossil fuels, so that a sufficient effect of reducing ground resistance can be obtained.

[0031] In this embodiment, the ground resistance reducing material 14 contains a mixture of carbonized powder and hydraulic powder, and by hardening this the ground electrode 11 can be integrated into the ground resistance reducing material 11. Therefore, by hardening the carbonized powder can be held in a fixed position, and by integrating the ground electrode 11 with the ground resistance reducing material 14 the contact area with the soil 12 can be increased, thereby improving the effect of reducing ground resistance.

[0032] In addition, the specific gravity of the carbide powder obtained by the incomplete combustion of biomass is significantly smaller than that of coke, a fossil fuel, making it possible to reduce the weight of the ground resistance reducing material 14. Therefore, the ground resistance reducing material can be easily transported and handled before construction, and the labor required for construction can be reduced, allowing the ground electrodes to be easily buried and fixed, greatly simplifying the labor required for construction.

[0033] The above embodiment can be modified as appropriate within the scope of the present invention. In the above embodiment, an example was described in which a groove-shaped recess 13 was provided in the soil 12 in the horizontal direction, and the grounding resistance reducing material 14 was placed along the groove-shaped recess 13 to embed the grounding electrode 11, but the recess 13 may be formed in the vertical direction as shown in Fig. 4. In that case, it is also possible to fill the vertical recess 13 with the grounding resistance reducing material 14 that has been mixed with water in advance to form a slurry, and then embed the grounding electrode 11 inside and harden it to integrate them.

[0034] In addition, in the above-mentioned grounding device 10, an example in which one grounding electrode 11 is buried in the soil 12 has been described, but the number of grounding electrodes 11 is not limited in any way. For example, in order to reduce the ground resistance, it is also possible to bury a grounding electrode 11 that branches into multiple electrodes, as shown in FIG. 5. In this case, as shown in Figure 6, by using connecting fittings 16 to connect the bare copper stranded wire serving as the ground electrode 11 to a coated wire 15 at the midpoint, the ground electrode 11 can be branched and multiple electrodes can be connected in parallel, and each of them can be buried in a ground resistance reduction material 14 and placed in the soil 12. Furthermore, although the above describes an example of using bare copper twisted wire as the ground electrode 11, the material, shape, etc. of the ground electrode 11 are not particularly limited as long as the material is a conductive material that is not easily corroded even when buried in the soil 12 or the ground resistance reduction material 14.

[0035] In the above embodiment, an example has been described in which carbide powder and hydraulic powder are contained in a predetermined mixture as the ground resistance reducing material, but the present invention is not particularly limited to this embodiment. EXAMPLES

[0036] The present invention will be described in further detail below with reference to examples. [Example 1] (Production of earth resistance reduction material) A ground resistance reducing material 14 was produced by mixing carbide powder made of biochar A (derived from wood chips such as cedar and cypress) with cement. We measured the change in resistivity depending on the mixing ratio of charcoal powder and cement, and as shown in Figure 7, we found that the resistivity could be kept below 100 Ω·cm when the mixing ratio of biochar A was 10% or more, that is, when the mixing ratio of biochar A:cement was in the range of 10:90 to 100:0. Therefore, in Example 1, taking into consideration the strength relationship described above, the ground resistance reducing material 14 was produced by uniformly mixing carbide powder and cement in a ratio of 45:55.

[0037] Biochar A is a powdered charcoal obtained from the residue after pyrolysis of wood chips to produce synthetic gas, and has a bulk density of 0.15 g / cm. 3 The mass fraction of moisture contained in the carbide powder was 5.20 to 7.47 wt%. The resistivity of the carbide powder was 12 Ω cm. The resistivity was measured after the carbide powder was added with water and kneaded to absorb water: 30 g of the carbide powder was placed in a test vessel, water was added and kneaded uniformly, and the powder was allowed to absorb the amount of water that did not float when stirred, and the resistivity was measured using the four-electrode method.

[0038] On the other hand, the cement was type B blast-furnace cement (more than 40% but not exceeding 70% Portland cement, more than 30% but not exceeding 40% blast-furnace slag).

[0039] A number of bags containing ground resistance reduction materials 14, each of which was a homogeneous mixture of biochar A and cement, were prepared. Each bag had a volume of 24,000 cm. 3 , weighing 13 kg.

[0040] (Making a grounding device) As shown in Figures 1 and 2, a trench-like recess 13 measuring 0.5 m wide, 0.7 m deep and 2.6 m long was excavated in soil 12, and a bare copper stranded wire measuring 2.6 m long was laid along the trench-like recess 13 as a ground electrode 11 connected to a covered wire 15. A bag of ground resistance reducing material 14 was laid in powder form on top of the bare copper stranded wire of the ground electrode 11. Thereafter, soil was backfilled to a thickness of 10 cm and compacted, and then the groove-like recess 13 was completely backfilled.

[0041] (Measurement of earth resistance value) After the earthing device was fabricated, the earth resistance value was measured over time. The measurement results are shown in Table 1 and Figure 8. The earth resistance value was measured using a direct-reading earth resistance meter (manufactured by Hioki E.E. Corporation, model number FT6031).

[0042] [Comparative Example 1] A grounding device 10 was produced in the same manner as in Example 1, except that a grounding resistance reducing material using powdered coal coke ("San-earth M5C", Sankosha Corporation, trademark) was used, and the grounding resistance was measured over time. The measurement results are shown in Table 1 and FIG.

[0043] The powdered coal coke that makes up the ground resistance reduction material "San-Earth M5C" has a bulk density of 0.72 g / cm 3 The mass fraction of moisture contained in the carbide powder was 0.5 wt%. The resistivity of the carbide powder in a water-kneaded state was 430 Ω·cm. The same cement as in Example 1 was used. The ground resistance reduction material "Sun Earth M5C" is a mixture of coal coke powder and cement in a 45:55 ratio.

[0044] This earth resistance reducing material "Sun Earth M5C" is in a bagged form, and the content of one bag is the same as that of Example 1, and the weight is 25 kg.

[0045] [Table 1]

[0046] [Example 2] The ground resistance value was measured in the same manner as in Example 1, except that a ground resistance reducing material 14 that had been mixed with water in advance to form a slurry was used and a grounding device 10 as shown in FIG. The grounding device 10 was prepared by excavating a vertical hole-like recess 13 having a diameter of 100 mm and a depth of 3 m, inserting a 2.6 m length of bare copper stranded wire as the grounding electrode 11 into the vertical hole-like recess 13, making a slurry of one bag of grounding resistance reduction material 14 with 25 kg of water, filling the vertical hole-like recess 13 with soil, and then completely backfilling the recess 13 with soil.

[0047] After producing such a grounding device 10, the ground resistance value was measured over time. The measurement results are shown in Table 2 and Figure 9. The ground resistance value was measured using the above-mentioned direct-reading ground resistance meter.

[0048] [Example 3] Except for using carbide powder made of biochar B (derived from wood chips such as cedar and cypress), the ground resistance reducing material 14 was produced in the same manner as in embodiment 2, and the ground device 10 was also produced, and the ground resistance value was measured over time. The results are shown in Table 2 and FIG. 9.

[0049] Biochar B, which constitutes the charcoal powder, is a charcoal powder obtained from the residue after pyrolysis of wood chips to generate synthetic gas, and has a bulk density of 0.17 g / cm 3The mass fraction of moisture contained in the carbide powder was 13.08%. The resistivity of the carbide powder in a water-kneaded state was 99 Ω·cm. The cement was the same as in Example 2.

[0050] A plurality of bags of ground resistance reducing materials 14, each of which was a uniform mixture of biochar B and cement, were prepared. The capacity of each bag was the same as that of Example 1, and the weight was 10 kg. To make this ground resistance reducing material 14 into a slurry suitable for use, it was necessary to use 20 kg of water for one bag of 10 kg of ground resistance reducing material 14.

[0051] [Comparative Example 2] A grounding device 10 was produced in the same manner as in Example 2, except that the same grounding resistance reducing material ("San-earth M5C", Sankosha Corporation, trademark) as in Comparative Example 1, which used powdered coal coke, was used, and the grounding resistance value was measured over time. The measurement results are shown in Table 2 and FIG. 9. In order to make this ground resistance reducing material into a slurry suitable for use, it was necessary to use 20 kg of water for one bag of 25 kg of ground resistance reducing material 14.

[0052] [Table 2]

[0053] As is clear from the above results, the ground resistance reduction material 14 using biochar A or biochar B was able to be made lighter while maintaining the same volume as the ground resistance reduction material using coal coke. Furthermore, when the grounding electrode 11 was buried in soil 12 using the same volume as the grounding resistance reduction material using coal coke, the grounding resistance reduction material using biochar A or biochar B was able to achieve a grounding resistance value similar to that of the grounding resistance reduction material using coal coke. As a result, it was confirmed that the ground resistance reducing material 14 of the embodiment can be used in the same manner as the ground resistance reducing material using coke from fossil fuel of the comparative example. [Explanation of symbols]

[0054] 10 Earthing device 11 Ground electrode 12,12' Soil 13 Recess 14. Earth resistance reduction material 15 Covered Wire 16 Connection fittings

Claims

1. A ground resistance reducing material to be placed between a ground electrode buried in soil and the soil, A ground resistance reducing material characterized by containing carbonized powder obtained by incomplete combustion of biomass.

2. 2. The ground resistance reducing material according to claim 1, wherein the carbide powder has a resistivity of 430 Ω·cm or less.

3. The bulk density of the carbide powder is 0.40 g / cm ３ The ground resistance reducing material according to claim 2, wherein:

4. The ground resistance reducing material according to claim 3, wherein the mass fraction of moisture contained in the carbide powder is 7.5 wt % or less.

5. The ground resistance reducing material according to claim 1, wherein the carbide powder and hydraulic powder are contained in a mixed state, and the ground electrode can be integrated by hardening.

6. The ground resistance reducing material according to claim 5, wherein the carbide powder and the hydraulic powder are mixed in a weight ratio of 10:90 to 50:

50.

7. 7. A grounding device comprising the ground resistance reducing material according to claim 1, which is hardened and buried in soil, and which is integrated with a grounding electrode.

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