CN113035404A

CN113035404A - Resistance reducing agent, foundation pit, preparation method and application thereof

Info

Publication number: CN113035404A
Application number: CN202110272426.2A
Authority: CN
Inventors: 陈泽阳; 蓝灿荣; 邱灿树; 林伟彬; 陈卫钢; 蔡哲; 陈旭华; 陈佳鹏; 郑泽涛; 陈超
Original assignee: Guangdong Power Grid Co Ltd; Chaozhou Power Supply Bureau of Guangdong Power Grid Co Ltd
Current assignee: Guangdong Power Grid Co Ltd; Chaozhou Power Supply Bureau of Guangdong Power Grid Co Ltd
Priority date: 2021-03-12
Filing date: 2021-03-12
Publication date: 2021-06-25

Abstract

The invention provides a resistance reducing agent and a preparation method and application thereof, wherein the resistance reducing agent comprises a combination of carbon, a sodium chloride source and copper powder, and the resistance reducing agent has excellent resistance reducing effect, excellent corrosion resistance, long-acting property and stability through the cooperation of the carbon, the sodium chloride source and the copper powder; when the resistance reducing agent is used for reducing the resistivity of soil around a ground pole, the construction amount is small, the transportation cost is low, the economic benefit is remarkable, the resistance reducing agent has no influence on the environment such as the surrounding soil, the ecological environment cannot be damaged, and the application value is high.

Description

Resistance reducing agent, foundation pit, preparation method and application thereof

Technical Field

The invention belongs to the technical field of electric power engineering materials, and particularly relates to a resistance reducing agent, and a preparation method and application thereof.

Background

The way of resistive grounding of the transformer neutral point involves economic and technical problems in the whole power system. In order to control the voltage of the transformer in a safe range, the voltage must be effectively regulated and controlled by applying a transformer resistance grounding technology. According to the requirement of national standard on the grounding resistance of electrical equipment, when the capacity of a transformer does not exceed 100 kilovolts, the grounding resistance is not more than 10 ohms, and when the capacity of the transformer exceeds kilovolts, the grounding resistance is not more than 4 ohms; the ground resistance of the ground is proportional to the resistivity of the soil in the area and inversely proportional to the square root of the total area of the ground grid. In high-resistivity areas with neutral pH value of soil, such as mountainous areas and sandy soils, the grounding resistance of a grounding grid is difficult to be effectively reduced, and the effect of enabling the grounding resistance to reach the standard without increasing the area of the grounding grid is generally realized by methods of enlarging the contact area of a grounding body, improving the resistivity of surrounding soil, increasing the current dispersion area and the like.

At present, the addition of a resistance reducing agent is a common technology for effectively reducing the resistivity of soil around a grounding body, and the resistance reducing agent is composed of various components, such as fine graphite, bentonite, a curing agent, a lubricant, conductive cement and the like, so that the resistance reducing agent becomes a good conductor. CN110818311A discloses a sodium bentonite composite resistance-reducing agent for high-resistivity soil, belonging to the technical field of conductive grounding materials. Mainly comprises sodium bentonite, carbon nano tubes, graphite, polyacrylamide, mirabilite, ammonium chloride, active carbon, sodium molybdate and sodium hexametaphosphate. The physical grounding resistance reducing agent solves the problems that the existing resistance reducing agent has high resistivity, is easy to lose water and soil and is greatly influenced by environmental factors. The long-acting stability is achieved, the grounding body is not corroded, and the method is particularly suitable for high soil resistivity and water-deficient areas and has wide application prospects. CN107622813A discloses a soil resistance reducing agent, which is granular and comprises the following components in parts by weight: 30-50 parts of expanded graphite, 50-70 parts of bentonite, 5-12 parts of calcium bicarbonate, 10-15 parts of polyaniline, 20-40 parts of sodium carboxymethylcellulose, 8-12 parts of barium sulfate and 12-15 parts of sodium polyacrylate. The resistance reducing agent is prepared into particles by adopting a specific formula process, so that dust can be avoided, and construction, transportation and storage are facilitated; meanwhile, the resistivity is low, and the durability is strong. CN105957577A discloses a calcium bentonite resistance-reducing agent for grounding, which comprises the following components: calcium bentonite, carbon fiber, ammonium chloride, calcium oxide, zinc powder, nickel powder, ammonium persulfate, sodium molybdate, conductive cement, graphene, aluminum powder, aniline and sodium tripolyphosphate. The resistance reducing agent solves the defects of common resistance reducing agents such as high packaging and construction difficulty and the like, and solves the problem that the grounding body cannot be normally used for a long time.

However, research shows that the friction reducer provided in the prior art mostly uses graphene, carbon fiber and other components, which results in higher cost of the friction reducer; on the other hand, in the process of practical use, the resistance reducing agent provided by the prior art has poor resistance reducing continuity, can only maintain the resistance reducing effect for 3-4 months generally, and needs to be replaced at irregular time, otherwise, the safe and stable operation of the transformer and the line equipment thereof can be damaged.

Therefore, it is necessary to develop a sustainable resistance-reducing agent which has low cost, convenient transportation, good resistance-reducing effect, no influence from seasons and no damage to the environment.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a resistance reducing agent, a foundation pit, a preparation method and application thereof, wherein the resistance reducing agent comprises the combination of carbon, a sodium chloride source and copper powder, and the prepared resistance reducing agent has the characteristics of obvious resistance reducing effect, good corrosion resistance and excellent stability by selecting specific components and matching, can effectively prolong the service life of the resistance reducing agent and has wide market application prospect.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the present invention provides a friction reducer comprising a combination of carbon, a sodium chloride source, and copper powder.

The resistance reducing agent provided by the invention comprises the combination of carbon, a sodium chloride source and copper powder; wherein, the carbon has excellent conductivity, corrosion resistance, stability and water absorption, can reduce the resistivity of the soil near the earth and can exist stably for a long time; the sodium chloride source also has good hydrophilicity and can absorb water in soil near the earth pole, so that the resistance reducing agent has higher water content when in use, can reduce barriers for particle migration and reduce migration resistance of charged particles, the sodium chloride source generates free sodium ions when meeting water, and the pore structure of the carbon can well absorb the free sodium ions and fix the free sodium ions in the pore structure, thereby avoiding the loss of the sodium ions; the copper powder has good conductivity, and has the main functions of filling gaps existing between carbon and a sodium chloride source to improve the stability of the resistance reducing agent when in use, and in addition, the interface of various materials is connected, so that the interface resistance of the materials can be effectively reduced, and the resistivity of soil near the earth pole is further reduced. Therefore, the resistance reducing agent with good resistance reducing effect, stability and excellent corrosion resistance is finally obtained through the combination of the carbon, the sodium chloride source and the copper powder.

Preferably, the resistance reducing agent comprises the following components in percentage by mass:

carbon 10-24%, such as 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20%, 20.5%, 21%, 21.5%, 22%, 22.5%, 23%, or 23.5%, and specific points between the above points, are not intended to be limiting to the space and for brevity and the present disclosure is not intended to be exhaustive of the specific points included in the scope.

Sodium chloride source 40-60%, such as 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, or 59%, and specific points therebetween, limited to space and for brevity, the invention is not exhaustive of the specific points included in the ranges.

Copper powder 20-46%, such as 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, or 45%, and specific points therebetween, not to be limited in space and for brevity, the invention is not exhaustive of the specific points included in the ranges.

As a preferred technical scheme, the resistance reducing agent with excellent resistance reducing effect can be obtained only when the mass percentage of the carbon is 10-24%, the mass percentage of the sodium chloride source is 40-60%, and the mass percentage of the copper powder is 20-46%; if the carbon content is too much, the mass percentage content of the copper powder is not changed, and the content of the sodium chloride source is too low, the water absorption of the resistance reducing agent is poor, and the migration resistance of the charged particles is increased; if the carbon content is too much and the sodium chloride source is not changed, the content of the copper powder is too low, so that the interfaces of the copper powder and the copper powder cannot be well connected, and the interface resistance is increased; if the carbon content is too low and the copper powder content is not changed, the sodium chloride source is too much, the generated free sodium ions cannot be completely absorbed by the carbon, and finally the loss of the sodium ions is caused, and in addition, the resistance reducing agent is also unstable; if the carbon content is too low and the sodium chloride source content is not changed, the copper powder content is too high, and the cost is increased. Therefore, the mass percentages of the carbon, the sodium chloride source and the copper powder are related to each other, each component cannot be too much or too little, and only within the range limited by the preferred technical scheme of the invention, the obtained resistance reducing agent has excellent resistance reducing effect, stability and low cost.

Preferably, the char comprises charcoal and/or coke.

Preferably, the coke comprises any one of coal coke, petroleum coke, or pitch coke, or a combination of at least two of the foregoing.

Preferably, the sodium chloride source comprises any one of common salt, sea salt or sodium chloride purities or a combination of at least two of the foregoing.

In a second aspect, the present invention provides a method for preparing the resistance reducing agent according to the first aspect, the method comprising: and mixing carbon, a sodium chloride source and copper powder to obtain the resistance reducing agent.

In a third aspect, the present invention provides the use of a friction reducer according to the first aspect for reducing the resistivity of soil.

In a fourth aspect, the present invention provides a foundation pit, comprising, from bottom to top, a resistance reducing agent region and a backfill region, wherein the resistance reducing agent region comprises the resistance reducing agent according to the first aspect and a ground pole; the backfill region comprises backfill soil.

Fig. 1 shows a schematic cross-sectional structure of a foundation pit, wherein 1 represents a ground surface, 2 represents a backfill region, 3 represents a drag reduction agent region, 4 represents a position for installing a ground pole, and 5 represents an upper lead.

The foundation pit prepared by the resistance reducing agent provided by the first aspect of the invention can reduce the resistivity of the soil near the earth pole, and the foundation pit is mainly caused by the following two aspects: on one hand, the resistance reducing agent is tightly wrapped around the ground pole and tightly connected with the adjacent soil layer to form a conductor with a larger diameter, and the conductor can form a dendritic extension body in the ground to generate dendritic benefits, so that the resistance reducing agent becomes a best medium, the inner layer of the resistance reducing agent is tightly connected with the ground pole, and the outer layer of the resistance reducing agent is tightly connected with the surrounding soil, thereby greatly reducing the contact resistance of the ground pole and the soil; on the other hand, the size of the ground pole is increased by the resistance reducing agent wrapped on the ground pole, so that the resistance of the ground pole is reduced, because the resistivity of the resistance reducing agent is very small, the resistance reducing agent is wrapped around the ground pole, and compared with the resistivity of soil, the resistivity of the resistance reducing agent is generally two orders of magnitude smaller, so that the resistance of the resistance reducing agent can be ignored, and the resistance reducing agent is regarded as metal, which is equivalent to the size increase of the ground pole, so that the purpose of reducing the ground resistance is achieved, and the effect of connecting a plurality of foundation pits in parallel is better.

Preferably, the depth of the foundation pit is 1-1.5 m, such as 1.1m, 1.15m, 1.2m, 1.25m, 1.3m, 1.35m, 1.4m or 1.45m, and the specific values therebetween are limited by the space and for the sake of brevity, and the invention is not exhaustive.

Preferably, the shape of the top view of the foundation pit is an isosceles triangle.

Preferably, the depth ratio of the resistance reducing agent area to the backfill soil area is 1 (1-1.2), such as 1:1.02, 1:1.04, 1:1.06, 1:1.08, 1:1.1, 1:1.12, 1:1.14, 1:1.16 or 1: 1.18.

Preferably, the material of the ground pole is angle steel.

Preferably, the shape of the electrode is an isosceles triangle.

Preferably, the electrode is a mesh structure.

As a preferable technical scheme, the earth pole of the resistance reducing agent area in the foundation pit is arranged in a grid structure, so that the area of the grounding grid can be increased, and the resistance is further reduced.

In a fifth aspect, the invention provides a method for preparing a foundation pit according to the fourth aspect, wherein a pit with a depth of 1-1.5 m is arranged in soil near a ground pole, the resistance reducing agent according to the first aspect is poured into the resistance reducing agent area, the ground pole is connected, and backfill soil is used for filling up the backfill soil area.

According to the preparation method of the foundation pit, provided by the invention, firstly, a pit comprising a resistance reducing agent area and a backfill area is arranged near a ground pole, the ground pole is connected, the resistance reducing agent is placed in the resistance reducing agent area, and finally, the backfill area is filled and leveled by using backfill. The whole process has the advantages of small construction amount, convenient operation and suitability for large-scale use.

Compared with the prior art, the invention has the following beneficial effects:

the resistance reducing agent provided by the invention comprises a combination of carbon, a sodium chloride source and copper powder, and has excellent resistance reducing effect, excellent corrosion resistance, long-acting property and stability through the cooperation of the carbon, the sodium chloride source and the copper powder; the resistance obtained by testing the resistance reducing agent applied to the method for reducing the resistivity of the soil near the earth pole is 2.3-15 omega, and the resistance reducing agent has excellent stability and long-acting property; and when the resistance reducing agent is used for reducing the resistivity of soil around the earth pole, the construction amount is small, the transportation cost is low, the economic benefit is obvious, the resistance reducing agent does not damage the environment such as the surrounding soil, and the like, and the application value is high, and the market application prospect is wide.

Drawings

Fig. 1 is a schematic cross-sectional structure diagram of a foundation pit provided by the present invention, wherein 1-ground, 2-backfill region, 3-resistance-reducing agent region, 4-position of earth pole, and 5-lead-up line;

fig. 2 is a top view structural diagram of the ground pole provided in embodiment 1.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

Examples 1 to 8

The specific components of the resistance reducing agent are shown in Table 1, and the unit of the usage of each component is weight portion; wherein the sea salt is from salt monopoly bureau market in Chaozhou city, the coal tar is from maple spring market in Chaozhou city, and the copper powder is from market.

TABLE 1

	Coal coke (parts by weight)	Sea salt (parts by weight)	Copper powder (parts by weight)
				Example 1	17	50	33
Example 2	10	60	30
				Example 3	24	48	36
Example 4	20	60	20
				Example 5	15	39	46
Example 6	5	57	38
				Example 7	23	67	10
Example 8	13	37	50

The preparation method comprises the following steps:

and mixing the coal tar, the sea salt and the copper powder to obtain the resistance reducing agent.

Example 9

A resistance reducing agent which is different from example 1 only in that common salt is used instead of sea salt, and other components, amounts and preparation methods are the same as example 1, and the resistance reducing agent is obtained.

Example 10

A resistance reducing agent, which is different from example 1 only in that charcoal (maple spring market, tidal city) is used instead of coal tar, and other components, amounts and preparation methods are the same as those of example 1, to obtain the resistance reducing agent.

Comparative example 1

A resistance reducing agent differing from the examples only in that copper powder was replaced with reduced iron powder (akafeng iron ore, Chaozhou city).

Comparative example 2

The resistance reducing agent comprises 17 parts by weight of coal coke and 33 parts by weight of copper powder; the preparation method is the same as that of example 1, and the resistance reducing agent is obtained.

Comparative example 3

The resistance reducing agent comprises 50 parts by weight of sea salt and 33 parts by weight of copper powder; the preparation method is the same as that of example 1, and the resistance reducing agent is obtained.

Comparative example 4

The resistance reducing agent comprises 17 parts by weight of coal coke and 50 parts by weight of sea salt; the preparation method is the same as that of example 1, and the resistance reducing agent is obtained.

Application examples 1 to 10

A foundation pit is prepared by the following steps: a foundation pit with a depth of 1.5m and an isosceles triangle top view is dug in soil near the ground pole, the foundation pit comprises a resistance reducing agent area and a backfill soil area with depths of 750m from bottom to top, the resistance reducing agents obtained in the embodiments 1-10 are poured into the resistance reducing agent area, the ground pole (angle steel) with a grid structure is connected, and the backfill soil area is filled with backfill soil with a top view structure diagram as shown in fig. 2.

Application example 11

The foundation pit is different from the foundation pit in application example 1 only in that a ground pole (angle steel) with a triangular top view is adopted to replace the ground pole with a grid structure in application example 1, and other components, use amounts and steps are the same as those in application example 1.

Comparative application examples 1 to 4

The foundation pit is different from the application example only in that the resistance reducing agents obtained in comparative examples 1-4 are respectively adopted to replace the resistance reducing agent obtained in example 1, and other components, the using amount and the steps are the same as those of the application example 1.

And (3) performance testing:

(1) resistance: using a ground resistance meter model WK-ZC29B (mechanical) or VICTOR4106 (electronic), 3 measurements were averaged per position;

(2) stability: after testing the resistivity for one week, the resistance value is in accordance with the national standard, namely the stability is good. (national standard: ground resistance less than 100kvA (dry tile) is not more than 10 ohm, and ground resistance more than 100kvA is not more than 4 ohm) (3) long-term effect: after testing the resistivity for one year, the resistance value is in accordance with the national standard, namely the long-term effect is good. (national standard: ground resistance less than 100kvA (dry tile) should not be greater than 10 ohm, ground resistance greater than 100kvA should not be greater than 4 ohm)

The testing method is used for testing the resistance reduction effect of the foundation pit in application examples 1-11 and comparative application examples 1-4, and the test results are shown in table 2:

TABLE 2

As can be seen from the data in table 2:

the resistance reducing agent provided by the invention has excellent conductivity, stability and long-acting property;

specifically, the resistance of the soil near the earth pole obtained by testing the method for reducing the resistivity of the soil near the earth pole provided by application examples 1-11 is 2.3-15 omega, and the stability and the long-term effect can reach the standard;

comparing application example 1 with application example 1, the resistance of application example 1 is higher, which shows that the effect of copper powder matched with sea salt and coal coke is better; comparing application example 1 with comparative application example 2, the resistance of comparative application example 2 is much higher because sodium ions can be provided in the sea salt, effectively reducing the resistance; compared with the comparative application example 3, the comparative application example 3 has poor stability and long-term effect because the coal coke or the charcoal is a material with good adsorbability and is fused with the contacted soil after adsorbing saturated sodium ions, so that the resistivity of the soil is reduced, and if no coal coke or charcoal is used for protecting free sodium ions, the sodium ions are lost quickly, so that the resistance is increased quickly, and the stability and the long-term effect are poor; compared with comparative application example 4, the stability is general, and the long-term effect is poor, because the sodium ion protection property of the coke or charcoal pores is poor, and the copper powder bonding effect is needed to ensure the resistivity stability and the long-term effect.

The resistances obtained by tests in the method for reducing the resistivity of the soil near the earth pole provided in application example 5 and application example 8 are 18 Ω and 10 Ω, respectively, and the stability and the long-term durability are also poor, because the addition amount of the sea salt is too small to provide enough sodium ions, thereby resulting in higher resistance.

The reason why the stability and the long-term effect of application example 6 are poor is that the addition amount of the coal coke is too low to provide effective protection for sodium ions, so that the loss of the sodium ions is rapid, and the stability and the long-term effect are poor.

The reason why the stability of application example 7 is good but the long-term effect is poor is that the copper powder is added in too small amount, and although the coke protects sodium ions, the protection strength is not enough, and the sodium ions are still easy to lose in severe weather, and the copper powder needs to be added to play a role in bonding, so that the long-term effect of the resistivity is ensured.

Comparing application example 1 and application example 11, it can be seen that the resistance of application example 1 is lower because the contact area between the grid-shaped electrode and the soil is larger, and the grounding resistance is effectively reduced.

The applicant states that the present invention is illustrated by the above examples to provide a resistance reducing agent, a preparation method thereof and a process method applied thereto, but the present invention is not limited to the above process steps, i.e. it is not meant that the present invention must rely on the above process steps to be implemented. It will be apparent to those skilled in the art that any modification of the present invention, equivalent substitutions of selected materials and additions of auxiliary components, selection of specific modes and the like, which are within the scope and disclosure of the present invention, are contemplated by the present invention.

Claims

1. A drag reducing agent, characterized in that the drag reducing agent comprises a combination of carbon, a sodium chloride source and copper powder.

2. The resistance reducing agent according to claim 1, characterized in that the resistance reducing agent comprises the following components in percentage by mass:

10-24% of carbon;

40-60% of a sodium chloride source;

20-46% of copper powder.

3. The friction reducer of claim 1 or 2, wherein the char comprises coke and/or charcoal;

4. The resistance reducing agent according to any one of claims 1 to 3, wherein the sodium chloride source comprises any one of salt, sea salt, or a pure sodium chloride, or a combination of at least two of the above.

5. The method for preparing the resistance reducing agent according to any one of claims 1 to 4, wherein the method comprises: and mixing carbon, a sodium chloride source and copper powder to obtain the resistance reducing agent.

6. Use of the drag reducer of any one of claims 1-5 for reducing the resistivity of soil.

7. A foundation pit is characterized by comprising a resistance reducing agent area and a backfill soil area from bottom to top, wherein the resistance reducing agent area comprises the resistance reducing agent and the earth pole according to any one of claims 1-5; the backfill region comprises backfill soil.

8. The foundation pit according to claim 7, wherein the depth of the foundation pit is 1-1.5 m;

preferably, the shape of the top view of the foundation pit is an isosceles triangle;

preferably, the depth ratio of the resistance reducing agent area to the backfill soil area is 1 (1-1.2).

9. The foundation pit according to claim 7 or 8, wherein the material of the ground pole is angle steel;

preferably, the shape of the electrode is an isosceles triangle;

preferably, the electrode is a mesh structure.

10. A method for manufacturing a foundation pit according to any one of claims 7 to 9, wherein a pit with a depth of 1 to 1.5m is provided in the soil near the earth pole, the drag reducer according to any one of claims 1 to 5 is poured into the drag reducer area, the earth pole is connected, and the backfill soil area is filled with backfill soil.