DE102014111469B4 - Electrical grounding system and method for creating an electrical grounding system - Google Patents

Abstract

An electrical grounding system comprising at least one electrical earthing conductor (4) received in an excavation (2) in the ground (3), characterized in that the at least one electrical earthing conductor (4) for reducing an earth propagation resistance of the earthing system completely and directly into an electrical grounding conductive liquid bottom (6) is embedded, with which at least the electrical grounding conductor (4) receiving portion of the excavation (2) is filled, the liquid soil (6) to set a constant specific earth resistance based on its total amount of sand, preferably fine sand content, between 60% and 70%, a water content between 25% and 30%, a plasticizer content in the form of a mixture of different clay materials between 1% and 2% and a cement content between 2% and 3%.

Description

The invention relates to an electrical grounding system according to the preamble of claim 1 and a method and method for creating an electrical grounding system according to the preamble of claim 8.

Electrical earthing systems are well known. These usually comprise at least one preferably made of strip steel electrical grounding conductor, also called Erder, which is introduced into an excavation in the ground and then backfilled with soil, preferably the excavated material. The embedding of the earthing conductor was carried out here directly in the surrounding soil, so that in the event of overvoltage via the grounding conductor, the overvoltage is discharged into the earth's environment. The Erdausbreitungswiderstand the electrical grounding system is determined here essentially by the specific earth resistance of the surrounding earth conductor filling material. If the earthing conductor is surrounded by wet moor soil, for example, it is approx. 10-80 Ωm. For rocky rocks the specific earth resistance can even reach values above 2000 Ωm. For example, normal humus or arable soil has a specific earth resistance between 50-200 Ωm. In addition, the specific earth resistance is strongly temperature-dependent.

Electrical grounding systems can be designed in different ways, for example as surface earth, Tiefenerder, foundation earth or as Ringerder. In the case of the surface earth electrode, the electrical earthing conductor is laid approximately parallel to the surface of the earth or horizontally at a depth of between 0.5 m and 1 m. The earth electrode comprises a rod-shaped earth conductor, which may be formed, for example, as a solid rod, tube or profiled bar and is introduced approximately perpendicular to the earth's surface into the ground, preferably into a deep hole. At the foundation earth electrode, the earthing conductor is completely surrounded by concrete, which forms a corrosion protection for the electrical earthing conductor. The Ringerder has an annular bent earthing conductor made of steel strip and is also embedded directly in the soil. With the exception of the costly foundation earth, the earthing conductors of all grounding systems are subject to corrosion due to the moisture present in the soil, resulting in a deterioration in the effectiveness of the earth electrode.

From the DE 1 069 242 B is already an electrical grounding system with improved, ie reduced Erdausbreitungswiderstand known, in which an earth electrode is embedded in a standing in contact with him electrically conductive, clay-like mass. Here, the investment material used is a predominantly fine-grained clay which has a permanent bond with water and has a pH of about 7.

Also commercially available materials are known which can be used in electrical grounding systems for embedding electrical grounding conductors to reduce the earth propagation resistance. These products are so-called "Ground Enhancement Compounds" or "Ground Enhancement Materials". For example, a product is sold under the trade name LPI RESLO-10. A test report on electrical resistance measurements of this material is available to the public
(Http://www.lpi.com.au/portals/0/Earthing_Calculator/English/download/reslo-report-v3.pdf). For another product with the trade name GEM Ground Enhancement Material ERICO, a long-term study with the corresponding results regarding the mechanical and electrical properties or resistance of the material in electrical grounding systems has been published (F. D'Alessandro, W. Judson, M. Havelka, International Conference on Grounding and Earthing & 1st International Conference on Lightning Physics and Effects, November 2004).

It is also known to improve electrical grounding systems by adding bentonite to a concrete used to embed the electrical grounding conductors (Siow Chun Lim, Chandima Gomes and Mohd Zainal Abidin Ab Kadir, Int J Electrochem, Sci., 8 (2013) 11429 -11,447).

Also known is an innovative building material and a method for its production, for example from the DE 103 02 772 A1 and the associated subsequent application WO 2004/065330 A2 consisting of a excavated soil and an initially temporarily liquefied, self-hardening soil-additive mixture of aggregates, recycled material and additives in liquefied form. This mixture of the stated proportions of material is introduced in liquefied form in a Erdaushebung and installed therein. This building material is referred to in geotechnical engineering as "liquid soil", which is used for the installation of buried components such as pipes and conduits or ground improvement and in which preferably provided for refilling excavated soil material is made to flow. Liquid soil is a temporary flowable filling material, which compresses itself and thus the Reconsolidation without external compaction work done. The reconsolidation is based on crystalline water retention and incorporation by nanostructural reaction mechanisms.

Proceeding from this, the present invention seeks to provide an electrical grounding system, which has an improved Erdausbreitungswiderstand and in particular over the entire year has a constant specific earth resistance. The object is achieved on the basis of the preamble of claim 1 by its characterizing features. Furthermore, the object is achieved by a method according to the features of claim 8. Advantageous developments are the subject of the dependent claims.

The essential aspect of the electrical grounding system according to the invention is the fact that the at least one electrical grounding conductor for reducing Erdausbreitungswiderstandes the grounding system is completely and directly embedded in an electrically conductive liquid soil, with which at least the electrical grounding conductor receiving portion of the excavation is filled. Particularly advantageous is the use of liquid soil, the Erdausbreitungswiderstand the electrical grounding system significantly reduced, which is between 4 Ωm and 5 Ωm. The liquid soil has to set a constant specific earth resistance, a sand content, preferably fine sand content, and a Plastifikatoranteil in the form of a mixture of different clay materials, a cement content and a water content, the liquid soil based on its total amount of sand, preferably fine sand content, between 60% and 70%, a water content between 25% and 30%, a plasticizer content between 1% and 2% and a cement content between 2% and 3%.

• – Sand, vorzugsweise Feinsand 1250 kg/m³
• – Wasser 501 kg/m³
• – Plastifikator 33 kg/m³
• – Zement 45 kg/m³

A particularly preferred composition of the liquid soil has the following proportions, based on its total amount of the liquid soil:

• - Sand, preferably fine sand 1250 kg / m ³
• - Water 501 kg / m ³
• - Plasticizer 33 kg / m ³
• - Cement 45 kg / m ³

This composition allows a reduction in the earth propagation resistance to approximately 4.23 Ωm.

In a preferred embodiment, the at least one electrical grounding conductor with an embedding depth between 15 cm and 50 cm is embedded in the electrically conductive liquid bottom. With such a complete and direct embedding of the electrical earthing conductor in the liquid soil, it could be demonstrated that the moisture in the liquid soil remains almost constant throughout the year, ie. H. there is a constant specific earth resistance.

Further advantageously, the liquid soil has a uniaxial compressive strength between 0.10 N / mm ² and 0.60 N / mm ² , wherein the deformation modulus (EV ² value) of the liquid soil which can be determined by a static plate pressure test is greater than or equal to 45 MN / m ² ,

In a preferred embodiment, the liquid soil has a pH of between 9 and 11, preferably 10.5. This effectively suppresses the corrosion of the electrical ground conductor embedded in the liquid soil.

The invention likewise relates to a method for producing an electrical grounding system comprising at least one electrical earthing conductor, in which a excavation in the ground is created, in which the electrical grounding conductor is introduced and embedded in electrically conductive liquid soil. Advantageously, a deep vertical drilling is performed to create the excavation, which is at least partially filled with the electrically conductive liquid soil. In this case, the electrical grounding conductor can be introduced into the excavation either before or after the at least partial filling of the excavated area with the electrically conductive liquid soil and optionally fixed there.

Further advantageously, the remaining, unfilled portion of the excavation is filled with a further filling material, preferably the excavated material.

The electrical grounding conductor is assembled in a variant embodiment before insertion into the excavation or the vertical deep hole of several parts to form a Tiefenerders.

The expressions "approximately", "substantially" or "approximately" in the context of the invention mean deviations from the respective exact value by +/- 10%, preferably by +/- 5% and / or deviations in the form of changes insignificant for the function ,

Further developments, advantages and applications of the invention will become apparent from the following description of exemplary embodiments and from the figures. In this case, all described and / or illustrated features alone or in any combination are fundamentally the subject of the invention, regardless of their summary in the claims or their dependency. Also, the content of the claims is made an integral part of the description.

The invention will be explained in more detail below with reference to the figures of exemplary embodiments. Show it:

1 FIG. 2 a schematic sectional view through an electrical grounding system according to the invention in the form of a surface earth electrode, FIG.

2 a schematic sectional view through the electrical grounding conductor and the surrounding liquid soil and

3 a schematic sectional view through an alternative embodiment of an inventive electrical grounding system in the form of a depth commuter.

1 shows by way of example in a schematic sectional view a cross section through an inventive electrical grounding system 1 comprising at least one in a excavation 2 in the ground 3 received electrical grounding conductor 4 ,

The excavation 2 in the ground 3 is formed in the present embodiment by a shaft-like pit and has, for example, a depth T between 0.5 m and 1.5 m. 1 thus shows a realization of an electrical grounding system 1 in the form of a surface earth, in which the grounding conductor 4 approximately parallel to the earth's surface 5 in the excavation 2 to be led.

The electrical grounding conductor 4 is preferably formed in the form of a metal strip which has an approximately rectangular cross-section. The installation of the electrical earthing conductor 4 This is preferably edgewise, ie the opposite broad sides of the metal strip are perpendicular to the earth's surface 5 , For example, the electrical grounding conductor 4 made of steel strip. The electrical grounding conductor 4 is connected via grounding lines not shown in the figures with an electrical system to be protected against overvoltage, for example a domestic power network, and forms the ground connection thereof.

According to the invention for laying an electrical grounding system according to the invention 1 first an excavation 2 in the ground 3 created, depending on the type of earth to be realized an excavation 2 in the form of a shaft-like pit at a surface soil or a excavation 2 in the form of a vertical deep hole in a depth drill.

After completion of the excavation 2 becomes the excavation 2 at least in sections with the flowable electrically conductive liquid soil 6 filled, preferably up to a predetermined embedding depth ET for the electrical grounding conductor 4 is reached. The electrical grounding conductor 4 is either after or during the at least partial backfilling of the excavation 2 with the liquid soil 6 embedded in this, in such a way that the electrical grounding conductor 4 completely from the liquid soil 6 is enclosed and in direct contact with it. The electrical grounding conductor 4 is arranged, for example, with horizontal orientation in the shaft-like pit of a Oberflächenerders or vertical orientation in the vertical depth hole of a Tiefenderders. Following this, the remaining section of the excavation 2 preferably to the earth's surface 5 with the excavated material 7 and / or another filling material filled. Preferably, the filling of the remaining portion of the excavation takes place 2 after solidification of the liquid soil 6 in the excavation 2 ,

Alternatively, the electrical ground conductor 4 before filling the excavation 2 in the excavation 2 are introduced and fixed therein, for example by means of spacers in a mounting position. This ensures that during subsequent filling with the liquid soil 6 no unwanted displacement of the electrical earthing conductor 4 from the mounting position.

The electrical grounding conductor 4 is preferably completely in the liquid soil 6 is embedded, in such a way that the embedding depth ET is between 15 cm and 50 cm. Under the embedding depth ET in the sense of the invention becomes the electrical grounding conductor 4 radially surrounding layer thickness of the liquid soil 6 Understood. In 2 is exemplary of a first circular electrical grounding conductor 4 surrounding dashed line a first embedding depth ET1 of 15 cm and a second embedding depth ET2 of 50 cm shown. In the 2 illustrated first or second embedding depth ET1 or ET2 thus forms the radius of a cross-section approximately circular embedding layer of liquid soil 6 ,

The liquid soil 6 According to the invention comprises a sand content, preferably fine sand content and a Plastifikatoranteil in the form of a mixture of different clay materials, a cement content and a water content. Based on the total amount of liquid soil 6 the sand content is between 60% and 70%, thus providing the base material of the liquid soil 6 The proportion of water or the addition of water is between 25% and 30%. The plasticizer content is between 1% and 2% and the cement content is also only between 2% and 3%.

A preferred mixture of liquid soil 6 has the following recipe: Sand content, preferably fine sand content 1250 kg / m ³ water content 501 kg / m ³ Plastifikatoranteil 33 kg / m ³ cement content 45 kg / m ³

For example, the product RSS Liquid Soil Compound (RSS FBC) from PROV Produktions- und Vertriebsgesellschaft mbH can be used as a plastic component, which is a light, free-flowing powder with the other ingredients mentioned above with the addition of water to produce the liquid soil 6 is mixed. The fluidity and reconsolidation of the liquid soil 6 is controlled by the amount of plasticizer.

In a preferred embodiment, the liquid soil 6 a uniaxial compressive strength between 0.10 N / mm ² and 0.60 N / mm ² and the deformation modulus (E _V2 value) of the liquid soil which can be determined by a static plate pressure test 6 is preferably greater than or equal to 45 MN / m ² .

In a further embodiment of the invention, the liquid soil 6 a PH value between 9 and 11, preferably 10.5, to corrosion of the electrical grounding conductor 4 to suppress.

LIST OF REFERENCE NUMBERS

1

Electrical grounding system

2

excavation

3

ground

4

electrical grounding conductor

5

ground surface

6

liquid soil

7

filling material

T

depth

ET

embedment depth

ET1

first embedment depth

ET2

second embedment depth

Claims (12)

Electrical earthing system comprising at least one electrical earthing conductor ( 4 ), in an excavation ( 2 ) in the ground ( 3 ), characterized in that the at least one electrical grounding conductor ( 4 ) for reducing a Erdausbreitungswiderstandes of the grounding system completely and directly into an electrically conductive liquid soil ( 6 ) is embedded, with which at least the electrical grounding conductor ( 4 ) receiving section of the excavation ( 2 ), the liquid soil ( 6 ) To set a constant specific earth resistance based on its total amount of sand, preferably fine sand content, between 60% and 70%, a water content between 25% and 30%, a Plasticizer content in the form of a mixture of different clay materials between 1% and 2% and a cement content between 2% and 3%. Electrical grounding system according to claim 1, characterized in that the liquid soil ( 6 ) based on its total amount has the following proportions: - sand, preferably fine sand 1250 kg / m ³ - water 501 kg / m ³ - plasticizer 33 kg / m ³ - cement 45 kg / m ³ Electrical grounding system according to claim 1 or 2, characterized in that the at least one electrical grounding conductor ( 4 ) with an embedding depth (ET, ET1, ET2) between 15 cm and 50 cm in the electrically conductive liquid soil ( 6 ) is embedded. Electrical grounding system according to one of claims 1 to 3, characterized in that the liquid soil ( 6 ) has a uniaxial compressive strength between 0.10 N / mm ² and 0.60 N / mm ² . Electrical grounding system according to one of claims 1 to 4, characterized in that the determined by a static plate pressure test deformation module (EV2 value) of the liquid soil ( 6 ) is greater than or equal to 45 MN / m ² . Electrical grounding system according to one of claims 1 to 5, characterized in that the liquid soil ( 6 ) has a pH between 9 and 11, preferably 10.5. Electrical grounding system according to one of claims 1 to 6, characterized in that the liquid soil for reducing the Erdausbreitungswiderstands the electrical grounding system ( 1 ) has a specific earth resistance between 4 Ωm and 5 Ωm, preferably 4.23 Ωm. Method for creating an electrical grounding system ( 1 ) comprising at least one electrical grounding conductor ( 4 ), in which an excavation ( 2 ) in the ground ( 3 ) into which the electrical grounding conductor ( 4 ) and to reduce a Erdausbreitungswiderstandes the grounding system completely and directly into electrically conductive liquid soil ( 6 ), wherein the liquid soil for setting a constant specific earth resistance, a sand content, preferably fine sand content, between 60% and 70%, a water content between 25% and 30%, a plasticizer content in the form of a mixture of different clay materials between 1% and 2% and a cement content of between 2% and 3%. A method according to claim 8, characterized in that for the creation of the excavation ( 2 ) is carried out a vertical deep hole which at least partially with the electrically conductive liquid soil ( 6 ) is filled. Method according to claim 8 or 9, characterized in that the electrical grounding conductor ( 4 ) before or after the at least partial filling of the excavation ( 2 ) with the electrically conductive liquid soil ( 6 ) in the excavation ( 2 ) is introduced and possibly fixed there. Method according to one of claims 8 to 10, characterized in that the remaining, unfilled portion of the excavation ( 2 ) with another filling material ( 7 ), preferably the excavated material is filled. Method according to one of claims 8 to 11, characterized in that the electrical grounding conductor ( 4 ) before insertion into the excavation ( 2 ) is assembled from several parts to form a depth gauge.

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