huawei wireless sites lightning protection and grounding system

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HUAWEI TECHNOLOGIES CO., LTD. www.huawei.com Huawei Confidential Security Level: Guide to Building Huawei Wireless Sites Lightning Protection and Grounding System Site Design and Implementation Management Dept. July 2007

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How to build Huawei Wireless Sites Lightning Protection and Grounding System.

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Page 1: Huawei Wireless Sites Lightning Protection and Grounding System

HUAWEI TECHNOLOGIES CO., LTD.

www.huawei.com

Huawei Confidential

Security Level:

英文标题 :40-47pt 副标题 :26-30pt

字体颜色 : 反白内部使用字体 :

FrutigerNext LT Medium外部使用字体 : Arial

中文标题 :35-47pt字体 : 黑体

副标题 :24-28pt字体颜色 : 反白

字体 : 细黑体

Guide to Building Huawei Wireless Sites

Lightning Protection and Grounding System

Site Design and Implementation Management Dept.

July 2007

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HUAWEI TECHNOLOGIES CO., LTD. Page 2Huawei Confidential

Contents

1. Overview of the Grounding System

2. Earthing Body and Its Construction

3. External Equipment Grounding of Wireless Base Station

4. Methods of Reducing the Earth Resistance

5. Technical Requirements for and Earth Resistance Test of

the Grounding System

6. Main Factors Affecting the Earth Resistance

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Purpose and Classification of Grounding

Purpose Grounding is intended to improve the communications quality and to ensure safety of the

communication devices and the human being.

Classification of ground Working grounding of a device

Working ground is an even and stable conductor for radio-frequency current. It stabilizes the

potential to earth of the circuit and provides a natural path to discharge the transient power noise. Protection ground of a device

Protection ground prevents the destruction of insulation lest the device should carry electric charge

to endanger the personal safety. It also eliminates the static and high-frequency potential. Lightning protection ground

Lightning protection ground provides a path of discharge to the earth and thus protects the devices

and human being from electric discharge of lightning.

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Common Materials of the Grounding System

1. Earthing body Horizontal earthing bar:

40x4 mm galvanized flat steel or 25x3 mm copper bar of any length required Vertical earthing rod:

50x50x5 mm galvanized steel angle of a length ranging from 2000 mm to 2500 mm

or Φ50x3.5 mm galvanized steel pipe of a length ranging from 2000 mm to 2500 mm Earthing plate used for towers:

1200x600x10 mm galvanized steel plate or 600x600x6 mm copper plate

2. Earthing leadin

40x4 mm galvanized flat steel (used in China) of any length required

or 95 mm2 copper conductor (used in western countries) of any length required

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Common Materials of the Grounding System

3. Earthing bar

The earthing bar is generally a copper busbar with a sectional area not less than 120 mm2, which is commonly used and preferred. A piece of galvanized flat steel of the same sec

tional area is an alternative.

4. Equipment earthing cable

The protection grounding cable is a stranded copper conductor ranging from 35 to 95 mm2 . But 50 mm2 is recommended.

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Contents

1. Overview of the Grounding System

2. Earthing Body and Its Construction

3. External Equipment Grounding of Wireless Base Station

4. Methods of Reducing the Earth Resistance

5. Technical Requirements for and Earth Resistance Test of

the Grounding System

6. Main Factors Affecting the Earth Resistance

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Earthing Body and Its Construction — a Single Vertical Earthing Rod

1. A single vertical earthing rod Composition

The grounding system comprises only one vertical earthing rod.

Construction

(1) Excavate a pit 90 cm deep, and drive a 50x50x5x2500 mm steel angle into the soil, with 20 cm of the upper end above the soil. If the soil is solid, make a ¢ 80 hole with a Luoyang shovel or geological drilling rig. Weld the earthing leadin, a piece of 40x4 mm galvanized flat steel, using a qualified steel electrode. The length of the fillet of double-side welding is twice that of the long side of the flat steel. Coat the welding joint with diluted asphalt to prevent corrosion. Fill the whole 90 cm-deep pit with soil, that is, the depth of burial is 70 cm.

(2) Test the earth resistance.

90CM

230CM

20CM

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2. Multiple vertical earthing rods Composition

The grounding system comprises multiple vertical earthing rods spaced out a given distance apart and a horizontal earthing bar.

Construction

(1) The vertical earthing rods can be arranged in a straight line, fold line or pitch arc that is not closed.(2) Excavate a 90 cm-deep channel along the line or arch you have designed. Drive the vertical earthing rods

into the soil one by one, with 20 cm of the upper end above the soil for welding. The spacing between any two adjacent earthing rods is 1.5 to 2.5 times the length of an earthing rod. Weld the earthing rods at the part 10 cm away from the upper end to the earthing bar. Coat the welding joints with asphalt to prevent corrosion.

(3) Use three pieces of 40x4 mm galvanized flat steel to lead out the working ground, protection ground and lightning protection ground respectively from both ends and the middle of the horizontal earthing bar.

(4) Test the earth resistance.

Earthing Body and Its Construction — Multiple Vertical Earthing Rods

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Earthing Body and Its Construction — Multiple Vertical Earthing Rods

20CM

230CM

90CM

1.5~2.5 L

L is the length of a vertical earthing rod.

Horizontal earthing bar Vertical earthing rod

Grounding system of straight-line shape (top view)

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Earthing Body and Its Construction — Ring Grounding

3. Ring earthing body Composition

The grounding system comprises a piece of 40x4 mm galvanized flat steel (or a tinned bare copper wire) buried around the equipment room and a group of vertical earthing rods connected to the flat steel.

Equipment room

Ring earthing body around the equipment room

Vertical earthing rod (steel angle)

Horizontal earthing bar (flat steel)

Construction

◆ Excavate a 90 cm-deep channel 1.5 m away from the wall footing of the building. Drive the vertical earthing rods into the soil at the bottom of the channel at intervals of 5 m. For how to do this, see the construction method presented to you earlier.

◆ Weld three pieces of 40x4 mm galvanized flat steel to the horizontal earthing bar in the ring ground grid, at three points that are 5 m or more apart, as lead-in of the working ground, protection ground and lightning protection ground.

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Earthing Body and Its Construction — Ring Grounding

The foundation reinforcement bars (including the post reinforcement bars) of a switching equipment room, especially, a

large equipment room, must be connected to the ring ground grid. Among the building posts and foundation, at least two

main reinforcement bars must be welded to lead out connection lines to the ring ground grid. Such connection lines must

be available in four directions of the foundation and made of 40x4 mm galvanized flat steel. In this way, the earth

resistance of the ground grid can be easily made below one ohm.

Foundation reinforcement bars of the equipment room

Ring earthing body

A connection line between the ground grid and the foundation reinforcement bars

Connection of the ring earthing body to the foundation reinforcement bars of the equipment room

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Earthing Body and Its Construction — Mesh Grounding

4. Mesh earthing bodyRing earthing body

Foundation reinforcement bars of the tower

A connection line between the foundation reinforcement bars of the tower and the ring ground grid

A connection line between tower foundations

Relation between the foundation ground grid of the tower and the ring ground grid

The mesh earthing body works effectively. Among the reinforcement bars that meet at right angles in a building such

as the switching equipment room or tower foundation, the points of crossing are an integral part of the earthing body

after they are welded or fixed by a strong clip. Before pouring the concrete, weld connection lines toward the special

ground grid. The connection lines led out from the foundation ground grid of the tower must be welded to at least two

main reinforcement bars in the foundation ground grid.

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Earthing Body and Its Construction — Radial Horizontal Earthing Bars

5. Radial horizontal earthing bars

Application

Radial horizontal earthing bars apply to the sites which are so geologically complex that the vertical earthing rods cannot be buried and the length of a single horizontal earthing bar is restricted. On such sites, bury horizontal earthing bars in a radial manner from the center to reduce the earth resistance.

Key points in construction

△ Excavate channels 50–70 cm deep in a radial way around the building. △ Use 40x4 mm galvanized flat steel as a horizontal earthing bar. Connect a 1200x600x10 mm

galvanized steel plate to the end of the radial ground cable as an earthing plate to discharge the current. △ The horizontal earthing bar must be made connective to the galvanized steel plate by welding. The

length of the fillet must be 160 mm or more. Coat the welding joints with asphalt to prevent corrosion. The horizontal earthing bars must not be longer than 30 m. To get the required earth resistance, you can use more than one radial horizontal earthing bar.

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Earthing Body and Its Construction — Radial Horizontal Earthing Bars

Ring earthing body

Foundation reinforcement bars of the tower

A connection line between the foundation reinforcement bars of the tower and the ring ground grid

A connection line between the tower foundations

Radial horizontal earthing bar

Earthing plate

Radial ground cables of a tower (marked by dashed lines)

Radial horizontal earthing bars often apply to towers. They are routed from four feet of the tower outward alon

g the diagonal lines in a radial way, and effectively connected with the tower feet.

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Earthing Body and Its Construction — Mesh Earthing Body + Vertical Earthing Rods

6. Grounding system that comprises a mesh earthing body and vertical earthing rods Advantages

(1) The grounding system is effective in ensuring a stable earth resistance.(2) The vertical earthing rods are reliable sources of earthing. The ground grid is a safety measure to balance the fault

potential on the surface of the ground, and can protect the workers and those who pass by against lightning. Composition

The grounding system comprises the vertical earthing rods arranged in a square matrix and the horizontal earthing bars that connect the top of the vertical earthing rods.

Construction

(1) Excavate a 90 cm-deep channel in the shape of 3x3 m square boxes. Drive the vertical earthing rods into the soil at the bottom of the channel at the points of crossing, with 20 cm of the upper end above the soil for welding.

(2) Use 40x4 mm galvanized flat steel to weld the vertical earthing rods 10 cm away from the upper end to form a ground grid, of which the four sides are closed but not equilong. Coat the welding joints with asphalt to prevent corrosion.

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Earthing Body and Its Construction — Mesh Earthing Body + Vertical Earthing Rods

(3) Weld three pieces of 40x4 mm galvanized flat steel to the horizontal earthing bars of the ground grid, at three points

not less than 5 m apart, as lead-in of the working ground, protection ground and lightning protection ground

respectively. Coat the welding joints with asphalt to prevent corrosion.

(4) Backfill the channel with soil and tamp the soil. Restore the ground environment to its original appearance. Ensure

the top of the vertical earthing rods is buried 70 cm below the ground.

(5) Test the earth resistance.

Vertical earthing rod

ground grid that comprises a mesh earthing body and vertical earthing rods

Horizontal earthing bar

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Earthing Body and Its Construction — Multi-Grid Joint Grounding

7. Multi-grid joint grounding Conditions of multi-grid joint grounding

In some sites, there is a ground grid of the equipment room, a ground grid of the tower and a ground

grid of the transformer, which are no more than 30 m apart. In this case, the three ground grids must

be connected to form a large closed ground grid.

Horizontal earthing bar Vertical earthing rod

Ground grid of the towerGround grid of the equipment room

Ground grid of the transformer

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8. Building Roof Grounding

Building roof grounding requires you to make full use of the established

grounding system of the building. If the grounding system of the building

meets the resistance requirement, connect galvanized flat steel to the

grounding system of the building and test the resistance. If the grounding

system of the building does not meet the resistance requirement, expand the

grounding system of the building or build a separate ground grid based on

the working drawings designed by the site design department.

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GroundingGrounding

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GroundingGrounding

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Joint Grounding System of a Base Station

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Joint Grounding System of a Base Station

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Contents

1. Overview of the Grounding System

2. Earthing Body and Its Construction

3. External Equipment Grounding of Wireless Base Station

4. Methods of Reducing the Earth Resistance

5. Technical Requirements for and Earth Resistance Test of

the Grounding System

6. Main Factors Affecting the Earth Resistance

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External Equipment Grounding of Wireless Base Station

Grounding of the tower and aviation obstruction light Connect the tower and aviation obstruction light to the grounding system through the tower feet.

For the aviation lights fed by AC, use a cable with a metal jacket as the power cable. Ground the metal

jacket nearby at the tower top and the outside of the inlet to the equipment room. Equip each phase line

of the tower light control cable and power cable with a lightning arrester at the inlet to the equipment

room, and ground the zero lines directly. Grounding of the lightning arrester at the tower top

Construction method for using a piece of 40x4 mm galvanized flat steel as the grounding

downlead:(1) Weld a piece of 40x4 mm galvanized flat steel to the lower part of the lightning arrester. Make two holes

larger than Φ10 mm on the flat steel and galvanize the holes.

(2) Use a piece of 40x4 mm galvanized flat steel of the proper length, and make two holes larger than

Φ10mm at each end of the flat steel. Connect the upper part of the flat steel to the tail of the lightning

arrester with bolts and the lower part to the lead-out wire of the ground grid.

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External Equipment Grounding of Wireless Base Station

(3) Fix the downlead to the tower body without insulation processing.(4) Weld the galvanized flat steel instead of riveting it. The length of the lap welding at the joint should b

e over twice the width of the flat steel, or over ten times the diameter if round steel is used. (5) Do not route the downlead of the lightning arrester along the ladder. Instead, route it along the tower

body at the side far from the equipment room.

Construction method for using a copper conduction with a sectional area more than 95

mm2 as the grounding downlead of the lightning arrester:(1) Weld a piece of 40x4 mm galvanized flat steel to the lower part of the lightning arrester. Make two h

oles larger than Φ10 mm on the flat steel and galvanize the holes. (2) Use a copper conductor of the proper length, and weld a copper lug at each end of the copper cond

uctor. Lap the upper part of the copper conductor to the tail of the lightning arrester with bolts and the lower part to the lead-out wire of the ground grid. Process the lapped joint to prevent corrosion.

(3) Fix the downlead to the tower body without insulation processing.

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External Equipment Grounding of Wireless Base Station

Lightning protection grounding of a microwave device and its support, a GSM

antenna and its support The integrated microwave device and its support, GSN antenna and its support are generally no more than 2 m away from the grounding downlead of the lightning arrester. To escape the harm caused by side striking in the case of lightning, they must be connected to the grounding downlead of the lightning arrester so that they are located in the equipotential environment.

Grounding of a GSM feeder At the part where the upper part of the feeder is bent to run downward and outside the feeder window, ground the coaxial external conductor of the feeder through a special grounding device. If the tower is over 60 m high, add a grounding point in the middle. The grounding cables should be short and straight, and routed from the top down.

Grounding of the base station equipment room The equipment room, for example, a container and shelter, covered by prefabricated steel-structured metal should preferably be grounded at four corners when the side lengths are less than 18 m. One more grounding point is needed for every additional 18 m or an additional length less than 18 m.

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Contents

1. Overview of the Grounding System

2. Earthing Body and Its Construction

3. External Equipment Grounding of Wireless Base Station

4. Methods of Reducing the Earth Resistance

5. Technical Requirements for and Earth Resistance Test of

the Grounding System

6. Main Factors Affecting the Earth Resistance

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Methods of Reducing the Earth Resistance

Classification:

Chemical treatment method

Resistivity reduction agent method

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Chemical Treatment Method

Definition Chemicals are added to the soil to reduce the earth resistance. A common chemical serving this purpose is salt (NaCl). Classification of construction methods

Stacking Pouring

Effect Sandy soil: The earth resistance drops to 1/6–1/3 of the original value. Sandy clay: The earth resistance drops to 2/5–1/3 of the original value.

Valid term two years. Salt must be supplemented every two years in the

quantity that is half of the quantity initially added to the soil. Disadvantage Chemicals always corrode the earthing body.

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Chemical Treatment Method — Stacking

Key points of construction of stacking

Divide the earth around the upper part of each earthing body at the height of about one third of

the length of the earthing body, that is, 600–800 mm, into six to eight layers. Lay 20–30 mm salt

at each layer and then add 100 mm conductive humus soil. Tamp the soil and pour one to two

liters of water for each kilogram of salt to the soil. Deal with the other seven layers of earth in the

same way. Each pipe needs 30 to 40 kilograms of salt. Connect the top ends of adjacent earthing bodies into one unit through 40x4 mm galvanized flat

steel. Then lead this unit to the grounding busbar in the equipment room or connect it to the

lightning protection downlead of the tower through the same flat steel. For easy test, connect it to the reserved 40x4 mm galvanized connecting terminal with three

bolts.

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Chemical Treatment Method — Pouring

Key points of construction of pouring

The pouring method applies to the circumstances where the earth resistivity is so high that many

holes must be made. Make 5–6 holes of a diameter of 10 mm every 200 mm in different directions on the steel pipes

driven into the earth, and then pour saturated salt water in the holes. Use 20–40 kilograms of salt for each steel pipe and mix each kilogram of salt with one to two

kilograms of water. Weld the steel pipes with galvanized flat steel to lead out a grounding electrode, using the same

material as in the stacking method introduced earlier.

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Resistivity Reduction Agent

Types of resistivity reduction agents Urea-formaldehyde resin Acrylamide Polyacry lamide

General principle followed in using the resistivity reduction agent

Each earthing body, whether in the form of a rod, plate or thread and whether laid horizontally or

vertically, must be placed in the middle of the resistivity reduction agent and in good contact with the

electrode and soil to reduce the resistivity sharply.

Formula and construction method of the resistivity reduction agent

See pages 12 through 14 in the Guide to Building Huawei Wireless Sites – Lightning Protection and

Grounding System.

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Contents

1. Overview of the Grounding System

2. Earthing Body and Its Construction

3. External Equipment Grounding of Wireless Base Station

4. Methods of Reducing the Earth Resistance

5. Technical Requirements for and Earth Resistance Test of the

Grounding System

6. Main Factors Affecting the Earth Resistance

7. Design Specification of the Lightning Protection and

Grounding System

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Technical Requirements for and Earth Resistance Test of the Grounding System

Technical requirements The earth resistance of the general communications building must be preferably no more than

one ohm. Among the wireless sites, the earth resistance of the BTS site should be no more than five ohms,

and that of the BSC and MSC sites no more than one ohm. Voltage resistance and equipotential measures are adopted lest the lightning should produce a

high step voltage to injure the human being.

Test methods of earth resistance Trielectrode method Triangle method

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Testing the Earth Resistance — Trielectrode Method

G: tested grounding device

D: maximum diagonal length of the ground grid

P: voltage electrode used for the test

C: current electrode used for the test

dGc: distance between the current electrode and the edge

of the ground grid

dGP : distance between the voltage electrode and the edge

of the ground grid

D

G

dGc

dGp

P C

Electrode arrangement of the trielectrode method

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Testing the Earth Resistance — Trielectrode Method

dGP is about 50%– 60% of dGc.

dGc is four to five times the D.

In an area with even soil resistivity, if you have trouble in assigning 4D–5D to dGc, assign 2D to dGc and D to dGP.

In an area with uneven soil resistivity or in an urban area, assign 3D to dGC and 1.7D to dGP.

In measurement, move three times along the connection line between G and C, moving 5% of dGC each time. It is okay if

the three values tested are close to each other.

Since dGC and dGP are counted from the edge of the ground grid, dGP is not 0.618 dGC, but 0.5– 0.55dGC, which takes the

distance from the ground grid edge to the ground grid center into account. In this way, the distance from the ground grid

center to the voltage electrode is about 0.618 of the distance from the ground grid center to the current electrode.

G

E

A

V

P C

i

Rationale of the trielectrode method

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G: tested grounding device

D: maximum diagonal length of the ground grid

P: voltage electrode used for the test

C: current electrode used for the test

dGc: distance between the current electrode and the edge of the

ground grid

dGP: distance between the voltage electrode and the edge of the

ground grid

dGP=dGC>2D, included angle = 29 30

Testing the Earth Resistance — Triangle Method

Rationale of the triangle method

D

G

P

C

dGp

dGc

?30º

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Contents

1. Overview of the Grounding System

2. Earthing Body and Its Construction

3. External Equipment Grounding of Wireless Base Station

4. Methods of Reducing the Earth Resistance

5. Technical Requirements for and Earth Resistance Test of

the Grounding System

6. Main Factors Affecting the Earth Resistance

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Main Factors Affecting the Earth Resistance

Electrical conductivity of the earth

Moisture content of the earth

Salt content of the earth

Depth of the grounding resistor

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Main Factors Affecting the Earth Resistance — Electrical Conductivity of the Earth

Classification of the earth Soil Sandy Rock Coagulative Mine

For the electrical conductivity of different types of earth, refer to page 17 in the Guide to

Building Huawei Wireless Sites – Lightning Protection and Grounding System .

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Main Factors Affecting the Earth Resistance — Water Content of the Earth

The electrical resistivity of the earth changes sharply with the water content. For

example, for sandy clay, the electrical resistivity is 10 x 106 ·m when the water

content is zero, and 42 ·m when the water content is 30%.

Factors affecting the water content of the earth

Seasonal rainfall Geological depth

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Main Factors Affecting the Earth Resistance — Salt Content of the Earth

Soluble salt particles contained in the soil water can reduce the electrical

resistivity of the earth

Salt, copper sulfate and magnesium sulfate can be used as resistivity reduction

agents.

Some resistivity reduction agents, for example, salt, corrode the earthing bodies.

In construction, use the salt of small corrosive action and long-acting resistivity

reduction agents.

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Main Factors Affecting the Earth Resistance — Depth of the Grounding Resistor

The electrical resistivity of the soil 1–2 m away from the ground surface is high and changes sharply with

the change of seasonal rainfall. The deeper the soil, the less the water content changes with the season and the more stable the

electrical resistivity.

Relation between the earth resistance and the depth of burial of the earthing body (assume the soil is

even)

R: earth resistance () : electrical resistivity (·cm) L: length of the vertical earthing rod (L+70 cm refers to the depth of burial) (cm) S: equivalent semidiameter of the earthing body (cm)

1

4

L2 s

lLnR

πρ

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Attachments

Huawei Wireless Node-B Construction Spec

Checklist for Grounding Net Installation

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Winning Together!Winning Together!Winning Together!Winning Together!

The end