design for site grounding system

7/29/2019 Design for Site Grounding System

1/65

Design for Site Grounding

Engineering Planning & Design

Department


2/65

Objective of Machine Room Grounding

For advancing communication quality ensuring communication equipment andpersonal safety, there ought to be wellgrounding device in AC and DC powersupply system of communication bureau.


3/65

Course Contents

First Chapter Sorting for Grounding System

Second Chapter Grounding Language andMaterials

Third Chapter Sorting for Grounding Body

and Construction Method

Fourth Chapter Computing Method of

Grounding Resistance and Frequently Used

Data

Fifth Chapter Method of Reducing GroundingResistance

Sixth Chapter Grounding for External

Equipment of Base Station


4/65

Sorting for Grounding System

AC Grounding

AC working groundingprotective

groundinglightning grounding

DC Grounding

DC working groundingcabinet bonding


5/65

Sketch Map of Grounding System


6/65

Course Contents







Data





7/65

Grounding Language

The ground we called in grounding system is generic ground, it has

conductive characteristic and infinity capacity, it can be used as nicerreference potential.

1Grounding BodyThe conductor embed underground and contact with the earth (includes:

vertical grounding bodyhorizontal grounding bodycurrent dischargeboard).

1. Grounding ringIt is grounding ring body which is embed underground by stipulating

depth, around the mobile communicating base station (includes: horizontal

grounding body and vertical grounding body).2. Grounding net

It is the grid grounding body according to certain request combined and

close around, by horizontal grounding body or associated with horizontal

grounding body and vertical grounding body.


8/65

2Grounding leadinThe connecting thread which is educed to grounding bar by the

grounding body.

3Grounding BarThe commonality grounding generatrix which is all kinds of grounding

cables imported to the roomelectric power room.4Equipment Grounding CableThe connecting thread that is between communication equipments and

grounding bar.

5Grounding SystemThe floorboard of grounding cablegrounding bargrounding leadinand grounding body.

The grounding system we usually mentioned always means underground

part, includes grounding body and grounding leadin.

Grounding Language


9/65

Grounding Materials in Common Use

1Grounding BodyGrounding Horizontal Bar

404mm galvanized flat steelor 253mm copper bar the length needsto be ordered.

Grounding Vertical Rod50505 mm galvanized angle ironthe commonly length:2000

2500mm.

Or 503.5mm galvanized steel tube, the commonly length : 20002500mm.

Grounding Plate by iron tower using120060010mm galvanized armor plateor 6006006mm copperplate


10/65

2Grounding Leadin:Galvanized flat steel (using in our country ),the length needs to be

ordered.

Or 95mm2 copper lead (using in western country ), the length

needs to be ordered.3Grounding Bar:Using the copper line commonly of which the section area is more

than 120mm2, or galvanized flat steel which has the same section.4Equipment Grounding CableProtection grounding cables use 35-95mm2 copper leads,

recommending 50mm2 copper leads.

Grounding Materials in Common Use


11/65

Course Contents







Data





12/65

Sorting for Grounding Body

1Vertical Grounding Bodya. tubular grounding body b. all kinds of steel section grounding body

2Horizontal Grounding Bodya. lead grounding body b. flat steel grounding body

3Annular Grounding Bodya. annular lead grounding body b. annular grounding body

4Slabby Grounding Bodyacircular plate grounding body b. square plate

grounding body

5Reticular Grounding Body


13/65

Construction Method for Grounding Body

1Single Grounding Stick1. Constitutes

The system that has only one vertical grounding body (or called

grounding stick).2. Construction Method1dig a hole which has 90cm depth, put one 50505

2500mm galvanized angle iron( nib one end ) into the bottom of the

soil layer, leaving over 20cm above, then jointing grounding leading

404mm galvanized flat steel, the length of welding line should betwice over the length of flat steel, the position of the jointing shouldbe antisepsis to deal with. And then fill 90cm soil, that is means

depth is 70cm.2Test Grounding Resistance.


14/65

2Many Vertical Grounding Bodies1. Constitutes

Many vertical grounding body is according to a certainty space disposalassociate with horizontal grounding body according to a certainly demand fittogether.

2. Construction Method1Permutation Method: As a result of lots of reasons such as landform, it islikely to be beelinefold linearc line ranged, but no return no close. It

looks almost beeline ranged.2Construction Method: We can dig channels according to permutation

figure designed in advance, the depth is 90cm, to put vertical grounding bodypriority drive into the bottom of the soil with bareness 20cm in order tojointing above, the space between the vertical grounding body is 1.52.5times than the length of the vertical grounding body. At the 10cm top of thevertical grounding body. We can use the horizontal grounding body to makethem joined together by jointing smeared asphaltum to defend at the jointingsection.

3In the middle and the two end of the horizontal grounding body, we usethe 404mm galvanized flat steel educed separately working groundingprotection grounding and lightning protection grounding.



15/65

4Figure 1Vertical Grounding BodySketch Map of Grounding System of BeelineModel( Planform )

Figure 1

Vertical

grounding body

5Test Grounding Resistance

Horizontal

grounding body



16/65

3Annular Grounding Body1. Constitutes:

Annular grounding system is made up of 404mm galvanized flat steelembedding around machine room and vertical grounding body that isconnected with it .

2. Construction Method:1The depth of the annular grounding body (horizontal) is more than

70cm,the distance to the building wall is more than 1.5m.2dig channels outside the building wall 1.5m,the depth is 90cm,and put onevertical grounding body into the bottom of the soil with bareness 20cm in orderto jointing above, At the 10cm top of the vertical grounding body, We can usethe 404mm galvanized flat steel to make them joined together by jointing, andthen make the horizontal grounding body joint to closed annular body, payattention not to turn ankylosis bending, finally smeared asphaltum to defend at

the jointing section.3Backfill the soiltampingresuming the road surface and conditions.4Educe separately three 404mm galvanized flat steel by the horizontal

grounding body of annular grounding grid as working groundingprotectiongrounding and lightning protection grounding, the distance between the threesections is more than 5m.

5Test Grounding Resistance.



17/65

Machine Room

Figure 2

Vertical

grounding body

(angle iron)

Horizontal

grounding body

(flat steel)

Annular grounding gridding sketch map of a

machine room that has no basic steel bar.

If one annular grounding resistance cant reach the design demand, we can

add an annulus outside of it, the distance between two annulus should be

more than 1.52.5 times of the vertical grounding body. On the top of the

two vertical grounding bodies also should be joined together by jointing,

smeared asphaltum to protect at the jointing section.



18/65

The sketch map of the switching room specially basic reinforcing steel bar of big

room connect with the annular grounding grid .

At least two of the reinforcing steel bar by jointing in room pole and

foundation educe connecting line to the annular grounding grid, needing such

a connecting line in four direction, the connecting line also needs 404mmgalvanized flat steel. So it is very easy to make the grounding resistance of

grounding grid down to 1ohm.



19/65

4Grid Grounding BodyIt is one of the effective grounding way in common use. The constructions such as

switching roomvertical across reinforcing steel bar in basic iron tower, theacross point has been joint or been tightened by the clamp, can be a part of the

grounding body. Before the concrete has been poured in, educing to the

connecting line of the expert ground grid request.

The construction way of using iron tower basic reinforcing steel bar as a part of the

grounding body, viewing the figure below:

The connecting line educed by iron tower basic ground gridding, at least jointing to

the two main reinforcing steel bar in basic ground gridding.



20/65

5Radiancy Horizontal Grounding CableIn the actual application, the geologic circs is very complex, for the terrene circs of the soilabove and the stone below, there is no way to bury vertical grounding body; because of the

ground, the length of the singleness horizontal grounding body comes in for limiting again.

We can bury radiancy horizontal grounding line from the middle to the outside, in order to

reduce the grounding resistance.

Construction Method:Dig channels from the construction around to outside radiantly, the depth is 5070cm, the

common soil channel length is no less than 3.6m.The sand channel length is no less than

7.2m,the depth is 5070cm.

The horizontal body adopt 404mm galvanized flat steel, in the end of the radiancy

grounding line can also connect a piece of 120060010mm galvanized armor plate as

leakage board. The horizontal grounding body and the galvanized armor plate should bejointing together, the welding line is no less than160mm,the jointing section need asphaltum

antisepsis. the length of the horizontal grounding body is no more than 30m.in order to

satisfying the requests of grounding resistance , we can lay more radiancy horizontal

grounding bodies.



21/65

The sketch map for iron tower radiancy grounding line

(broken line)



22/65

6Grounding System Composing by Gridding and VerticalGrounding Body

1. Excellence1Ensure a jarless value of grounding resistance, is an effective grounding

system.

2Horizontal grounding body can provide trusty grounding headstream,grounding net can be qua safety precautions of uniform earths surface malfunction

voltage, for preventing hurt the workers and the foot passengers by the falling thunder.

2. ConstitutesUnited by phalanx arranged horizontal grounding body and making the top of them

connect vertical grounding body.



23/65

3. Construction Method1Dig pane channel according 33m, the depth is 90cm, to put vertical

grounding body drive into the crossing bottom of the soil with bareness 20cm

in order to jointing above;

2Use 404mm galvanized flat steel to make every vertical grounding joined

together by jointing, and then combined gridding grounding net that is closed

aroundinequilateral, the jointing section needs asphaltum antisepsis.

3Use the 404mm galvanized flat steel that is educed separately working

groundingprotection grounding and lightning protection grounding from

horizontal grounding body of grounding net, the distance of three points is no

less than 5m, the jointing section needs asphaltum antisepsis.

4Backfill the soiltampingresuming the road surface and conditions

(ensure that the depth on the top of the vertical grounding body is 70cm).

5Test grounding resistance.



24/65

Ground Net Sketch Map of Gridding + Vertical

Grounding Body

The grounding system according to the picture above constructed,

comparatively easily contenting the request that the grounding resistance

is less than 5 ohm, in the soil that has a quite high mother earth resistance,

such as sand soil, we can use the way above adding proper resistivity

reduction mixture, it also contents the request.



25/65

7United Networks1. Condition of United Networks

It may has machine ground gridiron tower ground grid and transformerground grid in some stations, the space between the three ground grid is no

more than 30m,they should be connected to constitutes a blocking outside

big ground grid.2. The Way of Three Networks Connected

It has at least two connecting between any of two networks, pay attention to

making them compose a blocking annulus that is silken outside; if the sides

is longer, also adding some connecting line.

The mobile communication base station should be equipotential

theory ,uniting the working groundingprotection grounding and lightningprotection grounding to be a combined ground grid. The grounding cables

should be imported separately from the grounding bar or the grounding

grid .



26/65

Constitutes of ground net below:

3. When the machine room is under the iron tower and theelectric transformer set up in the bottom of the room ,can use the

ground grid together, or said that the three parts can use one

ground grid that is suitable.


C C t t


27/65

Course Contents







Data

Fifth Chapter Method of Reducing Grounding

Resistance



Computing Method of Grounding resistance


28/65


Vertical Grounding Body

a. Tubular Grounding

Body

R=[/2]Ln(4(+2t)/(d(+4t)))-----------1In formulaR-grounding resistance of single tube ()-soil resistivity.m-length of vertical tubular grounding bodymd-diameter of vertical tubular groundingbodymt-buried depth from ground to tube topm



29/65

b. All kinds of steel section grounding bodyIf adopting steel section instead of steel tube as grounding body,it should use equivalent diameter instead of d in (1) formula:

flat steeld=b/2 (b is side length of flat steel)equal angled=0.84b (b is side length of angle steel)unequal angle: d=0.71ab(a2+b2))1/4 (a, b is side length of angle steel)

So computing formulation of grounding resistance can be expressed as:flat steel:

R=[/2] Ln((8(+2t)/(b(+4t))-----2equal angle

R=[/2] Ln((4.81(+2t))/(b(+4t))-----3unequal angle

R=[/2] Ln((5.6(+2t))/( (+4t)(ab(a2+b2)1/4)---4


Vertical Grounding Body

Computing Method of Grounding Resistance


30/65


Horizontal Grounding body

a. Lead grounding body

when l d, and t dthe computingformulation of grounding resistance belowR=[/2] . Ln(2/(bt))----5In formulaR-grounding resistance of single horizontal lead()-soil resistivity.m-length of horizontal lead grounding bodymd-diameter of horizontal lead grounding body (mt-buried depth from ground to horizontal leadgrounding bodym



31/65

b. Flat Steel Grounding Body

If adopting flat steel grounding body instead of lead groundingbody, also use equivalent diameter instead of d, d=b/2(b islong side length of flat steel).When lb and tbgrounding resistance isR=[/2l] . Ln(22/(bt))----------6BRACE

YOURSELF


Horizontal Grounding body

Computing Method of Computing Resistance


32/65


Annular Grounding Body

a. Annular lead

grounding body

When buried depth is t meterits groundingresistance can be computed according toformulation belowR=[/22D] Ln(8d2/(dt))---7In formulaRgrounding resistance of annular leadgrounding body ()soil resistivity.mDdiameter of annular grounding bodym

d--- conductor diameter of grounding body (mt---laying depthm



33/65

b. Annular Grounding Body

Computing of grounding resistance for flat steel annulargrounding body refer to computing formulation of annular leadgrounding body, use equivalent diameter 0.5b instead of d:R=[/22D] Ln(8d2/(dt)) 8In formula:bbroadside length of flat steel sectionm


Annular Grounding Body

Computing Method of Grounding


34/65


ResistanceSlabby Grounding Body

aCircular plate grounding bodyIts grounding resistance usebelow formula to computeR=/4D-----------------9

In formula Rgrounding resistance ofcircular plate grounding bodysoil resistivity.mD---diameter of circular plategrounding bodym



35/65

b. Square Plate Grounding BodyIts grounding resistance can use belowformula to computeR=0.22/a---------------10

In formulaais side length of squaremsoil resistivity.m

Tiger is

coming


ResistanceSlabby Grounding Body

Computing Method of Grounding Resistance reticular


36/65

Computing Method of Grounding Resistance reticular

Grounding Body

R=0.44/(A)1/2+0.159 Ln(8A/(hd*104))/ -------11

In formulaR-grounding resistance of reticular grounding body ()A-total area of reticular grounding bodym 2-soil resistivity.m-total length of reticular grounding bodymd-diameter of horizontal grounding bodymh-buried depth from grounding to horizontal grounding bodym

Computing Method of Grounding ResistanceTotal Resista


37/65

Computing Method of Grounding Resistance Total Resista

of Multi-Grounding Body1Multi-Grounding BodyGrounding tape is insulating to soila. grounding resistance of several same vertical grounding

body is RN=R1/n1-------------12in formulaRNgrounding resistance of several same verticalgrounding bodyR1 grounding resistance of single vertical groundingbodyn quantum of vertical grounding bodyentries1 use factor of vertical grounding bodyA/ 0.5 1 1.5 2 2.5 3 10 0.35 0.54 0.6 0.74 0.79 0.85 Level

off to 1The relation between use factor and a/l by test is showing in listabove is length of vertical grounding body, a is distance betweenVertical grounding bodies.

Computing Method of Grounding ResistanceTotal Resista


38/65

b. Grounding resistance of several same horizontalgrounding body isRn=R2/n2----------------------------------13In formulaRngrounding resistance of several same horizontalgrounding bodyR2 grounding resistance of single horizontal groundingbodynquantum of horizontal grounding bodyentries2---use factor of vertical grounding bodyUse factor of striatus horizontal grounding body and leadradiancy grounding body is in back two lists.

Computing Method of Grounding Resistance Total Resista

of Multi-Grounding Body

Computing Method of Grounding ResistanceMulti-


39/65

p g g

Grounding BodyGrounding Tape is not insulated to soil

When there are n entries vertical grounding bodyconnect themwith horizontal grounding bodies, the resistance is computedbelowR=R1R2/[R12+ R21 n]----------------------14

In formulaR ---total grounding resistance of vertical grounding body whichis connected with horizontal n entries vertical grounding bodyR1---grounding resistance of single vertical grounding bodyR2---grounding resistance of grounding tape between verticalgrounding bodies1 use factor of vertical grounding body2 use factor of connecting tapen---- quantum of vertical grounding body

Frequently Used Data of Grounding Resistance


40/65


Computation

Use factor of parallel connection striatus grounding body

Length of

each striatus

grounding

body (m)

Parallel

number

The use factor if distance between strips is thevalue below1 2.5 5 10 15

15 2 0.63 0.75 0.83 0.92 0.965 0.37 0.49 0.6 0.73 0.7910 0.25 0.37 0.49 0.64 0.72

25 5 0.35 0.45 0.55 0.66 0.7310 0.23 0.31 0.43 0.57 0.66

50 2 0.6 0.69 0.78 0.88 0.935 0.33 0.4 0.48 0.58 0.6510 0.2 0.27 0.35 0.46 0.53

Width of striatus horizontal grounding body is 2040millimeter; the buried depth is 0.30.8 m.



41/65

Use factor of lead radiancy grounding body

Lead

length of

radiancem

Use factor of multi-radiancy grounding body( when thenumber is 345)3 4 5

Conductive diameter is separately the value belowcm)1 2 1 2 1 22.5 0.76 0.74 0.63 0.61 0.5 0.48

5 0.78 0.76 0.67 0.65 0.53 0.5110 0.81 0.79 0.7 0.59 0.57 0.5515 0.82 0.8 0.72 0.7 0.59 0.5720 0.84 0.82 0.75 0.73 0.62 0.6

when flat steel is acting as radiation belt, equivalentdiameter is b/2,b is length of flat steel broadside


Computation



42/65

a/ Quantity n of verticalgrounding bodyUse factor

1use factor of VGB 2---use factor of connectiveband1 2 0.85 0.93 0.78 0.825 0.7 0.7510 0.6 0.6220 0.49 0.422 2 0.9 0.933 0.87 0.95 0.8 0.8710 0.73 0.7515 0.7 0.6720 0.69 0.593 2 0.94 0.953 0.9 0.945 0.86 0.9310 0.8 0.8420 0.77 0.68

Use factor of in line arrangement settingsadistance of verticalgrounding bodieslength of vertical grounding body

eque t y Used ata o G ou d g es sta ce

Computation



43/65

a/ Quantity n of eachcolumn VGBUse factor

1use factor of VGB 2---use factor ofconnective band1 3 0.5 0.754 0.45 0.656 0.4 0.610 0.35 0.5520 0.25 0.540 0.2 0.42 3 0.6 0.84 0.55 756 0.5 0.710 0.4 0.6620 0.3 0.613 3 0.75 0.94 0.7 0.856 0.65 0.810 0.56 0.75

Use factor of rectangle settingsadistance between vertical grounding bodieslength ofvertical grounding body, assumed that space between columns is 48m

q y g

Computation



44/65

Resistances of all kinds or soil

SortName

Approximation of

resistance(m)

The changed range of resistances in different conditions(m)

Damper(commonly area

raininess area)Drier(rainless areadesert

area)

Groundwater comprise

salt and alkali

Soil

China clay 10 520 10100 310

Pulpy carbonMarlite

Everglade

20 1030 50300 330

Mashed charcoal 40

BlacklandArgilGardenland

Malm

50 30100 50300 1030

Clunch 60 30100 50300 1030

Sandiness clunch 100 30300 801000 1030

Loess 200 100200 250 30

Soil comprise sandClunch

comprise sand300 1001000 upwards 1000 30100

Sand in river beach 300

Coal 350

Much-rock soil 400

Uplayer red rotten clunch

Underlayer red rock50030% humidity

Surface layer rockUnderlayer

gravel

60015% humidity

Sand

SandGravel 1000 2501000 10002500

The depth of sand bed deeper than

10 mThe groundwater deeper

grassland

1000

The depth of surface clunchdeeper than 1.5mStratum with

much rock

1000

Rock

GravelMashed rock 5000

Hill with rock 5000

Granite 200000

Concrete

In water 4055

In wet soil 100200

In dry soil 5001300

In dry atmosphere 1200018000

Mine Metalline ore 0.01

1

q y g

Computation



45/65

Temperature 0C Soil Resistivity.m20 7210 99

0water 1380ice 300

-5 790-15 3,300

Relation between soil resistivity (contains 15 percent water)andtemperature

q y g

ComputationSoil Resistivity



46/65

Water content of

percent by weight

Common value of resistivity.mClay mixed withsand sand

0 10,000,000 __2.5 1,500 3,000,0005 430 50,00010 185 2,10015 105 63020 63 29030 42 _

Relation between soil resistivity and humidity

q y g




47/65

sort name Approximatevalue of

resistivity.m)

sort name Approximatevalue of

resistivity.m)water Seawater 15 water Branch water 50100Lake and poolwater 30 River water 30600

Water in mud andcarbon 1520 Dirtinesswater 300fountain 4050 Distilledwater 1,000,000

Underground water 2070

Resistivity of all kinds of water

q y g




48/65

halometry% Soil resistivity.m0 107

0.1 181 4.65 1.910 1.320 1

Relation between salt content and soil resistivity in sand soil

q y g




49/65

Season coefficient of correction

for soil resistivity

Because of climatic influence in each month of whole year(includes temperature and humidity), the testing resistivityis different, for ensuring grounding resistivity which isbiggest in certain month of whole year is also satisfiedoperating requirement, need adopting season coefficient ofcorrection, that is:

= --------15in formula

----soil resistivity when computing grounding body---testing resistivity in different month of wholeyear. The below list is coefficient of correction which istesting in different season of Beijing area, as reference.----season coefficient of correction of soil

resistivity

q y g




50/65

Test region1 2 3 4 5 6 7 8 9 10 11 12

Beijing+220

C-120C

1.08 1 0.96 1.35 1.42 1.42 1.42 1.93 1.8 1.6 1.42 1.35

a. Season coefficient of correction for Beijing area




51/65

Climatic conditions Fist area Second area Third area Fourth area

Climatic index

Donkeys years

average low

temperature (Jan.)

-200-150C -150-100C -10000C 0050C

Donkeys years

average high

temperature (Jul.)

+160+180C +180+220C +220+240C +240+260C

Average precipitation

(mm)

400 500 500 300500

Freeze date (day) 190170 150 100 0

Season coefficient of

correction

Length of angle steel

grounding body

is 1.5-2.5 m,

buried depth of

top end is 0.5-

0.8m

1.82.0 1.51.8 1.41.6 1.21.4

Buried depth of Band

or wire steel

grounding body

is 0.8m

4.57.0 3.54.5 2.02.5 1.52.0

Buried depth of band

or wire steel

grounding body

is 0.4m

6.08.0 4.55.5 2.53.0 2

b. Season coefficient of correction in kinds of areas

Based on climatic conditions to other area, choose proper upper limit

range of season coefficient of correction according to below list.


Course Contents


52/65

Course Contents







Data


Resistance



Method of Reducing Grounding Resistance


53/65


Method of Chemical Treatment

Add chemicals to soil to reduce grounding resistance. Generally

the most economical method is adding Nacl, there is layer changed

method and flooding method. This method can make grounding

resistance in goz soil reduce to 1/61/3in sand clay reduce to2/51/3its grounding resistance has little influence by humiture.But chemicals have certain corrosive action to grounding body, its

processing valid for two years, it is to say that add salt every two

years, magnitude of recruitment is half of first adding.



54/65

Main MethodLayer Changed MethodFlooding Method


Method of Reducing Grounding


55/65

Dig doup of which diameter is 0.5m around each grounding body,

from top of grounding body to ground the distance is 0.71m deep;tubular grounding body of which length is 2.5m, diameter is 50cm

and wall thickness is 5mm all drive into underground, on top of

grounding body about 1/3 deep to divide into 68 layers, eachlayer spread 23cm salt, and add one story well conduction 10cmmuck, after tamping add water according to proportion of each

kilogram salt pour 12 liter, and infuse seven layer in same way,use 404 galvanized flat steel on top of grounding body to weld topof consecutive grounding body to a whole, and use same flat steel to

lead to tandem grounding strip in room surface or lead wire of irontower lightning protection to connectfor testing convenience, use3 bolts to connect 404 galvanized terminal post which is in roomleaving behind.

ResistanceLayer Changed Method

Method of Reducing Grounding


56/65

The method is a adopting method when grounding

resistance is higher and need more holes. It is on steel

tube and on different direction each 20cm space to dig

56 holes of which diameter is 1cm, then pour intosaturation saline solution, and use galvanized flat steelto weld, educe to be earthed pole; materials is the same

to front.

ResistanceFlooding Method



57/65

Used Materials:a. urea formaldehyde resin drag reduction

b. acrylamide drag reduction

c. polyacrylamide drag reduction




58/65

Material detail is in this accessory


Course Contents


59/65







Data


Resistance



Grounding for External Equipment of Base Station


60/65


1Grounding for Iron Tower and Obstruction LightingEffectively connecting by tower feet and grounding system.

Iron tower should use solar tower light. For using aviation sign

light of AC feed, the electrical source thread should use cables

that have metal protection layer, the metal protection layershould be grounding in the tower top and the side of the

entrance. The tower light controlling line and every phase line

should fit on lightning arrester to the earth separately in the

entrance, neutral line should be directness grounding.



61/65

2Grounding for Lightning Arrester of Tower TopThe lightning arrester uses one 404mm galvanized flat steel, also

can use one copper lead whose section is over 95mm2 as groundingdown lead bar of lightning arrester.

1. Construction method of using 404mm galvanized flat steel1the lightning arrester below welds a section 404mm galvanized

flat steel, digging two over 8m holes, plating zinc for using;

2

A suitable 40

4mm galvanized flat steel, digging two over 8mholes in the two end, connecting the tail of lightning arrester with bolttower above, connecting with the educed line tower of grounding grid.

3Fastened on tower body, with no insulation.2. Construction method using one copper lead whose section is over

95mm2 as grounding down lead bar of lightning arrester

1welding a section 404mm galvanized flat steel on the lightningarrester below, digging two over8m holes, plating zinc for using;

2A suitable copper lead with welding a copper nose in two end,connecting the tail of lightning arrester with bolt tower above,connecting with the educed line tower of grounding grid.

3Fastened on tower body, with no insulation.




62/65

3Lightning Protection Grounding for Microwave Equipmentsand the Bracket, GSM Antenna and the Bracket

Incorporate microwave equipment and the bracket GSM antennaand the bracket, which is apart from the lightning arrester groundingdown lead bar is always no more than 2m, for hurting by thunderfalling, we must connect with arrester grounding down lead bar asmuch as nearing, let them be equipotential conditions.

4Grounding for GSM FeederOn the bending below position in the feeder above and outside offeeder windows, the feeder conductor get across special groundingequipment to grounding ;if the tower is over 60m high, we will addone position to grounding in the middle. The grounding cable shouldbe short and straight, from up to below.

5Grounding for Base Station RoomPrefabricate machine rooms that have steel structure and metalcovered, such as containershelter and so on, when the border is lessthan 18m, suggesting grounding on the four corner; if the border addeach 18m or remainder, we should add one position to grounding.




63/65

6Grounding for AC Power Supply System(1) Mobile communication base station intercalates appropriative electric power transformer,

electric power wire should use cables that is metal covering or insulation covering through

steel tube to burying to mobile communication base station, the two end of electrical powercable metal covering or steel tube should credibility grounding.

(2) When the transformer set up outside, for aerial high voltage electric power circuitry ofdiscovering areas whose thunderstorm times are over 20 daysthe mother earth resistivityis over 100 ohm m, should add a set of zinc oxide arrester separately on the firstthird orthe secondfourth pole, at the time adding a set of high voltage fuse on the third pole orthe fourth pole.

(3) When the transformer set up inside the base station, its high voltage should use electricpower cable underground pulled in, the length is no less than 200m, the connected positionof electric power cable and the aerial electric power wire, the three phase line should addzinc oxide arrester, on the two end the metal outer sheath should grounding nearly.

(4) The three phase lines of high voltage side of mobile communication base station AC electricpower transformer ,should add zinc oxide arresters separately to the earth, low voltageside of mobile communication base station AC electric power transformer should add noclearance zinc oxide arresters separately to the earth, the shell of transformerACneutral of low voltage side ,and the metal outer sheath of electric power cables that isconnecting with transformer, should grounding to the earth . all the electric power cablesshould install the lightning arrester.

(5) Low voltage electric power cables of coming into mobile communication base stationshould import to the room underground, the length is no less 50m(when transformer highvoltage side uses electrical power cables , the low voltage is not limited). It should installthe lightning arrester when coming into the room, the neutral that is imported in the

screen is not grounding again.




64/65

7Keep Low Resistance Releasing Conditions1Soil Condition`2Contact surface between conductor and soil3long effective grounding device long effective4Rational design of grounding path

Aendurance and continuanceBconductor surface accord with request of ampacityCcurvature radius of conductor is no less than 20cm,curved angle is no less than 90DWherever it is, grounding conductor should alwayskeep down or level.



65/65

THANK YOU

That is all for today.

design for site grounding system

Documents