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Design for Site Grounding

Design for Site Grounding. Engineering Planning & Design Department. Objective of Machine Room Grounding.

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Design for Site Grounding

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  1. Design for Site Grounding Engineering Planning & Design Department

  2. Objective of Machine Room Grounding For advancing communication quality 、ensuring communication equipment and personal safety, there ought to be well grounding device in AC and DC power supply system of communication bureau.

  3. Course Contents First Chapter Sorting for Grounding System Second Chapter Grounding Language and Materials 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 Grounding Resistance Sixth Chapter Grounding for External Equipment of Base Station

  4. Sorting for Grounding System AC Grounding AC working grounding、protective grounding、lightning grounding DC Grounding DC working grounding、cabinet bonding

  5. Sketch Map of Grounding System

  6. Course Contents First Chapter Sorting for Grounding System Second Chapter Grounding Language and Materials 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 Grounding Resistance Sixth Chapter Grounding for External Equipment of Base Station

  7. Grounding Language The ground we called in grounding system is generic ground, it has conductive characteristic and infinity capacity, it can be used as nicer reference potential. 1）Grounding Body The conductor embed underground and contact with the earth (includes: vertical grounding body、horizontal grounding body、current discharge board). 1. Grounding ring It 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. Grounding Language 2）Grounding leadin The connecting thread which is educed to grounding bar by the grounding body. 3）Grounding Bar The commonality grounding generatrix which is all kinds of grounding cables imported to the room、electric power room. 4）Equipment Grounding Cable The connecting thread that is between communication equipments and grounding bar. 5）Grounding System The floorboard of grounding cable、grounding bar、grounding leadin and grounding body. The grounding system we usually mentioned always means underground part, includes grounding body and grounding leadin.

  9. Grounding Materials in Common Use 1）Grounding Body Grounding Horizontal Bar： 40×4mm galvanized flat steel，or 25×3mm copper bar， the length needs to be ordered. Grounding Vertical Rod： 50×50×5 mm galvanized angle iron，the commonly length:2000—2500mm. Or Φ50×3.5mm galvanized steel tube, the commonly length : 2000—2500mm. Grounding Plate by iron tower using： 1200×600×10mm galvanized armor plate or 600×600×6mm copperplate

  10. Grounding Materials in Common Use 2）Grounding 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. 3）Grounding Bar: Using the copper line commonly of which the section area is more than 120mm2, or galvanized flat steel which has the same section. 4）Equipment Grounding Cable Protection grounding cables use 35-95mm2 copper leads, recommending 50mm2 copper leads.

  11. Course Contents First Chapter Sorting for Grounding System Second Chapter Grounding Language and Materials 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 Grounding Resistance Sixth Chapter Grounding for External Equipment of Base Station

  12. Sorting for Grounding Body （1）Vertical Grounding Body垂直接地体 a. tubular grounding body b. all kinds of steel section grounding body （2）Horizontal Grounding Body a. lead grounding body b. flat steel grounding body （3）Annular Grounding Body a. annular lead grounding body b. annular grounding body （4）Slabby Grounding Body a．circular plate grounding body b. square plate grounding body （5）Reticular Grounding Body

  13. Construction Method for Grounding Body 1）Single Grounding Stick 1. Constitutes The system that has only one vertical grounding body (or called grounding stick). 2. Construction Method （1）dig a hole which has 90cm depth, put one 50×50×5× 2500mm galvanized angle iron( nib one end ) into the bottom of the soil layer, leaving over 20cm above, then jointing grounding leading 40×4mm galvanized flat steel, the length of welding line should be twice over the length of flat steel, the position of the jointing should be antisepsis to deal with. And then fill 90cm soil, that is means depth is 70cm. （2）Test Grounding Resistance.

  14. Construction Method for Grounding Body 2）Many Vertical Grounding Bodies 1. Constitutes： Many vertical grounding body is according to a certainty space disposal associate with horizontal grounding body according to a certainly demand fit together. 2. Construction Method （1）Permutation Method: As a result of lots of reasons such as landform, it is likely to be beeline、fold line、arc line ranged, but no return 、no close. It looks almost beeline ranged. （2）Construction Method: We can dig channels according to permutation figure designed in advance, the depth is 90cm, to put vertical grounding body priority drive into the bottom of the soil with bareness 20cm in order to jointing above, the space between the vertical grounding body is 1.5—2.5 times than the length of the vertical grounding body. At the 10cm top of the vertical grounding body. We can use the horizontal grounding body to make them joined together by jointing smeared asphaltum to defend at the jointing section. （3）In the middle and the two end of the horizontal grounding body, we use the 40×4mm galvanized flat steel educed separately working grounding、protection grounding and lightning protection grounding.

  15. Construction Method for Grounding Body （4）Figure 1Vertical Grounding Body Sketch Map of Grounding System of Beeline Model( Planform ) Horizontal grounding body Figure 1 Vertical grounding body （5）Test Grounding Resistance

  16. Construction Method for Grounding Body 3）Annular Grounding Body 1. Constitutes: Annular grounding system is made up of 40×4mm galvanized flat steel embedding around machine room and vertical grounding body that is connected with it . 2. Construction Method: （1）The depth of the annular grounding body (horizontal) is more than 70cm,the distance to the building wall is more than 1.5m. （2）dig channels outside the building wall 1.5m,the depth is 90cm,and put one vertical grounding body into the bottom of the soil with bareness 20cm in order to jointing above, At the 10cm top of the vertical grounding body, We can use the 40×4mm galvanized flat steel to make them joined together by jointing, and then make the horizontal grounding body joint to closed annular body, pay attention not to turn ankylosis bending, finally smeared asphaltum to defend at the jointing section. （3）Backfill the soil、tamping、resuming the road surface and conditions. （4）Educe separately three 40×4mm galvanized flat steel by the horizontal grounding body of annular grounding grid as working grounding、protection grounding and lightning protection grounding, the distance between the three sections is more than 5m. （5）Test Grounding Resistance.

  17. Vertical grounding body (angle iron) Machine Room Horizontal grounding body (flat steel) Figure 2 Construction Method for Grounding Body Annular grounding gridding sketch map of a machine room that has no basic steel bar. If one annular grounding resistance can’t reach the design demand, we can add an annulus outside of it, the distance between two annulus should be more than 1.5—2.5 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. Construction Method for Grounding Body 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 40×4mm galvanized flat steel. So it is very easy to make the grounding resistance of grounding grid down to 1ohm.

  19. Construction Method for Grounding Body 4）Grid Grounding Body It is one of the effective grounding way in common use. The constructions such as switching room、vertical across reinforcing steel bar in basic iron tower, the across 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. Construction Method for Grounding Body 5）Radiancy Horizontal Grounding Cable In the actual application, the geologic circs is very complex, for the terrene circs of the soil above 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 50—70cm, the common soil channel length is no less than 3.6m.The sand channel length is no less than 7.2m,the depth is 50—70cm. The horizontal body adopt 40×4mm galvanized flat steel, in the end of the radiancy grounding line can also connect a piece of 1200×600×10mm galvanized armor plate as leakage board. The horizontal grounding body and the galvanized armor plate should be jointing 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. Construction Method for Grounding Body The sketch map for iron tower radiancy grounding line (broken line)

  22. Construction Method for Grounding Body 6）Grounding System Composing by Gridding and Vertical Grounding Body 1. Excellence： （1）Ensure a jarless value of grounding resistance, is an effective grounding system. （2）Horizontal grounding body can provide trusty grounding headstream, grounding net can be qua safety precautions of uniform earth’s surface malfunction voltage, for preventing hurt the workers and the foot passengers by the falling thunder. 2. Constitutes： United by phalanx arranged horizontal grounding body and making the top of them connect vertical grounding body.

  23. Construction Method for Grounding Body 3. Construction Method： （1）Dig pane channel according 3×3m, 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; （2）Use 40×4mm galvanized flat steel to make every vertical grounding joined together by jointing, and then combined gridding grounding net that is closed around、inequilateral, the jointing section needs asphaltum antisepsis. （3）Use the 40×4mm galvanized flat steel that is educed separately working grounding、protection 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. （4）Backfill the soil、tamping、resuming the road surface and conditions (ensure that the depth on the top of the vertical grounding body is 70cm). （5）Test grounding resistance.

  24. Construction Method for Grounding Body 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. Construction Method for Grounding Body 7）United Networks 1. Condition of United Networks It may has machine ground grid、iron tower ground grid and transformer ground 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 grounding、protection grounding and lightning protection grounding to be a combined ground grid. The grounding cables should be imported separately from the grounding bar or the grounding grid .

  26. Construction Method for Grounding Body Constitutes of ground net below: 3. When the machine room is under the iron tower and the electric 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.

  27. Course Contents First Chapter Sorting for Grounding System Second Chapter Grounding Language and Materials 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 Grounding Resistance Sixth Chapter Grounding for External Equipment of Base Station

  28. Computing Method of Grounding resistance—Vertical Grounding Body a. Tubular Grounding Body R=[ρ/（2πι）]×Ln(4ι(ι+2t)/(d(ι+4t))) -----------（1） In formula： R-grounding resistance of single tube (Ω) ρ-soil resistivity（Ω.m） ι-length of vertical tubular grounding body（m） d-diameter of vertical tubular grounding body（m） t-buried depth from ground to tube top（m）

  29. Computing Method of Grounding resistance—Vertical Grounding Body b. All kinds of steel section grounding body If adopting steel section instead of steel tube as grounding body, it should use equivalent diameter instead of d in (1) formula: flat steel：d=b/2 (b is side length of flat steel) equal angle：d=0.84b (b is side length of angle steel) unequal angle: d=0.71×ab(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=[ρ/（2πι）] ×Ln((8ι(ι+2t)/(b(ι+4t))-----（2） equal angle： R=[ρ/（2πι）] ×Ln((4.81ι(ι+2t))/(b(ι+4t))-----（3） unequal angle： R=[ρ/（2πι）] ×Ln((5.6ι(ι+2t))/( (ι+4t) (ab(a2+b2)1/4)---（4）

  30. Computing Method of Grounding Resistance—Horizontal Grounding body a. Lead grounding body when l 》d, and t》 d，the computing formulation of grounding resistance below： R=[ρ/（2πι）] ×. Ln(ι2/(bt))----（5） In formula： R-grounding resistance of single horizontal lead (Ω) ρ-soil resistivity（Ω.m） ι-length of horizontal lead grounding body（m） d-diameter of horizontal lead grounding body (m） t-buried depth from ground to horizontal lead grounding body（m）

  31. Computing Method of Grounding Resistance—Horizontal Grounding body b. Flat Steel Grounding Body If adopting flat steel grounding body instead of lead grounding body, also use equivalent diameter instead of d, d=b/2(b is long side length of flat steel). When l》b and t》b，grounding resistance is： R=[ρ/（2πl）] ×. Ln(2ι2/(bt))----------（6） BRACE YOURSELF

  32. Computing Method of Computing Resistance—Annular Grounding Body a. Annular lead grounding body When buried depth is t meter，its grounding resistance can be computed according to formulation below： R=[ρ/（2π2D）] ×Ln(8πd2/(dt))---（7） In formula： R—grounding resistance of annular lead grounding body (Ω) ρ—soil resistivity（Ω.m） D—diameter of annular grounding body（m） d--- conductor diameter of grounding body (m） t---laying depth（m）

  33. Computing Method of Computing Resistance—Annular Grounding Body b. Annular Grounding Body Computing of grounding resistance for flat steel annular grounding body refer to computing formulation of annular lead grounding body, use equivalent diameter 0.5b instead of d: R=[ρ/（2π2D）] ×Ln(8πd2/(dt)) （8） In formula: b—broadside length of flat steel section（m）

  34. Computing Method of Grounding Resistance—Slabby Grounding Body a．Circular plate grounding body Its grounding resistance use below formula to compute： R=ρ/（4D）-----------------（9） In formula ： R—grounding resistance of circular plate grounding body（Ω） ρ—soil resistivity（Ω.m） D---diameter of circular plate grounding body（m）

  35. Computing Method of Grounding Resistance—Slabby Grounding Body b. Square Plate Grounding Body Its grounding resistance can use below formula to compute： R=0.22ρ/a---------------（10） In formula： a—is side length of square（m） ρ—soil resistivity（Ω.m） Tiger is coming！！！

  36. Computing Method of Grounding Resistance –reticular Grounding Body R=0.44ρ/(A)1/2+0.159 ρ×Ln(8A/(hd*104))/ ι-------（11） In formula： R-grounding resistance of reticular grounding body (Ω) A-total area of reticular grounding body（m 2） ρ-soil resistivity（Ω.m） ι-total length of reticular grounding body（m） d-diameter of horizontal grounding body（m） h-buried depth from grounding to horizontal grounding body（m） 钻研不息 学习不止

  37. Computing Method of Grounding Resistance—Total Resistance of Multi-Grounding Body （1）Multi-Grounding Body，Grounding tape is insulating to soil a. grounding resistance of several same vertical grounding body is ： RN=R1/（nη1）-------------（12） in formula： RN—grounding resistance of several same vertical grounding body（Ω） R1– grounding resistance of single vertical grounding body（Ω） n – quantum of vertical grounding body（entries） η1– use factor of vertical grounding body The relation between use factor η and a/l by test is showing in list above （ι is length of vertical grounding body, a is distance between Vertical grounding bodies）.

  38. Computing Method of Grounding Resistance—Total Resistance of Multi-Grounding Body b. Grounding resistance of several same horizontal grounding body is Rn=R2/（nη2）----------------------------------（13） In formula： Rn—grounding resistance of several same horizontal grounding body（Ω） R2– grounding resistance of single horizontal grounding body（Ω） n—quantum of horizontal grounding body（entries） η2---use factor of vertical grounding body Use factor of striatus horizontal grounding body and lead radiancy grounding body is in back two lists.

  39. Computing Method of Grounding Resistance—Multi-Grounding Body，Grounding Tape is not insulated to soil When there are n entries vertical grounding body，connect them with horizontal grounding bodies, the resistance is computed below： R=R1R2/[R1η2+ R2η1 n]----------------------（14） In formula： R ---total grounding resistance of vertical grounding body which is connected with horizontal n entries vertical grounding body（Ω） R1---grounding resistance of single vertical grounding body（Ω） R2---grounding resistance of grounding tape between vertical grounding bodies（Ω） η1– use factor of vertical grounding body η2– use factor of connecting tape n---- quantum of vertical grounding body

  40. Frequently Used Data of Grounding Resistance Computation Use factor of parallel connection striatus grounding body Width of striatus horizontal grounding body is 20～40 millimeter; the buried depth is 0.3～0.8 m.

  41. Frequently Used Data of Grounding Resistance Computation Use factor of lead radiancy grounding body when flat steel is acting as radiation belt, equivalent diameter is b/2,b is length of flat steel broadside

  42. Frequently Used Data of Grounding Resistance Computation Use factor of in line arrangement settings（a—distance of vertical grounding bodies， ι—length of vertical grounding body ）

  43. Frequently Used Data of Grounding Resistance Computation Use factor of rectangle settings（a—distance between vertical grounding bodies；ι—length of vertical grounding body, assumed that space between columns is 4～8m ）

  44. Frequently Used Data of Grounding Resistance Computation Resistances of all kinds or soil

  45. Frequently Used Data of Grounding Resistance Computation—Soil Resistivity Relation between soil resistivity (contains 15 percent water)and temperature

  46. Frequently Used Data of Grounding Resistance Computation—Soil Resistivity Relation between soil resistivity and humidity

  47. Frequently Used Data of Grounding Resistance Computation—Soil Resistivity Resistivity of all kinds of water

  48. Frequently Used Data of Grounding Resistance Computation—Soil Resistivity Relation between salt content and soil resistivity in sand soil

  49. Frequently Used Data of Grounding Resistance Computation—Soil Resistivity Season coefficient of correction for soil resistivity Because of climatic influence in each month of whole year (includes temperature and humidity), the testing resistivity is different, for ensuring grounding resistivity which is biggest in certain month of whole year is also satisfied operating requirement, need adopting season coefficient of correction, that is: ρ=ρ‘Κ --------（15） in formula： ρ----soil resistivity when computing grounding body ρ‘---testing resistivity in different month of whole year. The below list is coefficient of correction which is testing in different season of Beijing area, as reference. Κ----season coefficient of correction of soil resistivity

  50. Frequently Used Data of Grounding Resistance Computation—Soil Resistivity a. Season coefficient of correction for Beijing area

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