earthing -earthing req. relevent codes (1).ppt
- 1. Earthing & Grounding PRESENTATION BY: K.K.MEHTA MEMBER EXPERT NSC 28-12-2023 1
- 2. Reference documents for earthing IEEE Std 80 IS 3043 1987 code of practice of earthing IE Rule 1956 and Regulation 2010 28-12-2023 2
- 3. Indian Standard CODE OF PRACTICE FOR EARTHING (First Revision) IS : 3043 . 1987 This Indian Standard ( First Revision ) was adopted by the Bureau of Indian Standards on 6th August 1987, after the draft finalized by the Electrical Installations Sectional Committee, had been approved by the Electro technical Division Council. The Indian Electricity Rules, together with the supplementary regulations of the State Electricity Departments and Electricity Undertakings, govern the electrical installation work in generating stations, substations, industrial locations, buildings, etc, in the country. 28-12-2023 3
- 4. To ensure safety of life and apparatus against earth faults, it was felt necessary to prepare a code of practice for earthing. This code of practice is intended to serve as a consolidated guide to all those who are concerned with the design, installation, inspection and maintenance of electrical systems and apparatus 28-12-2023 4
- 5. IER 33/ Regulation 16 Earthed terminal on consumer’s premises The supplier shall provide and maintain on the consumers ‘s premises for the consumer’s use a suitable earthed terminal in an accessible position at or near the point of commencement of supply Earth Electrode 28-12-2023 10
- 6. The consumer shall take all reasonable precautions to prevent mechanical damages to the earthed terminal and its lead belonging to supplier The supplier may recover from the consumer the cost of installation on the basis of schedule of charges in advance as notified in relevant rule Earth Electrode 28-12-2023 11
- 7. IE Rule 61/Regulation 41. Connection with earth- (1) The following provisions shall apply to the connection with earth of systems at low voltage in cases where the voltage normally exceeds 125 volts and of systems at medium voltage: - [(a) Neutral conductor of 3 phase, 4-wire system shall be earthed by not less than two separate and distinct connections with a minimum of two different earth electrodes of such large number as may be necessary to bring the earth resistance to a satisfactory value both at the generating station and at the sub-station. The earth electrodes so provided, may be interconnected to reduce earth resistance. It may also be earthed at one or more points along the distribution system or service line in addition to any connection with earth which may be at the consumer’s premises. 28-12-2023 12
- 8. In an electrical installation, an earthing system or grounding system connects specific parts of that installation with the Earth's conductive surface for safety and functional purposes. The point of reference is the Earth's conductive surface. The choice of earthing system can affect the safety and electromagnetic compatibility of the installation. Regulations for earthing systems vary considerably among countries, though most follow the recommendations of the International Electrotechnical Commission. Regulations may identify special cases for earthing in mines, in patient care areas, or in hazardous areas of industrial plants. 28-12-2023 13
- 9. Concept of Earthing Systems All the people living or working in residential, commercial and industrial installations, particularly the operators and personnel who are in close operation and contact with electrical systems and machineries, should essentially be protected against possible electrocution. To achieve this protection, earthing system of an installation is defined, designed and installed according to the standard requirements.. 28-12-2023 30
- 10. What Is Earthing The process of connecting metallic bodies of all the electrical apparatus and equipment to huge mass of earth by a wire having negligible resistance is called Earthing. 28-12-2023 31
- 11. The term earthing means connecting the neutral point of supply system or the non current carrying parts of the electrical apparatus to the general mass of earth in such a manner that all times an immediate discharge of electrical energy takes place without danger. What Is Earthing 28-12-2023 32
- 13. • Provide an alternative path for the fault current to flow so that it will not endanger the user • Maintain the voltage at any part of an electrical system at a known value so as to prevent over current or excessive voltage on the appliances or equipment. 28-12-2023 34
- 14. Qualities Of Good Earthing Must be of low electrical resistance • Must be of good corrosion resistance • Must be able to dissipate high fault current repeatedly 28-12-2023 35
- 15. Purpose of Earthing • To save human life from danger of electrical shock or death by blowing a fuse i.e. To provide an alternative path for the fault current to flow so that it will not endanger the user • To protect buildings, machinery & appliances under fault conditions ie. To ensure that all exposed conductive parts do not reach a dangerous potential. 28-12-2023 36
- 16. To provide safe path to dissipate lightning and short circuit currents. To provide stable platform for operation of sensitive electronic equipments i.e. To maintain the voltage at any part of an electrical system at a known value so as to prevent over current or excessive voltage on the appliances or equipment 28-12-2023 37
- 17. An electric shock (electrocution)occurs when two portion of a person’s body come in contact with electrical conductors of a circuit which is at different potentials, thus producing a potential difference across the body. Electric shock 28-12-2023 38
- 18. The human body does have resistance and when the body is connected between two conductors at different potential a circuit is formed through the body and current will flow 28-12-2023 39
- 19. When the human body/birds comes in contact with only one conductor, a circuit is not formed and nothing happens 28-12-2023 40
- 20. How electrocution occurs Every where same potential There is no potential difference as his both the legs (Contact point) are in air while jumping Victim one contact point is on live part and other touching ground so flow of currant 28-12-2023 47
- 21. Equipment Earthing In case of insulation failure, the primary object of connecting all the above points and apparatus to earth is to release the charge accumulated on them immediately to earth so that the person coming in contact may not experience electric shock. 28-12-2023 52
- 22. Equipment Earthing(Cont.) The other object is that a heavy current when flows through the circuit that operates the protective devices that is fuse or CB, which open the circuit 28-12-2023 53
- 23. Un attended and corroded earth 28-12-2023 54
- 24. Max. Value of Earth Resistance to be achieved Equipment to be Earthed Max. Value of Earth Resistance to be achieved in Ohms Large Power Stations 0.5 Major Substations 1.0 Small Substations 2.0 Factories Substations 1.0 Lattice Steel Tower 3.0 Industrial Machine and Equipment 0.5 * The Earth Resistance depends upon the moisture content in the soil. 28-12-2023 55
- 25. Methods of Earthing Generally two types of earting is in use Conventional Earthing Maintenance Free Earthing/ Chemical Earthing 28-12-2023 56
- 26. Conventional Earthing The Conventional system of Earthing calls for digging of a large pit into which a GI pipe or a copper plate is positioned in the middle layers of charcoal and salt. It requires maintenance and pouring of water at regular interval. 28-12-2023 57
- 28. Maintenance Free Earthing • It is a new type of earthing system which is Readymade, standardized and scientifically developed. Its Benefits are • MAINTENANCE FREE: No need to pour water at regular interval- except in sandy soil. • CONSISTENCY: Maintain stable and consistent earth resistance around the year. • MORE SURFACE AREA: The conductive compound creates a conductive zone, which provides the increased surface area for peak current dissipation. And also get stable reference point. 28-12-2023 59
- 30. Why copper is preferred than steel Corrosion Allowance — On an average, steel corrodes about six times as fast as copper when placed in soil. The extent of corrosion depends upon the properties of soil. The generally accepted correlation between the electrical resistivity of soil and its corrosivity is as indicated in the table below Soil Resistivity and Corrosion 28-12-2023 61 Range of Soil Resistivity (ohm-metres) (Class of Soil) Less than 25 Severely corrosive 25-50 Moderately corrosive 50-100 Mildly corrosive Above 100 Very mildly corrosive
- 31. This following methods can be adopted to safeguard Conductor against excessive corrosion: a) Use of cathodic protection, and b) Use current conducting, corrosion resistant coating on steel (for example, zinc coating). The zinc coating on the tubes shall be in accordance with IS 4736 : 1986 'Hot dip zinc coatings on mild steel tubes with coating thickness 150 microns catholid protection of a metal structure from corrosion under water by making it act as an electrical cathode 28-12-2023 62
- 32. HO A CONCLUSION! Why Chemical Earthing is more DURABLE AND RELIABLE? W TO SELECT & INSTALL SLY Earthing Electrode EARTHGING SYSTEM? . A CONCLUSION! Draw backs in coventianal earthing LIFE OF EARTHING SYSTYEM:- A.COPPER PLATE:- 1. The conventional copper pit type earthing has a very erratic behavior and the ohmic values of earth resistance vary drastically on the following seasonal factor: a) SUMMER SEASON b) WINTER SEASON c) RAINY SEASON The humidity factors in all the seasons vary because ambient temperature of ground varies. The thumb rule for calculating humidity at a 20°c ambient temperature and 1° variation in either side (+/-) will vary the humidity level in the ground by 16%. This can now be understood why the ohmic values remain erratic during the life of the system 28-12-2023 63
- 33. •Why conventional earthing is not durable and reliable ? There is a general accepted fact and practice that pit type earthing is watered through an additional pipe running through the depth of pit in summer season obviously because of dry climate and low humidity. Contrary to the belief that winter is a wet climate and has a higher humidity level it is a myth that humidity is very low in winter because the ambient temperature is in the vicinity of 4 to 6°c and as per the standard the humidity is reduce by 16% of every degree of temperature. Therefore humidity is reduced by 16x (20-6) =224%. The coal used in the earthing pit burns and turns into ash under high level of fault currents and on the top of it the quality of coke is used is very poor(Generally in Powder form). The salt used becomes water itself and looses its hygroscopic properties. Conclusion: The life of pit type of earthing is not more then 3 years irrespective of maintenance. 28-12-2023 64
- 34. Maintenance Free Earthing(Contd.) LOW EARTH RESISTANCE: Highly conductive. Carries high peak current repeatedly. NO CORROSION: LONG LIFE. EASY INSTALLATION. 28-12-2023 65
- 35. HOW TO SELECT & INSTALL SLY Earthing EHlectrode EARTHGING SYSTEM HOW TO SELECT & INSTALL Maintenance free Earthing Electrode When the pipe earthing /chemical earthing/maintenance free earthing/Gel earthing or whatever name it is called by various manufacturers, its installation is done in following manner, Installation procedure:- Unlike Copper pit type earthing which used to be installed away from the equipment because it was cumbersome to install the earthing near to the equipments because of restriction of the space and other environmental factors. But chemical earthing is very compact and easy to install and placed near to the equipments may be 2-3 meters away depending on the situation. 28-12-2023 66
- 36. Test Results:- The results obtained will be as under: Earthing installed in a bore of 8-10 inch of diameter of appropriate length depending upon size of electrode used. The electrode is installed in the bore and additional space surrounding the electrode is filled with the slurry of 35-70kgs of GEM -KIMMOIST- (Al2O34SiO3H2O). The tests are carried after one week of the installation of the electrode. This time factor is necessary to allow curing time for the chemical to mix with soil conditions 28-12-2023 67
- 37. The results are obtained by Earth résistance measuring meters which are basically version of Wheatstone bridge method used for measuring the Unknown values of resistances. The Values obtained are well within the limit given as per IS: 3043-1987 i.e less than 2 ohms. In practical sense the values obtained are between 0.5 to 1.5 ohms depending upon the soil conditions (Resistivity of Soil) of the location The test certificate is provided by the manufactures certifying the values obtained. 28-12-2023 68
- 38. Chemical Electrode earthing:- In the this type of earthing the following important factor are taking into the consideration: a) The hollow pipe used in the chemical pipe earthing is fitted with a G.I. strip 40x6mm and CCM (Crystalline conducive mixture) is compressed in to the pipe and pipe is sealed at both the end. b) CCM is a semi metal and the hollow pipe filled with CCM behave like a salt pipe and therefore the current carrying capacity increases substantially. c) The CCM has a high melting temperature of 2500°c and unlike coal it will not burn into ashes under high temperatures of 1500°c under high fault currents occurring due to phase to phase or phase to earth fault 28-12-2023 69
- 40. d) The humidity factor (The moisture level) is maintained by KIMMOIST (GEM)surrounding the electrode in a slurry form. The KIMMOIST has a property of absorbing water 15 times its weight and doesn’t dissolve in the water. It remains moist and soft through out the life. A minimum rain fall of 2.5 cm in a year makes the KIMMOIST moist and humid for next one year and therefore the cycle keeps on repeating year of year. Therefore, because of quality of KIMMOIST no additional watering is done whether in summer, winter or rainy season i.e. under any climatic condition. e) In India the technology is only 14 years old and the failure record is almost negligible. The earthing system properly installed under the guidance of manufacturers can safely vouch for minimum ten years. 28-12-2023 71
- 41. B.. Conclusion:- The life of chemical earthing as per the reports from USA and other country is more than 15 years with no failure records. Some company in USA guarantees life of 30 year or may be above. Draw back-:They fear that metal may erode due to chloride and oxides are formed due to under ground chemicals. 28-12-2023 72
- 42. Methods of Conventional Earthing 1. Plate Earthing 2. Pipe Earthing 3. Rod Earthing 4. Strip Earthing 5. Earthing through Water Mains 28-12-2023 73
- 43. Earthing Electrode The resistance of a ground electrode has 3 basic components: A) The resistance of the ground electrode itself and the connections to the electrode. B) The contact resistance of the surrounding earth to the electrode. C) The resistance of the surrounding body of earth around the ground Electrode. It consist of three basic components: 1. Earth Wire 2. Connector 3. Electrode 28-12-2023 74
- 44. Plate Earthing In this type of earthing, the plate either of copper or of G.I. is buried into the ground at a depth of not less than 3 meter from the ground level. The earth plate is embedded in alternative layer of coke and salts for a minimum thickness of about 15cm. The earth wire(copper wire for copper plate earthing and G.I. wire for G.I. plate earthing) is securely bolted to an earth plate with the help of bolt nut and washer made of copper, in case of copper plate earthing and of G.I. in case of G.I. plate earthing. 28-12-2023 75
- 46. Pipe earthing Pipe earthing is best form of earthing and it is cheap also in this system of earthing a GI pipe of 38 mm dia and 2meters length is embedded vertically in ground to work as earth electrode but the depth depend upon the soil conditions, there is no hard and fast rule for this. But the wire is embedded up to the wet soil. The earth wire are fastened to the top section of the pipe with nut and bolts. The pit area around the GI pipe filled with salt and coal mixture for improving the soil conditions and efficiency of the earthing system. It can take heavy leakage current for the same electrode size in comparison to plate earthing. The earth wire connection with GI pipes being above the ground level can be checked for carrying out continuity test as and when desired, while in plate earthing it is difficult. In summer season to have an effective earthing three or four bucket of water is put through the funnel for better continuity of earthing. 28-12-2023 77
- 48. In this system of earthing 12.5mm diameter solid rods of copper 16mm diameter solid rod of GI or steel or hollow section of 25mm GI pipe of length not less than 3 meters are driven vertically into the earth In order to increase the embeded length of electrod under the ground, which is some time necessary to reduce the earth resistance to desired value more than one rod section are hammered one above the other. This system of earthing is suitable for area which are sandy in character . This system of earthing is very cheap ROD EARTHING 28-12-2023 79
- 50. In this system of earthing strip electrod of cross section not less than 25mm x 1.6mm of copper or 25mm x 4mm of GI or steel are buried in horizontal trenches of minimum depth of 0.5m If round conductor are used their cross sectional area shall not be smaller than 3 mm² if copper is used and 6mm² if GI or steel is used. STRIP OR WIRE EARTHING 28-12-2023 81
- 51. The length of buried conductor shall be sufficient to give the required earth resistance (about 0.5Ωto 1.5Ω) It shall however be not less than 1.5 m The electrod shall be as widely distributed as possible in a single straight or circular trenches radiating from a point This type of earthing is used in rockey soil earth bed because at such places excavation work for plate earthing is difficult 28-12-2023 82
- 52. Step A : Excavate the earthing pit size 2000 X 2000 X 2500 mm depth. Sprinkle sufficient quantity of water in the bottom and surrounding walls to become wetty only. Fill up the bottom layer of the pit up to 250 mm height from the bottom by mixture black soft soil + salt + wooden charcoal pieces. (Fig. I) Step B : Prepare the electrode assembly as per Sr. No. - 3 of the drawing and rest the entire Assembly in the pit as shown in (Fig. II) Procedure for filling up New Earthing Pit 28-12-2023 83
- 53. Step C : Collect thin C.R.C.(Cold Rolled Close) sheet approx 18 to 20 SWG having size 500 mm width 3.5 meter length approx. (joints of three to four pieces to achieve requirement of 3.5 meter length) (Fig. III-a) Prepare the Cylindrical Ring from the above sheet by bending both ends & joining each other. The diameter "D" of the cylindrical ring shall arrive approx. 1000 mm and height shall be 500 mm. Collect two pieces of scrap G.I. wire of approx. 8-SWG and prepare two lifting round handles (Hooks) on upper side of the cylindrical ring to facilitate the lifting of the Cylindrical Ring. (Fig. III-b) Now wear this cylindrical ring to the electrode pipe of the electrode assembly such a way that the electrode pipe remains in the centre of the cylindrical ring. (Fig III-c) Procedure for filling up New Earthing Pit 28-12-2023 84
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- 55. CRC SHEET (SCRAP) 3500mm 500mm Fig iii (a) cylindrical Handle (Hook) Handle (Hook) 1000mm 5000mm Fig. (iii b ) Cold Rolled Close 28-12-2023 86
- 57. Step D : Fill up the inner part of the Cylindrical Ring with Mixture - I ( Homogeneous mixture of Black Soft Soil. The remaining part i.e. the Gap between walls of the pit and outer periphery of the Cylindrical Ring by Mixture - II. After completing filling work of both the mixtures up to 500 mm height, proper ramming and watering is to be done. (Fig. IV) Procedure for filling up New Earthing Pit 28-12-2023 88
- 58. Step E : There after lift the Cylindrical ring by help of two lifting handles (hooks) and again rest it on the layer for carrying out filling of 2nd layer cycle. Again fill up the inner cylindrical part of the ring by Mixture - I and outer gap between walls of the pit & outer Cylindrical periphery by Mixture - II up to height of the Cylinder (i.e. 500 mm) (Fig. V) Procedure for filling up New Earthing Pit 28-12-2023 89
- 59. Step E : There after lift the Cylindrical ring by help of two lifting handles (hooks) and again rest it on the layer for carrying out filling of 2nd layer cycle. Again fill up the inner cylindrical part of the ring by Mixture - I and outer gap between walls of the pit & outer Cylindrical periphery by Mixture - II up to height of the Cylinder (i.e. 500 mm) (Fig. V) Procedure for filling up New Earthing Pit 28-12-2023 90
- 60. Step F : Lift the cylindrical ring by lifting handles (hooks) after proper ramming and watering. Now again place the cylindrical ring on upper layer and arrange 3rd cycle, subsequently complete the filling of entire pit. water content should be minimum 20 % Fill up upper layer of the pit by crushed rock pieces (Gravel) size 50 X 35 mm. 1 CMT. approx. to provide insulating layer to person moving side by the pit, and to prevent reptile movements subsequently causing hazards. Procedure for filling up New Earthing Pit 28-12-2023 91
- 61. • Design Details : 1. Earthing Pit : Size 1000 X 1000 X 1800 mm Depth.M.S. / C.I. Plate : 500 X 500 X 8 mm Thick. 2. Electrode Assembly : 40 mm Ø GI / CI Perforated pipe duly fitted or welded with base plate and 50 X 6 mm flat termination taken on top for equipment earthing as shown in drawing. Standard Pipe & Plate Type Earthing Design for the 11 Kv. System Equipments, Distribution Transformer Centers, L.T. Distribution System Equipments 28-12-2023 92
- 62. 4. Mixture - I : Homogeneous mixture of black soft soil 0.3 CMT. approx. 5. Mixture - II : Homogeneous mixture of common salt 25 Kgs. + wood charcoal pieces 25 Kgs. + Black soft soil 1 CMT. Approx. 6. Crushed Rock pieces Gravel Size 50 X 35 mm 0.1 CMT. Approx. 7. Arrangement for earthing lead terminations from equipment body, and connection for main earthing Grid. Standard Pipe & Plate Type Earthing Design for the 11 Kv. System Equipments, Distribution Transformer Centres, L.T. Distribution System Equipments 28-12-2023 93
- 63. • Design Details : 1. 75 mm thick RCC Cover. 2. 300 mm Ø 6000 mm deep (Approx. 20 ft.) bore in the earth. 3. 65 mm Ø 6000 mm long (Approx 20 ft.) G.I. pipe electrode. Forged at the top up to 75 mm length and 12 mm hole provided for taking earthing connection. 4. A homogeneous mixture of 50 kgs. wooden coal pieces + 50 kgs. common salt 5. Water pouring purpose at the time of routine maintenance Typical arrangement for Pipe electrode earthing pit (Bore Type) 28-12-2023 94
- 64. Applications • Telecommunication • Transmission • Substations & Power Generations • Transformer Neutral earthing • Lightning Arrestor Earthing • Equipment Body Earthing • Water Treatment Plants • Heavy Industries • College, Hospitals, Banks • Residential Building 28-12-2023 95
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