Diese Präsentation wurde erfolgreich gemeldet.
Wir verwenden Ihre LinkedIn Profilangaben und Informationen zu Ihren Aktivitäten, um Anzeigen zu personalisieren und Ihnen relevantere Inhalte anzuzeigen. Sie können Ihre Anzeigeneinstellungen jederzeit ändern.

IEEE 80 Ground System Design

60.515 Aufrufe

Veröffentlicht am

  • Your transcript is expiring! (accept here) ▲▲▲ http://t.cn/AirVsp6C
       Antworten 
    Sind Sie sicher, dass Sie …  Ja  Nein
    Ihre Nachricht erscheint hier
  • Mom of 3 loses 62lbs with morning "hack" (before/after pics) ★★★ http://t.cn/AirVsfPx
       Antworten 
    Sind Sie sicher, dass Sie …  Ja  Nein
    Ihre Nachricht erscheint hier
  • GIVE HER A BIGGER PACKAGE THIS VALENTINE'S DAY ➤➤ https://bit.ly/30G1ZO1
       Antworten 
    Sind Sie sicher, dass Sie …  Ja  Nein
    Ihre Nachricht erscheint hier
  • i Watch the Better PPT on ThesisScientist.com on the same Topic.
       Antworten 
    Sind Sie sicher, dass Sie …  Ja  Nein
    Ihre Nachricht erscheint hier
  • Hi All, We are planning to start new Salesforce Online batch on this week... If any one interested to attend the demo please register in our website... For this batch we are also provide everyday recorded sessions with Materials. For more information feel free to contact us : siva@keylabstraining.com. For Course Content and Recorded Demo Click Here : http://www.keylabstraining.com/salesforce-online-training-hyderabad-bangalore
       Antworten 
    Sind Sie sicher, dass Sie …  Ja  Nein
    Ihre Nachricht erscheint hier

IEEE 80 Ground System Design

  1. 1. Grounding Tutorial Substation Ground System Design & Standard IEEE 80 Terry Klimchack Revised 03/10/14
  2. 2. ERICO has met the standards and requirements of the Registered Continuing Education Providers Program. Credit earned on completion of this program will be reported to RCEPP. A certificate of completion will be issued to each participant. As such, it does not include content that may be deemed or construed to be an approval or endorsement by NCEES or RCEPP.”
  3. 3. Copyrighted Materials This educational activity is protected by copyright laws. Reproduction, distribution, display and use of the educational activity without written permission of the presenting sponsor is prohibited. Copyright ERICO International Corporation, 2014
  4. 4. Presentation Outline • Grounding System Design Theory • Grounding System Design Example • Grounding System Components • Questions
  5. 5. Grounding System Design Theory
  6. 6. Today’s Challenges • Power plans and substations are operating past their original design service life • Engineers and designers are faced with rising fault currents requirements
  7. 7. Theoretical Conditions (Assumes Homogeneous Environment)
  8. 8. Actual Field Conditions (Non-Homogeneous Environment) Illustration of substation ground potential rise equipotential lines
  9. 9. Wenner’s or Four Pin Method I V R = aR la a la a aR π π ρ 2 4 2 1 4 2222 = + − + + = 1ρ 2ρ
  10. 10. Fall of Potential Method or 3PM ) 2 ln( 2 1) 8 ln( 2 a l lR d l lR ππ ρ ≅ − = I V R = 1ρ 2ρ
  11. 11. Principle: RPrinciple: REE 3pole3pole
  12. 12. Maximum Theoretical Accuracy LEAD LENGTH MAXIMUM THEORETICAL ACCURACY 2L 50% 4L 75% 8L 87.5% 16L 93.7% 32L 96.8% L= radial ground mat dimension
  13. 13. Basic Shock Situation
  14. 14. Touch Potential • Touch Potential is the potential difference between GPR and the surface potential at the point where a person is standing, while at the same time having hands in contact with a grounded structure • Touch Potential is controlled by proper bonding and protective systems, such as personnel safety mats.
  15. 15. Touch Potential • 1,000A Fault current • 5Ω Ground resistance 5,000 V • Touch potential due to voltage gradient 2,500 V • Resistance of body: 1,000 Ω (IEEE® 80) 2.5A Current 2,500V IEEE is a registered trademark of The Institute of Electrical and Electronics Engineers, Inc.
  16. 16. Touch Potential Same potential as towerNo protection
  17. 17. Step Potential • Step Potential is the difference in surface potential experienced by a person’s feet bridging a distance of 1m without contacting any other grounded surface. • Step Potential is controlled by properly designed ground electrode system (grid) or the use of wire mesh.
  18. 18. Step Potential 50% Voltage Drop between feet Same potential between feet
  19. 19. Tolerable Voltages Touch Voltage Step Voltage Where Estep is the step voltage in V Etouch is the touch voltage in V Cs is determined from figure or equation ρs is the resistivity of the surface material in Ω-m ts is the duration of shock current in seconds If no protective surface layer is used, then Cs =1 and ρs = ρ. ( ) s sstouch t CE 116.0 5.1100050 ρ⋅+= ( ) s sstouch t CE 157.0 5.1100070 ρ⋅+= ( ) s ssstep t CE 116.0 6100050 ρ⋅+= ( ) s ssstep t CE 157.0 6100070 ρ⋅+=
  20. 20. Dalziel’s Equations Tolerable Body Current Limits for 50 kg body weight for 70 kg body weight ts time in seconds s B t I 116.0 = s B t I 157.0 =
  21. 21. Body Current Versus Time
  22. 22. C-Curves (Cs versus hs) C h s s s = − −       + 1 0 09 1 2 0 09 . . ρ ρ Cs = surface layer rerating factor hs = thickness of the surface material
  23. 23. Conductor Equations where I is the rms current in Ka Amm 2 is the conductor cross section in mm2 Tm is the maximum allowable temperature in o C Ta is the ambient temperature in o C Tr is the reference temperature for material constants in o C αo is the thermal coefficient of resistivity at 0o C in 1/o C αr is the thermal coefficient of resistivity at reference temperature Tr in 1/o C ρr is the resistivity of the ground conductor at reference temperature Tr in µΩ-cm Ko 1/αo or (1/αr ) - Tr in o C tc is the duration of current in s TCAP is the thermal capacity per unit volume from table 11-1, in J/(cm3 ·o C)       + +       ⋅ = − ao mo rrc mm TK TK t TCAP AI ln 10 4 2 ρα
  24. 24. Ultimate Current Carrying Capabilities of Copper Conductors Currents are RMS values, for frequency of 60 Hz, X/R = 40 Current in kilo-amperes Cable Size, AWG Nominal Cross Section, mm2 6 cycles (100 ms) 15 cycles (250 ms) 30 cycles (500 ms) 45 cycles (750 ms) 60 cycles (1 s) 180 cycles (3 s) #2 33.63 22 16 12 10 9 5 #1 42.41 28 21 16 13 11 7 1/0 53.48 36 26 20 17 14 8 2/0 67.42 45 33 25 21 18 11 3/0 85.03 57 42 32 27 23 14 4/0 107.20 72 53 40 34 30 17 250 kcmil 126.65 85 62 47 40 35 21 350 kcmil 177.36 119 87 67 56 49 29
  25. 25. Grounding System Design Example
  26. 26. Substation Design Flowchart
  27. 27. Step 1 - Parameters • Ground fault current to the grid on 13 kV bus = 3,180 A. • Fault duration tf = 0.5 s • Soil resistivity ρ= 400 Ωm • Wet crushed rock resistivity ρs = 2.500 Ωm • Thickness of crushed rock hs = 0.1 m • Depth of grid burial h = 0.5 m • Available grounding area 70m x 70m • Area occupied be the grid 4,900 m2
  28. 28. Step 1 - Parameters Current deviation factor Sf = 0.6
  29. 29. Step 2 – Fault Current & Conductor Size Ignoring the station resistance, the symmetrical ground fault current on 115 kV I E R R R R j X X Xf 0 1 2 0 1 2 03 = ⋅ + + + + + +( ) ( ) ( ) ( ) ( ) ( ) A j I 3180 0.400.100.100.100.40.403 3000,115)3( 3 0 = ++++++ =
  30. 30. For the 13 kV bus fault, the 115 kV equivalent fault impedances must be transferred to the 13 kV side of1 the transformer. It should be noted that, due to the delta-wye connection of the transformer, only the2 positive sequence 115 kV fault impedance is transferred. Thus3 [ ] 142.1085.0014.1034.00.100.4 115 13 2 1 jjjZ +=+++      = Z j0 0 034 1014= +. . ( ) ( ) ( ) Amps j I 814,6 014.1142.1142.1034.0085.0085.0)0(3 3000,13)3( 3 0 = ++++++ = Conductor size A I K tkcmil f c= ⋅ kcmilkcmilAkcmil 02.3402.345.006.7814.6 ==⋅= The 34.02 kcmil is approximately #4 AVG. To increase service life 2/0 is recommended. Step 2 – Fault Current & Conductor Size Decrement factor Df is approximately1.0; thus, the rms asymmetrical fault current is also 6814 A
  31. 31. Step 3 – Step and Touch Potentials For 0.1 m (4 in) layer of surface material, with a wet resistivity of 2500 ·m, and for an earth with resistivity of 400 ·m.Ω Ω 74.0 09.0)102.0(2 2500 400 109.0 09.02 109.0 1 = +       − = +       − −= s s s h C ρ ρ Reduction factor ( )E C tstep s s s70 1000 6 0157= + ρ . / ( )( )[ ] 6.26865.0157.0250074.061000 =+= ( ) ssstouch tCE /157.05.1100070 ρ+= ( )( )[ ] 2.8385.0157.0250074.05.11000 =+=
  32. 32. Step 4 - Initial Design Assume a preliminary layout of 70 m × 70 m grid with equally spaced conductors, with spacing D = 7 m, grid burial depth h = 0.5 m, and no ground rods. The total length of buried conductor, LT, is 2 × 11 × 70 m = 1540 m.
  33. 33. Step 5 -Determination of Grid Resistance For L = 1540 m, and grid area A = 4900 m2, the resistance is R L A h A g T = + + +            ρ 1 1 20 1 1 1 20 / R ohmsg = + ⋅ + +                 =400 1 1540 1 20 4900 1 1 1 05 20 4900 2 78 . .
  34. 34. Step 6 - Maximum grid current Ig Given from Step 2 – Df = 1.0, and Sf = 0.6 S I I f g o = ⋅3 I D IG f g= ⋅ Though the 13 kV bus fault value of 6814 A is greater than the 115 kV bus fault value of 3180 A, The wye-grounded 13 kV transformer winding is a “local” source of fault current and does not contribute to the GPR. Thus, the maximum grid current is based on 3180 A. I D S IG f f= ⋅ ⋅ ⋅3 0 ( )( )( ) AIG 190831806.01 ==
  35. 35. Step 7 - Ground Potential Rise GPR Now it is necessary to compare the product of IG and Rg, or GPR, to the tolerable touch voltage, Etouch70 Since GPR = 5,304 V far exceeds Etouch70 = 838 V (determined in Step 3) as the safe value, additional design evaluations are necessary. GPR I RG g= ⋅ GPR volts= ⋅ =1908 2 78 5304.
  36. 36. Step 8 - Mesh Voltage ( ) ( )               −⋅ ⋅+      ⋅ − ⋅⋅ ⋅+ + ⋅⋅ ⋅ ⋅ = 12 8 ln 48 2 16 ln 2 1 22 nK K d h dD hD dh D K h ii m ππ ( )n ii n K 2 2 1 ⋅ = ( ) 57.0 112 1 112 = ⋅ = 0 1 h h Kh += 225.1 0.1 5.0 1 =+= ( ) ( ) 89.0 1112 8 ln 225.1 57.0 01.04 5.0 01.078 5.027 01.05.016 7 ln 2 1 22 =               −⋅ +      ⋅ − ⋅⋅ ⋅+ + ⋅⋅ = ππ mK nKi ⋅+= 148.0644.0 p C a L L n ⋅ = 2 11 280 15402 = ⋅ = nb = 1 for square grid nc = 1 for square grid nd = 1 for square grid and therefore RC imG m LL KKI E + ⋅⋅⋅ = ρ volts1.1002 1540 272.289.01908400 = ⋅⋅⋅ = n = na ⋅nb ⋅nc ⋅nd 111*1*1*11 == 272.211148.0644.0 =⋅+=
  37. 37. Step 9 - Em vs. Etouch • The mesh voltage 1002.1 V is higher than the tolerable touch voltage 838.2 V. The grid design must be modified. • There are two approaches to modifying the grid design to meet the tolerable touch voltage requirements: – Reduce the GPR to a value below the tolerable touch voltage or to a value low enough to result in a value of Em below the tolerable touch voltage – Reduce the available ground fault current
  38. 38. Modified Design In this example, the preliminary design will be modified to include 20 ground rods, each 7.5 m (24.6 ft) long, around the perimeter of the grid.
  39. 39. Repeating Step 5 • Using Equation for LT = 1540 + 20 • 7.5 = 1690 m, and A = 4900 m2 yields the following value of grid resistance Rg: • Steps 6 and 7. The revised GPR is (1908)(2.75) = 5247 V, which is still much greater than 838.2 V.             + ++= AhAL R T g /201 1 1 20 11 ρ ohms75.2 4900205.01 1 1 490020 1 1690 1 400 =                 + + ⋅ +=
  40. 40. The step voltage has not been calculated yet, the new values of Ki, Es, LS, and Ks have to be also calculated. Note that the value for Ki is still 2.272 (same as for mesh voltage). Repeating Step 8 ( ) ( )               −⋅ ⋅+      ⋅ − ⋅⋅ ⋅+ + ⋅⋅ ⋅ ⋅ = 12 8 ln 48 2 16 ln 2 1 22 nK K d h dD hD dh D K h ii m ππ Kii = 1.0 with rods 0 1 h h Kh += 225.1 0.1 5.0 1 =+= ( ) ( ) 77.0 1112 8 ln 225.1 0.1 01.04 5.0 01.078 5.027 01.05.016 7 ln 2 1 22 =               −⋅ +      ⋅ − ⋅⋅ ⋅+ + ⋅⋅ = ππ mK R G L LL L L KKI E yx r C im m ⋅                 + ⋅++ ⋅⋅⋅ = 22 22.155.1 ρ volts4.747 150 7070 5.7 22.155.11540 272.277.01908400 22 =                 + ++ ⋅⋅⋅ =
  41. 41. Final Design • Step 9: Em vs. Etouch. Now the calculated corner mesh voltage is lower than the tolerable touch voltage (747.4 V versus 838.2 V), and we are ready to proceed to Step 10. • Step 10: Es vs. Estep. The computed Es is well below the tolerable step voltage determined in Step 3 of the initial design. That is, 548.9 V is much less than 2686.6 V. • Step 11: Modify design. Not necessary for this example. • Step 12: Detailed design. A safe design has been obtained. At this point, all equipment pigtails, additional ground rods for surge arresters, etc., should be added to complete the grid design details. ( )    −+ + + ⋅ = −2 5.01 11 2 11 n s DhDh K π ( ) 406.05.01 7 1 5.07 1 5.02 11 211 =      −+ + + ⋅ = − π RC isG s LL KKI E ⋅+⋅ ⋅⋅⋅ = 85.075.0 ρ volts9.548 15085.0154075.0 272.2406.01908400 = ⋅+⋅ ⋅⋅⋅ =
  42. 42. Other Areas of Concern • Substation Fences Fence grounding is of major importance because the fence is usually accessible to the general public. The NESC requires grounding metal fences used to enclose electric supply substations having energized conductors or equipment. • Gravel New studies are available on the Resistivity of various crushed gravel
  43. 43. Fence and Gate Jumpers
  44. 44. Same Design Parameters Using Software
  45. 45. Computer Software Calculations Single Phase Voltage or Current Source Accept Cancel Voltage Source Current Source Single Phase Current Source (3.18 kA) SOURCE_A Circuit Number 1 Current (kA) 3.18 First Node Name kA Phase Angle 0.0 Degrees Source Type SOURCE_N Second Node Name 60.0 Hz Source Frequency WinIGS - Form: IGS_M112 - Copyright © A. P. Meliopoulos 1998-2013 Cancel Isolated Grounding System Example Example Grounding System Study Case : Grounding System : Upper Layer Resistivity 400.00 (feet) h 1 Lower Layer Resistivity 400.00 Upper Layer Height (h) 40.00 (Ohm-meters) (Ohm-meters) 2 Accept Air 2-Layer Soil Model Program WinIGS - Form SOIL_TWOLAYER Ground System Resistance Report Close Study Case Title: Grounding System: MAIN-GND GRSYS_N 2.4795 7884.82 3180.00 Rp = 2.4795 Earth Current: 3180.00 Fault Current: 0.00 Split Factor: N/A Isolated Grounding System Example Example Grounding System Node Name (Ohms) Voltage CurrentResistance* (Volts) (Amperes) Group Name Driving Point Equivalent Circuit Shunt Branch * Resistance Definition: View Full Matrix View Equivalent Ckt Program WinIGS - Form GRD_RP01
  46. 46. Computer Software Calculations Close Native Soil 2500 Layer Resistivity 0.1000 Layer Thickness (m) IEEE Std80 (1986) Ref 1 (see Help) Standard Update k Factor Reduction Factor 0.7406 -0.7241 Reduction Factor - IEEE Std80 (2000 Edition) 400.0 IEEE Std80 (2000) Upper Layer Resistivity WinIGS - Form: GRD_RP02 - Copyright © A. P. Meliopoulos 1998-2013 IEEE Std80 (2000) Close 0.5 IEC Electric Shock Duration : Permissible Body Current : seconds Amperes 5 % 50 % 0.14 % 5 %0.5 % 70 kg 50 kg View Plot ( Probability of Ventricular Fibrillation : 0.5% ) Probability of Ventricular Body Resistance : Fibrillation : Body Weight : SafetyCriteria - IEEE Std80 (2000 Edition) 0.222 95 % 1.0000Decrement FactorFaulted Bus Fault Type 0.0000X/R Ratio DC Offset Effect N/A N/A Permissible Touch Voltage Hand To Hand (Metal to Metal) Over Native Soil Over Insulating Surface Layer 222.0 V 355.3 V 400.0 Ohm - m 838.7 V 400.0 Ohm - m 2500.0 Ohm - m Permissible Step Voltage Over Native Soil Over Insulating Surface Layer 754.9 V 2688.6 V 0.100 m Select WinIGS - Form: GRD_RP03 - Copyright © A. P. Meliopoulos 1998-2013
  47. 47. Computer Software Calculations
  48. 48. Computer Software Calculations
  49. 49. Comparison of Design Results Manual E touchperm = 838 V E touchdesign= 747 V E stepperm = 2,687 V E stepdesignma x= 549 V Software E touchperm = 839 V E touchdesign= 669 V E stepperm = 2,689 V E stepdesignma x= 755 V E stepdesign = 67 V The values listed above assume insulated layer of gravel
  50. 50. Grounding System Components
  51. 51. 51 • Mechanical (compression, bolted, wedge) – Rely on surface contact and physical pressure to maintain connection • Exothermic – Molecular bond Connectors
  52. 52. Comparison: Mechanical vs. Exothermic Connectors Molecular bonds guarantee uniform conductivity across the entire cross section of the conductor. Mechanical ConnectionMolecular Bond Apparent Contact Surface Actual Contact Surface
  53. 53. Connectors 2000 Edition Exothermic Connections - Rated the same as the conductor - 1083 °C Brazed Connections - 450 °C based on copper based brazing alloys melting at 600 °C Pressure Connectors - 250-350 °C Bolted Connectors - 250 °C 2000 Edition Connectors meet IEEE 837, IEEE Standard for Qualifying Permanent Connections Used in Substation Grounding
  54. 54. National Electrical Grounding Research Project (NEGRP) • 18 different types of buried grounding electrodes • Layout and electrode selection was similar for each site to facilitate direct comparison of data • Measurements were originally taken bi-monthly • See report for complete summary
  55. 55. 55 Mechanical vs. Exothermic Mechanical ExothermicCompression
  56. 56. 56 NEGRP Study - After 10 Years in the Same Soil Conditions Compression Mechanical Mechanical Exothermic
  57. 57. 57 •Exothermic - heat producing reaction ⇒Cu Oxide + AL -> Copper+ Al Oxide ⇒Reaction Temperature at 4500° F •Copperto numerous othermetals ⇒Steels; Stainless; Cast, Ductile, & Wrought Iron; Brass; Bronze ⇒Provides Maintenance Free MolecularBond
  58. 58. 58 Exothermic Process
  59. 59. 59 Exothermic Welding Reaction
  60. 60. 60 Typical Substation Connection Exothermic Welds in Grounding Applications
  61. 61. 61 Connector “A”, #2 CYCLE #4 Connector “B”, Type “L”, #1 CYCLE #8 Connector “B”, Type “C”, #1 CYCLE #10 CADWELD® TAC2V2V, #2 CYCLE #57
  62. 62. 62 Advantages of Exothermic Connections • Provides a molecular bond between conductors – Ensures equal current sharing between conductor strands • Current carrying capacity equal to or exceeding conductor ampacity • Permanent – Will not loosen or corrode or increase in resistance – Will last longer than conductors
  63. 63. IEEE Std 837 - 2002 • Four Tests – Classified As Mechanical or Sequential. • Four Samples of Each Connector Must Pass Each Test to Qualify Tests for Above Grade and Below Grade Connectors Tensile Tests Electromagnetic Force Withstand Test Pass if Connector Resistance Increase is No Greater than 50% and There is No Visible Movement Pass if Test Values are Greater Than Minimum Pullout and There is No Visible Movement Sequential Tests For Below Grade Connections Current Temperature Cycling Freeze- Thaw Acid Pass if Connector Resistance Does Not Increase 150% Over Intial Measurement Sequential Tests For Above Grade Connections Current Temperature Cycling Freeze- Thaw Salt-Fog Mechanical Tests Sequential Tests IEEE is a registered trademark of The Institute of Electrical and Electronics Engineers, Inc.
  64. 64. IEEE Std. 837 - 2002 • Mechanical Tests – Test 1 - Mechanical Pullout: • The Connector Pullout Values Shall Meet Minimum Pullout Values With No Visible Movement of the Pre-marked Conductor With Respect to the Connector – Conductors Can Not Move Under Load of 2225 N for Sizes up to 4/0 AWG • Mechanical Tests – Test 2 - Electromagnetic Force Withstand: • (3) Surges, 0.2 Second Each • The Connection Shall Remain Intact With No Visible Movement of the Pre-marked Conductor With Respect to the Connector • The Resistance of the Connection Shall Not Increase by More Than 50%. IEEE is a registered trademark of The Institute of Electrical and Electronics Engineers, Inc.
  65. 65. IEEE Std 837 - 2002 • Sequential Tests 3 and 4 – Current-thermal Cycling • 25 Cycles at 350° C – Freeze-thaw • 10 Cycles; -10° to +20° C for 2 Hours – Nitric (Acidic) and Salt Spray (Alkaline) • Nitric - 10% HNO3 Solution (Volume) • CU - Reduce Control Conductor Cross Sectional Area 80% of Original – Salt Spray (Per ANSI/ASTM B117-85) – Fault Current (3 Surges) • 90% Symmetrical RMS Fusing Current for 10 Seconds IEEE is a registered trademark of The Institute of Electrical and Electronics Engineers, Inc.
  66. 66. IEEE Std 837 - Future • Likely to be issued in 2014 • Changes to include • New wave forms and current levels for EMF testing • Removal of resistance criteria • Connections must be qualified for various conductor types in order to meet IEEE 837 requirements (i.e., connector manufacturers that claim compliance with CCSC must test with CCSC) • Above grade conductors can not be restrained IEEE is a registered trademark of The Institute of Electrical and Electronics Engineers, Inc.
  67. 67. Ground Electrodes Features & Service Life
  68. 68. 69 Ground Rod Choices • Solid copper rods – Expensive and difficult to drive due to softness of material • Stainless steel rods – Option for use in soils that are corrosive to copper – Cost prohibitive in most cases • Copper-bonded steel • Galvanized steel
  69. 69. 70 Comparing Copper-bonded & Galvanized Steel Ground Rods • Both rod types are composed of a steel core – Copper-bonded rods use cold drawn steel with a tensile strength of 90,000+ psi – Most galvanized steel rods use hot rolled steel with a tensile strength of 58,000+ psi • Higher tensile strength leads to less rod end deformation during installation
  70. 70. 71 Comparing Copper-bonded & Galvanized Steel Ground Rods • The thickness and type of coating material determines corrosion resistance and service life • Copper-bonded steel rods – Coated with 10 mils (.010” or .254mm) of copper • Galvanized steel rods – Coated with 3.9 mils (.0039” or .099mm) of zinc – Limited by hot dip galvanizing process • Thicker coating = longer service life
  71. 71. 72 • Copper is resistant to corrosion in most soils • Zinc is sacrificial in most soils and with respect to most metals • Corrosion protection mechanisms are different – The copper coating is designed to prevent corrosion of the steel core – The zinc coating will delay corrosion of the steel core by providing a sacrificial barrier Corrosion Protective Mechanism
  72. 72. 73 NEGRP Corrosion Protective Mechanism Galvanized Ground Rod Copper Bonded Steel Ground Rod
  73. 73. • Electrodes removed for corrosion analysis – Balboa: January 29, 2001 (9 years) – Pawnee: March 17, 2003 (11 years) – Pecos: April 12, 2004 (12 years) – Lone Mountain: April 14, 2004 (12 years) • Moderate to severe corrosion of galvanized rods • Minimal corrosion of copper-bonded rods • Observations were same at all sites National Electrical Grounding Research Project (NEGRP)
  74. 74. NEGRP: Electrodes H & I 5/8” x 8’ Cu bonded rod 11 years exposure ¾” x 10’ galvanized rod 11 years exposure
  75. 75. Microscopy Evaluation Average Cu plating loss on electrodes “E” and “G” over a 10 year period was 0.0018”
  76. 76. Ground Enhancement
  77. 77. 78 Ground Enhancement - Chemical Ground Rods
  78. 78. 79 Ground Enhancement - Bentonite Bentonite clay • Low initial cost • Ineffective when dry • Resistivity of 2.5 Ω·m at 300% moisture • Low resistivity results mainly from an electrolytic process • May shrink and pull away from rod or soil when it dries • IEEE® Std 80 – 2000 Section 14.5 o “It may not function well in a very dry environment, because it may shrink away from the electrode, increasing the electrode resistance” IEEE is a registered trademark of The Institute of Electrical and Electronics Engineers, Inc.
  79. 79. Ground Enhancement Material (GEM) Parameters: •Environmentally friendly •Hygroscopic •Permanent, maintenance free •Low resistivity •Unremarkable affect by wet, dry or freezing conditions •Works in any type of soil •Cost effective
  80. 80. 81 GEM Encased Electrode (NEGRP “E”)
  81. 81. 82 8 Years Data from NEGRP - Performance Evaluation of GEM Encased Electrodes 0 20 40 60 80 100 08/22/92 08/22/94 08/21/96 08/21/98 08/20/00 Vert. - driven Vert. - GEM Horiz. - concrete Horiz. - GEM Measuredresistance(Ω) 0 100 200 300 400 08/22/92 08/22/94 08/21/96 08/21/98 08/20/00 Soil resistivity, R (Ωm) Soil moisture, M (%) Soil temperature, T (°C) T,MandR Balboa, NEVADA
  82. 82. 83 NEGRP Study Investigation Results of GEM Encased Electrodes • For all investigated electrodes the resistance of GEM encased electrodes is on the average 50% lower than resistance of driven ground rods • GEM also reduces the seasonal and long-term variability of the resistance
  83. 83. GEM in Grounding Wells • Most effective way to enhance substation grounding. • Calculate the amount of GEM required to fill the hole size. • Place the ground rod in the hole. • Pump down GEM by a tube from bottom of the hole up. • Fill GEM to the top. • Holes deeper than 10 feet should use pump GEM Water Rock NCC
  84. 84. Conductors
  85. 85. Copper Theft • US Department of Energy estimates over US $1 Billion in copper theft annually From Surveillance Video of Actual Theft
  86. 86. Copper Theft Even birds are stealing copper…
  87. 87. Methods for Copper Theft Prevention • Painting • Signage • Alternative Coatings • Encoding / Marking • Covering (PVC Conduit, etc.) • CCTV Systems • Motion Detectors / lighting • Alternative Materials • Theft Monitoring systems
  88. 88. 89 • Material – Copper – Copper - bonded steel – Copper – clad steel – Composite • Size – Sufficient to withstand maximum fault current for maximum clearing time – Resist underground corrosion Conductors
  89. 89. 90 Advantages of Copper Conductors • Copper is the most common material used for grounding • Copper has high conductivity • Copper is resistant to most underground corrosions • Copper is cathodic with respect to most other metals that can be buried in it’s vicinity
  90. 90. 91 Advantages of Copper-Clad Steel & Copper-Bonded Steel Conductors • Combines the strength of steel with the corrosion resistance of copper • It is more economical • It is more resistant to damage and theft • Low scrap value adds to theft deterrence
  91. 91. Formed Copper-bonded Steel Conductors
  92. 92. 93 UL® 467 30o Bend Test UL is a registered trademark of UL LLC.
  93. 93. 94 UL® 467 30o Bend Test Galvanized Steel Conductors Copper Jacketed Steel ConductorCopper Bonded Steel Conductor
  94. 94. 95 Field-bent Copper-bonded Conductor Substation ground leads
  95. 95. 96 Pre-bent Copper-bonded Conductor
  96. 96. Composite Conductors
  97. 97. Composite Conductor Chart
  98. 98. ERICO Confidential 99 Composite Conductor Testing
  99. 99. Composite Conductor Features • Copper strands are hidden by outer tin plated copper bonded steel strands • Copper strands are tinned for superior corrosion resistance • The copper stranding increases conductivity and flexibility of the conductor • Comes in bare or insulated option • Available in five configurations
  100. 100. Composite Conductor Advantages • Has many years of proven record in successful field applications in all major rail companies in the USA • Combines conductivity of copper with strength of steel • Difficult to cut with hand tools • The outer steel strands are magnetic which further deters thieves looking for copper.
  101. 101. Composite Cable Applications
  102. 102. Thank you for your time! This concludes the educational content of this activity www.erico.com

×