Download - IEEE P80-2013 Draft Guide for Safety in AC Substation Grounding-Corrigendum 1 Dec 2014

IEEE P80-2013/Cor1/D3, December 2014

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P80-2013/Cor1/D3 1

Draft Guide for Safety in AC Substation 2

Grounding---Corrigendum 1 3

4

Sponsor 5

Substations Committee 6 of the 7 IEEE Power and Energy Society 8

Approved <XX MONTH 20XX> 9 IEEE-SA Standards Board 10 11

Copyright © 2014 by The Institute of Electrical and Electronics Engineers, Inc. 12 Three Park Avenue 13 New York, New York 10016-5997, USA 14 All rights reserved. 15

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Abstract: Corrections made to Clause 11, Clause 17, Annex C, and Annex H in 1 IEEE Std 80 2013. 2 3 Keywords: IEEE 80TM 4 5

6 7

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vi Copyright © 2014 IEEE. All rights reserved.


Participants 1

At the time this draft guide was submitted to the IEEE-SA Standards Board for approval, the Grounding 2 (PE/SUB/WGD7) Working Group had the following membership: 3

Richard P. Keil, Chair 4 Curtis R. Stidham,Secretary 5

6 Hanna Abdallah 7 Stan J. Arnot 8 Thomas Barnes 9 Bryan Beske 10 Dale Boling 11 Steven Brown 12 James Cain 13 Bill Carman 14 K. S. Chan 15 Koushik Chanda 16 Carson Day 17 Dennis DeCosta 18 E. Peter Dick 19

Marcia Eblen 20 William K. Dick 21 D. Lane Garrett 22 Joseph Gravelle 23 Steven Greenfield 24 Charles Haahr 25 Thomas Harger 26 Martin Havelka 27 Dave Kelley 28 Donald N. Laird 29 Henri Lemeilleur 30 Cary Mans 31 32

Sakis Meliopoulos 33 Mike Noori 34 Hamid Sharifnia 35 William Sheh 36 Douglas Smith 37 David Stamm 38 Greg J. Steinman 39 Brian Story 40 Yance Syarif 41 Keith Wallace 42 Alexander Wong 43 44

45 The following members of the individual balloting committee voted on this guide. Balloters may have 46 voted for approval, disapproval, or abstention. 47 48 (to be supplied by IEEE) 49 50 Balloter1 51 Balloter2 52 Balloter3 53

Balloter4 54 Balloter5 55 Balloter6 56

Balloter7 57 Balloter8 58 Balloter9 59

60 61 62

63

64

65

66

67

68

69

70

71

72

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v Copyright © 2014 IEEE. All rights reserved.


When the IEEE-SA Standards Board approved this guide on <XX MONTH 20XX>, it had the following 1 membership: 2

(to be supplied by IEEE) 3 <Name>, Chair 4

<Name>, Vice Chair 5 <Name>, Past Chair 6

<Name>, Secretary 7 8 SBMember1 9 SBMember2 10 SBMember3 11

SBMember4 12 SBMember5 13 SBMember6 14

SBMember7 15 SBMember8 16 SBMember9 17

*Member Emeritus 18 19 20 Also included are the following nonvoting IEEE-SA Standards Board liaisons: 21

<Name>, DOE Representative 22 <Name>, NRC Representative 23

24 <Name> 25

IEEE Standards Program Manager, Document Development 26 27

<Name> 28 IEEE Standards Program Manager, Technical Program Development 29

30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57



vii Copyright © 2014 IEEE. All rights reserved.


Introduction 1

This introduction is not part of IEEE P80-2013/Cor1/D3, Draft Guide for Safety in AC Substation Grounding---2 Corrigendum 1. 3

4 5



viii Copyright © 2014 IEEE. All rights reserved.


Contents 1

11. Selection of conductors and connections .................................................................................................. 2 2

17. Special areas of concern ........................................................................................................................... 3 3 17.3 Grounding of substation fence ........................................................................................................... 3 4

Annex C (informative) Graphical and approximate analysis of current division ........................................... 4 5 C.2 How to use the graphs and equivalent impedance table ...................................................................... 4 6

Annex H (informative) Benchmark ................................................................................................................ 5 7 H.3 Grounding system analysis ................................................................................................................. 5 8 H.4 Grid current analysis (current division) .............................................................................................10 9

10

11



1 Copyright © 2014 IEEE. All rights reserved.


Draft Guide for Safety in AC Substation 1

Grounding---Corrigendum 1 2

IMPORTANT NOTICE: IEEE Standards documents are not intended to ensure safety, health, or 3 environmental protection, or ensure against interference with or from other devices or networks. 4 Implementers of IEEE Standards documents are responsible for determining and complying with all 5 appropriate safety, security, environmental, health, and interference protection practices and all 6 applicable laws and regulations. 7

This IEEE document is made available for use subject to important notices and legal disclaimers. 8 These notices and disclaimers appear in all publications containing this document and may 9 be found under the heading “Important Notice” or “Important Notices and Disclaimers 10 Concerning IEEE Documents.” They can also be obtained on request from IEEE or viewed at 11 http://standards.ieee.org/IPR/disclaimers.html. 12

NOTE—The editing instructions contained in this corrigendum define how to merge the material contained therein 13 into the existing base standard and its amendments to form the comprehensive standard. 14

The editing instructions are shown in bold italic. Four editing instructions are used: change, delete, insert, and replace. 15 Change is used to make corrections in existing text or tables. The editing instruction specifies the location of the 16 change and describes what is being changed by using strikethrough (to remove old material) and underscore (to add 17 new material). Delete removes existing material. Insert adds new material without disturbing the existing material. 18 Insertions may require renumbering. If so, renumbering instructions are given in the editing instruction. Replace is used 19 to make changes in figures or equations by removing the existing figure or equation and replacing it with a new one. 20 Editing instructions, change markings, and this NOTE will not be carried over into future editions because the changes 21 will be incorporated into the base standard. 22

23 24





11. Selection of conductors and connections 1

Change the entire row in Table 1 for Aluminum-clad steel wire as shown: 2

Table 1 —Material constant 3

4

5

6

Change the entire row in Table 2 for Aluminum-clad steel wire as shown below: 7

Table 2 —Material constants 8

Description Materiala

conductivity (% IACS)

r factora at 20 °C (1/°C)

Ko at 0 °C (0°C)

Fusinga temperature

Tm (°C)

Resistivitya at 20 °C

r (μ -cm)

Thermala capacity TCAP

[J/(cm3.°C)] Copper, annealed soft-drawn 100.0 0.003 93 234 1083 1.72 3.4

Copper, commercial hard-drawn 97.0 0.003 81 242 1084 1.78 3.4

Copper-clad steel wire 40.0 0.003 78 245 1084e 4.40 3.8

Copper-clad steel wire 30.0 0.003 78 245 1084e 5.86 3.8

Copper-clad steel rodb 17.0 0.003 78 245 1084e 10.1 3.8 Aluminum-clad steel wire 20.3 0.00360 258 657 8.48 3.561

Steel, 1020 10.8 0.003 77 245 1510 15.90 3.8

Stainless-clad steel rodc 9.8 0.003 77 245 1400e 17.50 4.4

Zinc-coated steel rod 8.6 0.003 20 293 419e 20.10 3.9

Stainless steel, 304 2.4 0.001 30 749 1400 72.00 4.0

Material Conductivity (%) Tma (oC) Kf

Copper, annealed soft-drawn 100.0 1083 7.00 Copper, commercial hard-drawn 97.0 1084 7.06 Copper, commercial hard-drawn 97.0 250 11.78 Copper-clad steel wire 40.0 1084 10.45 Copper-clad steel wire 30.0 1084 12.06 Copper-clad steel rod 17.0 1084 14.64 Aluminum-clad steel wire 20.3 657 17.26 Steel 1020 10.8 1510 18.39 Stainless-clad steel rod 9.8 1400 14.72 Zinc-coated steel rod 8.6 419 28.96 Stainless steel 304 2.4 1400 30.05





17. Special areas of concern 1

17.3 Grounding of substation fence 2

Replace the following equations in 17.3 under Figure 45 as shown: 3

V1995/116.0)61000(50 sssstep tCE 4 5

V 2042/116.0)61000(50 sssstep tCE 6 7

v622/116.0)5.11000(50 ssstouch tCE 8 9

V 634/116.0)5.11000(50 ssstouch tCE 10 11 12





Annex C 1

(informative) 2

Graphical and approximate analysis of current division 3

C.2 How to use the graphs and equivalent impedance table 4

Add the following text to Clause C.2 as shown below: 5

Referring to Figure C.1 through Figure C.22, a family of curves is plotted, with each curve representing a 6 different number of transmission lines or distribution feeders. The abscissa is a range of grounding system 7

8 h (i.e., the grid current 9

Ig). 10

When using Category A curves and Table C.1, only the delta-connected bus fault current should be used as 11 the multiplier of the split factor, because this fault current is the one that is from remote sources and is the 12 basis of these curves. 13

When using Category B–D curves, the fault current and contributions should be determined for all 14 transmission voltage levels and the case resulting in the highest grid current should be used. In addition, the 15 following steps must be used to determine the local and remote contributions: 16

a) Obtain the total single-phase-to-ground fault current at the fault location being studied, in 17 amperes. 18

b) For the studied fault location, obtain the phase currents for the contributions from each 19 transmission line on all transmission voltage levels at the substation, in amperes on the voltage of 20 each transmission line. 21

c) With no adjustments for the voltage level of the transmission lines, add the phase a (faulted 22 phase) currents of all transmission lines “crossing the substation fence.”, in amperes. This is the 23 remote contribution. 24

d) Subtract this remote contribution from the total current, in amperes. This is the local contribution. 25

e) Choose the curves from Categories B-D that most closely match the remote and local 26 contributions. For conservatism, it is suggested that the category with the next higher remote 27 current contribution be used. For example, if the actual remote contribution is 60%, it is 28 suggested to use the Category B (25% local, 75% remote) curves be used. 29

f) Using the curve with the closest number of transmission lines and the grounding system 30 resistance, determine the split factor Sf. Multiply this split factor by the total fault current to 31 determine the grid current for this fault location. 32

g) Repeat steps a-f for single-phase-to-ground faults at each transmission level bus in the substation. 33

h) The design grid current is the maximum of all grid currents computed using steps a) through-g). 34





Annex H 1

(informative) 2

Benchmark 3

H.3 Grounding system analysis 4

Change the first paragraph of Clause H.3 as shown below: 5

In the 1961 edition of IEEE Std 80, the equations for touch and step voltages were limited to analysis at 6 very specific points and were limited to analysis of uniformly-spaced conductors in symmetrical grids. 7 IEEE Std 80-2000 included improvements on those equations to account for odd-shaped grids and ground 8 rods, but still analyzed only specific points for touch and step voltages. Other methods, and especially 9 computer programs based on a fine-element analysis of the grounding system, might allow more flexibility 10 in modeling the conductors and ground rods making up the grounding system, and might analyze touch and 11 step voltages and transferred voltages at any point desired. This clause analyzes the grid resistance, touch 12 and step voltages, and transferred voltages (if applicable) for grids ranging from simple evenly-spaced 13 symmetrical grids with no ground rods to non-symmetrically shaped and spaced grids with random ground 14 rod locations and with separately-grounded fences. The grid current for all cases is 744.8A. The grid 15 analysis is performed using the equations in IEEE Std 80, and computer programs CDEGS, ETAP and 16 WinIGS. Again in In order to make it possible to compare at least two computation methods for all 17 examples, the soil structure has been limited to uniform and two-layer soils, although there are situations in 18 which it is desirable to model more complex soil structures. 19

Change the last paragraph (one sentence) of Clause H.3 as shown: 20

Again, In in order to make it possible to compare at least two computation methods for all examples, the 21 soil structure has been limited to uniform and two-layer soils. 22

H.3.1 Grid 1 – symmetrically spaced and shaped grid, uniform soil, no ground rods 23

Replace Table H.5 with the following table: 24

Table H.5-Comparison of results for grid analysis 25 CASE RGRID

( ) RFENCE

( ) GPR

GRID (V)

TOUCH VOLTAGES

(V)

STEP VOLTAGES

(V)

TRANSFER VOLTAGE GRID-TO-FENCE (V)

T1 T2 T3 T4 S1 S2

Grid 1 STD 80 1.05 NA 780.0 232.0 NA NA NA 96.0 NA NA Grid 1

CDEGS 1.0 NA 743.9 194.9 147.4 202.7 NA 89.3 NA NA Grid 1 ETAP 1.01 NA 751.7 200.9 164.2 209.0 NA 87.2 NA NA Grid 1

WinIGS 1.0 NA 744.9 196.3 151.2 203.4 NA 88.7 NA NA

NOTE— Used average soil resistivity based on Equation (51) of Clause 13. 26





Change the cross-reference to Table H.5 to Table H.6 as shown in H.3.2. 1

H.3.2 Grid 2 – symmetrically spaced and shaped grid uniform soil, with ground rods 2

The ground grid for this comparison is shown in Figure H.4. This case is the same as Grid 1, with the 3 addition of twenty 7.5m (24.6 ft.) rods located at each intersection around the perimeter of the grid. The 4 touch and step voltages were computed at the same locations as for Grid 1. The comparisons are shown in 5 Table H.5 Table H.6 6

Insert Table H.6 after Figure H.2. 7

Table H.6-Comparison of results for grid 2 analysis 8 CASE RGRID

( ) RFENCE

( ) GPR

GRID (V)

TOUCH VOLTAGES

(V)

STEP VOLTAGES

(V)


T1 T2 T3 T4 S1 S2

Grid 2 STD 80 1.022 NA 761.0 163.0 NA NA NA 80.0 NA NA Grid 2

CDEGS 0.917 NA 682.8 145.4 85.8 149.6 NA 70.7 NA NA Grid 2 ETAP 0.92 NA 687.9 150.2 77.2 154 NA 79.3 NA NA

Grid 2 WinIGS 0.919 NA 684.8 146.9 91.0 151.3 NA 71.5 NA NA

NOTE— Used average soil resistivity based on Equation (51) in Clause 13. 9

Change the cross-reference to Table H.5 to Table H.7 in H.3.3 as shown: 10

H.3.3 Grid 3 – symmetrically spaced and shaped grid, two-layer soil, with ground tools 11

The ground grid for this comparison is the same as for Grid 2, except the soil model is changed to a two-12 layer soil with 1 -m, 2 -m, and h=6.096m (20ft). See Figure H.5. The touch and step 13 voltages were computed at the same locations as for Grid 1. The comparisons are shown in Table H.5 14 Table H.7. 15 16

17

18

19

20

21

22






Table H.7-Comparison of results for grid 3 analysis 2 CASE RGRID

( ) RFENCE

( ) GPR

GRID (V)

TOUCH VOLTAGES

(V)

STEP VOLTAGES

(V)


T1 T2 T3 T4 S1 S2

Grid 3 STD 80 1.395 NA 1039.0 222.0 NA NA NA 109.0 NA NA

Grid 3 CDEGS 0.97 NA 719.5 261.0 128.1 262.5 NA 101.9 NA NA

Grid 3 ETAP 0.97 NA 726.4 268.5 111.6 269.7 NA 117 NA NA

Grid 3 WinIGS 0.972 NA 723.8 264.5 136.3 266.2 NA 103.5 NA NA


Change the cross-reference from Table H.5 to Table H.8 in H.3.4 as shown: 4

H.3.4 Symmetrically spaced and shaped grid, separately-grounded fence, two-layer soil, 5 with ground rods 6

The ground grid for this comparison is the same as for Grid 3, except a separately-grounded fence is added, 7 located 3m outside the grid perimeter conductor, and with a fence perimeter ground conductor located 1m 8 outside the fence. The touch and step voltages were computed at similar locations as for Grid 1. In this 9 case, however, additional touch and step points were computed. For this case, touch voltages T1, T2 and 10 T3 were computed as differences between the surface potentials at these points and the GPR of the main 11 ground grid. T4 was computed as the difference between surface potential at the corner of the fence 12 perimeter conductor and the GPR of the fence perimeter conductor (connected only to the separately-13 grounded fence). Step voltages S1 and S2 were computed as differences between earth surface potentials 14 1m apart along the diagonal. S1 had the first point located over the corner of the perimeter conductor of the 15 main grid, while S2 had the first point located over the outer (fence) perimeter conductor. The comparisons 16 are shown in Table H.5 Table H.8 17

18

19

20

21

22

23

24






Table H.8-comparison of results for grid 4 analysis 2 CASE RGRID

( ) RFENCE

( ) GPR

GRID (V)

TOUCH VOLTAGES

(V)

STEP VOLTAGES

(V)


T1 T2 T3 T4 S1 S2

Grid 4 STD 80 NA NA NA NA NA NA NA NA NA NA Grid 4

CDEGS 0.96 1.6 717.9 259.7 127.1 261.1 51.1 97.4 38.1 309.2

Grid 4 ETAP NA NA NA NA NA NA NA NA NA NA Grid 4

WinIGS 0.97 1.62 722.6 263.6 130.1 264.9 49.9 97.0 37.4 312.4



H.3.5 Grid 5- symmetrically spaced non-symmetrically shaped grid, fence grounded to 5 main grid, two-layer, with ground rods 6

The ground grid for this comparison is shown in Figure H.7. This grid is non-symmetrical in shape (L-7 shaped), though it still has symmetrically spaced grid conductors. It also has ground rods of uniform length 8 at every other intersection around the perimeter, and has a grounded fence within the confines of the main 9 grid and bonded to the grid. The touch and step voltage equations in Clause 16 can be used for this type of 10 grid, but it is not known exactly where the touch and step voltages are being computed. For the computer 11 programs, the touch and step voltages were computed at numerous points to determine the worst case for 12 each. The worst case touch voltage was computed at all points 0.5m apart within the fence, plus all points 13 within reach (1m) outside the fence. The worst case step voltage (S1) was computed at all points 0.5m 14 apart within an area defined inward from 1m outside the perimeter of the grid. For direct comparison, the 15 step voltage (S2) was also compared by determining the difference between earth surface potentials 1m 16 apart along the diagonal at the upper left corner of the grid. The comparisons are shown in Table H.5 17 Table H.9. 18

19

20

21

22

23

24

25






Table H.9-comparison of grid 5 analysis 2 CASE RGRID

( ) RFENCE

( ) GPR

GRID (V)

TOUCH VOLTAGES

(V)

STEP VOLTAGES

(V)


T1 T2 T3 T4 S1 S2

Grid 5 STD 80

(1) 1.35 NA 1005.8 146.5 NA NA NA 110.6 NA NA

Grid 5 CDEGS 0.81 NA 602.7 131.6 NA NA NA 83.0 NA NA

Grid 5 ETAP 0.81 NA 606.4 138.1 NA NA NA 90.7 NA NA

Grid 5 WinIGS 0.81 NA 606.4 138.1 NA NA NA 90.7 NA NA

NOTE— Used average soil resistivity based on Equation (51) in .Clause 13 3


H.3.6 Grid 6 – non-symmetrically spaced and shaped grid, non-orthogonal conductors, 5 two-layer soil, with ground rods at random locations and unequal lengths 6

The final ground grid for comparison is similar to Grid 3, but with conductors on the diagonal and with 7 corner grounds 7.5m long and all other ground rods 2.5m long. The soil model is changed to a two-layer 8 soil with 1=100 -m, 2=300 -m, and h=6.091m (20ft). See Figure H.8. The touch and step voltage 9 equations in Clause 16 are not intended for this type of grid, so IEEE Std 80 results are not included in this 10 case. For the computer programs, the touch and step voltages were computed at numerous points to 11 determine the worst case for each. The worst case touch voltage was computed at all points 0.5m apart 12 within the perimeter conductor. The worst case step voltage (S1) was computed at all points 0.5m apart 13 within an area defined inward from 1m outside the perimeter of the grid. For direct comparison, the step 14 voltage (S2) was also compared by determining the difference between earth surface potentials 1m apart 15 along the diagonal at the upper left corner of the grid. The comparisons are shown in Table H.5 Table 16 H.10. 17 18

19

20

21

22

23

24






2

Table H.10-comparison of results for grid 6 analysis 3 CASE RGRID

( ) RFENCE

( ) GPR

GRID (V)

TOUCH VOLTAGES

(V)

STEP VOLTAGES

(V)


T1 T2 T3 T4 S1 S2

Grid 6 STD 80 NA NA NA NA NA NA NA NA NA NA Grid 6

CDEGS 1.42 NA 1054.4 134.4 NA NA NA 96.4 NA NA

Grid 6 ETAP 1.43 NA 1068.2 140.2 NA NA NA 99.2 NA NA

Grid 6 WinIGS 1.43 NA 1063.1 136.6 NA NA NA 77.4 84.9 NA


H.4 Grid current analysis (current division) 5

H.4.2 Grid current for transmission substation – remote and local sources 6

Change the following paragraph as shown: 7

Figure H.10 shows the system data for this example. The transmission lines have shield wires that are 8 grounded at each pole, with pole ground resistance equal to 15 . The autotransformer has a common 9 grounded winding, and includes a delta-connected tertiary winding. The substation grounding system (grid 10 plus ground rods, only) is 1.0 . All line configuration dimensions, line sequence impedances, and 11 equivalent source impedances are included in Figure H.10. The results are shown in Table H.7. Following 12 the guidelines in Annex C for the current split curves Std 80 results), the grid current is computed for both 13 230 and 115kV bus faults to determine the worst case grid current. Results are also given using the 50/50 14 remote/local split and the 25/75 remote/local split curves, as suggested in Annex C. Results are shown in 15 Table H.12 using the 25/75 local/remote split curve, as suggested in Annex C.2 (e). This calculation is done 16 for both 230 kV and 115 kV bus faults to determine the worst case grid current, as suggested in Annex C.2 17 (g). The 100% remote contribution split factor is also shown to illustrate the effect of having a portion of 18 the total fault current from local contributions. 19


Download - IEEE P80-2013 Draft Guide for Safety in AC Substation Grounding-Corrigendum 1 Dec 2014

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