IEEE Guide for Safety in AC Substation Grounding

Title page......Page 1
Participants......Page 3
CONTENTS......Page 5
1.2 Purpose......Page 9
2. References......Page 10
3. Definitions......Page 11
4.2 Conditions of danger......Page 16
5.2 Effect of magnitude and duration......Page 19
5.3 Importance of high-speed fault clearing......Page 20
6.2 Alternative assumptions......Page 21
6.3 Comparison of Dalziel’s equations and Biegelmeier’s curve......Page 22
6.4 Note on reclosing......Page 23
7.2 Current paths through the body......Page 24
7.3 Accidental circuit equivalents......Page 25
7.4 Effect of a thin layer of surface material......Page 28
8.1 Definitions......Page 31
8.2 Typical shock situations......Page 34
8.3 Step and touch voltage criteria......Page 35
8.4 Typical shock situations for gas-insulated substations......Page 36
9.1 Definitions......Page 37
9.2 General concept......Page 38
9.5 Design in difficult conditions......Page 39
9.6 Connections to grid......Page 40
10.1 Definitions......Page 41
10.3 Enclosures and circulating currents......Page 42
10.5 Cooperation between GIS manufacturer and user......Page 43
10.6 Other special aspects of GIS grounding......Page 44
10.8 Touch voltage criteria for GIS......Page 45
10.9 Recommendations......Page 46
11.1 Basic requirements......Page 47
11.2.5 Other considerations......Page 48
11.3.1 Symmetrical currents......Page 49
11.3.2 Asymmetrical currents......Page 53
11.3.3 Additional conductor sizing factors......Page 56
12.2 Effect of voltage gradient......Page 57
12.4 Effect of moisture, temperature, and chemical content......Page 58
13.1 Investigation of soil structure......Page 59
13.3 Resistivity measurements......Page 60
13.4 Interpretation of soil resistivity measurements......Page 63
13.4.1 Uniform soil assumption......Page 64
13.4.2 Nonuniform soil assumptions......Page 65
14.2 Simplified calculations......Page 72
14.3 Schwarz’s equations......Page 73
14.6 Concrete-encased electrodes......Page 76
15.1 Definitions......Page 80
15.2 Procedure......Page 81
15.3 Types of ground faults......Page 82
15.6 Effect of overhead ground wires and neutral conductors......Page 84
15.8 Worst fault type and location......Page 85
15.9 Computation of current division......Page 86
15.10 Effect of asymmetry......Page 91
15.11 Effect of future changes......Page 93
16.1 Design criteria......Page 94
16.2.4 Resistivity of surface layer (rs)......Page 95
16.4 Design procedure......Page 96
16.5.1 Mesh voltage (Em)......Page 99
16.5.2 Step voltage (Es)......Page 102
16.8 Use of computer analysis in grid design......Page 103
17.2 Switch shaft and operating handle grounding......Page 104
17.3 Grounding of substation fence......Page 107
17.4 Results of voltage profiles for fence grounding......Page 115
17.8 Separate grounds......Page 116
17.9.2 Rails......Page 117
17.9.6 Auxiliary buildings......Page 118
17.9.7 Fences......Page 119
18.2 Ground grid construction—conductor plowing method......Page 120
19.1 Measurements of grounding system impedance......Page 121
19.1.4 Staged-fault tests......Page 122
19.1.5 Fall-of-potential method......Page 123
19.2 Field survey of potential contours and touch and step voltages......Page 124
19.4 Ground grid integrity test......Page 125
20. Physical scale models......Page 126
Annex A—Bibliography......Page 127
Annex B—Sample calculations......Page 137
Annex C—Graphical and approximate analysis of current division......Page 153
Annex D—Simplified step and mesh equations......Page 172
Annex E—Equivalent uniform soil model for nonuniform soils......Page 175
Annex F—Parametric analysis of grounding systems......Page 178
Annex G—Grounding methods for high-voltage stations with grounded neutrals......Page 193