IEEE 80-1986

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IEEE Guide for Safety in AC Substation Grounding

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IEEE	1986

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Description

Revision Standard – Superseded. Outdoor AC substations, either conventional or gas-insulated, are covered in this guide. Distribution, transmission, and generating plant substations are also included. With proper caution, the methods described herein are also applicable to indoor portions of such substations, or to substations that are wholly indoors. No attempt is made to cover the grounding problems peculiar to dc substations. A quantitative analysis of the effects of lightning surges is also beyond the scope of this guide.

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PDF Pages	PDF Title
14	Lower Soil
17	Fig
18	Fig
19	1 Introduction Purpose and Scope Fig
20	Relation to Other Standards 1.3 KeyDefmitions
22	1.4 References
23	IF If and Of for Fault Duration tf
25	Safety in Grounding 2.1 Basic Problem
26	Ground Return Paths
27	Conditions of Danger
28	Without Ground Rods
29	3 Range of Tolerable Current 3.1 Effect offiequency Effects of Magnitude and Duration
30	Importance of High-speed Fault Clearing
33	Permissible Body Current Limit 4.1 Duration Formula
34	4.2 Alternative Assumptions Based on a Three-Second Shock
35	Note on Reclosing
37	Accidental Ground Circuit Resistance of Human Body Current Paths Through the Body
38	Accidental Circuit Equivalents
39	Step Voltage Circuit
40	Effect of a Thin Surface Layer of Crushed Rock Touch Voltage Circuit
42	Function F (X) Versus X and Reflection Factor K
43	Crushed Rock Layer Thickness h
45	Criteria of Permissible Potential Difference Typical Shock Situations
46	Basic Shock Situations
47	Typical Situation of External Transferred Potential
48	Step and Touch Voltage Criteria Typical Shock Situations for Gas-Insulated Substations
49	Effect of Sustained Ground Currents
50	Typical Metal-to-Metal Touch Situations in GIS Range of Enclosure Voltages to Ground
51	7 Principal Design Considerations 7.1 General Concept
52	Primary and Auxiliary Grounding Electrodes
53	Basic Aspects of Grid Design Design in Difficult Conditions
54	Connections to Grid
57	Special Considerations for Gas-Insulated Substation (GIS) 8.1 GIs Characteristics Enclosures and Circulating Currents
58	Grounding of Enclosures
59	Cooperation Between GIS Manufacturer and User
60	Other Special Aspects of GIS Grounding Notes on Grounding of GIS Foundations
61	Touch Voltage Criteria for GIS
63	Typical Faults in GIS
65	9 Selection of Conductors and Joints 9.1 Basic Requirements 9.2 Choice of Material and Related Corrosion Problems
66	9.3 Minimum Size Formula
68	9.4 Alternate Formulations Table 1 Material Constants
70	9.5 Selection of Joints Nomogram for Conductor Sizing Table 2 Minimum per Unit Conductor Sizes (cmils/A)
71	9.6 Additional Sizing Factors
72	9.7 Final Choice of Conductor Size
73	10 Soil Characteristics 10.1 Soil as Grounding Medium 10.2 Effect of Voltage Gradient 10.3 Effect of Current Magnitude 10.4 Effect of Moisture Temperature and Chemical Content
74	10.5 Use of Crushed-Stone Layer Fig 15 Soil Model
75	Effects of Moisture Temperature and Salt upon Soil Resistivity Table 3 Typical Crushed-Stone Resistivities
77	11 Soil Structure and Selection of Soil Model 11.1 Investigation of Soil Structure 11.2 Classification of Soils and Ranges of Resistivity 11.3 Resistivity Measurements
78	Table 4 Range of Earth Resistivity
79	11.4 Uniform Soil Assumption 11.5 Nonuniform Soil Assumptions 11.5.1 Two-Layer Soil Model
81	11.5.2 Comparison of Uniform and Two-Layer Soil Model
83	12 Evaluation of Ground Resistance 12.1 Usual Requirements 12.2 Simplified Calculations
84	Table 5 Typical Grid Resistances
85	12.3 Schwarz™s Formula
86	12.4 Note on Resistance of Primary Electrodes
87	Chemical Treatment of Soils and Use of Bentonite
88	12.6 Concrete-Encased Electrodes Coefficients K and K2 of Schwarz™s Formula
90	Ground Electrodes
92	Grid With Encased Vertical Electrodes
93	13 Determination of Maximum Ground Current 13.1 Procedure and Related Definitions
94	13.2 Types of Ground Faults
95	Fault Within Local Station; Local Neutral Grounded Fault Within Local Station; Neutral Grounded at Remote Location
96	Other Points
97	Substation
98	13.3 Effect of Station Ground Resistance
99	13.4 Effect of Fault Resistance 13.5 Effect of Ground Wires and Neutral Conductors 13.6 Effect of Pipes and Cables
100	13.7 Worst Fault Type and Location -Step (a)
101	13.8 Computation of Current Division – Step (b)
103	Example System for Computation of Current Division Factor Sf
104	13.9 Effect of Asymmetry- Step (c)
107	13.10 Effect of Future Changes – Step (d) Table 6 Typical Values of Df
109	14 Design of Grounding System 14.1 Design Criteria
110	14.2 Critical Parameters 14.2.1 Grid Current (IG) 14.2.2 Fault Duration (tf) and Shock Duration t, ) 14.2.3 Soil Resistivity (p) Table 7 Typical Ratio of Corner-to-Center Mesh Voltage
111	14.2.4 Resistivity of Surface Layer p, ) 14.2.5 Grid Geometry Index of Design Parameters 14.4 Design Procedure
112	Table 8 Index of Design Parameters
113	Design Procedure Block Diagram
114	Calculation of Maximum Step and Mesh Voltages
115	14.5.1 Mesh Voltage E, ) [B68] LEE W R Death from Electrical Shock Proceedings of the IEEE vol
116	14.5.2 Step Voltage (Es)
117	Estimate of Minimum Burried Conductor Length
118	Refinement of Preliminary Design
119	Limitations of Simplified Equations for E and E Use of Computer Analysis in Grid Design
121	15 Investigations of Transferred Potentials 15.1 Communication Circuits 15.2 Rails
122	Low-Voltage Neutral Wires Portable Equipment and Tools Supplied from Substation 15.5 Piping
123	15.6 Auxiliary Buildings
125	16 Investigation of Special Danger Points 16.1 Service Areas 16.2 Operating Handles
127	16.3 Fences
128	Cable Sheath Grounding
129	GIS Bus Extensions 16.6 Surge Arresters
130	Note on Separate and Common Grounds
131	17 Notes on the Construction of a Grounding System Ground-Grid Construction -Trench Method Ground-Grid Construction – Conductor Plowing Method
132	Installation of Joints Pigtails and Ground Rods
133	Installation Safety Considerations During Subsequent Excavations
135	18 Field Measurements of a Constructed Grounding System Measurements of Grounding System Impedance 18.1.1 Two-Point Method (Ammeter-Voltmeter Method) 18.1.2 Three-Point Method
136	18.1.3 Ratio Method 18.1.4 Staged-Fault Tests 18.1.5 Fall-of-Potential Method
137	Spacings ﬁXﬂ
138	Field Survey of Potential Contours and Touch and Step Voltages
139	Assessment of Field Measurements for Safe Design Periodic Checks of Installed Grounding System
141	19 Physical Scale Models
143	20 Bibliography
153	Mathematical Analysis of Gradient Problem
155	Experimental Data
157	Analysis of Gradient Problem – Basic Mathematical Model Table A1 KM K for Koch™s Model
158	per Eq A1 per EqA64 Full Model of Nonsimplifed Definition of KM E
160	Geometry for Derivation of E (1) per Eq A9 Conductors and Their Images
162	Derivation of Mesh Factor K for N 2 and h 2 4d Geometry for Derivation of E (k) per Eq A21
164	Series
165	Numerical Approximation of Krm 3. N) Series for h
168	Correction for K™ 3. N) Series for 0 < h I 2.5 m Development of Simplified Equations for Emesh
170	Three Identical Grids
171	Step Voltage Calculations Conductors N
173	Grid Resistance Formula
174	Fortran Routines for K K and R
177	Graphical Analysis of Square Ground Grids in Uniform Soil
178	Conductor Diameter Conductor Diameter
179	Conductor Diameter
180	Conductor Diameter Conductor Diameter
183	Sample Calculations
184	Square Grid Without Ground Rods – Example
186	Square Grid With Ground Rods – Example Square Grid Without Ground Rods Fig C1
187	Square Grid With Twenty 7.5 m Rods Fig C2
188	Rectangular Grid With Ground Rods – Example
189	Rectangular Grid With Thirty-Eight 10 m Ground Rods
190	Exhibit Equally Spaced Square Grid With Nine Rods in Two-Layer Soil
191	Diagonal Voltage Profile for a Grid of Fig C4 in Two-Layer Soil Fig C5
192	Unequally Spaced Square Grid With Twenty-Five 9.144 m Rods
193	Exhibit Fig C6
195	Equivalent Circuits and Calculation Notes Basic Concepts
196	Elementary Coupled Circuit Concepts Fig D1
197	Internal Faults T-Equivalent of an Ideal Transformer Fig D2
198	from the Fault Current Source Feed Point Near the Fault Current Feed Point Internal Fault Between Two Grounding Points Fig D5
200	Example of GIS Bus Installation Fig D6
202	External Faults Equivalent Model of Ungrounded Enclosure Circuits Fig D7
204	Ungrounded Bus Simpllfylng Concept of an Ungrounded Enclosure Loop Fig D8
206	and Bonding
207	Ground Faults Within and Outside GIS
209	Parametric Analysis of Grounding Systems El Uniform Soil El.l Current Density – Grid Only E1.2 Resistance – Grid Only
210	E1.3 Step and Touch Voltages – Grid Only One Mesh Grid Current Density
211	E1.4 Ground Rods Only Sixteen Mesh Grid Current Density
212	Grid and Ground Rod Combinations E1.6 Conclusions Four Mesh Grid Resistance
213	E2 Two-Layer Soil E2.1 Current Density – Grid Only E2.2 Resistance – Grid Only
214	E2.3 Step and Touch Voltages – Grid Only Sixteen Mesh Grid Resistance
215	Grid Resistance Versus Grid Depth Four Mesh Grid Touch Voltage
216	E2.4 Ground Rods Only Sixteen Mesh Grid Touch Voltage
217	E2.5 Grid and Ground Rod Combinations Four Mesh Grid Step Voltage
218	E3 Summary Sixteen Mesh Grid Step Voltage
219	Touch Voltage Versus Grid Depth Step Voltage Versus Grid Depth
220	Single Rod Current Density Multiple Driven Rod Current Density
221	Current Densities in Multiple Drive Rods Grid Current Densities – Rods and Grid
222	Rod Current Densities – Rods and Grid Rod and Grid Current Density-9 Rods and Grid in Two-Layer Soil
223	Rod and Grid Current Density-9 Rods and Grid in Two-Layer Soil
224	Table El Touch Voltages for Multiple Driven Rods Two-Layer Soil
225	Alphabetical Index of Definitions
227	Auxiliary Information Bibliography Not Cited in Text G1
236	Abstracts of References Not Readily Available G2
243	Appendixes H- J English Translations of Selected Papers Fundamental Considerations on Ground Currents Appendix H
287	Techniques
299	Jan 1973 pp 295 –
349	Grounded Neutrals