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Integrated Grounding System Design and Testing Grounding System Design Principles
Copyright 1994-2014, A. P. Sakis Meliopoulos1.1
Integrated Grounding System Design and Testing
Instructors:
A. P. Sakis Meliopoulos, George J. Cokkinides, GIT, Hilton Mills, HP&D
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Integrated Grounding System Design and Testing Grounding System Design Principles
Copyright 1994-2014, A. P. Sakis Meliopoulos1.2
NOTICE
This material may not be reproduced without the written consent of the developer.
The developer is neither responsible nor liable for any conclusions and results
obtained through the use of this material.
For further information, contact:
Dr. A. P. Sakis Meliopoulos,Georgia Power Distinguished Professor
School of Electrical and Computer Engineering,
Georgia Institute of Technology,
Atlanta, Georgia 30332-0250,Telephone: 404 894-2926
Email: [email protected] [email protected]
mailto:[email protected]:[email protected]:[email protected]:[email protected] -
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Integrated Grounding System Design and Testing Grounding System Design Principles
Copyright 1994-2014, A. P. Sakis Meliopoulos1.3
Day 1
Grounding System Design Principles
Basic Concepts
Accidental Electrocution Circuit Parameters
Safety Criteria
IEEE Std 80 2000 Edition
IEC-479-1
Lightning and EMC
Integrated 3-D Design Procedures
Grounding System Performance
Ground Potential Rise
Fault Current Distribution
Transferred Voltages
Touch and Step Voltages
Influence on Comm/Control Circuits
Influence on Pipelines
Analysis Methods
IEEE Std 80 Design Procedures
Conductor and Joint Selection
Recommended Design Procedures
Special Points of Danger
Comparison of IEEE Std 80 and IEC-479-1
Integrated Grounding System Design and Testing
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Integrated Grounding System Design and Testing Grounding System Design Principles
Copyright 1994-2014, A. P. Sakis Meliopoulos1.4
Day 2
Soil Characterization
Soil StructuresMeasurement Techniques
Soil Samples
Wenner Method
Three Pin Method
Measurement Interpretation
Theory and Limitations
SGM Method
Workshop
System Modeling for Grounding Design
General Principles
Modeling Requirements for GPR
Design Options for GPR Reduction
Modeling Requirements for Shielding Analysis
Workshop
Ground Mat Design for Safety
Touch/Mesh/Step Voltages
Metal to Metal Touch Voltages
Design Options for Touch Voltage Control
Safety Assessment
Workshop
Integrated Grounding System Design and Testing
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Integrated Grounding System Design and Testing Grounding System Design Principles
Copyright 1994-2014, A. P. Sakis Meliopoulos1.5
Day 3
Integrated Grounding System DesignCost/Benefit Analysis
Integrated Design EvaluationTransfer Voltages (Pipelines, Buildings, etc.)
Control Cable Shielding and Grounding
Electric Railroad Grounding Design
Wind Farm Grounding
Design Optimization
Workshop
Substation Lightning ShieldingBasic PrinciplesShielding Angle
The Rolling Sphere Method
The EGM Method
Risk Assessment
Design Procedures
Workshop
Ground Design for Lightning
Ground Surge Impedance
Lightning Points of Entry
Lightning Overvoltage and Propagation
Transfer Voltages to Control Circuits
Wind Turbine Protection
Mitigation Methods
Integrated Grounding System Design and Testing
Integrated 3-D Substation Design
Assessment of Clearances
Bus Design Evaluation
EMF Computations
Ground Impedance MeasurementsFall of Potential method
Theory and Limitations
Factors Affecting Test Accuracy
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Integrated Grounding System Design and Testing Grounding System Design Principles
Copyright 1994-2014, A. P. Sakis Meliopoulos1.8
Purpose of Grounding
Lightning and Surge Protection
Stabilize Circuit Potential and Assist in Proper Operation of:
- Communications
- Relaying
- Computers & Sensitive Electronic Equipment
Low Fault Circuit Path Impedance (Protection)
Safety, Safety, Safety
Improve Quality of Power Service
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Integrated Grounding System Design and Testing Grounding System Design Principles
Copyright 1994-2014, A. P. Sakis Meliopoulos1.9
Terms and Definitions
Body Current
Duration of Electric Shock
Permissible Body Current
Ground Potential Rise
Touch Voltage
Mesh Voltage
Step Voltage
Permissible Touch or Step Voltage
Transfer Voltages
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Integrated Grounding System Design and Testing Grounding System Design Principles
Copyright 1994-2014, A. P. Sakis Meliopoulos1.10
Body Current
Perception
About 1 mA
Muscular Contraction (Let Go) About 10-20 mA
Unconsciousness
Ventricular Fibrillation
About 300 mAfor three seconds
Respiratory Nerve Blockage
Burning
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Integrated Grounding System Design and Testing Grounding System Design Principles
Copyright 1994-2014, A. P. Sakis Meliopoulos1.11
PercentileR
ank
Perception Currrent, mA (RMS)
99.8
0.2
5
40
80
99
PredictedCurve forWomen
Men
0 1 2
Perception Current
Let-Go Current
Ventricular Fibrillation
Permissible Body Current
(Standards)
Body Current
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Integrated Grounding System Design and Testing Grounding System Design Principles
Copyright 1994-2014, A. P. Sakis Meliopoulos1.12
100 1,000 10,000 100,000
1
10
100
Percentile 50Threshold of Perception
Percentile 0.5
Percentile 99.5
P
erceptionCurrent(mArms)
Frequency (Hz)
Body Current
Perception Current
Let-Go Current
Ventricular
Fibrillation
Permissible BodyCurrent (Standards)
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Integrated Grounding System Design and Testing Grounding System Design Principles
Copyright 1994-2014, A. P. Sakis Meliopoulos1.13
5 10 50 100 500 1000 5000
0
20
40
60
80
100
Dangerous Current
Let-Go Threshold
Safe Current
Frequency (Hz)
Let-GoCurrent(M
illiamperes)-RMS
99.5%
50% 0.5%
Body Weight (kg)
FibrillatingCurrent(mARMS)
0
100
200
300
0 10020 40 60 80
MaximumNon-FibrillatingCurrent (0.5%)
MinimumFibrillatingCurrent (0.5%)
Dogs
sheep
calves
pigs
KiselevDogs
FerrisD
ogs
Body Current Perception CurrentLet-Go CurrentVentricular Fibri llation
Permissible Body Current (Standards)
Relationship of Fibrillating Current to
Body Weight for Various Animals
3 second electric shock
Iave= 3.68W + 28.5 (ma)
Effect of Frequency on Let-Go
Current for Men
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Integrated Grounding System Design and Testing Grounding System Design Principles
Copyright 1994-2014, A. P. Sakis Meliopoulos1.14
Effects of Current on Heart Beat CEI 1984
120
80
40
0
mm Hg
400ms
Blood Pressure
ECG
Ventricu lar Fibrillation
1
2 3
2
5
4
Auricles
Ventricles
Speed of
ExcitationRecovery from
Excitation
1 2 3 5T
4
Q
S
Vulnerable Period
of the Ventricles
R
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Integrated Grounding System Design and Testing Grounding System Design Principles
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The Electrocution Parameters
A2A1
B
A2A1
Veq
req
B
rbody
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Integrated Grounding System Design and Testing Grounding System Design Principles
Copyright 1994-2014, A. P. Sakis Meliopoulos1.16
45(23)
40(20)
50(30)
50(25)
65(30)
70(45)
70(50)
60
75
100
55
(30)
100(75)
Resistance to One Hand(Resistance to Both Hands)Body Impedance
CEI 1984
Resistance from one (or both)
hands to various points in percent
of total body impedance ZT
C
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Integrated Grounding System Design and Testing Grounding System Design Principles
Copyright 1994-2014, A. P. Sakis Meliopoulos1.17
Body Impedance Dependence on Voltage - CEI-1984
Total Body Impedance ZT
Values for the total body impedance (ZT)
that are not exceeded for a percentage(percentile rank) of
Touch
Voltage
5% of the
population
50% of the
population
95% of the
population
25
5075
100125220700
1000Asymptotic
Value
1750
14501250120011251000750
700650
3250
262522001875162513501100
1050750
6100
437535003200287521251550
1500850
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Integrated Grounding System Design and Testing Grounding System Design Principles
Copyright 1994-2014, A. P. Sakis Meliopoulos1.18
k50= 0.116 (Non-Fibrillating, 0.5%)
k50= 0.185 (Fibrillating, 0.5%)
k70= 0.157 (Non-Fibrillating, 0.5%)
k70= 0.263 (Fibrillating, 0.5%)
sb tIk =
Value of Constant k for Effective
RMS Values of Ib:
Body Weight (kg)
F
ibrillatingCurren
t(mARMS)
0
100
200
300
0 10020 40 60 80
Maximum
Non-FibrillatingCurrent (0.5%)
MinimumFibrillatingCurrent (0.5%)
Dogs
sheep
calves
pigs
KiselevDogs
FerrisDogs
IEEE Std 80, 1986 Edition
IEC P bli i 4 9 1 P i ibl B d C
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Integrated Grounding System Design and Testing Grounding System Design Principles
Copyright 1994-2014, A. P. Sakis Meliopoulos1.19
IECPublication 479-1 - Permissible Body Current
1 2 3 4
Body Current Is(ma)
0.1 0.1 2 5 10 20 50 100 200 1k 10k0.2 2k 5k50010
50
200
1000
5000
10000
2000
500
100
20Duration
ofCurrent
Flow
t(m
s)
a b c1 c2 c3
Zones Physiological Effects
Zone 1 Usually no reaction effects.
Zone 2 Usually no harmful physiological effects.
Zone 3 Usually no organic damage to be expected. Likelihood of muscular contractions and difficulty in breathing,
reversible disturbances of formation and conduction of impulses in the heart, including atrial fibrillation and
transient cardiac arrest, without ventricular fibrillation, increasing with current magnitude and time.
Zone 4 In addition to the effects in zone 3, probability of ventricular fibrillation, increasing up to about 5% (curve c2),
up to about 50% (curve c3), and above 50% (beyond curve c3). Increasing with magnitude and time,
pathophysiological effects such as cardiac arrest and heavy burns may occur.
Time Current Zones of Effects of AC Currents (15 Hz to 100 Hz) on Persons
IEC P bli ti 479 1 P i ibl B d C t
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Integrated Grounding System Design and Testing Grounding System Design Principles
Copyright 1994-2014, A. P. Sakis Meliopoulos1.20
Time Current Zones of Effects of AC Currents (15 Hz to 100 Hz) on Persons
IECPublication 479-1 - Permissible Body Current
1 2 3 4
Body Current Is(ma)
0.1 0.1 2 5 10 20 50 100 200 1k 10k0.2 2k 5k50010
50
200
1000
5000
10000
2000
500
100
20Du
rationo
fCurr
ent
Fl o
w
t( m
s)
a bc
1
c2
c3
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Integrated Grounding System Design and Testing Grounding System Design Principles
Copyright 1994-2014, A. P. Sakis Meliopoulos1.21
Threshold of Perception: 0.5 mA
Threshold of Let-Go Currents: 10 mA
Threshold of Ventricular Fibrillation:
500 mA @ 0.1 seconds
40 mA @ 3 seconds
IEC - Publication 479-1Effects of Current Passing Through the Human Body
C i f S d d
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Integrated Grounding System Design and Testing Grounding System Design Principles
Copyright 1994-2014, A. P. Sakis Meliopoulos1.22
Comparison of StandardsNon-Fibrillating Body Current as a Function of Shock Duration
C i f St d d
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Integrated Grounding System Design and Testing Grounding System Design Principles
Copyright 1994-2014, A. P. Sakis Meliopoulos1.23
Comparison of StandardsNon-Fibrillating Body Current as a Function of Shock Duration
F t t S il R i t
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Integrated Grounding System Design and Testing Grounding System Design Principles
Copyright 1994-2014, A. P. Sakis Meliopoulos1.24
Foot to Soil ResistanceIEEE Std80 Approximate Equations
Human foot is modeled as a plate in contact with the earth surface
The resistance of a circular plate to remote earth is: 4b
=R
Where b is the disk radius. For arbitrary shaped objects, b is
approximated as:
Ab =
where A is the area of the foot in contact with the
earth. For adults with large feet:metersb 08.0
Thus, the resistance of each foot in
contact with the earth is:
OhmsR
3(0.08)(4)
==
Two feet in parallel (touch voltage case):
5.1
3+3
)(3)(3==eqr
In Case of Resistive Top Material: req= 1.5cs s for touch voltage
req= 6.0cs s for step voltage
Two feet in series (step voltage case): 633 =+=eqR
R d ti F t
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Integrated Grounding System Design and Testing Grounding System Design Principles
Copyright 1994-2014, A. P. Sakis Meliopoulos1.25
Reduction Factor
Comparison of IEEE Std 80 and Computer Model
Human Body Resistance as a Function of Voltage
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Integrated Grounding System Design and Testing Grounding System Design Principles
Copyright 1994-2014, A. P. Sakis Meliopoulos1.26
Human Body Resistance as a Function of Voltage
Values for the total body impedance (ZT)
that are not exceeded for a percentage(percentile rank) of
Touch
Voltage
5% of the
population
50% of the
population
95% of the
population
2550751001252207001000
AsymptoticValue
175014501250120011251000750700650
32502625220018751625135011001050750
61004375350032002875212515501500850
IEC Total Body Impedance
IEEE Std 80
ZT= 1000 ohms
Safety Assessment IEEE Std 80
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Integrated Grounding System Design and Testing Grounding System Design Principles
Copyright 1994-2014, A. P. Sakis Meliopoulos1.27
Safety Assessment - IEEE Std 80Basic Idea: Compare Actual Maximum Body Current to Permissible
Conversion of Permissible Body Current to Permissible Touch Voltage
permbody
ii