IGS Section 01

7/24/2019 IGS Section 01

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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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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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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



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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



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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 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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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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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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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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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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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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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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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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The Electrocution Parameters

A2A1

B

A2A1

Veq

req

B

rbody


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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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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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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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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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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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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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Comparison of StandardsNon-Fibrillating Body Current as a Function of Shock Duration

C i f St d d


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Comparison of StandardsNon-Fibrillating Body Current as a Function of Shock Duration

F t t S il R i t


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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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Reduction Factor

Comparison of IEEE Std 80 and Computer Model

Human Body Resistance as a Function of Voltage


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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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Safety Assessment - IEEE Std 80Basic Idea: Compare Actual Maximum Body Current to Permissible

Conversion of Permissible Body Current to Permissible Touch Voltage

permbody

ii

Documents

IGS Section 01