Critical Facility Groundingy g

XIT GROUNDINGXIT GROUNDING

Agenda

Common Ground Importance / PyramidCommon Ground Importance / Pyramid

Grounding Resistance Defined

Site Specific Design Achieving 5 Ohms?

Electrode Choices Pros / Cons

Ground System Testing Why 95% is Invalid

Why Ground?

Equipment Protectionq p

Satisfy Warranty Requirements

Service Protection

System Performance

Personnel Safety (NEC)

Electrical Protection Systems

Protection Pyramid

Surge C ll t

RFCollectorsAC Surge

Telco / Data

LightningGroundingGrounding

Surge Dissipater

Typical Performance Reqs

National Electrical Code (NEC) < 25 OHMS a o a ec ca Code ( C) 5 O S

IEEE Standard 142 Equipment D d t

Practical Safeguarding of..

Dependent IEEE Standard 1100 < 5 OHMS

Motorola Standard R-56 < 10 OHMS

Verizon Wireless 8501 < 5 OHMS

Typical Telecom Switch < 2 OHMSTypical Telecom Switch 2 OHMS

Ground System Resistance

Defined!!Ground System Resistance?

Finite Resistance between the Ground System and Remote EarthGround System and Remote Earth

Ground System Resistance

What Two Factors Determine Ground System Resistance??

Soil Resistivity ( P )

Size of the Grounding System ( A )

Ground System Resistance

How Are They Related? The Relationship

R P / A

y p/ Simple Formula

R = P / AR = Ground System ResistanceR = Ground System Resistance

P = Soil ResistivityP Soil ResistivityA = Effective Cross Sectional

Area of The Ground System

Ground System Resistance

With Only Two Elements, Why is

P

y yResistance Difficult to Design/Predict?

P - Varies with Depth/Location Of SoilOf Soil

A - Determined by Size / ConfigurationOf The Grounding System

T fTypes ofGrounding ElectrodesGrounding Electrodes

Types of Grounding Systems

Driven Rods Ground Enhancement Materials

Copper Platespp Chemical Wells Ufer GroundsUfer Grounds Building Steel

Ground Ring Ground Ring Water Pipes

XIT El t l ti S t XIT Electrolytic Systems++

S il R i i iSoil ResistivityTestingTesting

(Determining P)

Soil Resistivity Testing

4-Pt. WENNER METHOD

R=E/I

METHOD

4-Pole Digital

R=E/Ig

Ground Tester

Voltage Drop

= 1 915 ARSoil Resistivity Testing

5 52 00 497 90

= 1.915 ARProbe Spacing Meter Reading Resistivity

5 52.00 497.90

10 19.68 370.87

15 10 16 292 0015 10.16 292.00

20 6.53 250.10

30 4.30 247.04

40 10.80 827.28

60 7.40 850.26

80 5.58 855.60

100 4.44 850.26

Soil Resistivity Testing

Site Area

Direction of Test

Grounding System Design

Grounding Calculationsg

Grounding System Design

The Simple Formula:

R = P / Ap

R = Ground System Resistance P = Soil ResistivityA = Effective Cross Sectional

Area of The Ground SystemArea of The Ground System

Grounding System Design

The Simple Formula:

R = P / Ap

R Is Known (Required Ohms, 5?)P P Is Known (Soil Resistivity)P & R A U d T D t i A

A P / R P & R Are Used To Determine A

A = P / R

Grounding System Design

Design Alternatives?

NomographIEEE T bl

g

IEEE Table Software Programs

Grounding System Design

Properly Designed System Benefits? Predictable Results

p y g y

Improved Personnel Safety

Improved Equipment ReliabilityImproved Equipment Reliability

Improved Equipment Performance

Improved Power Quality

Meet Mfgs Warranty RequirementsMeet Mfg s Warranty Requirements

Grounding System Resistance Testing

Ground System Testing

Why Test Grounds?y

Determine Baseline

Confirm Design Spec Validate Construction

Satisfied Satisfy Warranty Reqs Ensure Equip Protection & Performance

Ground System Testing

Two Test Methods

Fall Of Potential Test - Inserting Current / Measuring Voltage

Clamp-On Test - Inducing Voltage / Measuring Current

Fall of Potential Test

Advantageg Recognized As Accurate Most Commonly Utilized (IEEE Std 81)

DisadvantagesR lt F tl I lid (75 %)X

(95+%)

y ( )

Results are Frequently Invalid (75+%)X Requires Isolated Ground System Requires Large Area

Time Consuming Access To Soil

Fall of Potential Test

Required Equipment

3 / 4 Pole TesterAEMC / Megger

q q p

AEMC / Megger

Test Kit Probes

Conductor Conductor Tape Measure

Fall of Potential Test

3 Pole MeterCurrent Flow

R=E/I

Voltage

RemoteCurrentEl t d

Drop

Earth

Neutral Electrode

Fall of Potential Test

195

155165 175

G d R i t (Pl t )

185 195

Resistance

115125 135 145 155 Ground Resistance (Plateau)

7585 95

105 115

Voltage Probe Spacing (%)

55 65 75

0 10 20 30 40 50 60 70 80 90 100

Fall of Potential Test

You are testing every

d i

Neutral Connected

Currentground in parallel.

Connected

Fall Of Potential TestNeutral Connected

Ohms

Neutral Connected

Invalid

Test With Neutral Connected20

Test GraphPlot For

5 Oh G dPlot For

25 Oh G dPlot For

100 Oh G dPlot For

1000 Oh G d

15

5 Ohm Ground25 Ohm Ground100 Ohm Ground1000 Ohm Ground

5

10

Distance (Ground-Probe)

Clamp-On Resistance Test

Advantages Quick and Easy

No Disconnecting Neutral No Disconnecting Neutral

No Long Leads, Property

Disadvantage Ground Configuration Ground Configuration

Finding Proper Location To Test

Invalid Most Of The Time

Clamp-On Resistance Test

??? ohms 2 Control Xformers

R = E / IR = E / I 2 Control Xformers

One Induces 4 mvOne Induces .4 mv

One Measures Current Flow

Current Flow

Clamp-On Resistance Test

Neutral-Ground

Utility Neutral LineParallel Paths

Bond

Grounding G ou d gConductor

Series Loop

???Current Flow R = E/I???Current Flow R = E/I

Clamp-On Resistance Test

Neutral-Ground

Utility Neutral LineInvalid Ground

Bond

Grounding

Clamp-On Test

Grounding Conductor

Additional Grounding Conductor

???R = E/I

Current Flow

???R = E/I

Clamp-On Resistance Test

Main Reasons For Invalid Testingg

Fall Of Potential Test - Must Isolate Ground from Neutral

Clamp-On Test - Must have Single Point Ground

Ground Resistance Testing

Contributing Reasons For Invalid Testing

Grounding / Testing Not Taught

g g

IEEE G id / P d W k

Not Many Good Courses Available

IEEE Guidance / Procedures Weak

Mfgs Procedures Weak / WrongMfg s Procedures Weak / Wrong

Old Habits / Bad Assumptions / Pressure

Ground Resistance Testing

How To Improve Testing Results? Insist On Training

p g

Dont Insist On Results

Test Prior To Connecting Power

Design Facility For Testing

Dont Depend On Mfgs Procedures

Test Prior To Connecting Power

p g

Lyncole XIT GroundingPhone 1-800-962-2610

Fax 1-310-214-1114Fax 1-310-214-1114www.Lyncole.com

S @Support@Lyncole.com