GOOD GROUNDING PRACTICES FOR THE PLANT A

A grounding system is a critical safety component in electrical systems, providing a path for electrical current to safely dissipate into the earth. Here are the key elements and functions of a grounding system:

Key Components
Ground Electrode:

The physical connection to the earth, often made with rods, plates, or grids.
Grounding Conductor:

A wire that connects the electrical system to the ground electrode, ensuring that excess electricity has a safe path to the ground.
Grounding Bus:

A metal bar or strip where multiple grounding conductors can connect, often used in electrical panels.
Bonding:

Connecting different conductive parts to ensure they have the same electrical potential, which helps prevent electric shock.
Functions of a Grounding System
Safety:

Protects people and equipment by providing a low-resistance path for fault currents, reducing the risk of electrical shock.
Equipment Protection:

Prevents damage to electrical equipment by diverting excess current caused by faults or lightning strikes.
Electrical Noise Reduction:

Helps minimize electromagnetic interference (EMI) in sensitive equipment.
Voltage Stabilization:

Maintains the voltage at a safe level, preventing fluctuations that could damage systems.
Types of Grounding Systems
System Grounding:

Grounding of the electrical system itself, often used in power distribution systems.
Equipment Grounding:

Grounding of individual equipment to ensure they are safe and do not pose a shock hazard.
Lightning Grounding:

Special grounding systems designed to protect structures from lightning strikes.
Importance
A well-designed grounding system is essential for ensuring electrical safety in residential, commercial, and industrial settings. Regular inspections and maintenance of grounding systems are crucial to ensure their effectiveness. If you have more specific questions or need information about a particular type of grounding system, feel free to ask!
There are several types of earthing (or grounding) systems used in electrical installations to ensure safety and proper functioning. Here are the main types:

### 1. **System Earthing**
- **Solidly Grounded System:**
- The neutral point of the system is directly connected to the ground. This provides a low-resistance path for fault currents.
- **Resistance Grounded System:**
- A resistor is connected between the neutral point and the ground, limiting fault current while still providing some degree of protection.
- **Reactance Grounded System:**
- An inductor is used to ground the system, which can limit fault currents while allowing for the system to operate normally under certain conditions.

### 2. **Equipment Earthing**
- **Equipment Grounding:**
- Individual equipment is grounded to prevent electric shock and ensure safety. This typically involves connecting the equipment frame to the grounding system.
- **Bonding:**
- Ensures that all conductive parts are connected, so there is no potentia

1. GOOD GROUNDING GOOD GROUNDING
PRACTICESPRACTICES
A Brief Introduction to the A Brief Introduction to the
Basics of Electrical Grounding Basics of Electrical Grounding
for Power Systemsfor Power Systems
By:
Harry J. Tittel, E.E.
Vice President TEAMWORKnet, Inc.
TEAMWORKnet, Inc.
6550 New Tampa Highway
Suite B
Lakeland, Florida 33815
[phone]
[phone] fax

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Provides Complete Spectrum of
Electrical Engineering Services
Provides Electrical Testing Services
and Thermal Imaging Surveys
Complete Provider of AutoCAD or
Microstation V8 Services, including
Scanning, Printing and Archiving
Process Control Specialists

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Introduction to GroundingIntroduction to Grounding
TABLE OF CONTENTS
1.0 Introduction to Grounding
2.0 Standard Industrial Grounding Methods and Types of Grounding
3.0 Grounding System and Design Considerations
4.0 Open Question and Answer Session

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Introduction to GroundingIntroduction to Grounding

The primary goal of the grounding system throughout any facility is The primary goal of the grounding system throughout any facility is
SAFETY. Secondary are effective lightning protection, diminishing SAFETY. Secondary are effective lightning protection, diminishing
electromagnetic coupling (EMC), and the protection against electromagnetic coupling (EMC), and the protection against
electromagnetic pulses (EMP).electromagnetic pulses (EMP).

Grounding is implemented to ensure rapid clearing of faults and to Grounding is implemented to ensure rapid clearing of faults and to
prevent hazardous voltage, which in turn reduce the risks of fires and prevent hazardous voltage, which in turn reduce the risks of fires and
personnel injuries. Grounding serves the primary functions of referencing personnel injuries. Grounding serves the primary functions of referencing
the AC systems and providing a means to ensure fault clearing.the AC systems and providing a means to ensure fault clearing.

99.5% survival threshold – 99.5% survival threshold –

116 mA for one (1) second.116 mA for one (1) second.

367 mA for zero point one (0.1) second.367 mA for zero point one (0.1) second.

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Introduction to GroundingIntroduction to Grounding

A frequently quoted criteria is the establishment of a one (1) ohm A frequently quoted criteria is the establishment of a one (1) ohm
resistance to earth. A large number of equipment manufacturers have resistance to earth. A large number of equipment manufacturers have
this in their installation guides. The NEC requires only twenty-five (25) this in their installation guides. The NEC requires only twenty-five (25)
ohms of resistance for made electrodes, while the ANSI/IEEE Standard ohms of resistance for made electrodes, while the ANSI/IEEE Standard
141 (Red Book) and ANSI/IEEE 142 (Green Book) specifies a ground 141 (Red Book) and ANSI/IEEE 142 (Green Book) specifies a ground
resistance of one (1) to five (5) ohms. resistance of one (1) to five (5) ohms.

External changes in the grounding system (environment) may effect External changes in the grounding system (environment) may effect
the ultimate functionality of the entire electrical system.the ultimate functionality of the entire electrical system.

Frequency matters in very complex grounding systems. Leakage Frequency matters in very complex grounding systems. Leakage
currents of equipment do not return to the earth; high frequency currents of equipment do not return to the earth; high frequency
leakage currents return to the equipment which generated them, leakage currents return to the equipment which generated them,
while power frequency leakage currents return to the derived source. while power frequency leakage currents return to the derived source.

The impedance of the system is viewed from the perspective of power The impedance of the system is viewed from the perspective of power
frequencies and immediate harmonics (i.e., 60Hz and its associated frequencies and immediate harmonics (i.e., 60Hz and its associated
harmonics).harmonics).

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Introduction to GroundingIntroduction to Grounding

Generally accepted electrical wiring practices are not good ground Generally accepted electrical wiring practices are not good ground
system wiring practices (i.e. no sharp bends or turns).system wiring practices (i.e. no sharp bends or turns).

Grounding systems are not meant to last for ever. The best Grounding systems are not meant to last for ever. The best
grounding systems need to most attention paid to them as they will grounding systems need to most attention paid to them as they will
corrode the quickest.corrode the quickest.

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GROUNDING SYSTEMS
There are basically six (6) grounding systems in use. The six (6) systems
are the equipment grounds, static grounds, systems grounds,
maintenance grounds, electronic grounds and lightning grounds.
Equipment grounds: An equipment ground is the physical connection to earth
of non-current carrying metal parts. This type grounding is done so that all
metal part of equipment that personnel can come into contact with are always
at or near zero (0) volts with respect to ground. All metal parts must be
interconnected and grounded by a conductor in such away as to ensure a
path of lowest impedance for flow of ground fault current. Typical items
(equipment) to be grounded are; electrical motor frames, outlet boxes, breaker
panels, metal conduit, support structures, cable tray, to name a few.
Static grounds: A static ground is a connection made between a piece of
equipment and the earth for the purpose of draining off static electricity
charges before a flash over potential is reached. This type grounding system
is utilized in dry materials handling, flammable liquid pumps and delivery
equipment, plastic piping, and explosive storage facilities.

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Standard Industrial System Grounding MethodsStandard Industrial System Grounding Methods
Methods of System GroundingMethods of System Grounding
CharacteristicsCharacteristics UngroundedUngrounded Solid Solid
GroundGround
Low Resistance Low Resistance
GroundGround
High Resistances High Resistances
GroundGround
Susceptible to Transient overvoltagesSusceptible to Transient overvoltagesWORSTWORST GOODGOOD GOODGOOD BESTBEST
Under fault conditions (line-to-ground) Under fault conditions (line-to-ground)
increase of voltage stressincrease of voltage stress
POORPOOR BESTBEST GOODGOOD POORPOOR
Arc Fault DamageArc Fault Damage WORSTWORST POORPOOR GOODGOOD BESTBEST
Personnel SafetyPersonnel Safety WORSTWORST POORPOOR GOODGOOD BESTBEST
ReliabilityReliability WORSTWORST GOODGOOD BETTERBETTER BESTBEST
Economics' (Maintenance costs)Economics' (Maintenance costs) WORSTWORST POORPOOR POORPOOR BESTBEST
Plant continues to operates under Plant continues to operates under
single line-to-ground faultsingle line-to-ground fault
FAIRFAIR POORPOOR POORPOOR BESTBEST
Ease of locating ground faults (time)Ease of locating ground faults (time)WORSTWORST GOODGOOD BETTERBETTER BESTBEST
System coordinationSystem coordination NOT NOT
POSSIBLEPOSSIBLE
GOODGOOD BETTERBETTER BESTBEST
Upgrade of ground systemUpgrade of ground system WORSTWORST GOODGOOD BETTERBETTER BESTBEST
Two voltage levels on same systemTwo voltage levels on same system NOT NOT
POSSIBLEPOSSIBLE
POSSIBLEPOSSIBLE NOT POSSIBLENOT POSSIBLE NOT POSSIBLENOT POSSIBLE
Reduction in number of faultsReduction in number of faults WORSTWORST BETTERBETTER GOODGOOD BESTBEST
Initial fault current Into ground systemInitial fault current Into ground systemBESTBEST WORSTWORST GOODGOOD BETTERBETTER
Potential flashover to groundPotential flashover to ground POORPOOR WORSTWORST GOODGOOD BESTBEST

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TYPES OF GROUNDING SYSTEMSTYPES OF GROUNDING SYSTEMS

Ungrounded System:Ungrounded System:
The ungrounded system is one that has no intentional The ungrounded system is one that has no intentional
connection between the neutral or any phase and ground. connection between the neutral or any phase and ground.
Please note that an ungrounded system is grounded through Please note that an ungrounded system is grounded through
the concept of capacitively coupling. The neutral potential of an the concept of capacitively coupling. The neutral potential of an
ungrounded system, with balanced loading will be close to ungrounded system, with balanced loading will be close to
ground potential due to the capacitance between each phase ground potential due to the capacitance between each phase
conductor and ground.conductor and ground.
Low ground fault current.Low ground fault current.
Very high voltages to ground potential on unfaulted phases.Very high voltages to ground potential on unfaulted phases.
Sustained faults lead to system line-to-line voltages on unfaulted Sustained faults lead to system line-to-line voltages on unfaulted
line.line.
Insulation failure.Insulation failure.
Failure due to restrike ground faults.Failure due to restrike ground faults.
Continued operation of facility.Continued operation of facility.

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TYPES OF GROUNDING SYSTEMSTYPES OF GROUNDING SYSTEMS

Solidly Grounded System:Solidly Grounded System:
The solidly grounded system is one that has the neutral The solidly grounded system is one that has the neutral
connected to ground without an intentional impedance. In connected to ground without an intentional impedance. In
contrast to the ungrounded system the solidly grounded contrast to the ungrounded system the solidly grounded
system will result in a large magnitude of current to flow (Aids system will result in a large magnitude of current to flow (Aids
in coordination), but has no increase in voltage on unfaulted in coordination), but has no increase in voltage on unfaulted
phases.phases.
Low initial cost to install and implement, but stray currents then Low initial cost to install and implement, but stray currents then
become a possible consequence.become a possible consequence.
Common in low voltage distribution systems, such as overhead Common in low voltage distribution systems, such as overhead
lines.lines.
typically feeds to transformer primary with high side fuse typically feeds to transformer primary with high side fuse
protection.protection.
Not the preferred grounding scheme for industrial or commercial Not the preferred grounding scheme for industrial or commercial
facilities due to high magnitude fault currents.facilities due to high magnitude fault currents.

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TYPES OF GROUNDING SYSTEMSTYPES OF GROUNDING SYSTEMS

Low Resistance Grounded System:Low Resistance Grounded System:
The low resistance grounded system is one that has the neutral The low resistance grounded system is one that has the neutral
connected to ground through a small resistance that limits connected to ground through a small resistance that limits
the fault current. The size of the grounding resistor is the fault current. The size of the grounding resistor is
selected to detect and clear the faulted circuit..selected to detect and clear the faulted circuit..
The resistor can limit ground currents to a desired level based The resistor can limit ground currents to a desired level based
on coordination requirement or relay limitations.on coordination requirement or relay limitations.
Limits transient overvoltages during ground faults.Limits transient overvoltages during ground faults.
Low resistance grounding is not recommended for low voltage Low resistance grounding is not recommended for low voltage
systems due to the limited ground fault current. This reduced systems due to the limited ground fault current. This reduced
fault current can be insufficient to positively operate fuses fault current can be insufficient to positively operate fuses
and/or series trip units.and/or series trip units.
Ground fault current typically in the 100 – 600 Amp range.Ground fault current typically in the 100 – 600 Amp range.

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TYPES OF GROUNDING SYSTEMSTYPES OF GROUNDING SYSTEMS

High Resistance Grounded System:High Resistance Grounded System:
The high resistance grounded system is one that has the neutral The high resistance grounded system is one that has the neutral
connected to ground through a resistive impedance whose resistance connected to ground through a resistive impedance whose resistance
is selected to allow a ground fault current through the resistor equal is selected to allow a ground fault current through the resistor equal
to or slightly more that the capacitive charging current of the system. to or slightly more that the capacitive charging current of the system.
The resistor can limit ground currents to a desired level based on The resistor can limit ground currents to a desired level based on
coordination requirement or relay limitations.coordination requirement or relay limitations.
Limits transient overvoltages during ground faults.Limits transient overvoltages during ground faults.
Physically large resistor banks.Physically large resistor banks.
Very low ground fault current, typically under 10 Amps.Very low ground fault current, typically under 10 Amps.
Special relaying methods utilized to detect and remove ground faults.Special relaying methods utilized to detect and remove ground faults.
High resistance grounding is typically applied to situations where it is High resistance grounding is typically applied to situations where it is
essential to prevent unplanned outages.essential to prevent unplanned outages.
Recent trend has been to utilize high resistance grounding methods on Recent trend has been to utilize high resistance grounding methods on
600 volt systems and lower.600 volt systems and lower.

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GROUNDING SYSTEMSGROUNDING SYSTEMS
System grounds: A system ground refers to the point in an electrical System grounds: A system ground refers to the point in an electrical
circuit that is connected to earth. This connection point is typically at the circuit that is connected to earth. This connection point is typically at the
electrical neutral. The sole purpose of the system ground is to protect electrical neutral. The sole purpose of the system ground is to protect
equipment. This type ground also provides a low impedance path for fault equipment. This type ground also provides a low impedance path for fault
currents improving ground fault coordination. This ensures longer currents improving ground fault coordination. This ensures longer
insulation life of motors, transformers and other system components.insulation life of motors, transformers and other system components.
Maintenance grounds: This type ground is utilized for safe work Maintenance grounds: This type ground is utilized for safe work
practices, and is a temporary ground.practices, and is a temporary ground.
Electronic and computer grounds: Grounding for electronic equipment is Electronic and computer grounds: Grounding for electronic equipment is
a special case in which the equipment ground and the system ground are a special case in which the equipment ground and the system ground are
combined and applied in unity. Electronic equipment grounding systems combined and applied in unity. Electronic equipment grounding systems
must not only provide a means of stabilizing input voltage levels, but also must not only provide a means of stabilizing input voltage levels, but also
act as the zero (0) voltage reference point. Grounding systems for the act as the zero (0) voltage reference point. Grounding systems for the
modern electronics installation must be able to provide effective modern electronics installation must be able to provide effective
grounding and bonding functions well into the high frequency megahertz grounding and bonding functions well into the high frequency megahertz
range.range.
Lightning protection: Lightning protection grounding requirements are Lightning protection: Lightning protection grounding requirements are
dependent upon the structure, equipment to be protected, and the level dependent upon the structure, equipment to be protected, and the level
of lightning protection required of desired.of lightning protection required of desired.

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GROUNDING SYSTEMSGROUNDING SYSTEMS
►Several factures should be considered in the initial design of the Several factures should be considered in the initial design of the
grounding system.grounding system.
The area available for installation of the grounding system. This could The area available for installation of the grounding system. This could
lead to the requirement and utilization of chemical rods, or wells.lead to the requirement and utilization of chemical rods, or wells.
Water table and seasonal changes to it.Water table and seasonal changes to it.
Soil condition and resistivity, Please see chart of typical results. Also Soil condition and resistivity, Please see chart of typical results. Also
elevation above sea level and hard rocky soil are concerns that would elevation above sea level and hard rocky soil are concerns that would
need to be addressed.need to be addressed.
Available fault currents (i.e., three (3) phase, line-to-ground, and line-Available fault currents (i.e., three (3) phase, line-to-ground, and line-
to-line-to ground, etc.).to-line-to ground, etc.).
NEC and ANSI/IEEE requirements. Also include here the requirements NEC and ANSI/IEEE requirements. Also include here the requirements
of the process equipment to be installed.of the process equipment to be installed.
Consideration to the number of lightning strikes and thunder storm Consideration to the number of lightning strikes and thunder storm
days per year.days per year.
Utility ties and/or service entrance voltage levels.Utility ties and/or service entrance voltage levels.
Utilization of area were ground system is to be installed, (i.e., do not Utilization of area were ground system is to be installed, (i.e., do not
install under paved parking lot).install under paved parking lot).

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GROUNDING SYSTEMSGROUNDING SYSTEMS
SOIL RESISTIVITIES
(Approximate Ohm-Meters)
Description
1,2
Median Min. Max.
Topsoil's, loams 26 1 50
Inorganic clays of high plasticity 33 10 55
Fills-ashes, cinders, brine wastes 38 6 70
Silty or clayey fine sands with slight plasticity 55 30 80
Porous limestone, chalk 65 30 100
Clayey sands, poorly graded sand-clay mixtures 125 50 200
Fine sandy or silty clays, silty clays, lean clays 140 80 200
Clay-sand-gravel mixtures 145 40 250
Marls
3
155 10 300
Decomposed granites, gneisses
4
, etc. 300 100 500
Clayey gravel, poorly graded gravel 300 200 400
Silty sands, poorly graded sand-silt mixtures 300 100 500
Sands, sandstone 510 20 1,000
Gravel, gravel-sand mixtures 800 600 1,000
Slates, schists
5
, gneiss, igneous rocks, shales, granites, basalts 1,500 1,000 2,000
Quartzite's, crystalline limestone, marble, crystalline rocks 5,500 1,000 10,000
Notes: 1. Low resistivity soils are highly influenced by the presence of moisture.
2. Low resistivity soils are more corrosive than high resistivity soils.
3. Crumbly soil composed mostly of clay with a high limestone content.
4. Metamorphic rock formed by recrystallization of granite, separated into bands.
5. Metamorphic rock much coarser than gneiss.
This chart compiled from data published in:
IEEE Standard 142-1991, Recommended Grounding Practices
British Standard Code of Practice, CP-1013: 1965, Earthing
Megger: A Simple Guide to Earth Testing
Biddle: Getting Down to Earth

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GROUNDING SYSTEMSGROUNDING SYSTEMS
1.Parity sized grounding conductors.
2.Grounding symmetry in all parallel feeders.
3.Zones of equipment with localized transformers
to isolate the equipment and control leakage
current.
4.Limiting the quantity of devices grounded by
any single conductor.
5.Utilizing specialty transformers to limit ground
interference.
6.Faraday cage design concepts.
7.Use different networks throughout the facility
as opposed to a single ended data network.
8.Reference grids in all computer, data
processing and information technology rooms.
9.Perimeter ground ring bonded to the service
entrance.
10.Intentional continuity of structural steel.
11.Bonding of all communication cables to
structural steel.
12.Architectural steel treatment for lightning
protection.
13.Ufer ground treatment per NEC for all main
vertical steel footers.
14.Grounding grid below moisture barrier.
15.Bonding horizontal steel pans to structural
steel.

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GROUNDING SYSTEMSGROUNDING SYSTEMS
►Several factures can degrade initially good grounding systems. Several factures can degrade initially good grounding systems.
These factors indicate the importance of continuous periodic These factors indicate the importance of continuous periodic
testing (Typically once per calendar year unless problems arise). A testing (Typically once per calendar year unless problems arise). A
change (lower) in the water table across the USA would lead to a change (lower) in the water table across the USA would lead to a
degrade in the grounding system. Another consideration in the degrade in the grounding system. Another consideration in the
ground system would be in facility growth and the addition of non-ground system would be in facility growth and the addition of non-
metallic piping and conduit which do not provide low resistance metallic piping and conduit which do not provide low resistance
ground connections. Along with the these concerns are the ground connections. Along with the these concerns are the
increase load and associated increase in available fault currents. increase load and associated increase in available fault currents.
The better the ground system, the more attention should be paid The better the ground system, the more attention should be paid
to corroded electrodes. All these could result in the need for a to corroded electrodes. All these could result in the need for a
decrease in the grounding resistance.decrease in the grounding resistance.
Testing: Periodic testing should be done to assure grounding system Testing: Periodic testing should be done to assure grounding system
effectiveness.effectiveness.

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GROUNDING SYSTEMSGROUNDING SYSTEMS

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GROUNDING SYSTEMSGROUNDING SYSTEMS

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GROUNDING SYSTEMSGROUNDING SYSTEMS

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GROUNDING SYSTEMSGROUNDING SYSTEMS

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Florida Electrical Resources Earth Ground Test Report

A Division of TEAMWORKnet, Inc. Project : 302xxxx Test Page 1

FLORIDA ELECTRICAL RESOURCES 6550 New Tampa Hwy., Suite B Lakeland, Florida 33815 [phone] [phone] Fax [phone]
A Division of TEAMWORKnet, Inc.

Earth Ground Test Data Analysis & Problem Classification
Engineer Bill Engel, P.E. & Harry Tittel, E.E. Test Method Clamp on Ground Tester
Client / Facility Client Name Photograph No. 0
Amperage Reading 0 mA
Location Saw Mill Area Test Results 46.2


Notes: Ground Tested High. Perform
Date January 8, 2001 Maintenance on Ground or
Time 9:30 AM Replace.
Ambient Conditions 83 °F, Humid, Dry Ground


Test Point Digital Image Test Point Location Representation





















GROUND
CABLE

Saw Mill

23. TEAMWORKnet, Inc. 23
Florida Electrical Resources Earth Ground Test Report
A Division of TEAMWORKnet, Inc. Project : 302xxxx Test Page 2

FLORIDA ELECTRICAL RESOURCES 6550 New Tampa Hwy., Suite B Lakeland, Florida 33815 [phone] [phone] Fax [phone]
A Division of TEAMWORKnet, Inc.


Earth Ground Test Data Analysis & Problem Classification
Engineer Harry Tittel, E.E. Test Method Clamp on Ground Tester
Client / Facility Client Name Photograph No. 7
Amperage Reading 34 mA
Location Stacker, Sorter, C-N-S Area Test Results 1.5


Debarker Area Notes: Ground Tested Within
Date January 8, 2001 Parameters.
Time 11:35 AM
Ambient Conditions 93 °F, Humid, Dry Ground


Test Point Digital Image Test Point Location Representation





















GROUND

Stacker
Sorter
C-N-S
Oil
Log Deck
Debarker

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Open question and Answer session.