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ELECTRIC POWER SYSTEM GROUNDING By Steve Blume [email protected] (760) 612-8488

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Page 1: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

ELECTRIC POWER SYSTEM GROUNDING

BySteve [email protected](760) 612-8488

GND1

Page 2: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

Presentation Outline

Electric Power System Grounding

▪ 3-Phase Power Systems▪ Reasons for Grounding and Bonding▪ Substation, Transmission, and Distribution Grounding▪ Power Faults and Lightning Strikes▪ Fault current distribution▪ Ground Potential Rise (GPR)▪ Touch and Step Potentials▪ Safety

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Page 3: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

Single Phase Generation

3-Phase Power Systems

N

S

+ Volts

- Volts

Faraday’s Law:

Voltage is produced on any conductor in

a changing magnetic field!

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Page 4: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

N

S

+ Volts

- Volts

Three Phase Generation

3-Phase Power Systems

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Page 5: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

3-Phase AC Generator

3-Phase Generator

N

S

Exciter

ControlsAC Voltage Out

Field/Rotor

Stator

Slip Rings

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Page 6: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

ToLoad

Winding 2

Winding 3 Winding 1

Delta

Winding 3

Winding 1

Winding 2

WYE

Neutral

ToLoad

Symmetrical Connections

3-Phase Power Systems

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Page 7: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

Neutral vs. Ground vs. Bond

3-Phase Power Systems

Neutral

Ground

BondNeutral

Winding 2

Winding 1

Winding 3

To the loadWYE

L

L

L

N

▪ Grounding: the neutral is connected to earth via ground rods, grids, or conductors. Unbalanced neutral currents flow through the earth connection.

▪ Bonding: electrical connections between equipment and grounded conductors to provide equipotential during faults.

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Page 8: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

3-Phase Power Systems

▪ Control power fault and Lightning strike currents▪ Protect equipment and trip energizing equipment▪ Equipotential Grounding▪ Effects of Ground Potential Rise▪ Touch and Step Potentials▪ Detect and minimize unbalanced currents

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Reasons for Grounding and Bonding

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Page 9: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

System Grounding

3-Phase Power Systems

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Page 10: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

Substation Grounding

3-Phase Power Systems

Ground grids

FenceStructures

Equipment

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Page 11: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

Rod Line

60º

60º

60º shield angle is typical

Shield Wires andOptical Ground Wires

Lightning Protection through Grounding

Transmission Line Shielding and Grounding

3-Phase Power Systems

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Page 12: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

Distribution Lines: Wye Configuration

3-Phase Power Systems

A

B

C

N

A

N

Multi-GroundedNeutral

Grounded neutral

Multi-grounded Neutral: At least four times per mile per the National Electric Safety Code

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Page 13: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

Distribution Lines: Delta Configuration

3-Phase Power Systems

A

B

C

A

B

Delta three-phase distribution lines use three wires, no neutral. Transformer tanks and lightning arresters are connected to ground rods at each pole.

No grounded neutral!

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Page 14: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

Source Balanced 3-Phase Currents

NO Earth Return Current!

GridGrid

Load

Generator Transformer

Balanced Conditions

3-Phase Power Systems

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Page 15: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

Ground Grid Wires Ground Rods

Lightning RodsPower Fault

or Lightning Strike

Substation Fault

Power System Fault

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Page 16: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

G

Phase Currents

Earth Return Current

XFMRGPRs

GridGrid

Assumptions• Homogenous Soil (i.e., round contours)• Power Fault at substation transformer bushing

Ground Potential Rise (GPR) – unbalanced current

Power System Fault

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Page 17: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

G

Un-Balanced 3-Phase Current

Grid

XFMR

Neutral Currents

Shield Wire Currents

GPRs

Grid

Earth Return Current

Multiple Ground Paths and GPR’s

Power System Fault

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Page 18: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

NO Earth Return Currents!!!

NO GPR!!!

Current flow through grid: YES

Voltage drop on grid: YES

G

Un-Balanced 3-Phase Current

XFMR

Metropolitan Grids

Power System Fault

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Page 19: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

Homogeneous Soil

300 volt point

GPR“Zone of Influence”

x

SubstationGnd Grid

GPR - Zone of Influence

Power System Fault

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Page 20: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

SubstationsStructures

Distance From Fault

Touch StepGround Potential Rise

Ground Grid

Touch & Step Potentials

Electrical Grounding Safety

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Page 21: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

Human Characteristics

Electrical Grounding Safety

The average 155-lb man takes the following currents:▪ 1.2ma to produce a slight tingling feeling, called perception threshold▪ 9ma can produce a painful shock, but still below lock-on conditions▪ 16ma can cause the loss of muscle control▪ 23ma can cause difficulty breathing▪ 50ma approximately can cause burning▪ 100ma for 3 seconds can cause heart fibrillation▪ 1 amp for 30ms can cause heart fibrillation

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NOTE: Current path through body is a critical factor!

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Page 22: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

2-Ways to be Safe!

Electrical Grounding Safety

CONDUCTION – Equipotential GroundingThe use of materials in situations where good conduction (low resistance) will result in small potential differences and high current flow. (Ground Jumpers)

ISOLATION – Personal Protective EquipmentThe use of materials in situations where good insulation (high resistance) will result in large voltage differences and low current flow. (Rubber Insulation)

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Page 23: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

Conduction - Ground Source Preferences

Electrical Grounding Safety

1. Substation Ground Grid2. Multi-Grounded Neutral (MGN)3. Steel Tower or Steel Pole4. Driven or Screw-in Ground Rods5. Anchor Rods

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Page 24: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

YOUYOUR

JUMPERS

FAULT CURRENT

Earth

"TRUE" GROUND

Conduction - Jumper Voltage Drop Protection

Electrical Grounding Safety

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Page 25: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

Example:

Single Point

Grounding a

metal lattice

tower

Electrical Grounding SafetyConduction - Transmission Structure Safety

Example: Single Point Grounding for one worker

on a wooden “H” frame structure with overhead

ground wiresSteel Towers Wood Structures 25

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Page 26: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

Conduction - Distribution Structure Safety

Electrical Grounding Safety

Single Point Grounding

Example: Worker minimizing

exposure to touch potential by

operating equipment controls

from a conductive mat

Vehicle Arrangement26

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Page 27: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

Neutrals and Lightning Arresters are Grounded.

Conduction - Underground Equipment

Electrical Grounding Safety

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Page 28: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

Isolation - Personal Protective Equipment (PPE)

Electrical Grounding Safety

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Page 29: ELECTRIC POWER SYSTEM GROUNDING - exacterinc.com Power... · ELECTRIC POWER SYSTEM GROUNDING By Steve Blume swblume@gmail.com (760) 612-8488 GND1. Presentation Outline Electric Power

Electric Power System Grounding

Any Questions?

Thank you!

BySteve [email protected](760) 612-8488