Chapter 2 Flashcards
Grounding and Bonding
What is the focus on, when working on De-Energized Lines and Equipment?
Protecting the workers in case the line becomes energized unexpectedly.
What is installing Protective Grounds and Bonds designed to do?
- Minimize the time it takes to trip the circuit
- Limit the current flow and voltage drop across the lineworker’s body.
What must be done to ensure proper installation of Protective Grounds and Bonds?
Each step must occur in the correct order and the entire crew should work together to help ensure safety of all employees and the public.
What does every job begin with?
A Job Briefing or (Tailboard)
How does a tailboard improve the effectiveness of the grounding process?
Identifies:-The locations of all possible energy sources
- Fault Current Levels
- Overall Grounding Scheme
- How many grounds are to be installed, and where
- The size of the grounding components
- The specific installation and removal process
- Who is responsible to install and remove the grounds
What are the 5 Steps to properly ground a line?
- ) Identify
- ) Disconnect
- ) Test
- ) Clean
- ) Ground
When completing the Identify Step what does it entail?
Identify the section of line to be cleared by using circuit maps, cable tags, or other information sources. Consult with system operator f there is any confusion about what is being cleared, and when and how it will be done.
When completing the Disconnect Step what does it entail?
Disconnect the section from all possible energy sources of electrical energy. This may involve opening switches, standing off cable, removing jumpers, or other tasks. All devices in the path of the flow of power are opened, checked open, locked if possible, and tagged.
When completing the Test Step what does it entail?
Test the line for presence of voltage. Do not contact the line without first testing it, even if you are “sure” the crew did everything right during the clearance process.
When completing the Clean Step what does it entail?
Clean all connection points-including the clamps, conductors, cluster bracket, ground rods, anchors-prior to applying grounds. This minimizes resistance an improves the effectiveness of the grounds.
When completing the Ground Step what does it entail?
Ground the section of line after it has been disconnected, tested, and cleaned-and before employee contact is made. Install grounding components according to grounding scheme and follow the Golden Rule.
What does OSHA require before applying grounds?
TEST ALL LINES AND EQUIPMENT
How should you act when testing the line for voltage?
As if it is energized.
When is the line officially De-Energized?
After you Test and Ground it.
What should you know when using tools to test the line?
- Use Live-Line Tools to conduct the testing
- Know the voltage level at the work location and the voltage range of your tester
- Observe the minimum approach
- Understand that the testers are not precise measurement devices-they indicate approx. voltages
What kind of tester should you use?
An approved tester, and verify that it’s working.
What are the industries best practices for using a tester?
- ) Test the tester to make sure it’s working
- ) Test the line for voltage
- ) Test the tester one more time to make sure it is still working
What are the common tools used for testing the line for voltage?
- Multirange Voltage Detector
- Audible Tester
Essentially, what is a Multirange Voltage Detector?
A Multiple-range field intensity meter, this instrument has a switch for selecting kilovolt ranges.
How does a Multirange Voltage Detector differ from a voltmeter?
It uses the field strength to estimate the line-to-line voltage.
What are some properties of Multirange Voltage Detector?
- All readings should be regarded as estimates
- Can detect the presence of voltage through capacitance test points on underground elbow connectors
- Working condition is easily checked
- The user must apply the proper test to get a result
How does an Audible Tester work?
An electronic instrument that attaches to a live-line tool. The unit is placed close to or in contact with the conductor and will produce and audible warning and flashing light if voltage is detected.
What are some properties of an Audible Tester?
- Runs on a battery
- Simple to operate, and working condition is easily checked
- Does not indicate the level of voltage
Which of the two is said NOT to be used to test the line for voltage?
Audible Tester
What do apprentices do?
A LOT of cleaning
What is the purpose of installing protective grounds?
To create a low-resistance path for current to flow.
What can increase the resistance of any metal equipment or tool?
- Dirt
- Oxidation
- Corrosion
What do we use a wire brush for?
To properly clean and prepare the conductor and any current-carrying grounding components prior to installation.
What happens to the surface of an aluminum conductor?
It oxidizes quickly.
What happens when making connections of dissimilar metals?
Galvanic Corrosion
What should you focus on when assigned to clean connection points?
Every contact surface-Every part where the connections meet
What is the for cleaning when grounding?
To decrease resistance by clearing a path for as much current to flow as possible.
What does proper grounding require?
A good ground source to connect to.
What does the best ground source to use depend on?
Your location and the type of line or equipment being grounded.
Where is a System Neutral found?
In a Four-Wire WYE Distribution Circuit.
How far does the System Neutral run?
The entire length of the circuit.
What is a System Neutral?
An extension of the Substation Ground Grid.
How many times should the System Neutral be grounded?
4x/mi
What is a TGR?
A Temporary Ground Rod is a steel rod (5/8”-3/4” in diameter) or a screw type ground rod placed deep into the earth to provide an effective path for current to flow.
The deeper the TGR is place the ____ resistance.
Less
What should you be sure to do if installing a TGR?
Barricade the site.
What risk does installing a TGR carry?
Encountering Underground Utilities
What should you call in a couple days before installing a TGR?
Underground Service Alert (USA)
What is a Static/Shield Wire?
Conductor installed on transmission lines above the phase conductors.
What would you install Static/Shield Wires?
To intercept lightning strikes.
What do some companies allow anchor rods to be used as?
A Ground Source due to their depth and availability throughout the system.
Why would other companies prohibit using Anchor Rods as a Ground Source?
A Fault Current may damage the anchor’s structural integrity.
On transmission lines, the resistance of the structure’s footing and its integrity as a ground source are ______
Unknown
What do you install when working on Steel Lattice Towers?
A Butt Ground
What is a Butt Ground?
Consists of a Ground Cable connecting the Steel member to a TGR.
What are the Grounding Sources in order for Overhead Distribution?
- ) Substation Ground Grid
- ) System Neutral
- ) Temporary Ground
- ) Anchor Rod
What are the Grounding Sources in order for Transmission?
- ) Metal Structure
- ) Temporary Ground Rod
- ) Static/Shielding Wire
- ) Anchor Rod
For Underground Distribution how is the Ground Source readily available?
In the form of: Ground Rods
- Equipment Grounds
- Concentric Neutrals
- Cable Shielding
What is the only way to completely prevent current from flowing through a lineworker?
Insulate and Isolate
What does EPZ do?
Provides a low-resistance, short-circuited connection from the line to a ground source. It creates a zone of protection to reduce hazardous differences in electrical potential between objects in the work area.
What is the best grounding method for limiting current flow through the body and should be applied to the structure being worked on?
EPZ
What does Bracket Grounding do?
Provides a low-resistance, a short circuited connection from the line to a ground source at key locations on one or both sides of the work site.
How is Bracket Grounding used?
Primarily to trip the line’s protection devices as quickly as possible. This protects the worker and the system as a whole.
Even with an EPZ in place and Bracket Grounds in use what happens?
Small amounts of current will flow through the lineworker because the EPZ Grounds and the lineworker form a parallel path to ground.
When choosing your ground:
- Use EPZ Grounding, even if the utility does not require it.
- Use a combination of EPZ an Bracket Grounding particularly on larger jobs.
- Pay attention to all the elements that influence current flow. The resistances of the grounding sources can vary based on connections, soil types, the neutral conductor size, and how well the grounds are installed.
What is the Golden Rule of Grounding?
Connect to the Ground Source first and then connect to the conductor or equipment with a live-line tool. When removing the grounds, do the reverse: detach from the conductor before detaching from the ground source.
Why do we use insulated live-line tools?
It helps the lineworker maintain minimum approach distance (MAD) until the grounding process is complete.
What are the steps taken for EPZ Grounding on Distribution lines?
- ) Test all phases for the presence of voltage.
- ) Clean all conductors
- ) Install cluster bracket and connect to ground source
- ) Connect grounding cable to cluster bracket first, and then to any phase using live-line tools
- ) Connect grounding cable to grounded phase first and then to next closest phase.
- ) Connect grounding cable to grounded phase first and then to next closest phase.
What are the steps taken for EPZ Grounding on Transmission lines?
- ) Test all phases for the presence of voltage.
- ) Clean all conductors
- ) Install cluster bracket and connect to ground source
- ) Connect grounding cable to cluster bracket first, and then to any phase using live-line tools
- ) Connect grounding cable to grounded phase first and then to other phases.
- ) Wire brush shield wire and connect grounding cables from phases to shield wire.
How do you choose grounding components?
- They need to fit the systems being worked on.
- Including Construction Standards
- Fault Current Levels
- Conductor Sizes
What size are most Transmission Grounds?
2/0 Copper
What size wire does OSHA require as a minimum?
2 AWG Copper
What are ground clamps?`
They form the connection between the low-resistance ground cable and conductor.
What style clamps are most often used on Distribution circuits?
C-Clamps and Snap-On (Duckbill)
What style clamps are most often used on Transmission Circuits (Lattice)?
Flat-Style Clamps
What makes installation of clamps safer?
Supporting Studs or be mounted into clusters
What does the Grounding Cluster Bracket do?
Functions as a terminal point for the grounding cables and provides contact with the pole to establish the equipotential zone.
What do Running Grounds do?
Protect lineworkers when stringing wire.
What do Stringing Block Grounds do?
Provide direct grounding between the conductor or pulling line and the ground source.
How are Running Grounds installed?
They are installed on the conductor as it leaves the reel.
Where are Stringing Block Grounds used?
These blocks can be placed at key loctions along the path of the wire stringing.
How do you inspect Grounding Components?
- Movable portions of ground clamps should be tight and void of any free-play
- Eye screw of the ground clamp should not be bent
- Contact area of the jaws should be clean and free of corrosion
- Connection between the cable and clamp should be clean and tight
- Cable should be free of broken strands
- Cluster bracket should be free of cracks and warping
How should you store grounding components?
In a way that protects them from damage.
What are Ground Sets exposed to during normal use?
- Moisture
- Chemicals
- Dirt
- Temperature Extremes
What can happen to the insulation?
Can be cut or scraped and the clamps and ferrules damaged.
What’s the only way to determine the resistance of the clamps and cable?
TEST IT
How often should Grounding Sets be tested?
Periodically and tag them with the test date.
How do Ground Testers work?
They place a voltage across the clamps of the grounding cables to determine the resistance that occurs based on a voltage.
What are the common reasons for failure on ground sets?
- Loose Connections
- Corroded Connections
- Corroded Clamp Jaws
- Moisture Intrusion in the cable
- Improper Crimping of the ferrule
What are the 4 components of a Grounding Plan?
- ) Creation of the EPZ
- ) Grounding Cable Size
- ) Grounding Cable Placement
- ) Fault Current
How do you ensure safety when grounding?
- Use grounding cables of the proper length
- Avoid excess slack
- Avoid coiling grounding cable around metallic objects because this reduces the current-carrying capacity of the cable.
What do you need to maintain while installing grounds?
MAD Minimum Approach Distance
What does the greater phase separation mean for grounding?
That the grounding cables are longer and heavier and the live-lines tools are typically longer, and the clamps may be larger to fit the conductor size.
Because both circuits in a Transmission line are rarely De-Energized, what is a major concern?
Induction from the adjacent circuit.
What might larger lines require when grounding?
More than one set of Protective Grounds to handle the fault current.
How might grounds be installed when working on Lattice Structures?
They may have to be installed from above the conductors because of the weight of the grounding cable. (>345kV)
How do you remove grounds on lattice towers?
Remove the conductor end of the grounding cable before removing the grounded end, which is attached to the tower.
What is a Foreign Ground?
Any conductive object that is:
- ) Connected to Ground
- ) Within your EPZ
- ) Not bonded to the EPZ
What are some examples of Foreign grounds?
- Guy-Wires
- Communication Messengers
- Aerial Lifts
What do you install before opening a conductor?
Grounding Cable before cutting the conductor.
Why do you install the Grounding Cable before cutting the conductor?
It prevents the opened or cut side of the conductor from being separated from the protective grounds.
What does continuity mean?
An uninterrupted flow of current.
How do you ground a Two-Pole Project?
Install a Cluster Bracket to each pole in the work area and connect them together.
In a Multiple-Pole Project what do you do after completing work at one location?
Move the grounds to the next work location.
What are some possible energy sources when working on Mutltiples Poles?
Transformers and Capacitors
What does OSHA require after disconnecting a capacitor bank?
5 Minute Wait to bleed off any charge before short-circuiting and grounding the terminals.
Where do you apply grounds on capacitor banks?
On the leads that attach to disconnects.
What is the best way to ensure protective equipment operates as fast as possible?
Ground the vehicle to the System Neutral
What is a personal ground?
A Ground Cable connected just to the supply conductor, or phase being worked on.
Where is a Personal Ground only allowed and what must it establish?
Between Bracket Grounds. EPZ
Why can Grounding a Wire-Stringing Operation be a challenge?
Because it occurs over a long stretch of circuit and (particularly with transmission lines) adjacent conductors are often energized.
What are OSHA’s regulations for Overhead Wire Stringing?
- Ground the pulling and tensioning equipment
- Ensure employees working near the equipment and conductors wear rubber gloves
- If possible use an EPZ at both ends of the stringing operation
How do you choose Grounding Components for Underground?
- Match the Construction Standards
- Fault Current Levels
- Common Conductor Sizes
How do Underground Bushing Test Probes work?
It is inserted into the bushing or placed in direct contact with capacitance test points.
Why use a Portable Feedthru?
To disconnect, test, and ground a circuit, and available in both horizontal and vertical configurations to ease installation.
How does a Portable Feedthru work?
The underground conductor to be grounded is positioned on one of the bushings and the grounding elbow can then be positioned on the other bushing.
How does a Grounding Elbow work?
Sized for the Fault Current. The ground clamp is attached to the ground source, while the elbow end is placed on the Portable Feedthru along with the cable to be grounded.
What does a Grounded Bushing do?
Provides a temporary ground for elbows. Test the disconnect cable for voltage through the capacitance test point before installing it on the grounded bushing.
What does an Insulated Protective Cap do?
Insulates, shields, and seals any load break bushing interface.
What does a Grounding Spike Clamp do?
The penetrating clamp is typically used to prove that a cable is De-Energized at the work location. When installed properly, the point will penetrate through the shielding to the conductor, creating a path to ground for the conductor. Its is not used a protective ground.
What does and EPZ Mat do?
Also known as a grounding mat, these conductive mats help provide an EPZ between the work surface and the equipment. They are made of interconnected bare conductors, metallic, or fiber surface mats, or welded wire grating.
What is critical with Underground Circuits?
Cable Identification
Why is Cable Identification critical in Underground Circuits?
Because the cables cannot be physically traced from the clearance points.
What should you always consider connecting so that it is not open at the work location?
The Concentric Neutral
When should Cable Tags be created?
Before beginning the job and verify their accuracy
What are the steps taken to ground an Underground Circuit?
- ) Identify the cable to be cleared
- ) Disconnect the cable to be cleared
- ) Test for presence of voltage
- ) Install Protective Grounds
