Ch. 2 - Grounding and Bonding

Multirange Voltage Detector

1. All readings should be regarded as estimates. 2. Can detect the presence of voltage through capacitance test points on underground elbow connectors. 3. Working condition is easily checked. 4. The user must apply the proper test to get a result.

Key Grounding Question

1. Are the grounding cables placed as far from the pole as possible? 2. Is the grounding cable length minimized? 3. Are the grounding cables of adequate size regarding fault current?

Four components of a Grounding Plan

1. Creation of equipotential zone (EPZ) 2. Grounding cable size. 3. Grounding cable placement. 4. Fault Current.

Equipotential Zone Grounding

1. EPZ is the best grounding method for limiting current flow through the body. 2. Provides a low-resistance, short-circuited connection from the line to a ground source.

Grounding Process

1. Identify 2.Disconnect (visual open) 3.Test (voltage) 4.Clean (the conduit for less resistance) 5. Ground (2 objectives for grounding lines and equipment)

Under Ground General Procedure

1. Identify the cable to be cleared 2. Disconnect the cable to be cleared 3. Test for the presence of voltage 4. Install protective grounds

Common reasons for failure of grounding components

1. Loose connections 2. Corroded connections. 3. Corroded clamps jaws. 4. Moisture intrusion in the cable 5. Improper crimping of the ferrule

Ground Sources Ranked (transmission)

1. Metal structures or tower 2. Temporary ground rod 3. Static/ sheilding wire (not always available) 4. Anchor Rod (when allowed: do not use guy-wire as a ground)

Two objectives for grounding lines and equipment

1. Minimize the time it takes to trip the circuit. 2. Limit the current flow and voltage drop across the line-worker's body.

Inspection of Grounding Components

1. Movable portions of ground clamps should be tight and void of any free-play. 2. Eye screw of the ground clamp should not be bent. 3. Contact area of the jaws should be clean and free of corrosion. 4. Cable should be free of broken strands (especially check near the clamp when bending is maximized.) Free of oxidation. 5. Cluster Bracket should be free of cracks and warping.

Basic EPZ installation

1. Test all phases for the presence of voltage. 2. Clean all conductors with wire brush. 3. Install cluster bracket and connect to ground source. 4. Connect grounding cable to cluster bracket first, and then to any phase using live-line tool. (Preferred to connect to the middle phase first.) 5. Connect grounding cable to ground phase first and then to next closest phase. 6. Connect grounding cable to ground phase first and then to next closest phase.

Transmission Lines EPZ installation

1. Test all phases for the presence of voltage. 2. Clean all conductors with wire brush. 3. Install cluster brackets and connect to ground source. 4. Connect grounding cables to cluster brackets first, and then to any phase using live-line tool. (Preferred to connect to the middle phase first.) 5. Connect grounding cables to grounded phase first and then to other phases. 6. Wire brush shield wire and connect grounding cables from phases to shield wire.

Industry best practices for using a tester

1. Test the tester to make sure it's working. 2. Test the line for voltage. 3. Test the testers one more time to make sure it's still working.

Testing the line

1. Use live-line tools to conduct the testing. 2. Know the voltage level at the work location and the voltage range of your tester. 3. Observe the minimum approach distance. 4. Understand that the testers are not precise measurement devices- they indicate approximate voltage.

Audible Tester

1.Runs on battery 2. simple to operate, working condition is easily checked. 3. does not indicate the level of voltage.

Ground Sources Ranked (overhead)

1.Substation ground grid. 2. System Neutral 3. Temporary Ground Rod 4.Anchor Rod (when allowed: do not use guy-wire as a ground)

Choosing a Grounding Guidelines

1.Use EPZ grounding, even if the utility does not require it. 2. Use combination of EPZ and bracket grounding, particularly on larger jobs. 3. Pat attention to all the electrical,ents that influence current flow. The resistances of the grounding sources can vary based on connections, sail types, the neutral conductor size, and how ell the grounds are installed.

Foreign Ground

Any conductive object that is 1. connected to ground 2. within your EPZ 3. not bonded to the EPZ Examples: guy-wires, communication messengers, aerial lifts

Two-Pole Project

Attach a cluster bracket to each pole in the work area and connect them together.

Critical in underground

Cable identification is critical in underground systems because the cables cannot be physically traced from the clearance point.

Golden Rule of Grounding

Connect to the ground source first, and then connect to the conductor or equipment with a live-tool. When removing the grounds, do the reverse: detach from the conductor before detaching from the ground source.

Ground Clamp

Connection between the low-resistance ground cable and the conductor. Distribution- Snap-on (duckbill) and c-clamps are widely used. Transmission- Bigger for larger conductors, lattice towers require flat-style clamp.

Metal Structures (Butt Ground)

Consists of a ground cable connecting the steel member to a TGR.

Substation Ground Grid

Designed to carry any fault that may reach the station.

Buzz Testing

Do not use for testing. Attach a

Grounding Components

Ground Cable Ground Clamp Cluster Bracket Running Grounds and Stringing Block Grounds Voltage Meters Wire Brush System Neutral Ground Grid Temporary Grounding Rod static/shield wire Anchor Rods Hot Stick

Anchor Rods

Grounding cable is directly clamped to the anchor room not the guy-wire. As the anchor rod corrodes over time, its resistance will increase.

EPZ Mat

Help provide an EPZ between the work surface and equipment. They are made of interconnected bare conductors, metallic or fiber surface mats, or welded wire grating.

Storage of Grounding Components

In a way that protects them from damage.

Mutli-pole Projects

Install EPZ grounds at every work location.

Static- Shielding Wire

Installed above the phase conductors for the purpose of intercepting lightning strikes.

Insulated Protective Cap

Insulates, shields, and seals any load break bushing interface.

Nominaal Voltage

Normal voltage

Ground Cable Size

OSHA requires a minimum #2 AWG cooper for ground cable.

Testing Grounding Components

Only testing can determine the resistance of the clamps and cable.

Running Grounds

Protect line-workers when stringing wire. They are installed on the conductor as it leaves the reel.

Stringing Block Ground

Provide direct grounding between the conductor or pulling line and the ground source. These blocks can be placed at key locations along the path of the wire stringing.

Grounded Bushing

Provided temporary ground for elbows. test the disconnect cable for voltage through the capacitance test point before installing it on the grounded bushing.

Bracket Grounding

Provides a low-resistance , short-circuited connection from the line to a ground source at key locations on one or both sides of the work.

System Neutral

Runs the entire length of the circuit and should be grounded at least 4 times per mile and can typically handle the available fault current.

Capacitor Banks

Short-circuited by grounding prior to working on them. OSHA requires 5-min wait.

Grounding Elbow

Sized for the fault current, Attached to ground source, the elbow end is placed on the portable feedthru along with the cable to cable to be grounded. Grounding elbows also are manufactured in a three-way terminal assembly.

Ground Sources

Substation Ground Grid System Neutral Temporary Grounding Rod Static/ Shielding Wire Anchor Rods Metal Structures Butt Ground

Cluster Bracket

Terminal Point, Jumpers, Equipotential Zone, Equipotential Zone Grounding

Line is considered de-energized when

Tested and grounded

Fault Current Study

The amount of verified and expected fault current on a given section of line. example: the further away from a station, the lower the amperage.

Temporary Grounding Rod (TGR)

The deeper a TGR is placed, the less resistance it has.

Minimum Approach Distance

The minimum approach distance varies according to the voltage involved.

minimum approach distance

The minimum distance varies according to the voltage according to the voltage involved. A disconnected line must be treated and respected as if it where energized until it is proven de-energized through testing and grounding.

Cleaning Connection Points

To decrease resistance by clearing a path for as much current flow as possible.

Grounding Spike Cap

Typically used to prove that a cable is de-energized at the work location. When insulated properly, the point will penetrate through the shielding to the conductor, creating a path to ground for the conductor. It is not used as a protective ground.

Electrical Continuity

Uninterrupted flow of current

Portable Feedthru

Used to disconnect, test, and ground a circuit, and available in both horizontal and vertical configurations to ease installation.The underground conductor to be grounded is positioned on one of the bushings and the grounding elbow can be positioned on the other bushing.

Underground Distribution Ground

a. Ground Rods b. Equipment grounds c. concentric neutrals d. the cable shielding

OSHA Testing line procedure

live-dead-live