Values
What should be used to identify grounded conductors from a distance?
Ground flags.
What does the term 'step potential' refer to in grounding?
the voltage difference that can occur between two points on the ground, which can be hazardous between feet.
What must be done after de-energizing a line?
Visually verify all open points that could potentially re-energize the work area and tag them.
What is the first step after determining the work location is isolated?
Test all conductors to be handled with a high voltage tester.
1
Human Error
What is the resistance requirement for grounding sets according to IEEE?
Grounding sets must have a resistance lower than 5 Ohms.
What is the purpose of a grounding mat?
A grounding mat can be used to create an area of one electrical potential, minimizing hazards.
What additional protection methods (beyond an equipotential zone) does OSHA recognize for downed conductors?
Insulation and isolation.
How should grounding jumpers be handled during installation?
All grounds must be handled with a shotgun stick to maintain minimum approach distance (M.A.D) to all lines.
2
Inductive & Capacitive Coupling
What is the resistance of a human body?
A person has anywhere from 300-1,000 Ohms of resistance, depending on factors like moisture and clothing.
How can touch potential be eliminated when using a grounding mat?
By bonding the mat to the structure or vehicle that may become energized prior to touching.
What must be done before handling any conductor on the ground?
The conductor must be tested and box grounds applied.
What is the importance of inspecting jumper heads?
To ensure they are clean and provide a reliable connection.
3
Backfeed
What does an equipotential zone accomplish?
It protects against hazardous differences of potential.
What hazard exists when stepping on/off a mat without insulated footwear?
Feet can bridge potentials, creating a risk of electric shock.
Why are insulation methods insufficient for worker protection with downed transmission lines?
Because the nominal circuit voltage may be higher than what insulation means are rated for.
What is the role of bracket or "box" grounds?
To ensure circuit protection opens quickly in case of accidental energization.
4
Lightning
How far can master grounds be applied on an adjacent structure to be effectively used as part of the EPZ?
Within 300 feet of the work zone.
How can we ensure a low-resistance connection of a grounding jumper?
Brushing clean the conductors and verifying clamps are in good condition prior to installing grounds
What should be done with open points that cannot be locked?
Install short-circuiting grounds at these locations to prevent human error re-energization.
What is a cluster bar used for?
To bring a structure to the same potential as other conductive objects in the work area.
5
Contact with an energized circuit