Grounding and Protective Grounds Flashcards
System grounding on a power system means electrically connecting the ? of every wye-connected transformer or generator to earth.
Neutrals
Under normal conditions, an electrical system delivers power without good grounding.
true
Good system grounding can ? a dangerous voltage rise that can occur on the neutral and everything connected to it.
limit
Good system grounding provides both protection for people and ?
circuit protection
To improve the likelihood of a circuit breaker, recloser, or a fuse tripping out the circuit for a phase-to-ground fault, ? is/are essential.
Good grounding
A ? device is installed to reduce step and touch potentials around equipment such as a pad-mount transformer or a switching station
ground-gradient control grid
Crushed rock is used around equipment in a substation because it ? under the feet of workers.
increases electrical resistance
Grounding the system neutral at frequent intervals provides a good return path for current from a line-to-ground fault.
true
Grounds are connected from transformer tanks and metal clad equipment to earth because grounding reduces ?
shock hazards
When a energized circuit neutral is cut or opened, voltage can be ? the circuit voltage across the open point.
equal to
Wire used as a down ground to a ground rod on a single bushing transformer may be opened at any time without fear of electrocution.
False
All the current leaving a source must return to the source to form a complete circuit.
True
In a balanced 3-phase circuit, the return flow occurs in the ?
phase conductor
In a single-phase, wye-distribution circuit, the current finds its way back to the source through the ?
neutral
During a ground fault, the current uses the ? as return paths to flow back to the source.
neutral and earth
Under a ? condition, the voltage on a neutral can become very high.
Line to Ground fault
If a live conductor falls to the ground, the fuse or breaker will open and isolate the line if there are frequent groundings of the neutral to good earth.
true
Good grounding does not help to dissipate a voltage (lighting) surge.
false
The ground resistance of a driven ground rod should be low, preferable below ?
25 ohms
The best place to install a ground rod is in ?
Loam
If investigating tingle voltage, high-neutral voltage, excessive vulnerability to lighting, or failure of protective switchgear to operate, first measure the ground resistance with an instrument such as a clamp-on tester.
True
A system of grounding called “counterpoise” is normally made of ? seven-strand soft-drawn copper.
1/0
A “swinging” ground on a primary circuit is a way of describing a ground that is intermittent and is present at irregular intervals
True
? is due to differences in the potentials of copper and steel is buried in the soil.
Galvanic Action
