grounding in a substation Flashcards
(14 cards)
Substations are unique because they do not have any of the same hazards as other areas of the electrical industry.
false
Asymmetrical current flow, as found in a substation, is current that at the beginning of flow becomes significantly offset from the ?
zero axis of a normal symmetrical current
The high fault current levels available in substations require ?
larger grounding cables and clamps
Loops that carry induced current are formed in substations because ?
the use of multiple grounding points are all connected to the substation grid
Asymmetrical currents are ?
non symmetrical currents
Asymmetrical current in a substation is caused by ?
the larger amount of inductance present from reactors and transformers.
The effect of asymmetrical currents on aluminum welded grounding connection points is that they often ?
break off under the force
The difference between symmetrical and asymmetrical current is that an asymmetrical current ?
has greater initial peaks than symmetrical current
If instrument transformers are not grounded during testing, ? may develop.
high voltage
When working between grounds in a substation, be sure that there are no outside line connections between the grounds.
true
Voltage dividers (transformers) must be disconnected and grounded when testing because ?
transformers are bi directional they step voltage up as well as down
When performing maintenance work in a substation, a key recommendation is to keep the personal protective ground connected from the bus or equipment to the grid ?
as close to the worksite as possible
Mechanical forces during asymmetrical current flow ?
increase as the square of the current increases
In a substation, the use of multiple grounding points such as grounding switches and personal protective grounds will form a loop, allowing current flow. The use of multiple connections to the grid ?
divides the current among multiple paths
