Personal Protective Grounding-Grounding in Substations

Question 1

Substations have many of the same hazards as other areas of the electrical industry.

Answer 1

True

Question 2

A type of current found in substation that is not found on lines some distance from substations is the ? type.

Answer 2

Asymmetrical

Question 3

A common method of protection used in substations is to ?

Answer 3

establish an equipotential zone

Question 4

The large variety of equipment types in substations present problems

Answer 4

true

Question 5

Substation grounding schemes must take into account the presence of XL (inductive reactance). Sources of XL are power transformers, reactors, and ?

Answer 5

instrument transformers

Question 6

Loops that carry induced current are formed in substations because ?

Answer 6

the use of multiple grounding points are all connected to the substation grid

Question 7

Fault currents in substations are typically greater than at remote worksites.

Answer 7

true

Question 8

Asymmetrical currents are ?

Answer 8

Non-symmetrical currents

Question 9

Asymmetrical current in a substation is caused by ?

Answer 9

the large amount of inductance present from reactors and transformers

Question 10

Aluminum welded grounding points ? due to the effect of asymmetrical currents

Answer 10

can break off from the bus

Question 11

The difference between symmetrical and asymmetrical current is ?

Answer 11

an asymmetrical current has greater initial peaks than symmetrical current

Question 12

The cause of asymmetrical current is due to the large amount of inductance present from reactors and transformers versus the ?

Answer 12

small amount of resistance present in the buses

Question 13

In all instances, the personal protective ground should be kept as close to the worker as possible to minimize ?

Answer 13

parallel resistance

Question 14

When working between grounds in a substation, be sure that there are no outside line connections between the grounds

Answer 14

True

Question 15

The use of ? such as grounding switches and personal protective grounds will form a loop allowing induced current to flow.

Answer 15

Multiple grounding points

Question 16

Voltage dividers (transformers) must be disconnected and grounded when testing because ?

Answer 16

transformers are bi-directional; they step voltage up as well as down

Question 17

A worker in a substation must be aware of a wide variety of hazards and be prepared to deal with each.

Answer 17

True

Question 18

Back-feed may also be a hazard in substation maintenance.

Answer 18

true

Question 19

Over time, the direct current component of an asymmetrical current increases.

Answer 19

false

Question 20

The mechanical force associated with asymmetrical current flow varies with the square of the current. The resulting force ? the mechanical force caused by the same symmetrical level.

Answer 20

can be four or more times