LE3

Question 1

What are the design considerations for transmission lines?

Answer 1

Conductors, insulators, and support structures

Question 2

What are the considerations for designing the conductors?

Answer 2

Type and size of conductor, Sag of conductor, Span between conductors, Whether or not the atmosphere is corrosive, Voltage drop, Climate at the line location,
Thermal capacity, and Economic consideration

Question 3

What are the types of conductors?

Answer 3

ACSR, AAC, AAAC, ACAR, Alumoweld

Question 4

What do ACSR stands for?

Answer 4

Aluminum clad steel reinforced

Question 5

What do AAC stands for?

Answer 5

All aluminum conductor

Question 6

What do AAAC stands for?

Answer 6

All aluminum alloy conductor

Question 7

What do ACAR stands for?

Answer 7

Aluminum conductor alloy reinforced

Question 8

What is the other term for alumoweld?

Answer 8

Aluminum clad steel conductor

Question 9

This is done to reduce the tension in the line and to compensate for the stretching and compression of the line.

Answer 9

Sag

Question 10

The voltage drop of the transmission line must be a maximum of ___ of the supplied power

Answer 10

5%

Question 11

The Conductor is assumed to withstand a temperature of _______ without a decrease in strength

Answer 11

75 degrees celsius

Question 12

What are the types of insulators?

Answer 12

Pin, suspension, strain, and shackle type

Question 13

Pin type insulators are used for voltages up to ______.

Answer 13

33kV

Question 14

Suspension type insulators are used for voltages greater than ______.

Answer 14

33kV

Question 15

Where does the strain type insulators are applied?

Answer 15

At dead ends or sharp corner.

Question 16

This type of insulator was used before the development of strain type insulators

Answer 16

Shackle type

Question 17

What are the design considerations of support structures?

Answer 17

Type of supports, terrain, workspace, location of poles, and whether or not guy wire is required

Question 18

What are the types of support structures for the overhead transmission line?

Answer 18

Wooden poles, steel poles, reinforce concrete poles, and steel towers

Question 19

What is the maximum line span and materials that wooden poles are made up of?

Answer 19

50m line span ; sal or ehir

Question 20

What are the different types of the steel poles?

Answer 20

Rail, tubular, and rolled steel joints

Question 21

What are the different support structures for the underground transmission line?

Answer 21

Solid dielectric cross-linked polyethylene, self-contained, fluid-filled, and high pressure, fluid-filled

Question 22

Are power outages are less frequent with underground transmission lines?

Answer 22

Yes

Question 23

Do repairs take longer with underground transmission lines, usually up to six weeks?

Answer 23

Yes

Question 24

Do repair in overhead transmission line can be made in one day?

Answer 24

Yes

Question 25

Do overhead transmission lines have longer life span compared with underground?

Answer 25

Yes

Question 26

Do corona discharge happens in underground transmission lines?

Answer 26

No

Question 27

What are the purposes of underground transmission system?

Answer 27

Aesthetic, property increase of 5%-10%, protection from storms, and reliability of power supply

Question 28

Most distribution voltages are between what range of kV?

Answer 28

4 and 35kV

Question 29

Voltages are always given as line-to-line. True or False?

Answer 29

True

Question 30

What are the four major voltage classes?

Answer 30

5, 15, 25, and 35kV

Question 31

What are the advantages of higher-voltage distribution?

Answer 31

Small voltage drop and losses, higher capacity, longer reach or distance of transmission, fewer substation

Question 32

What are the disadvantages of higher voltage distribution?

Answer 32

Low reliability, dangerous to handle, higher equipment cost

Question 33

Most of the three-phase distribution feeders and transformers connections use the ______.

Answer 33

Wye system. It offers more advantages than disadvantages

Question 34

Most systems use grounded-wye connections and current is usually present in the neutral line because the three phase currents are not normally balanced. True or False?

Answer 34

True

Question 35

Delta connected feeders are more vulnerable to stray currents and voltages through the earth as the earth tries to balance the current flow. True or False?

Answer 35

True

Question 36

What are the advantages of wye connection?

Answer 36

``` Common Ground Reference , Better Voltage Stability , Lower Operating Voltage , Smaller Equipment Size , Can Use Single Bushing Transformers , Easier to Detect Line-to Ground Faults , Better Single-Phase Protection with Fuses ```

Question 37

What is the disadvantage of wye connection?

Answer 37

It requires 4 conductors

Question 38

What are the advantages of delta connection?

Answer 38

It only requires 3 conductors, power quality is enhanced, lighting performance

Question 39

What are the disadvantages of delta connection?

Answer 39

No ground reference, stray currents, unbalanced circuit

Question 40

Grounded wye systems have voltages of line-to-line and line-to-neutral. True of False

Answer 40

True

Question 41

What are the different transformer connections?

Answer 41

gY-gY, D-gY, fY-D, D-D, oY-oD

Question 42

What is the most common three-phase transformer supply connection?

Answer 42

gY-gY

Question 43

What is the advantage and disadvantages of gY-gY

Answer 43

Reduced ferroresonance ; Tank Heating, Cannot supply 120 and 240v

Question 44

What is the advantage and disadvantages of D-gY?

Answer 44

No tank heating ; susceptible to ferroresonance, cant supply 120 and 240v, cant act as a grounding source

Question 45

What are the advantages and disadvantages of fY-D?

Answer 45

can supply ungrounded service, can supply 4-wire with 240/120v ; voltage unbalance, susceptible to ferroresonance

Question 46

What are the advantages and disadvantages of D-D?

Answer 46

can supply ungrounded service, can supply 4-wire service with 240/120V ; ferrorresonance, circulating current

Question 47

What are the advantages and disadvantages of oY-oD

Answer 47

Can supply 3-phase load from 2-phase supply, immune to ferroresonance ; high secondary voltage unbalance, primary ground current