Line P-5

Question 1

Regarding the transmission of electricity over long distances, what is the key job of transformers?

Answer 1

To increase the voltage of electricity transmitted

Question 2

The loss of energy over long transmission lines at a rate proportional to the square of current flow is known as what?

Answer 2

an I (squared) R loss

Question 3

Solid iron cores suffer excessively from what type of electrical loss?

Answer 3

Eddy-currents

Question 4

Modern high-power transformers typically have cores made of what alloy?

Answer 4

Silicon steel

Question 5

Laminated cores are made from alternating layers of metal and what type of material?

Answer 5

Dielectric

Question 6

What is the term used to describe the characteristic of some magnetic materials that allow more magnetic flux to flow from less electrical current?

Answer 6

High permeability

Question 7

For every 7 °C to 10 °C increase in operating temperature, one can expect the life expectancy
of electrical insulation to decrease by how much?

Answer 7

Half

Question 8

Liquids that fill large power transformers perform what two roles?

Answer 8

Coolant and winding insulator

Question 9

What exists between a high-voltage line conductor and a transformer’s metal enclosure that an insulating bushing must adequately control?

Answer 9

The electric field gradient

Question 10

When terminating HV cables, what is the term used to describe the distance between the back of the live conductor and the edge of the insulation shield?

Answer 10

Creepage distance

Question 11

At the point where the grounded insulation shield ends and the insulation below it emerges, a high concentration of electric field lines permeates the insulation. What is the term used to describe the provisions taken to help prevent possible termination failure caused by this phenomenon?

Answer 11

Stress relief

Question 12

What are the two most common types of stress relief in use today?

Answer 12

Geometric and capacitive

Question 13

Which class of HV termination provides stress relief, anti-tracking, and a seal to the environment?

Answer 13

Class 1

Question 14

What are the three most common forms of insulated HV cable termination?

Answer 14

Stress cone, Hi-K termination, pothead termination

Question 15

When the specifications call for the highest quality of insulated HV cable termination, which type is considered the termination of choice?

Answer 15

Pothead termination

Question 16

Which form of insulated HV cable termination involves pulling on a plastic cord, thereby collapsing its stress control tube around its insulation?

Answer 16

The Hi-K termination

Question 17

Regarding outdoor terminations, what is the purpose of varying the diameters of skirting layers?

Answer 17

To avoid establishing an continuous pattern of water along the skirting

Question 18

The presence of moisture and contaminants on a termination’s insulation will promote current tracking over the insulation, which in time may lead to what?

Answer 18

Flashover