High Voltage

Question 1

Main hazards associated with working in a high voltage facility
(5)

Answer 1

• inadvertent contact
• step and touch potential
• backfeed, mutual induction and cap charge
• arc flash/blast
• high voltage transients

Question 2

Reduces the conductor skin effect, especially in higher voltages

Answer 2

Annular

Question 3

Used to obtain a smaller cables diameter multi-conductor cable

Answer 3

Compact sector

Question 4

Normally used with smaller conductors (2 AWG and less)

Answer 4

Solid

Question 5

Used for single conductor cable where high current carrying capacity must be combined with minimum diameter and reduced skin effect

Answer 5

Segmental

Question 6

Used to obtain a smaller diameter, but less flexible conductor with the same conducting area as the concentric round

Answer 6

Compact round

Question 7

The first layer contains six strands of the same size, which are helically wrapped around a single centre strand.

Answer 7

Concentric round

Question 8

Two types of thermoplastic insulation

Answer 8

• PVC (polyvinyl chloride)

- PE (polyethylene)

Question 9

Name a type of thermoset insulation

Answer 9

XLPE (cross-linked polyethylene)

Question 10

Name the two (2) types of insulation shielding

Answer 10

• non-metallic

- metallic

Question 11

Nicking or disturbing the metallic shield in a high-voltage cable can cause high electrical _________ areas.

Answer 11

Stress

Question 12

Terminations must provide four (4) functions

Answer 12

• Provide stress relief at end of terminated shield
• protect against tracking
• keep moisture out of cable in damp or humid locations
• protect against flashover

Question 13

A class ___ termination is used in a clean dry location

Answer 13

3

Question 14

A class ___ termination is track resistant, moisture proof and stress resistant.

Answer 14

1

Question 15

Flashover and ___________ are always a concern in high-voltage cable splices and terminations.

Answer 15

Tracking

Question 16

Distance along surface between the insulation shield and the bare conductor at termination is the

Answer 16

Creepage or flashover distance

Question 17

When air voids are created in the insulation of high-voltage cable, the electrostatic forces cause ___________, which leads to _________ discharge.

Answer 17

Ionization; corona discharge

Question 18

Most common method of reducing electrical stress points at terminations

Answer 18

Stress cone

Question 19

Multi conductor cable having a layer of insulation over the assembled insulated conductors.

Answer 19

Belted type cable

Question 20

Common to central point

Answer 20

Concentric

Question 21

Results from ionization of air molecules into ozone

Answer 21

Corona

Question 22

Thermoplastic material is converted to thermoset material

Answer 22

Cross-linking

Question 23

Excellent insulator and has ability to sustain electrostatic field

Answer 23

Dielectric

Question 24

Rate at which electric energy is lost to heat in a dielectric

Answer 24

Dielectric loss

The lower the value, better the dielectric material

Question 25

Highest voltage a dielectric can withstand before breakdown occurs

Answer 25

Dielectric strength

Question 26

Ability of a substance to return quickly to its original state

Answer 26

Elasticity

Question 27

Can be stretched at room temp to at least 2x its length and returns to original shortly after

Answer 27

Elastomer

Question 28

Arching caused by a high-voltage difference between the insulation shield and exposed conductor

Answer 28

Flashover

Question 29

Semi or conducting tape or extrusion over insulation to create uniform radial voltage stress

Answer 29

Insulation shielding

Question 30

Effect of high voltage on atmospheric molecules; major factor of insulation failure

Answer 30

Ionization

Question 31

Rubber, metal or synthetic covering placed over a cable for mechanical protection

Answer 31

Jacket

Question 32

Thermoset elastomer used as a jacketing material over insulated conductors.

Answer 32

Neoprene

Question 33

Thermoplastic insulating material

Answer 33

PE (polyethylene)

Question 34

Thermoset insulating material

Answer 34

XLPE (cross-linked polyethylene)

Question 35

Electrostatic stress field perpendicular to the conductor or across the conductor

Answer 35

Radial stress

Question 36

Reduces voltage on a cable to below which is necessary to cause corona

Answer 36

Shielding

Question 37

Cable termination or spice constructed to reduce the concentration of high voltage stress points

Answer 37

Stress cone

Question 38

Electrostatic stress field in parallel to the conductor

Answer 38

Tangential stress

Question 39

Plastic that may discolour, blacken, turn clear, crack but does not soften above normal heat

Answer 39

Thermoset

Question 40

Plastic that softens above normal heat

Answer 40

Thermoplastic