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4th Year Electrical - Code > High Voltage > Flashcards

Flashcards in High Voltage Deck (40)
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1

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

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

2

Reduces the conductor skin effect, especially in higher voltages

Annular

3

Used to obtain a smaller cables diameter multi-conductor cable

Compact sector

4

Normally used with smaller conductors (2 AWG and less)

Solid

5

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

Segmental

6

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

Compact round

7

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

Concentric round

8

Two types of thermoplastic insulation

- PVC (polyvinyl chloride)
- PE (polyethylene)

9

Name a type of thermoset insulation

XLPE (cross-linked polyethylene)

10

Name the two (2) types of insulation shielding

- non-metallic
- metallic

11

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

Stress

12

Terminations must provide four (4) functions

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

13

A class ___ termination is used in a clean dry location

3

14

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

1

15

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

Tracking

16

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

Creepage or flashover distance

17

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

Ionization; corona discharge

18

Most common method of reducing electrical stress points at terminations

Stress cone

19

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

Belted type cable

20

Common to central point

Concentric

21

Results from ionization of air molecules into ozone

Corona

22

Thermoplastic material is converted to thermoset material

Cross-linking

23

Excellent insulator and has ability to sustain electrostatic field

Dielectric

24

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

Dielectric loss

(The lower the value, better the dielectric material)

25

Highest voltage a dielectric can withstand before breakdown occurs

Dielectric strength

26

Ability of a substance to return quickly to its original state

Elasticity

27

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

Elastomer

28

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

Flashover

29

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

Insulation shielding

30

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

Ionization

31

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

Jacket

32

Thermoset elastomer used as a jacketing material over insulated conductors.

Neoprene

33

Thermoplastic insulating material

PE (polyethylene)

34

Thermoset insulating material

XLPE (cross-linked polyethylene)

35

Electrostatic stress field perpendicular to the conductor or across the conductor

Radial stress

36

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

Shielding

37

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

Stress cone

38

Electrostatic stress field in parallel to the conductor

Tangential stress

39

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

Thermoset

40

Plastic that softens above normal heat

Thermoplastic