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4th Year Electrical - Code > High Voltage > Flashcards

High Voltage Flashcards

1
Q

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

A
  • inadvertent contact
  • step and touch potential
  • backfeed, mutual induction and cap charge
  • arc flash/blast
  • high voltage transients
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2
Q

Reduces the conductor skin effect, especially in higher voltages

A

Annular

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3
Q

Used to obtain a smaller cables diameter multi-conductor cable

A

Compact sector

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4
Q

Normally used with smaller conductors (2 AWG and less)

A

Solid

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5
Q

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

A

Segmental

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6
Q

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

A

Compact round

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7
Q

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

A

Concentric round

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8
Q

Two types of thermoplastic insulation

A
  • PVC (polyvinyl chloride)

- PE (polyethylene)

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9
Q

Name a type of thermoset insulation

A

XLPE (cross-linked polyethylene)

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10
Q

Name the two (2) types of insulation shielding

A
  • non-metallic

- metallic

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11
Q

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

A

Stress

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12
Q

Terminations must provide four (4) functions

A
  • Provide stress relief at end of terminated shield
  • protect against tracking
  • keep moisture out of cable in damp or humid locations
  • protect against flashover
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13
Q

A class ___ termination is used in a clean dry location

A

3

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14
Q

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

A

1

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15
Q

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

A

Tracking

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16
Q

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

A

Creepage or flashover distance

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17
Q

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

A

Ionization; corona discharge

18
Q

Most common method of reducing electrical stress points at terminations

A

Stress cone

19
Q

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

A

Belted type cable

20
Q

Common to central point

A

Concentric

21
Q

Results from ionization of air molecules into ozone

A

Corona

22
Q

Thermoplastic material is converted to thermoset material

A

Cross-linking

23
Q

Excellent insulator and has ability to sustain electrostatic field

A

Dielectric

24
Q

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

A

Dielectric loss

The lower the value, better the dielectric material

25
Q

Highest voltage a dielectric can withstand before breakdown occurs

A

Dielectric strength

26
Q

Ability of a substance to return quickly to its original state

A

Elasticity

27
Q

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

A

Elastomer

28
Q

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

A

Flashover

29
Q

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

A

Insulation shielding

30
Q

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

A

Ionization

31
Q

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

A

Jacket

32
Q

Thermoset elastomer used as a jacketing material over insulated conductors.

A

Neoprene

33
Q

Thermoplastic insulating material

A

PE (polyethylene)

34
Q

Thermoset insulating material

A

XLPE (cross-linked polyethylene)

35
Q

Electrostatic stress field perpendicular to the conductor or across the conductor

A

Radial stress

36
Q

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

A

Shielding

37
Q

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

A

Stress cone

38
Q

Electrostatic stress field in parallel to the conductor

A

Tangential stress

39
Q

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

A

Thermoset

40
Q

Plastic that softens above normal heat

A

Thermoplastic

4th Year Electrical - Code (3 decks)

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