P Ch 31 Flashcards

1
Q

Transmission lines are used for the purpose of…

  • transmitting highest voltage circuits on any given system
    -tying together the major generating stations
  • interconnecting major electrical systems for the interchange of power
  • all of the above
A

All of the above

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2
Q

In discussion related characteristics of transmission lines, it can be said that the higher the voltage…
- the larger the conductor size
- lower i2R losses
- Higher voltage drop
- all of the above

A

the lower the IR^2 losses

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3
Q

Electrostatic and electromagnetic unbalance between phase in a three phase transmission line is reduced by…

A

Transposing or rotating the conductor

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4
Q

The energy stored in the magnetic field of a conductor is…
- always lost to the system
- called I2R losses
- given back to system w an increase in current or voltage
- called wattless energy

A

Called wattless energy

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5
Q

This steel core of ACSR conductros does not

A

carry any appreciable amount of load current

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6
Q

Suspension type inuslator

A
  • All of the above
  • must be able to accept flashover without shattering
  • are designed to resist thermal shock
  • should be able to accept some amount of mechanical impact
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7
Q

Transmissions line losses, due to corona, may be reduced by all of the below except

• Increasing voltage values
• increase diameter of conductor
• keep surface clean and smooth
• increase space between conductors

A
  • Increasing voltage values
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8
Q

Bundled conductors:
- increase flux density
- reduce inductive reactance
- encourage formation of corona
- decrease clearance requirement at the tower

A

Reduce inductive reactance

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9
Q

An electrical transmission system may be caused to drop out of step or become unstable by
- a sudden increase in load
- a sudden decrease in load
- a short circuit
- all of the above

A

All of the above

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10
Q

Switching preformed under short circuit conditions is apt to be most disturbing to transmission lines when
- done on high voltage side
- done in low voltage side
- done under no-load conditions
- all of the above

A

Done on the low voltage-side (due to higher current and smaller capacitance)

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11
Q

The voltage induced in the lead sheath of underground cables may be eliminated by…
- installing porcelain insulators to sectionalize the sheath
- transposing
- cross-bonding
-all of the above

A

All of the above

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12
Q

A material such as Thyrite would be most likely in
- expulsion type lightning arrestor
- pellet type arrestor
- valve type lighting arrestor
- none of the above

A

a valve type lighting arrestor

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13
Q

All of the below are considered an advantage in the transmission of HVDC as compared to AC except for:
- HVDC may be used to interconnect AC systems of different frequencies
- Earth may be used as one conductor
- the overall insulation requirements may be based on the peak rather than actual voltages
- fault current may be limited to much lower percentages of rated current

A

The overall isolation requirements may be based on the peak rather than the actual voltage (no peak vs actual in DC!)

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14
Q

HVDC transmission lines:
- are always subject to the effects of inductive capacitance
- can never use more than two conductors
- cannot be protected from faults with conventional circuit breakers
- require no overhead wires for protection

A

cannot be protected from faults by using conventional circuit breakers (since DC does not go to 0 twice a cycle, a breaker would have to interrupt full load and those breakers aren’t available right now)

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15
Q

In HVDC transmission systems…
- the quantity and direction of power flow may be controlled with high accuracy and extreme rapidity
- the amount of power is determined by difference in phase angle
- the amount of power is determined by line characteristics
- power flow is affected by load characteristics

A

The quantity and direction of power flow may be controlled with high accuracy and extreme rapidity.

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