P Ch 31 Flashcards
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
All of the above
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
the lower the IR^2 losses
Electrostatic and electromagnetic unbalance between phase in a three phase transmission line is reduced by…
Transposing or rotating the conductor
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
Called wattless energy
This steel core of ACSR conductros does not
carry any appreciable amount of load current
Suspension type inuslator
- must be able to accept flashover without shattering
- are designed to resist thermal shock
- should be able to accept some amount of mechanical impact
- all of the above
- All of the above
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
- Increasing voltage values
Bundled conductors:
- increase flux density
- reduce inductive reactance
- encourage formation of corona
- decrease clearance requirement at the tower
Reduce inductive reactance
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
All of the above
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
Done on the low voltage-side (due to higher current and smaller capacitance)
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
All of the above
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 valve type lighting arrestor
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
The overall isolation requirements may be based on the peak rather than the actual voltage (no peak vs actual in DC!)
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
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)
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
The quantity and direction of power flow may be controlled with high accuracy and extreme rapidity.
