68 Questions
What is the equation for the DC resistance of a conductor at temperature T?
$R_{dc,T} = \frac{\rho_T l}{A}$
What are the SI units for resistivity?
Wm
What is the temperature constant for copper?
100%
What factor makes the dc resistance of a stranded conductor 1 or 2% larger than the calculated resistance?
Spiraling
What is the equation for DC resistance (Rdc) of a conductor?
$R_{dc} = \frac{\rho_T l}{A}$
What is the effect of frequency on current distribution in a solid cylindrical conductor for AC?
Current tends to crowd toward the conductor surface
In the equation for DC resistance (Rdc), what does A represent?
Cross-sectional area
How does the resistivity of a conductor change with temperature according to the given information?
Resistivity increases with increasing temperature
What is the effect of current magnitude on resistance for magnetic conductors?
Resistance increases with increasing current magnitude
What is the equation for the skin effect phenomenon?
$I = \frac{1}{r}$
What is the formula to calculate the total copper cross-sectional area (A) for 12 strands of a given diameter?
$A = 12 \pi (\frac{d}{2})^2$
How does the resistance of ACSR conductors change with current magnitude compared to steel conductors?
Resistance of ACSR conductors increases less than steel conductors with increasing current magnitude
According to the given information, the resistance of a stranded conductor is 1 or 2% larger than that calculated from the equation $R_{dc,T} = rac{ρ_T l}{A}$ due to _______.
spiraling
The equation for the DC resistance of a conductor at temperature T is _______.
$R_{dc,T} = rac{ρ_T l}{A}$
The temperature constant for copper is _______.
3.93 x 10^{-3} Ω·cm/°C
AC resistance or effective resistance of a conductor is given by the equation:
R_{\text{dc},T} = \dfrac{\rho_T l}{A} \Omega
The resistivity of iron at 20°C is _______.
10.37 Wm x 10^{-8} or 1.59 Ω·cm
Total copper cross-sectional area (A) in mm2 is given by the equation:
A = 12 \pi r^2 = 12 \pi \left(\dfrac{d}{2}\right)^2 = 12 \pi \left(\dfrac{3.373 \text{ mm}}{2}\right)^2 = 107.23 \text{ mm}^2
The resistivity at 20°C for hard-drawn copper is
1.77$ W-cmil/ft
The equation to calculate the DC resistance of a conductor at temperature T is
R_{\text{dc},T} = \dfrac{\rho_T l}{A} \Omega
The equation for the DC resistance of a conductor at 50°C with a length of 1 km is given by:
R_{\text{dc},50°C} = \left[\left(1.973 \times 10^{-8} \Omega\text{m}\right) \times \left(\dfrac{103 \times 1.02 \text{ m}}{107.23 \text{ mm}^2}\right)\right] = 0.1877 \Omega/\text{km}
The temperature constant for copper is listed in
Table 4.3
The resistivity at 20°C for aluminum is
2.83$ W-cmil/ft
The resistivity at 20°C for steel is
61$ W-cmil/ft
According to the given information, the resistance of a stranded conductor is 1 or 2% larger than that calculated from the equation $R_{dc,T} = \frac{\rho_T l},{A}$ due to
spiraling
The equation for the DC resistance of a conductor at temperature T is
$R_{dc,T} = \frac{\rho_T l},{A}$
The resistivity of iron at 20°C is
9.6
The equation for the skin effect phenomenon is
$\text{ac resistance or effective resistance} = R_{dc} \sqrt{1 + (2 \pi f \rho)/\mu}$
Total copper cross-sectional area (A) in mm2 is given by the equation
$A = 12 \pi r^2$
Rdc at 50o C with length of 1 km. Use hard-drawn copper, assume a 2% increase in resistance due to Spiraling
0.1877 Ω / km
The equation for the DC resistance of a conductor at 50°C with a length of 1 km is given by
$R_{dc,50°C} = \rac{ρ_{T} l},{A}$
The equation for the skin effect phenomenon is
For AC, the current distribution is non-uniform.
The equation for DC resistance (Rdc) of a conductor is
$R_{dc,T} = \rac{ρ_{T} l},{A}$
The resistivity at 20°C for hard-drawn copper is
1.77 x 10^{-8} Ωm
The resistivity at 20°C for steel is
10.37 x 10^{-8} Ωm
What are the main factors affecting insulator leakage current?
Amount of dirt, salt, and other contaminants, and meteorological factors
The temperature constant for copper is listed in
Table 4.3
What causes corona loss in overhead lines?
Electrically ionized air due to high electric field strength at conductor surface
Why is conductance usually neglected in power system studies?
It is a very small component of the shunt admittance
What is the main cause of power loss due to corona?
High electric field strength at conductor surface causing air ionization
Why is conductance usually neglected in power system studies?
It is a very small component of the shunt admittance
What factor primarily determines the insulator leakage current?
Accumulation of dirt, salt, and contaminants on insulators
Flux linkage inside the conductor is denoted by the symbol λ
True
The equation to calculate inductance from flux linkages per ampere is $L = \frac{\lambda}{I}$
True
The permeability of free space, $\mu_0$, is equal to $4\pi \times 10^{-7} H/m$
True
The magnetic flux density B can be calculated using the equation $B = \mu H$
True
What is the equation to calculate the magnetic flux density B?
$B = \mu H$
What is the equation to calculate inductance from flux linkages per ampere?
$L = \frac{\lambda}{I}$
What is the unit of magnetic flux density B?
All of the above
What is the permeability of free space, $\mu_0$, equal to?
$4\pi \times 10^{-7} H/m$
Calculate the inductance of each conductor due to both internal and external flux linkages.
The inductance of each conductor due to both internal and external flux linkages is given by $Lx = Ly = 2 \times 10^{-7} \ln \left( \frac{D},{r'} \right) , \text{H/m}$, which can be converted to mH/km by multiplying by 1000.
What is the total inductance of the line with a 60-Hz single-phase, two-wire overhead line?
The total inductance of the line, denoted as $L$, is the sum of inductance of each conductor: $L = Lx + Ly = 0.8899 + 0.8899 = 1.780 , \text{mH/km}$ per circuit.
What is the formula to calculate the inductance of each conductor due to both internal and external flux linkages?
The inductance of each conductor due to both internal and external flux linkages is given by $Lx = Ly = 2 \times 10^{-7} \ln \left( \frac{D},{r'} \right) , \text{H/m}$, where $D$ is the spacing between conductors and $r'$ is the effective radius of the conductor.
What is the equation for the total inductance of a single-phase circuit?
The total inductance of the single-phase circuit, called loop inductance, is not provided in the given text.
What is the equation to calculate the inductance of each conductor due to internal flux linkages only?
The equation to calculate the inductance of each conductor due to internal flux linkages only is $Lint = \frac{1}{2} \times 10^{-7} H/m = 0.05 mH/Km$ per conductor.
In Example 1, what is the inductance of each conductor due to internal flux linkages only?
In Example 1, the inductance of each conductor due to internal flux linkages only is 0.05 mH/Km per conductor.
What is the flux linkage in phase a conductor for a three-phase three-wire line?
The flux linkage in phase a conductor for a three-phase three-wire line is not provided in the given text.
Calculate in mH/km b) the inductance of each conductor due to both internal and external flux linkages
0.8899 mH/Km per conductor
Calculate in mH/km c) the total inductance of the line
1.780 mH/Km per circuit
The conductors are arranged in a horizontal configuration with 0.5 m spacing between conductors. Calculate in mH/km b) the inductance of each conductor due to both internal and external flux linkages
0.8899 mH/Km per conductor
Flux linkage in phase a conductor for a three-phase three-wire line is denoted by the symbol
\lambda_{a}$
Total inductance of the line with a 60-Hz single-phase, two-wire overhead line is denoted by the symbol
L_{total}
Calculate in mH/km c) the total inductance of the line
$L_{total} = 2 \times L_{int}$
In Example 1, the inductance of each conductor due to internal flux linkages only is denoted by the symbol
L_{int}
Inductance is the property of a circuit that opposes any change in ______
current
The total inductance of the single-phase circuit, called loop inductance, is represented by the symbol ______
L
The inductance of phase a is represented by the symbol ______
La
The inductance of each conductor due to internal flux linkages only is calculated using the formula ______
Lint = \frac{1}{2} \times 10^{-7} \frac{H}{m} = 0.05 \frac{mH}{Km} per conductor
Test your knowledge of resistance calculations in electrical conductors with this quiz. Explore the relationship between resistance, temperature, length, and cross-sectional area of conductors, and compare SI and English units for resistance calculations.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
