Line Generator Exercise

Compute the per km resistance, inductance, and capacitance values for a three-phase single circuit transposed transmission line carrying 60 Hz voltages. The details of the conductor arrangement and geometry are given in the figure below.

What will be the effect on the values of the impedance parameters if the transmission line is untransposed?

The internal inductance of the conductors is obtained from the T/D ratio. Its value for phase conductors is 0.375 and ground wires is 0.5. The DC resistance of the phase conductors is 0.04304 Ω/km, while that of the ground wires is 3.107 Ω/km. The outside diameter of the ground wire is 1.27 cm. Also, assume there is no sag.

Conductor Arrangement Diagram

Conductor Arrangement Diagram

Conductor Geometry Diagram

Conductor Geometry Diagram

The figures provide conductor information.

Use the Line tab. Before proceeding to the Line tab, make sure to complete the information in the following table using data from the geometrical configuration.

1	Frequency of voltage transmitted by the line (Hz)
2	Ground resistivity (omega m)
3	Number of phases conductor bundles
4	Number of ground wires
5	Horizontal distance between each phase bundle (m)
6	Vertical distance between each phase bundle (m)
7	Vertical distance of conductor bundle at the tower (m)
8	Horizontal distance between ground wires
9	Vertical distance of ground wire at the tower
10	Vertical distance of ground wire at mid-point of line (m)
11	Transposition information
12	Method to compute internal inductance
13	Outside diameter of individual conductor in bundle (cm)
14	DC resistance of individual conductor (omega per km)
15	Number of conductors per bundle
16	Bundle diameter (cm)
17	Position of first conductor in the bundle counter-clockwise from x-axis (degrees)

SOLUTION:

Open the mask of the line
Go to Line Generator tab.
Verify if the values in your table match below.
After verifying these values, enter them in the Line Generator tab.
Click the Compute icon.
In the log tab, you should have the required results.
Change the transposition option and re-compute to notify the impact.

List of values needed for this exercise (with answers)

1	Frequency of voltage transmitted by the line (Hz)	60
2	Ground resistivity (omega m)	100
3	Number of phases conductor bundles	3
4	Number of ground wires	2
5	Horizontal distance between each phase bundle (m)	-12.80 for phase A, 0 for phase B and 12.80 for phase C
6	Vertical distance between each phase bundle (m)	20.73 for all phases
7	Vertical distance of conductor bundle at the tower (m)	20.73 as there is no sag
8	Horizontal distance between ground wires	-8.99 and +8.99
9	Vertical distance of ground wire at the tower	32.92 for both wires
10	Vertical distance of ground wire at mid-point of line (m)	32.92 as there is no sag
11	Transposition information	Transposed
12	Method to compute internal inductance	T/D 0.375 for phases, 0.5 for ground
13	Outside diameter of individual conductor in bundle (cm)	3.556 for phases, 1.27 for ground
14	DC resistance of individual conductor (omega per km)	0.04304 omega/km for phase conductors and 3.107 omega/km for ground wires
15	Number of conductors per bundle	4 for phase and 1 for ground
16	Bundle diameter (cm)	45.72 * sqrt(2) = 64.65 for phase and ground
17	Position of first conductor in the bundle counter-clockwise from x-axis (degrees) Answer: 45 degrees