Number of phase conductors (bundles)

Specify the number of phase conductors (single conductors or bundles of sub conductors) to be used. This parameter, together with the Number of ground wires (bundles) parameter, will determine the number of rows of the table of conductors.

Specify the number of ground wires (single conductors or bundles of sub conductors) to be used. Ground wires are usually not bundled. This parameter, together with the Number of phase conductors (bundles) parameter, will determine the number of rows of the table of conductors.

In the table of conductors, five rows are visible at a time. If more than five conductors (phase conductors plus ground wires) are specified, a scroll bar appears at the right side of the table to give you access to the different rows of the table.

Conductor (bundle)

Number of conductor defined by the number of phase plus the number or ground wires.

Specify the phase number to which the conductor belongs. Several conductors may have the same phase number. All conductors having the same phase number are lumped together and will be considered as a single equivalent conductor in the R L C matrices.

For example, if you want to compute the line parameters of a three-phase line equivalent to a double-circuit line, you specify phase numbers 1, 2, 3 for conductors p1, p2, p3 (circuit 1) and phase numbers 3, 2, 1 for conductors p4, p5, p6 (circuit 2), respectively.

If you prefer to simulate this line as two individual circuits and have access to the six-phase conductors, you would rather specify phase numbers 1, 2, 3, 6, 5, 4 respectively for conductors p1, p2, p3, p4, p5, and p6.
In three-phase systems, the three phases are usually labeled A, B, C. The correspondence with the phase number is 1, 2, 3, 4, 5, 6, 7, 8, 9,. = A, B, C, A, B, C A, B, C.
You can also use the phase number to lump conductors of an asymmetrical bundle. For ground wires, the phase number is forced to zero. All ground wires are lumped with the ground and they do not contribute to the R L C matrix dimensions.

Specify the horizontal position of the conductor in meters or feet. The location of the zero reference position is arbitrary. For a symmetrical line you normally choose X = 0 at the center of the line.

Specify the vertical position of the conductor (at the tower) with respect to ground, in meters.

Specify the vertical position of the conductor with respect to ground at mid-span, in meters.

The average height of the conductor is given by:

Where:

• Y_tower: height of conductor at tower

• Y_min: height of conductor at mid span

• sag=Y_tower-Y_min

Instead of specifying two different values for Y_tower and Y_min, you may specify the same Y_average value.

Specify one of the conductor or bundle type numbers listed in the first column of the table of conductor characteristics. See section Conductor & bundle characteristics

Number of conductor types (or Conductor type)

Specify the number of conductor types (single conductor or bundle of subconductors) to be used. This parameter sets the number of rows for the conductors types table.. The phase conductors and ground wires can be either single conductors or bundles of subconductors.

Select one of the following three parameters to specify the transposition:

• Untransposed

A constant real transformation matrix is determined automatically by the program with the eigen analysis routines.

• Transposed

The line is modeled as perfectly transposed. The generalized Clarke transformation is used for an m-phase line.

• Transposed by 3 phases (double-circuit only)

Applies only to the double-circuit lines. It is assumed that there is only zero-sequence coupling between the two separate circuits. Each circuit is perfectly balanced.

Select one of the following three parameters to specify how the conductor internal inductance is computed:

• T/D ratio

The conductor self-inductance and resistance are computed from the conductor diameter, T/D ratio, DC resistance, and relative permeability of conducting material and specified frequency.

If you select T/D ratio, the internal inductance is computed from the T/D value specified in the table of conductors, assuming a hollow or solid conductor, where D is the conductor diameter and T is the thickness of the conducting material.

• Geometric Mean Radius (GMR)

If you select Geometric Mean Radius (GMR), the conductor GMR is used to evaluate the internal inductance. When the conductor inductance is evaluated from the GMR, the specified frequency does not affect the conductor inductance. You have therefore to provide the manufacturer's GMR for the desired frequency (usually 50 Hz or 60 Hz).

• Reactance Xa at 1- meter spacing

Selecting Reactance Xa at 1-meter spacing uses the positive sequence reactance at the specified frequency of a three-phase line having 1- meter spacing between the three phases to compute the conductor's internal inductance.

Select this check box to include the impact of frequency on conductor AC resistance and inductance (skin effect).

If this parameter is not checked, the resistance is kept constant at the value specified by the Conductor DC resistance parameter and the inductance is kept constant at the value computed in DC, using the Conductor outside diameter and the conductor T/D ratio.

When skin effect is included, the conductor AC resistance and inductance are evaluated considering a hollow conductor with T/D ratio (or solid conductor if T/D = 0.5). The T/D ratio is used to evaluate the AC resistance even if the conductor inductance is evaluated from the GMR or from the reactance at one-foot spacing or one-meter spacing. The ground skin effect is always considered and it depends on the ground resistivity.

Type

Lists the conductor or bundle types by increasing number, starting from 1 and ending at the value specified in the parameter Number of conductor types or bundle types.

Outside diameter (cm)

Specify the conductor’s outside diameter in centimeters or inches.

T/D ratio

The T/D ratio is used to compute the conductor AC resistance when the Include conductor skin effect parameter is checked. It is also used to compute the conductor self inductance when the parameter box Conductor internal inductance evaluated from is set to T/D ratio.

A T/D value of 0.5 indicates a solid conductor. Specify the T/D ratio of the hollow conductor, where T is the thickness of conducting material and D is the outside diameter.

This parameter can vary between 0 and 0.5. For Aluminum Cable Steel Reinforced (ACSR) conductors, you can ignore the steel core and consider a hollow aluminum conductor (typical T/D ratios comprised between 0.3 and 0.4).

DC resistance (Ohm/km)

Relative permeability

Specify the relative permeability r of the conducting material. r = 1.0 for nonmagnetic conductors (aluminum, copper). This parameter is not accessible when the Include conductor skin effect parameter is not checked.

Conductors per bundle

Specify the number of subconductors in the bundle or 1 for single conductors.

Bundle diameter (cm)

Specify the bundle diameter in centimeters or inches. This parameter is not accessible when the Number of conductors per bundle is set to 1.

When you specify bundled conductors, the subconductors are assumed to be evenly spaced on a circle. If this is not the case, you must enter individual subconductor positions in the Line Geometry tab and lump these subconductors together by giving them the same Phase number parameter.

Angle conductor 1 (degre)

Specify an angle in degrees that determines the position of the first conductor in the bundle with respect to a horizontal line parallel to ground. This angle determines the bundle orientation. This parameter is not accessible when the number of “Conductors per bundle” is set to 1.

GMR (cm)

This parameter is accessible only when the parameter box Conductor internal inductance evaluated from is set to Geometric Mean Radius (GMR).

Specify the GMR in centimeters or inches. The GMR at 60 Hz or 50 Hz is usually provided by conductor manufacturers. When the parameter box “Conductor internal inductance evaluated from” is set to T/D ratio, the value of the corresponding GMR giving the same conductor inductance is displayed.

Xa 1-meter spacing (Ohm/km)

When the parameter box Conductor internal inductance evaluated from is set to Reactance Xa at 1-meter spacing, the title of the column changes to the parameter name as explained below.