Transmission Line Data

This dialog box includes the following areas and tabs:

See Common Tabs for information on the Location, Reliability, Comments, Hyperlinks, Media Gallery, or Collected Data tabs.

Figure 1: Transmission Line Data Dialog Box

Connection Information

Option Description
ID Name

Uniquely identifies the equipment item. The program automatically assigns a name, but you can change it, if needed. The name can be up to 16 characters long.

For transmission lines, the program automatically assigns the names X-1, X-2, X-3, and so on.

From Bus

The bus from which the transmission line connects, which must already exist on the one-line. Ensure that the From Bus has the same base kV as the transmission line's To Bus. For reference, the From Bus base kV is displayed next to the bus name.
To Bus

The bus to which the transmission line connects, which must already exist on the one-line. Ensure that the To Bus has the same base kV as the transmission line's From Bus. For reference, the To Bus base kV is displayed next to the bus name.

Phase

The phase of the item. Currently, this is for reference only.

Show Entire Line

This check box is selected by default and causes the entire line to be displayed. By clearing the check box, the line is only be shown as a short section at each end with labels indicating the bus to which the other end is attached.

Style

The style of the line that appears on the one-line. This setting is specific to the selected item and overrides any default styles specified for the equipment.

Weight

The weight of the line that appears on the one-line. This setting is specific to the selected item and overrides any default weights specified for the equipment.

Specifications Tab

Option Description
Unit

Choose either US, Metric, or Per Unit.

If Per Unit is selected, only the impedance and amp rating fields are available.
No/Phase Total number of lines modeled. The default of one (1) means one conductor per phase. Two (2) means two conductors in parallel per phase, and so on. When two or more conductors are in parallel, the impedance of the circuit is decreased by that factor. The impedances shown in the dialog box are for one conductor only, and are not based on the No./Phase field. If you enter these values instead of using Calculate, make sure they are for one conductor only. This lets you to easily check handbook values without additional arithmetic. The Calculate button does not consider bundled conductors at this time.
Material Material (copper, aluminum, aluminum cable steel reinforced, or Copperweld®).
Size Conductor size in AWG or MCM. For more information, see the Aluminum Electrical Conductor Handbook.
Length

The length of the line in miles or meters.
Temp

Temperature of the loaded conductor. This can be varied from 25°C to 250°C depending on the type of study being performed. This temperature is used in determining the resistance of the conductor.
Earth Res Earth resistivity in ohm-meters. This value is used to determine ground impedance. A default value of 100 ohm-meters is typically used when measured data is not available. For more information, refer to IEEE Std. 142.
GMD Geometric Mean Distance of the conductor spacing. This value is used to determine the impedance of the line. Typical default values are used based on the kV of the line.
Average Height Average height of the transmission line in feet. This value is also used to determine the line impedance. Typical default values are used based on the kV of the line.

Impedances

Impedances are described in ohms/mile or ohms/km, except for Xc, which is in megaohm miles or megaohm km. For more information, see the Westinghouse Transmission and Distribution (T&D) book.

R1

Positive sequence resistance.

The resistance values are used in power flow, ANSI short circuit, harmonics, dynamic stability and auto design analysis.

For IEC 60909 short circuit, separate resistance values are used. Maximum short circuit currents use resistance at 20°C. Minimum short circuit currents use the resistance at the final conductor temperature at the end of the short circuit. EasyPower calculates these resistances based on the resistances R1 and R0 and the Field Temperature of Conductor from the Specifications 2 tab. If you enter the R1 and R0 values manually, be sure to set the Field Temperature of Conductor to get the appropriate resistances for IEC short circuit. The Database Browser shows the per-unit resistances for maximum and minimum short circuit currents.
X1 Positive sequence reactance.
R0

Zero sequence resistance. If you enter this value as zero (0.0), the positive sequence impedance is used.

The resistance values are used in power flow, ANSI short circuit, harmonics, dynamic stability and auto design analysis.

For IEC 60909 short circuit, separate resistance values are used. Maximum short circuit currents use resistance at 20°C. Minimum short circuit currents use the resistance at the final conductor temperature at the end of the short circuit. EasyPower calculates these resistances based on the resistances R1 and R0 and the Field Temperature of Conductor from the Specifications 2 tab. If you enter the R1 and R0 values manually, be sure to set the Field Temperature of Conductor to get the appropriate resistances for IEC short circuit. The Database Browser shows the per-unit resistances for maximum and minimum short circuit currents.
X0 Zero sequence reactance. If you enter this value as zero (0.0), the positive sequence impedance is used.
Xc Shunt capacitive reactance. If you enter this value as zero (0.0), "infinity" is assumed.
Xc0 Shunt capacitive zero sequence reactance. If you enter this value as zero (0.0), "infinity" is assumed.
Rating Conductor rating in amperes. This field is used to determine line overloads in power flow analysis. If you use Calculate, this value is calculated as the No./Phase times the rating of one conductor, which is brought from the device library.

Harmonics Tab

Use the Harmonics tab to indicate whether this equipment item is introducing harmonics into your power system.

Figure 2: Harmonics Tab

Option Description
Resistance Factor

EasyPower offers two methods for calculating RH:

  • Resistance varying with a power of the harmonic (R-EXP):

    • RH = RFund * H R-EXP

  • Resistance varying with a percent eddy current factor (%ECF):

    • RH = RFund * (1+ECF*H2)/(1+ECF)

EasyPower defaults all skin effect correction to R-EXP and a value of 0.5.

Typical Resistance Correction Factors

  R-EXP %ECF

Transformer

0.5-1.0

1.0-3.0

Utility

0.0-0.8

    -

Generator

0.3-0.6

    -

Line/Cable

0.5

    -

Reactor

0.5-1.0

0.8-3.0

Motor

0.2-0.4

    -
Fundamental Amps

Use to set the fundamental amps. The options are as follows:

  • Equipment Rating sets Fundm Amps to the equipment rating of the item described in the Specifications tab. 
  • User Specified activates the Fundm Amps field, enabling you to specify a value. 

To use fundamental current calculated by power flow, select Calculated from Power Flow in the Summation Fundamental Voltage area of the Harmonics Options > Control dialog box.

Other Tabs

See Common Tabs for information on the Location, Reliability, Comments, Hyperlinks, Media Gallery, or Collected Data tabs.

More Information

Database Technical Reference Common Tabs
Media Gallery