# Three-Phase PI Section Line

Implement three-phase transmission line section with lumped parameters

Elements

## Description

The Three-Phase PI Section Line block implements a balanced three-phase transmission line model with parameters lumped in a PI section.

Contrary to the Distributed Parameter Line model where the resistance, inductance, and capacitance are uniformly distributed along the line, the Three-Phase PI Section Line block lumps the line parameters in a single PI section as shown in the figure below where only one phase is represented.

The line parameters R, L, and C are specified as positive- and zero-sequence parameters that take into account the inductive and capacitive couplings between the three phase conductors as well as the ground parameters. This method of specifying line parameters assumes that the three phases are balanced.

Using a single PI section model is appropriate for modeling short transmission lines or when the frequency range of interest is limited around the fundamental frequency. You can obtain a more accurate model by cascading several identical blocks. See the PI Section Line for explanations of the maximum frequency range that can be achieved by a PI line model.

 Note   The Powergui block provides a graphical tool for the calculation of the resistance, inductance, and capacitance per unit length based on the line geometry and the conductor characteristics. See the Powergui to learn on how to use this tool.

## Dialog Box and Parameters

Frequency used for R L C specification

The frequency used for specification of line parameters, in hertz (Hz). This is usually the nominal system frequency (50 Hz or 60 Hz).

Positive- and zero-sequence resistances

The positive- and zero-sequence resistances in ohms/kilometer (Ω/km).

Positive- and zero-sequence inductances

The positive- and zero-sequence inductances in henries/kilometer (H/km).

Positive- and zero-sequence capacitances

The positive- and zero-sequence capacitances in farads/kilometer (F/km).

Line section length

The line section length in kilometers (km).

## Example

The power_triphaseline demo illustrates voltage transients at the receiving end of a 200 km line when only phase A is energized. Voltages obtained with two line models are compared: 1) the Distributed Parameters Line block and 2) a PI line model using two Three-Phase PI Section Line blocks.