# Decoupling Line (Three-Phase)

Three-phase decoupling distributed parameters line

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• Simscape / Electrical / Specialized Power Systems / Power Grid Elements

## Description

The Decoupling Line (Three-Phase) block implements a three-phase distributed parameters line model that transmits the electrical signal entering its conserving ports to an associated Decoupling Line (Three-Phase) block in your model. The two Decoupling Line (Three-Phase) blocks form a pair that represents the send and receive ends of a three-phase transmission line.

The behavior of the pair of blocks is equivalent to using one Distributed Parameters Line block:

Refer to Distributed Parameters Line for a detailed description of the equations used to represent wave propagation phenomena and line-end reflections.

Use the Decoupling Line (Three-Phase) block pairs when you want to model a transmission line with no physical electrical connections between the send and receive ends of the line. This technique is used, for example, in applications where a large network is decoupled into smaller sections that are simulated into different subsystems or models with no electrical connections between them. This decoupling technique is often used to model complex electrical networks on multi-core real-time computers, or to allow faster simulation of large networks.

The blocks in the a pair can be associated by using the Pairing ID parameter, which transmits the electrical signal information travelling from one terminal to the other by using internal Simulink® Goto and From blocks or connecting the blocks with Simulink signals.

The parameters of each Decoupling Line (Three-Phase) block in the a pair must be identical and correspond to the parameters you would enter in an equivalent Distributed Parameters Line block. For example, to model a 100 km transmission line with the given R, L, and C values, use two Decoupling Line (Three-Phase) blocks with a length of 100 km each and the same R, L, and C values.

To model a transmission line in your model, add two Decoupling Line (Three-Phase) blocks to your model and set the block parameters to the same values. Alternatively, use the Specify Decoupling Lines App to find, select, and automatically replace existing Distributed Parameters Line blocks in your model with equivalent pairs of Decoupling Line (Three-Phase) blocks. For more information, see Specify Decoupling Lines.

## Limitations

• The Decoupling Line (Three-Phase) block can be used only in a discrete model, that is, when the Simulation type parameter of the powergui block is set to `Discrete`.

## Ports

### Input

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Connect this input to the s output port of the other Decoupling Line (Three-Phase) block forming the pair.

#### Dependencies

To enable this port, select the Show send and receive ports parameter.

### Output

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Connect this output to the r input port of the other Decoupling Line (Three-Phase) block forming the pair.

#### Dependencies

To enable this port, select the Show send and receive ports parameter.

### Conserving

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Specialized electrical conserving port associated with the send terminal or the receive terminal of a transmission line when the block is used in pair with another Decoupling Line (Three-Phase) block.

Specialized electrical conserving port associated with the send terminal or the receive terminal of a transmission line when the block is used in pair with another Decoupling Line (Three-Phase) block.

Specialized electrical conserving port associated with the send terminal or the receive terminal of a transmission line when the block is used in pair with another Decoupling Line (Three-Phase) block.

## Parameters

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### Parameters

Transmission line length, in km. Because the block is used with another Decoupling Line (Three-Phase) block, enter the same line length in each of the two blocks; do not split the value between each of the two blocks. For example, to model a 100 km line, specify 100 in each block, not 50 in one block and 50 in the other block.

Specify the frequency used to compute the per-unit length of the resistance R, inductance I, and capacitance C matrices of the line model.

Resistance R per unit length, specified as a two-element vector or a 3-by-3 matrix, in ohms/km (Ω/km).

• For a symmetrical line, specify either the 3-by-3 matrix or the sequence parameters.

• For a three-phase continuously transposed line, enter the positive and zero-sequence resistances [r1 r0].

• For asymmetrical lines, specify the complete 3-by-3 resistance matrix.

Inductance I per unit length, specified as a two-element vector or a 3-by-3 matrix, in henries/km (H/km).

• For a symmetrical line, specify either the 3-by-3 matrix or the sequence parameters.

• For a three-phase continuously transposed line, enter the positive and zero-sequence inductances [l1 l0].

• For asymmetrical lines, specify the complete 3-by-3 inductance matrix.

Capacitance C per unit length, specified as a two-element vector or a 3-by-3 matrix, in farads/km (F/km).

• For a symmetrical line, specify either the 3-by-3 matrix or the sequence parameters.

• For a three-phase continuously transposed line, enter the positive and zero-sequence capacitances [c1 c0].

• For asymmetrical lines, specify the complete 3-by-3 capacitance matrix.

Select to show the r and s input and output ports. When selected, the Decoupling Line (Three-Phase) blocks can be paired by connecting them with Simulink signals. You connect the s output of the first block to the r input of the second block, and connect the s port of the second block to the r port of the first block

The internal model of the Decoupling Line (Three-Phase) block is directly connected to the external r and s block ports.

To break the algebraic loop created by this type of connection, you can add Unit Delay block at the output of each Decoupling Line (Three-Phase) block.

When Show send and receive ports is cleared, the Decoupling Line (Three-Phase) blocks are associated by using the Pairing ID parameter, which transmits the electrical signal information travelling from one terminal to the other by the use of internal Simulink Goto and From blocks. A Unit Delay block is also added to the output signal path to break the algebraic loops. The sample time parameter of this delay corresponds to the sample time delay specified in the powergui block.

When the Show send and receive ports parameter is cleared, internal Goto and From blocks are used to pair two Decoupling Line (Three-Phase) blocks in your model. In both blocks, the first part of the pairing identifier is the same, but you must append `_S` to the end of the identifier of one block, and `_R` to the end of the identifier of the other block. An error is produced if the identifier does not end in `_S` or `_R`. For example, suppose you add two Decoupling Line (Three-Phase) blocks to your model. To pair the blocks, you must set the Pairing ID parameter of one block to `L001_S` and the other block to `L001_R`.

### Initial Values

Initial value of the terminal voltage, in volts.

Angle of the initial voltage, in degrees.

Initial value of the current flowing out the block, in Amperes.

Angle of the initial current, in degrees.

## Version History

Introduced in R2020b