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Constant Param, 2-ph

Description

The constant parameter (CP) line model assumes that the line parameters R, L, and C are independent of the frequency effects caused by the skin effect on phase conductors and on the ground. The model considers L and C to be distributed (ideal line) and R to be lumped at three places (R/4 on both ends and R/2 in the middle). The shunt conductance G is taken as zero. The frequency dependence of the line parameters (represented in the FD model) is an important factor for the accurate simulation of waveform and peak values. However, the CP model is very robust, simple, and fast. It also provides a good alternative for a first approximation analysis.

A transposed or untransposed CP line is represented by a) its sequences, or b) its propagation modes and the transformation matrix (Ti) between mode currents and phase currents. Implementation details can be found in [1].



Table of Contents





Mask and Parameters

Parameters

Name

Description

Unit

Variable = {Possible Values}

Name

Description

Unit

Variable = {Possible Values}

Description

Use this field to add information about the component



Description = {'string'}

EMTP (.pun) file for line parameters calculation

The location (path) of the EMTP file (pun file) containing the line parameters



File = {'path.name'}

L-C units in EMTP (.pun) file

The units from the pun file can be taken using two options  



L-C units = { 0, 1}

mH/km, uF/km {0}

Inductance (L), capacitance (C) 

Ohm/km, uS/km {1}

Inductive reactance (Xl) and capacitive susceptance (1/Xc) 

Line length

The length of the line

km

length = {0, 1e64}

R

Per unit length resistance for each phase (mode)

Ω/km

R = {'-1e64, 1e64'}

L

Per unit length inductance for each phase (mode)

H/km

L = {'-1e64, 1e64'}

C

Per unit length capacitor for each phase (mode)

F/km

C = {'-1e64, 1e64'}

Base power (perPhase)

Base value for PU conversion

MVA per phase

pBase = { [1, 1e64] }

Base voltage (rmsLN)

Base value for PU conversion

kV rms LN

vBase = { [1, 1e64] }

Base frequecy

Base value for PU conversion

Hz

fBase = { [1, 1e64] }

Continuously transposed line

Transposition (Untransposed/Transposed)



transp = { 0, 1}

No {0} 

Untransposed line



Yes {1}

Transposed line



Transformation matrix

Transformation matrix between mode current and phase current ([Iphase] = [Ti] x [Imode]); not used in the case of transposed line.



Ti = { [-1e64, 1e64] }

Ports, Inputs, Outputs and Signals Available for Monitoring

Ports

This component supports a 2-phase transmission line.

Name

Description

Name

Description

net_1_1

Network connection of phase 1 left (+) side

net_1_2

Network connection of phase 1 right side

net_2_1

Network connection of phase 2 left (+) side

net_2_2

Network connection of phase 2 right side

Inputs

None

Outputs

None

Sensors

At acquisition, the signals available by the sensors are:

Name

Description

Unit

Name

Description

Unit

V_Node(phase 1, phase 2)_(1,2)

Bus voltage for each phase (phase 1, phase 2)

V

I(phase 1, phase 2)_Node(phase 1, phase 2)_(1,2)

Current for each phase (phase 1, phase 2)

A

P(phase 1, phase 2)_Node(phase 1, phase 2)_(1,2)

Active power on each phase (phase 1, phase 2)

W

Q(phase 1, phase 2)_Node(phase 1, phase 2)_(1,2)

Reactive power on each phase (phase 1, phase 2)

VAR

The (1,2) in the previous table indicates the name of the bus at each end of the line (1 for the left (+) side and 2 for the right side)

Electrical parameters

Calculation of electrical parameters

The Electrical parameters of CP lines can be calculated by using the Line Generator.

Propagation Delay

The propagation delay is calculated as follows: 

Where i is for each of the phases, L and C stands for the inductance and capacitance of the line per unit length.


When the propagation delay is smaller than the time step, the Constant Param block is automatically replaced by an equivalent PI Line.


If the 'Transposed' parameter is set to 'yes', the following warning is printed in the console:

WARNING in line: <Name of Block>: The propagation delay ( X ) is less than the sample time ( Y ). A PI line is automatically used.

If the 'Transposed' parameter is set to 'no', an error message with similar text appears.

Reference

  1. H. W. Dommel, "Digital computer solution of electromagnetic transients in single and multiphase networks," IEEE Trans. Power App. Syst., vol. pas-88, pp. 388-99, 04/ 1969.

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