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) by its propagation modes and the transformation matrix (Ti) between mode currents and phase currents. Implementation details can be found in [1].

The 12-phase CP model is used to simulate a quadruple-circuit line or four lines with the same right of way. The parameters for 12-phase lines are the same as for 3-phase lines. The only difference is that the modal transformation matrix of double transmission lines is a 12x12 matrix because each bundle of conductors is considered as a separate phase.

Table of Contents

Mask and Parameters

General Parameters

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 selected from the 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 (per phase)	Base value for PU conversion			MVA total	pBase = { [1, 1e64] }
Base voltage (rmsLN)	Base value for PU conversion			kV rms LN	vBase = { [1, 1e64] }
Base frequency	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] }

Line Generator

For more information see Line Generator

Ports, Inputs, Outputs and Signals Available for Monitoring

Ports

This component supports a 12-phase transmission line

Name	Description
net_1_1(a,b,c)	Network connection of phases (a,b,c) of the left (+) side of line 1
net_1_2(a,b,c)	Network connection of phases (a,b,c) of the right side of line 1
net_2_1(a,b,c)	Network connection of phases (a,b,c) of the left (+) side of line 2
net_2_2(a,b,c)	Network connection of phases (a,b,c) of the right side of line 2
net_3_1(a,b,c)	Network connection of phases (a,b,c) of the left (+) side of line 3
net_3_2(a,b,c)	Network connection of phases (a,b,c) of the right side of line 3
net_4_1(a,b,c)	Network connection of phases (a,b,c) of the left (+) side of line 4
net_4_2(a,b,c)	Network connection of phases (a,b,c) of the right side of line 4

Inputs

None

Outputs

None

Sensors

At acquisition, the signals available by the sensors are:

Name	Description	Unit
*V(a,b,c)1_Node1_(1,2)*	Bus voltage for each phase (a,b,c) of line 1	V
*V(a,b,c)2_Node2_(1,2)*	Bus voltage for each phase (a,b,c) of line 2	V
*V(a,b,c)3_Node3_(1,2)*	Bus voltage for each phase (a,b,c) of line 3	V
*V(a,b,c)4_Node4_(1,2)*	Bus voltage for each phase (a,b,c) of line 4	V
*I(a,b,c)1_Node1_(1,2)*	Current for each phase (a,b,c) of line 1	A
*I(a,b,c)2_Node2_(1,2)*	Current for each phase (a,b,c) of line 2	A
*I(a,b,c)3_Node3_(1,2)*	Current for each phase (a,b,c) of line 3	A
*I(a,b,c)4_Node4_(1,2)*	Current for each phase (a,b,c) of line 4	A

The (1,2) in the previous table indicates the name of the bus at each end of the line (1 for 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

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.

Constant Param, 12-ph