Description
The constant parameter (CP) line model assumes that the line parameters R , L and C are 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.
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Mask and Parameters
Parameters
| Name | Description | Unit | Variable = {Possible Values} | |||
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| 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] } | ||||
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 calculation of the electrical parameters for a CP line can be done with the Line Data auxiliary module. The pun file generated with this module must be loaded in the form.
Alternatively, the electrical parameters of CP lines can be calculated by using the HyperView Line Tab module in HyperView.
Steps are as follows:
- Load a file into the Line Data GUI or enter the geometrical line parameters; details are found in Line Geometry.
- Select the transpositions options
- Run the program
- The electrical parameters are displayed in the Line Data Report.
To transfer the electrical parameters to the CP model, follow these steps:
- Go to the Line Data GUI
- All the names of the lines in your network appear at the bottom of the page
- To transfer electrical parameters, choose the name of the line and click Apply
- See the parameters in the forms of the line
Propagation Delay
The propagation delay is calculated as follows:
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Propagation\_delay = length\_of\_line * \sqrt {L[i] * C[i] } |
Where i is for each of the phases, L and C stands for the inductance and capacitance of the line per unit length.
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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.