A p-section is primarily used to represent a very short overhead transmission line or underground cable. Although a p-section representation will provide the correct fundamental frequency impedance, it will not accurately model properties at other frequencies. In other words, p-sections provide a simplified means to represent transmission systems for steady-state studies (such as a load flow), but do not provide an accurate, full-frequency transient response.
A p-section is formed by using lumped R, L and C elements, based on information entered by the user. The R and L elements are represented in matrix format and thereby provide coupling between the three phases. There is also both a mutual capacitance C and a capacitance to ground Cm at each end:
Coupled P-Section Representation in PSCAD
Whenever possible, the Coupled P-Section option should be chosen. This option uses the coupled RL transformer model in EMTDC (as shown above) to model the zero sequence effects, thus avoiding the extra neutral branch in the Nominal P-Section for the zero-sequence.
Important Notes on Nominal P-Section:
Caution should be exercised when using the Nominal P-Section option, in order to ensure that zero-sequence parameters and ground connections are correctly represented. The Nominal P-Section has neutral connections at each end of the line, with an RL zero-sequence branch connected between the neutrals. The zero-sequence component of current will therefore flow through this neutral branch (thus creating the higher zero sequence impedance), whereas the positive and negative-sequence components will add up to zero. All voltages should be measured as either line-to-line, or from the line to the neutral point (not to ground!). Similarly, faults should be applied from the line to the neutral (again, not to ground!).
The Nominal P-Section option should not be used when connecting to distributed transmission line models as they utilize a local ground concept.
More: |
Basic Overview Of Modeling Techniques Constructing Transmission Line Systems |
Main ConfigurationMain Configuration
T-Line Name |
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Text |
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Just an identifier. A name should be entered here to avoid compilation warnings |
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Enter Imped./Admit. Data in |
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Choice |
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Select R,Xl,Xc (pu), R,Xl,Xc (Ohms), Zsurge,Tau. or R,X,B (pu). This of course depends on the format of your data! |
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Nominal PI or Coupled PI Model |
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Choice |
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Select Nominal or Coupled. Wherever possible, the Coupled option should be selected. See PI-Sections (Single Circuit) for an explanation. |
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Line Rated Frequency |
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REAL |
Constant |
Enter the system rated frequency [Hz] |
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Line Length |
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REAL |
Constant |
Enter the PI section line length [m] |
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Enter 0 Seq. Data or Estimate |
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Choice |
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Select Enter or Estimate. Select Enter if you have the zero-sequence data. If not, you may estimate the zero-sequence by providing ratios in the Zero Sequence Estimation ParametersZero Sequence Estimation Parameters dialog. NOTE: These parameters are enabled only if Enter 0 Seq. Data or Estimate is selected as Estimate.
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Graphics Display |
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Choice |
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Select 3 phase view or Single line view. |
Zero Sequence Estimation ParametersZero Sequence Estimation Parameters
NOTE: These parameters are enabled only if Enter 0 Seq. Data or Estimate is selected as Estimate.
0 Seq. R / +ve Seq. R |
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REAL |
Constant |
Enter the ratio of zero sequence resistance to positive sequence resistance |
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0 Seq. Z0 / +ve Seq. Z0 |
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REAL |
Constant |
Enter the ratio of zero sequence surge impedance to positive sequence surge impedance |
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0 Seq. Trav. Time / +ve Seq. TAU |
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REAL |
Constant |
Enter the ratio of zero sequence travel time to positive sequence travel time |
R,Xl,Xc Data (pu)R,Xl,Xc Data (pu)
NOTE: These parameters are enabled only if Enter Imped./Admit. Data in is selected as R,Xl,Xc (pu).
Rated Voltage L-L |
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REAL |
Constant |
Enter the rated RMS line-to-line voltage [kV] |
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MVA for All Phases |
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REAL |
Constant |
Enter the total 3 Phase MVA [MVA] |
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+ve Seq. Resistance |
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REAL |
Constant |
Enter the positive sequence resistance [pu/m] |
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+ve Seq. Inductive Reactance |
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REAL |
Constant |
Enter the positive sequence inductive reactance [pu/m] |
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+ve Seq. Capactive Reactance |
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REAL |
Constant |
Enter the positive sequence capacitive reactance [pu*m] |
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0 Seq. Resistance |
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REAL |
Constant |
Enter the zero sequence resistance [pu/m] |
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0 Seq. Inductive Reactance |
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REAL |
Constant |
Enter the zero sequence inductive reactance [pu/m] |
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0 Seq. Capactive Reactance |
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REAL |
Constant |
Enter the zero sequence capacitive reactance [pu*m] |
R,Xl,Xc Data (ohms)R,Xl,Xc Data (ohms)
NOTE: These parameters are enabled only if Enter Imped./Admit. Data in is selected as R,Xl,Xc (Ohms).
+ve Seq. Resistance |
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REAL |
Constant |
Enter the positive sequence resistance [W/m] |
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+ve Seq. Inductive Reactance |
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REAL |
Constant |
Enter the positive sequence inductive reactance [W/m] |
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+ve Seq. Capactive Reactance |
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REAL |
Constant |
Enter the positive sequence capacitive reactance [MW*m] |
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0 Seq. Resistance |
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REAL |
Constant |
Enter the zero sequence resistance [W/m] |
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0 Seq. Inductive Reactance |
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REAL |
Constant |
Enter the zero sequence inductive reactance [W/m] |
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0 Seq. Capactive Reactance |
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REAL |
Constant |
Enter the zero sequence capacitive reactance [MW*m] |
Surge Impedance, Travel Time DataSurge Impedance, Travel Time Data
NOTE: These parameters are enabled only if Enter Imped./Admit. Data in is selected as Zsurge,Tau..
+ve Seq. Resistance |
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REAL |
Constant |
Enter the positive sequence resistance [W/m] |
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+ve Seq. Travel Time |
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REAL |
Constant |
Enter the positive sequence travel time [ms] |
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+ve Seq. Surge Impedance |
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REAL |
Constant |
Enter the positive sequence surge impedance [W] |
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0 Seq. Resistance |
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REAL |
Constant |
Enter the zero sequence resistance [W/m] |
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0 Seq. Travel Time |
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REAL |
Constant |
Enter the zero sequence travel time [ms] |
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0 Seq. Surge Impedance |
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REAL |
Constant |
Enter the zero sequence surge impedance [W] |
R,X,B Data (pu)R,X,B Data (pu)
NOTE: These parameters are enabled only if Enter Imped./Admit. Data in is selected as R,X,B (pu).
Rated Voltage L-L |
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REAL |
Constant |
Enter the rated RMS line-to-line voltage [kV] |
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MVA for All Phases |
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REAL |
Constant |
Enter the total 3 Phase MVA [MVA] |
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+ve Seq. Resistance |
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REAL |
Constant |
Enter the positive sequence resistance [pu/m] |
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+ve Seq. Inductive Reactance |
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REAL |
Constant |
Enter the positive sequence inductive reactance [pu/m] |
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+ve Seq. Capactive Susceptance |
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REAL |
Constant |
Enter the positive sequence capacitive susceptance [pu/m] |
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0 Seq. Resistance |
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REAL |
Constant |
Enter the zero sequence resistance [pu/m] |
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0 Seq. Inductive Reactance |
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REAL |
Constant |
Enter the zero sequence inductive reactance [pu/m] |
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0 Seq. Capactive Susceptance |
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REAL |
Constant |
Enter the zero sequence capacitive susceptance [pu/m] |