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# PI-nominal model, Printout of modal parameters, Shunt Conductance option

# PI-nominal model

This option is available in “Output options” tab of the “Line Data” device for the Line Parameters module.

The nominal-PI or PI-nominal model is a short-line approximation which is not valid for electrically long lines. It allows to generate a model data file to be used in the “PI multiphase” device. The generated data file can be loaded by selecting the model data file (also called “model file”) through the “Load data file” option in the device data. It can be used for all simulation options of this device.

The currently used format version of this data file is the same as in EMTP-V3 for the PI-circuit branch with the alternate high precision format. The selected units (Units in Model Data File) are not saved and the user must select them manually after loading the data with the “Load data file” option in the “PI multiphase” device.

# Printout of modal parameters

This option is available in the “Output options” tab of the “Line Data” device for Line Parameters. Modal parameters are calculated from the exact phase domain Z and Y matrices at the specified frequency. The modal transformation matrix i T is also presented in the output file. In all these calculations the shunt conductance matrix G is assumed to be zero.

In addition to the “Exact modal parameters”,** the user can request:**

- Exact modal parameters with R=0: The resistances are set to zero before the modal parameters are calculated. The modal parameters are then evaluated exactly. This produces a lossless approximation. The wave velocity of the zero sequence mode will be less that the wave velocity of the aerial modes, which is closer to the actual exact case.

- Lossless high frequency approximation: Resistances are ignored and modal quantities are calculated from high-frequency approximations. This approximation is often used in lightning studie

# Shunt Conductance option

This option is available in the “Options” tab of the “Line Data” device. This option allows the specification of values for the line shunt conductance G other than the internal default value of 0.2x10-9 S/km (for those line models that assume nonzero G). The specified values are the diagonal elements of the reduced (not the full conductors matrix) phase G matrix. The off-diagonal elements of phase G are assumed to be zero. When the conductance of a phase is set to 0, it means that the default 0.2x10-9 S/km value will be used.

# Transposition Option

This option is available in the “Options” tab of the “Line Data” device.

This option produces a line model for transposed lines based on the averaging of the series impedance and shunt admittance matrices. This procedure is only an approximation to the correct solution of modelling each transposition segment explicitly and then specifying the appropriate node connections in EMTPWorks. Averaging is valid only when the length of the transposition sections is several times smaller than the wavelength of the propagating signals.

The sum of the lengths of all the transposition sections must equal the total length of the line as specified in the “Line length” tab. This provides a check on the correct specification of the transposition sections. There is no check, however, on the specification of the phase sequence.

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