How do you model cable systems in detail for the harmonic analysis?
Cable systems can be modeled in PowerFactory using either sequence data or geometrical data of the single core cable and cable system arrangement.
The PowerFactory project which is attached with this FAQ shows the various options for modelling such systems.
Model based on sequence data:
- Models based on the sequence data (TypLne) are limited to the positive and zero sequence impedance which is defined for the nominal frequency only. Thus, the frequency dependency of R(1), R(0), L(1) and L(0) is not considered. However, on the PowerQuality/Harmonic Page of the TypLne it is possible to define a frequency characteristic for R(1), R(0), L(1) and L(0) to obtain a more realistic model.
Model based on geometric data:
- Models based on geometric data using the TypCab / TypCabsys include the frequency dependency automatically because PowerFactory will calculate the impedance and admittance matrix of the complete cable system for each harmonic load flow / frequency impedance calculation. Thus, it is recommended to use geometrical models for frequency sweep calculations.
- Geometrical based models can further be distinguished with regard to the modeling of the sheath. The sheath can be reduced, modelled explicitly assuming a perfect cross bonding along the complete length or modelled explicitly, including the actual sheath design. The latter is expected to represent the cable system most accurately.
The frequency sweep calculation in the attached example shows the impact of the different cable models with regard the frequency dependent impedance.
Generally, distributed parameter line models should be used for harmonic analysis.