How do you model cross bonding in cable systems?
Refer to detailed answer.
The currents and voltage in the sheath / metallic screen (MSC) depend on the bonding configuration. There are different bonding configurations for cables:
- Double bonding: MSC is grounded on both sides
- Single point bonding: MSC is grounded on one side only
- Cross-bonding: MSC is grounded on both sides and transposed along the cable
The cross-bonding of a cable can be modelled either ideally by a adapting the impedance and admittance matrix of the cable system (TypCabsys) in PowerFactory or explicitly by modelling each minor and major section with the corresponding transposition at each junction point.
The attached project contains 3 examples that show the impact cross-bonding model with regard to the network impedance. The cable system represents a 132 kV cable with a length of 30 km. the following modelling approaches are compared:
- Explicit cross-bonding with a very large number (180) of minor sections (detailed)
- Explicit cross-bonding with only 3 minor sections (simplified)
- Ideal cross-bonding in the TypCabsys
The comparison of the three models shows significant differences between the modelling approaches. The results for 1.) and 3.) match almost perfect up to a frequency of 2 kHz while there are significant differences with regard to 2.)