Conductor to screen Capacitance & Zero sequence Impedance of HV 3 core individually screened cab

[EddyWirbelstrom]

Manufacturers of high voltage three core , individually screened cables, include the electrical characteristics ‘Conductor to Screen Capacitance ( μF/km )’ and ‘Zero Sequence Resistance and Impedance ( Ω/km )’ in their cable catalogs.
How are the ‘Conductor to Screen Capacitance ( μF/km )’ and ‘Zero Sequence Resistance and Impedance ( Ω/km )’ measured ?
Are the screens of the individual cores connected together and earthed at both ends or only at one end ?

 

[EddyWirbelstrom]

Assuming the screens of the individual conductor cores provide the only return path, then the screens must be connected to earth at both ends.
The cable zero sequence impedance is the sum of the phase conductor impedance plus three times the impedance of the return path.
The return path is the parallel connection of each of the three screens.