Zero impedance of transmission line of 4 machine 2 area Kundur's system

Hi all

Can anybody tell me how the tansmission line zero impedance comes out in the matlab simulink example:Performance of Three PSS for Interarea Oscillations

I only get the following parameters from Kundur's book p813 The transmission line 230kv 100MVA base r=0.0001pu/km Xl=0.001pu/km bc=0.00175pu/km

These parameters are filled into positive impedance in PI section line block,and the zero sequence parameters are also filled with numbers 1.61ohm/km,0.0061H/km and 5.2489e-9F/km.

I am wondering how these parameters come out? Thank you very much for your help!