S-parameter in four (five) -port two-wire line

I build up a four-port two wire transmission line which is used to explain power line distribution in ICs or PCBs.
I expected less reflection from input port than other ports where power is distributed equally at low frequecy.
However, all S-parameters are same.. I put more ports and ports the reflection becomes significantly from the input port.
Anybody can explain this phenomena?
Thanks in advance.