Psse

[PemulA]

you work (normally) using per-unit values for the line parameters (for eg. ohms/mile or ohms/km) and the length is in user-units (is up to you if one unit of length means 1 km or 1 inch or whatever), ofc your pu values must be entered accordingly (have you seen in pss/e miles as a unit?)

Following is taken from POM of PSSE

R Branch resistance; entered in pu. A value of R must be entered for each branch.
X Branch reactance; entered in pu. A non-zero value of X must be entered for each
branch. Refer to Zero Impedance Lines for details on the treatment of branches as
zero impedance lines.
B Total branch charging susceptance; entered in pu. B = 0.0 by default.