In PSSE, the line (and transformer) rating can be expressed in MVA or as "current expressed as MVA". It is selected in Program Settings.

"Current expressed as MVA" is the best choice since the loading of the branch is then calculated as current load. The thermal stress of a line is determined by the current and not by the MVA load.

For example the transformer between bus 205 and 206 in savnw network is loaded to 927.1 MVA. The first rate is 900 MVA. The voltage at bus 205 is 0.949 pu.

When using **MVA** rate, the loading of the transformer is 927.1/900 = **103%**

When using **current expressed as MVA** rate, the loading of the transformer is 927.1/900/0.949
= **108.5%**

In the code you are using MVA rate while the saved case is most probably set to "current expressed as MVA" and the bus voltage is above 1 pu!

The rating is calculated as In * Ubase * sqrt(3), i.e. the nominal line current limit in kA is multiplied with bus base voltage in kV and the square root of 3.