The rated current is the basic device value. The permissible current is the value which is affected by the ambient temperature of the device. For example, the rated current is 125 A at an ambient temperature of 60°C , whereas the permissible current is only 116.25A.

Simultaneity factor gi
The ratio of outputs of all simultaneously operated consumers to the rated outputs of all connected consumers. The simultaneity factor (for distribution boards only) is directly incorporated into network dimensioning (cable cross sections, protective devices, transformer size).

Capacity factor ai (for motors only)
The motor capacity factor indicates to which proportion of the rated motor power the motor loads the network. The capacity factor has no impact on the dimensioning of cables and protective devices for the motor circuit. The motor circuit is designed for the nominal motor current. The capacity factor is incorporated into the dimensioning of the higher-level network (cable cross section, protective devices, transformer size).

At first you do have default values for medium and low voltage. If you change them once when working on a project, these changed values are retained when you open a new project in Simaris design.