System Units | Transformer Neutral Impedance

In transformers, the base voltage will be determined by the windings (primary or secondary). In addition, the neutral impedance, not being referenced to a winding, can be specified in SI or amperes, using the symbol “A”.

Users can choose the system that best suits them in the mask of every component where they are supported through a right-click menu on the relevant parameters' unit:

The two unit choices are:

SI	Input parameters in International System of Units format (volt, ampere, watt, ohm, henry, farad)
A	Input parameters in current ratio (A)

To calculate the RLC parameters based on current ratio, first the current I_b through every branch is calculated as follows:

where V_b and F_b are the base values of the voltage and frequency, respectively.

Then, the RLC are expressed in the “A” system using the following relations:

The “PQ” system is not available for neutral impedance. However, the parameters can be calculated using: