IMPORTANCE OF PERCENTAGE IMPEDANCE

Importance of Percentage Impedance (%Z):

1. It decides suitability of transformer to the system
2. It limits Short Circuit Current (Inversely)
3. It causes voltage drop (Directly)

For transformers up to 2 MVA it is around 5%, Above 2 MVA it varies up to 25% also.

Note: %Z is depends on Resistance value (%Z = V R^2 + X^2). Resistance value may affect with temperature, so, all resistance and Impedance values must convert in to standard temperature of 75%.