A three phase transformer of 100 MVA and 220/33 kV nominal voltage ratio has tap-winding on it's HV side to control the secondary winding voltage, with a provision of +/- 10% change in voltage, at 1.25% additional voltage per tap. If I choose the 100 MVA as the base, how would the base voltage at both sides of the transformer change with change in taps? One can assume the current tap position is (-2). I need some help regarding the calculations. Thank you.