Sample Voltage Drop Calculation Across Transformer

See figure 1 and figure 2 below
XF2-001:

 Given:
Connection: D-Y (4160V/480V)  Size = 300KVA Ipri = 79.92A Isec = 692.62A
PF = Cosq = 0.25  Sinq = Sin(Cos-1q) = 0.968
R = 1.7% = 0.017pu @ 300KVA base   X = 4.96% = .0496pu @ 300KVA base

Using primary side:
Zact = Zpu  x  Zbase  I = 79.92A        Zbase = V2/Sbase = (4160)2 / 300KVA = 57.685W
Ract = (.017)( 57.685) = 0.98065W              
Xact = (0.0496)(57.685) = 2.86119W

VD = IRCosq   + IXSinq       ß From IEEE Red Book
VD = I[RCosq   + XSinq]
VD = 79.92[(0.98065)( 0.25) + (2.86119)( 0.968)] = 240.85V
VD3q = VD x √3  = 240.85V  x  √3  = 417.16V
V D3q % =  (417.16V / 4160V) x 100 = 10.03%         ß Same as PTW32 result

Using secondary side:
Zact = Zpu  x  Zbase                   I = 692.62A                Zbase = V2/Sbase = (480)2 / 300KVA = 0.768W
Ract = (.017)( 0.768) = 0.013056W              
Xact = (0.0496)( 0.768) = 0.0380928W
VD = I[RCosq   + XSinq] = 692.62[(0.013056)( 0.25) + (0.0380928)( 0.968)] = 27.80 V
VD3q = VD x √3  = 27.80 x √3  = 48.15 V
V D3q % =  (48.15V / 480V) X 100 = 10.03%                       ß Same as PTW32 result

Figure 1

Figure 2