Answer:
 The  high-leg voltage is [tex]V_h= 497.76V[/tex]
Explanation:
A diagram showing the arrangement of this three phase transformer is shown on the first uploaded image
The high - leg terminal is in the diagram is from [tex]Z_1 - n[/tex]
Generally the high-leg terminal is 1.732 times of the the voltage from line to center tap which is given as 277 V
  The high -voltage can be computed as follows Â
     [tex]V_h = 1.732 *277[/tex]
        [tex]V_h= 497.76V[/tex]