Is that transformer designed for on load tap changing ?
Large 10, 20, 50 MVA substation TX's with TCOL usually have the electric tapchanger bolted on and switch under load by means of double contacts from which one has a heavy resistor in series to avoid parralleling 2 windings at the same time.
A 110 Volt VT usually drives the voltage regulator. An ac motor with heavy flywheel does the change over, which only does so, when up to speed and the flywheels kinetic energy can do the complete tapchange in one go avoiding the tap getting stuck between two taps.
As your TX has 17 taps which is the normel industry norm.
please take a photo of the nameplate.