Digital voltage stabilizer relay diagram
I might consider a binary ladder and change the 6,12,24,36,...128 = 206 to 6,12,24,48,..128= 218 total.

A 128V min to 254 Viacom seems excessive and if everyone in a India or Pakistan used this the grid would see a negative resistance load, ( when voltage sags load current increases and result in grid instability if everyone switches around the same time.  So keep in mind you and your comrades are contributing to grid instability while you are trying to compensate for the unreliable grid.

That’s why we don’t use them in North America. It’s better to upgrade the infrastructure.

You might want to reduce a few secondary windings or recalculate your primary to your desired input/output winding ratio like 220Vac to 240Vac input rather than add up to 206Vac unless you are working with 208Vac.(!?)

Doing this then performs better as a 4 bit binary DAC AND lowers the 23Vac output by 5% or two steps with 4 bit control or 16 steps , you have shifted  all the steps down by 2/16 steps. 

But your schematic is non-binary perhaps due to excessive series resistance. Your inductance ought to not exceed 10% no load current ratio with rated primary current.  This is your excitation current to minimize losses at no load. But also the DCR of any combination determines the actual waste power at no load. This can also be computed by L/R ratios in choosing the optimal conductor size. Mutual coupling needs to be high with low loss CRGOS silicate coated laminations fabricated without shorting edge burrs nor silicate iron dust that is prone to partial discharge from contamination.

If this is a dry type transformer, then cleanliness is critical in the primary secondary insulation with clean epoxy over mica tape or Kapton tape that is free of voids by vacuum and vibration degassing. These voids or minute gas entrapment can also create Partial Discharges, which can lead to epoxy carbonization and insulation breakdown.  ( imagine a tiny um gap with a 1pF gas bubble in series with 1nF epoxy. The bubble arcs and burns silently while growing over time.

If this an oil filled 10kVa traffo then similar contamination from silicate iron dust can also lead to H2 generation of dissolved combustible gas so “cleanliness is godliness”. there are special cleaning processes used by some.  PD is something that also occurs in CMOS defects with contaminants as 30kV/mm becomes 30 mV/nm for Partial discharge.