The choice of protection method depends on many things.
What voltage transformation if any is going on in the substation, and what are you protecting, against what fault modes?
What protection is already there and how is that done ?
If there is transformation and or intelligent load or reactor switching, if so is control of that to be integrated with the parts you are designing, or is it separate ?
High impedance schemes are essentially based on current transformers with the secondary windings in a parallel, that vector sum to a near zero voltage when all is well, but current flows between the CTs proportional to loads (reference).
While low impedance schemes allow adding them in series (reference ) so total current is near zero when all is well, but the voltages on the individual CTs may be quite significantly different.
A current based approach may be advantageous if there is a need to interlock tripping with detectors or breakers on the far side of transformers at other voltages, on other parts of the system and the current is monitored for for diagnostics to inform other actions on other branches of the network.
Also 220kV is not a standard UK transmission voltage, so I assume that you are not in the UK - so there are probably other local factors, either national regulatory ones or even just house style and what is available, that favour one method over the other in your location - that I cannot help you with.
