What is the relationship between Ground Potential Rise (GPR) and Source Voltage?
This looks like the specifications for a 1 MVA transformer (2.4kA*415V) with a Zo of 10% so the Short Circuit current If = 2.4k/10%

Vp/Vs=25.1 and secondary , if shorted to earth ground with If =24kA max and a GRP rise of 4kV max until the fault is tripped.  Vp would also be attenuated while current rises 10x on the primary as the surge goes from ground to grid source.  

When tripped there will also be some expected transient voltage. (V=LdI/dt) But I'm guessing lightning arrestors may clamp this.







simulate this circuit &ndash; Schematic created using CircuitLab

I am thinking of a grid with only 2 sources with a local fault and remote feeders.

There is a better way to show this. But 1st cut above.