I'm confused. Where are the circuit conductors connected to the load? At the panelboard, at the transfer switch, or both? Can you provide a one-line showing the circuits? Your other post said that the panelboard provided o/c protection when connected to the utility and the transfer switch...
There are many choices for splicing 15 kV cables. All capable of being under water. Being above ground pretty much requires an enclosure and splices like elbow connectors that do not have be in-line. I would rule out hand taping.
I think the missing 36A is because phase angles are not shown and the different currents do not have the same angles.
The diagram would be clearer if they showed the currents flowing into and out of the structure grounds.
Neglecting phase angle errors, the current flowing from the...
I also would worry more about the secondary. Primary elbow connectors are submersible and shouldn't create a fault when flooded. You could use submersible connectors on the secondary also. This doesn't prevent faults at flooded building service entrances, which would be a problem even if the...
Your use of the term "earthed" instead of "grounded" makes me think that you are from the IEC world (UK, Europe, SA, etc.) not North America. The MV distribution systems in NA are very different than those in the IEC world. NA utilities have a lot of single phase transformers and laterals that...
A lot depends on how variable the soil resistivity is. Of course, that's hard to tell without making several measurements. Variation with depth can only be determined with long traverses. It also depends on critical the resistivity is. I'm not familiar with grounding wind turbines, but...
I would suggest 2 cross measurements for each wind turbine. The maximum probe spacings depend on the diagonal dimension of the turbine ground grid. See IEEE std 81, Guide for Measuring Earth Resistivity, Ground Impedance, and Earth Surface Potentials of a Grounding System, for guidance.
