To be sure we’re on the same page, reference on this end is IEEE C62.92.2-1989 (R1993, 2001) Guide for the Application of Neutral Grounding in Electrical Utility Systems, Part II-Grounding of Synchronous Generator Systems and seem to deal exclusively with medium-voltage systems. I agree that the text can be considered to be the IEEE “party line” of sorts. It is authored by a committee through consensus of attending utility engineers, but for MV applications, there is no reason why an industrial application would be significantly different. Section 3—Generator Grounding Types—seems like it adequately parallels variations of the OP’s described system, but with GSU transformer higsides on a commoon bus. Tradeoffs considered, wouldn’t a common connection at all H0 wyepoint bushings to the yard ground grid be in order, except in the one case where zero-sequence fault-current contribution exceeded the switchgear rating? That would be the major determining factor in this case, right?
The poleline section is of no consequence, for fault magnitudes from earth return do not appreciably change regardless of the state of HO connections.
{As for utility-versus-industrial configuration and operating differences, for decentralized groups of low-voltage systems, agreed utilities treat the situation somewhat differently than industrials. There will be forseeable variation in understanding of how a localized low-voltage system should be grounded, but it’s a mistake to base lesser differences on the opinions of a line crew compared to that of an electrical contractor or inside wireman. One should not consequentially extend that admittedly quite different thinking mode to other electrical systems.}