“…a solid ground connection does not provide a Zero-impedance neutral circuit.” I think possibly the author(s) mean is that a phase-to-ground fault does not provide infinite short-circuit current because the source impedance cannot be zero—given inescapable reactance (and resistance} of the “inserted” transformer winding.
I am terrible at symmetrical components, but I believe that zero-sequence voltage and current quantities exist where there is neutral-to-ground current or “neutral-shift” voltage [or deviation of the neutral terminal from the electrical center of the three-phase source] present during a ground fault where there is impedance in the transformer winding and neutral-to ground connection and ground-path impedance.
Positive-sequence voltage and current quantities exist in a (normal) balanced condition. Negative-sequence voltage and current exist where there are imbalances in the typically wye “source” 3ø system that do not involve the neutral connection. This seems to be consistent with §1.4.7 with respect to obtaining the system neutral.
Based on §1.4.3, in standard 142, the “overvoltage” problem seems almost inconsequential in solidly-grounded systems with, compared to a high-resistance-grounded system, excessive voltage to ground is prevented by connecting a resistor neutral-to-ground that is of a somewhat lower value than the zero-sequence capacitive reactance inherent in phase-to-ground insulation. The associated “charging current” is fairly small—on the order of 2 amperes/MVA of the serving transformer. It seems to me that if this condition can be suitably “damped” with addition of grounding resistance, then the system will be devoid of voltages outside the phase-to-phase voltage triangle.
Donald Beeman illustrates and compares the variations in system grounding in his 1955
Industrial Power Systems Handbook. His material is preferable for its ‘scaling’ of industrial systems versus typically larger utility distribution systems.
A couple of miscellaneous links on symmetrical components:
Introduction To Symmetrical Components
www.selinc.com/techpprs/6066.pdf Simple Calculator
www.ece.utexas.edu/~grady/ABC012.html
