(2) Ungrounded and single-grounded systems.
grounding conductors will be directly intercon-
Primary and secondary grounding conductors of
ungrounded or single-grounded systems will not be
single, continuous, vertical grounding conductor
run down the pole to a driven ground rod installa-
interconnected except through a secondary surge
arrester as permitted by ANSI C2. Grounding
tion. Pole-butt grounds will not be used. Figures
8-1 and 8-2 illustrate aerial transformer ground-
conductors will be run separately to separate
ing. All equipment, neutrals, surge arresters, and
ground rods located not less than 20 feet apart as
required by the NESC. The secondary grounding
other items required to be grounded will be con-
conductor will be insulated to the same level as
nected to this vertical grounding conductor.
(b) For pad-mounted transformer installations,
the secondary connectors. Interconnection of
grounding conductors below grade will not be
grounding conductors will be connected directly to the
permitted. Spark gaps will not be used.
c. Medium-voltage riser poles. Medium-voltage
rods, mat, or ring. Figure 8-3, 8-4, 9-2, and 9-3
riser poles will be provided with surge arresters,
illustrate pad-mounted transformer grounding.
US Army Corps of Engineers
Figure 9-3. Grounding of Secondary Unit Substation Installation