US Army Corps of Engineers
Figure 4-6. Main Electric Supply Switching Station, 35 kV Maximum.
Table 4-5. Primary Insulator Ratings by Class.
ter, varmeter, and watthour demand meter. Pro-
vide strip-chart recorders if approved by the
(d) Phase and ground undercurrent relays.
A separate undercurrent relay shall be provided
for each phase and for ground fault detection.
group/gang operated, vacuum, sulfur hexafluoride
Directional overcurrent relays shall be used to
(SF,), or other dielectric as approved by the Host
detect short-circuit current flowing in a particular
Command coordinated with the Requiring Com-
direction. Directional power relays shall be used to
mand (HOST/REQ CMD).
detect power flow from Air Force generators into a
(b) Circuit breakers. Outdoor power type,
commercial system. Other relays, such as trans-
metal-clad, sheltered aisle type, vacuum or air
former differentials, should also be installed as
dielectric, group mounted, or individually mounted
required by sound engineering practices.
(2) Feeder sections. Metal-clad sheltered aisle
with vacuum, SF,, or other dielectric as approved
by the HOST/REQ CMD.
type, vacuum or air, dielectric, group mounting