These grounds are jumpered common and
b. Black Alarm System. The black alarm system is
extended to the building ground systems buried
similar to the red system (a above). The major/minor
externally. The three grounds are the shield, DC, AC
panel is mounted in bay 1.21 (fig. 1-7). In addition, the
.AU/CCU and station clock alarms are connected into
a. AC Ground.
The AC ground is extended
throughout the TCF where it serves the AC ground
requirements as well as bonding all the iron work within
2-21. Grounding System
the site to common.
Grounding systems are connected separately to the red
b. Shield Ground. The shield ground is extended
and black equipment and circuits (fig. FO-9). Each
to both the VF and DC IDF's, where it is commonly used
grounding system consists of three separate and
to terminate the shields or armor of cables.
isolated grounds. The shield and DC systems are tied
together only at the station ground box. Each ground
c. DC Ground. The DC ground runs from the
provides a fixed ground reference for the various
ground box to the power supplies and distribution
equipments and systems within the building. The
boards, where it is distributed to power boxes and alarm
grounds are isolated from one another to minimize
panels throughout the site.
ground current loops and, therefore, reduce unequal
ground potentials throughout the site. Each ground
cable is tied to a separate isolated ground bar within the