
471Grounding
the ratio of the tower height h
1
and h
2
is about 6:1. This structure is heavily
dependent on the mechanical strength of the tower and must be designed to
take into account the natural environment, for example, the highest possible
wind velocity.
7. 2 . 3 Underground Cable
Figure 7.5 illustrates a cable system with grounding. Figure 7.5a is called
“single-bonded cable,” which means that the metallic sheaths of three-phase
cables are grounded only at a single point. Figure 7.5b shows a “solidly-
bonded (normal-bond) cable,” in which both ends of the cable are grounded.
Figure 7.6 shows the cross-bonded cables, in which the steady-st ...