structure using fiberglass rods, where the insulators are replaced by the tower itself. Although the
development of nonmetallic structures was unsuccessful, the development of tubular steal towers led
to a more pleasing appearance. Figure 19.4 shows tubular steel tower used in Arizona at the 220 kV high-
voltage lines.
FIGURE 19.2 High-voltage transmission lines. (a) Single circuit line with horizontally arranged conductors.
(b) Double circuit line with vertically arranged conductors.
FIGURE 19.3 Transmission line corridor.