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difference between the initial and final limits at 60 8 F is approximately 460 lb. Even the initial tension

(equal at 60 8 F) differs by almost 900 lb at 208 F and 600 lb at 167 8 F.

14.4.2 Tension Equalization by Suspension Insulators

At a typical suspension structure, the conductor is supported vertically by a suspension insulator

assembly, but allowed to move freely in the direction of the conductor axis. This conductor movement

is possible due to insulator swing along the conductor axis. Changes in conductor tension between

spans, caused by changes in temperature, load, and time, are normally equalized by insulator swing,

eliminating horizontal tension differences across suspension structures.

14.4.3 Ruling Span Calculation

Sag-tension can be found for a series of suspension spans in a line section by use of the ruling span

concept (Ehrenberg, 1935; Winkelman, 1959). The ruling span (RS) for the line section is defined by the

following equation:

RS¼

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi

S 13 þS 23 þþSn^3

S 1 þS 2 þþSn

s

(14:26)

TABLE 14.11 Typical Sag and Tension Data 795 kcmil-Type 16 ACSR=SD, 300- and 1000-ft Spans

Conductor: Drake

795 kcmil-Type 16 ACSR=SD Span¼300 ft

Area¼0.7261 in.^2

Creepisa factor NESC Heavy Loading District

Final Initial

Temp, 8 F Ice, in.

Wind,

lb=ft^2 K, lb=ft

Weight,

lb=ft Sag, ft

Tension,

lb Sag, ft

Tension,

lb

30 0.00 9.00 0.05 1.409 1.59 9980 1.31 12373

30 0.00 0.00 0.00 1.093 1.26 9776 1.03 11976

60 0.00 0.00 0.00 1.093 1.60 7688 1.16 10589 a

90 0.00 0.00 0.00 1.093 2.12 5806 1.34 9159

120 0.00 0.00 0.00 1.093 2.69 4572 1.59 7713

167 0.00 0.00 0.00 1.093 3.11 3957 2.22 5545

212 0.00 0.00 0.00 1.093 3.58 3435 3.17 3877

aDesign condition.

Conductor: Drake
795 kcmil-Type 16 ACSR=SD Span¼1000 ft
Area¼0.7261 in.^2
Creepisa factor NESC Heavy Loading District
Final Initial

Temp, 8 F Ice, in.

Wind,

lb=ft^2 K, lb=ft

Weight,

lb=ft Sag, ft

Tension,

lb Sag, ft

Tension,

lb

30 0.00 9.00 0.05 1.409 17.21 10250 15.10 11676

30 0.00 0.00 0.00 1.093 15.22 8988 12.69 10779

60 0.00 0.00 0.00 1.093 17.21 7950 a 13.98 9780

90 0.00 0.00 0.00 1.093 19.26 7108 15.44 8861

120 0.00 0.00 0.00 1.093 21.31 6428 17.03 8037

167 0.00 0.00 0.00 1.093 24.27 5647 19.69 6954

212 0.00 0.00 0.00 1.093 25.62 5352 22.32 6136

aDesign condition.

Note:Calculations based on:(1) NESC Light Loading District. (2) Tension Limits: a. Initial Loaded – 60% RBS @ 30 8 F;

b. Initial Unloaded – 25% RBS @ 60 8 F; c. Final Unloaded – 15% RBS @ 60 8 F.