Electric Power Generation, Transmission, and Distribution

conductor is to be sagged in a series of suspension spans where span lengths vary widely or more
commonly, where the terrain is steep, then clipping offsets may need to be employed in order to yield
vertical suspension strings after installation.
Clipping offsets are illustrated in Fig. 14.19, showing a series of steeply inclined spans terminated in a
‘‘snub’’ structure at the bottom and a ‘‘deadend’’ structure at the top. The vector diagram illustrates a
balance of total conductor tension in the travelers but an imbalance in the horizontal component of
tension.

B

T

S

A

METHOD 1: S = ( )

METHOD 2: S =

METHOD 1 METHOD 2

Note: When using Method 2, value, "T" should lie between 3/4 "S" & 4/3 "S"

S = ( )

S =

t = 59.12'

t/2 = 29.56'

T/2 = 20.0

M = 0.061

S 608 F = 20.0 + 29.56 −

S 608 F = 49.1'

EXAMPLES

Given:

A = 1400.0' T = 40.0'

B = 60.0' f = +1 8 40' 21 @ 60 8 F

(Field Measured)

S = Sag

t = Vertical distance below support to line of sight.

= T +_ B − A tan f when angle f is above horizontal.

= T+_ B + A tan f when angle f is below horizontal.

T = Vertical distance below support for transit.

B = Vertical distance between points of support - obtanied from plan & profile,

tower site data sheets or field measurement.

+ B when support ahead is higher.

− B when support ahead is lower.

A = Horizontal distance between points of support - obtained from structure list

or plan & profile

f = Angle of sight

M = Determined from cure on Fig. 2.17.

f

t

T + t^2

2

B t tM

2 2 8+ −

T + t^2

2 B

2

t

2

tM

+ − 8

(59.12) (0.061)

Sag is based on parabolic functions. if sag exceeds 5% of span, do not use this chart.

t = 40.0 + 60.0 − 1400.0 tan 1 8 40' 21"

= 59.12'

t = 7.689

T = 6.325

S 608 F = 49.1' 8

FIGURE 14.19 Conductor sagging for checking sag S.