Factor affecting sag in the transmission line

The equation of the sag is

S = W_C L² / 8T

Where

    S = Sag

   W_C = Weight of conductor per meter

    L = Length of conductor

    T = Tension on conductor

Weight of conductor

• As the weight of conductor increases, the sag also increases. 
• The ice formation on the conductor also increases the sag on the transmission line.

        S α ( W_C )

Span ( length of conductor )

• The sag is directly proportional to square of length of conductor. 
• If the length of conductor double, the sag increases four times.

        S α ( L² )

Tension

• The sag and tension are inversely proportional. 
• As the tension on the conductor increases, the sag decreases. 
• The tension on the conductor increases by wind pressure, ice loading and natural disasters.

       S α ( 1 / T )

Temperature

• As the temperature increases, the length of conductor expand and vice versa therefore the sag increases as the temperature increases.

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