What is SAG and span in transmission line?

In a transmission line, sag is defined as the vertical difference in level between points of support (most commonly transmission towers) and the lowest point of the conductor. Consider a transmission line conductor AOB suspended freely between level supports A and B at the same level (equal span).

What is the main reason for SAG in the transmission line?

The lines are often heavily loaded because of increased power consumption, and the conductors, which are generally made of copper or aluminum, expand when heated. That expansion increases the slack between transmission line structures, causing them to sag.

How do I make a SAG template?

How to make a Sag Template?

1. Step 1: Gather the design data.
2. Step 2: Determine the weather conditions that may affect your conductor.
3. Step 3: Calculate the sag and tension of the conductor.
4. Step 4: Plotting of the parabolic/catenary curve.
5. Step 5: Transfer the plotted curve to a transparent paper or celluloid.

How do you calculate sag conductor?

Calculation of Sag:

1. Case1: When the conductor supports are at equal level.
2. Sag = WL2/8T.
3. Case2: When the conductor supports are at unequal level.
4. Sag = WtL2/2T.

What is transmission line template?

Sag Template consists of a set of parabolic curves drawn on a transparent paper, a celluloid or acrylic clear sheet duly cut In between the curves to allow surveyor to see through them on the Survey Charts placed underneath it.

What is sag in overhead transmission line conductor?

Sag in overhead Transmission line conductor refers to the difference in level between the point of support and the lowest point on the conductor. As shown in the figure above, a Transmission line is supported at two points A and B of two different Transmission Towers. It is assumed that points A and B are at the same level from the ground.

How do you calculate the weight span of a transmission line?

Weight Span Calculation of Sag in Transmission Line The analytical method for calculating weight span is given below: The distance of ‘Null point’ or ‘Low point’ of the conductor from a center of the span is given by the formula. x = (Th) / (w l)

Why dip or sag is provided in transmission line?

Therefore, in order to have safe tension in the conductor, they are not fully stretched rather a sufficient dip or Sag is provided. The dip or Sag in Transmission line is so provided to maintain tension in the conductor within the safe value in case of variation in tension in the conductor because of seasonal variation.

What is the shape of the SAG span curve of conductor?

(i) When the conductor is suspended between two supports at the same level, it takes the shape of a catenary.However, if the sag is very small compared with the span, then the sag span curve is like a parabola. (ii) The tension at any point on the conductor acts tangentially.