Each wire lines are often heavily loaded because of increased increase 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.
Why do electrical wires sag in the summer and hang tight in the winter?
Because the cores of overhead wires are made from copper. Metals expand with heat and contract with cold. The higher temperatures in summer make the copper expand – so the lines get slightly longer. In winter, the reverse happens – the lines contract and tighten up.
Why telephone wires are installed sag?
The telephone wires will sag in summer due to expansions and will break in winter due to contraction. Therefore, while putting up the wires between the poles, care is taken that in summer they are kept slightly loose so that they may not break in winter due to contraction.
Why do electrical cables between pylons sag a little?
The conductor material (copper, aluminum, whatever) expands when heated. When the temperature increases, the length of the power line between two towers increases due to thermal expansion, and the line sags because of the increased slack.
Which causes sagging of electric wires during summer?
This process is called thermal expansion. The same process happens in the electric wire. During summer, the heat makes the molecules move wider apart and hence it sags and during the winter follows the opposite process and gets contacted.
Why telephone wires are kept tight in winter?
Telephone wires are kept tight between the two poles in winter because the cores of overhead wires are made from copper. … The higher temperatures in summer make the copper expand – so the lines get slightly longer. In winter, the reverse happens – the lines contract and tighten up.
What is sagging in electrical?
Sag literally means to be bending in shape. In. overhead transmission lines, the difference in level. between points of supports (towers or utility poles) and the lowest point on the conductor is called sag.
Why are the wire that is connected in the posts outside are lightly saggy not tightly tied by the line man?
The reason is to minimize the tension in the wire. The wires expand when exposed to intense heat from sun and contract during cold weather. Stretching the wire and connecting to the poles will make the wires loosen up and tear easily. … So they are allowed to sag and tied loosely to the electric poles.
Why are overhead cables hung loosely?
During transmission of electricity, heat is being dissipated. The heat generated by cables is being minimized via high voltage transmission. … So, the cables are loose so that even if contraction should occur, there won’t be much tension which would lead to the damage of the cables.
What is a sag point?
What is Sag in a 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.
What is cable sag?
Cable sag (h) is value of cable form equation for point l/2 (formula 12), where l is the straightline distance between the position transducer and the application (Figure 1). … The length of the cable is the catenary length from point -l/2 to point l/2 (formula 14).
How is SAG calculated?
Calculation of Sag:
- Case1: When the conductor supports are at equal level.
- Sag = WL2/8T.
- Case2: When the conductor supports are at unequal level.
- Sag = WtL2/2T.