Sagging and tension 1. When the sagging of a line is too tight, it can lead to excessive tension on the conductor, which can result in mechanical stress and potential damage to the line. This can cause the conductor to elongate, increase the risk of conductor breakage, and decrease the overall performance and reliability of the line. On the other hand, if the sagging is too loose, it can cause the conductor to hang too low, increasing the risk of it coming into contact with obstacles such as trees or buildings. This can lead to electrical faults, power outages, and safety hazards.
Conductor arrangement refers to how the conductors are positioned and connected in the line. If the sagging is too tight, it can put excessive strain on the conductor arrangement, potentially causing it to become misaligned or disconnected. Ground clearance refers to the distance between the lowest point of the conductor and the ground. If the sagging is too tight, the ground clearance can be reduced, increasing the risk of the conductor coming into contact with the ground or other objects. Wire crossing clearance refers to the distance between two conductors that cross each other. If the sagging is too tight, the wire crossing clearance can be reduced, increasing the risk of the conductors touching each other and causing electrical faults. The sag table provides information on how much sag should be applied to the conductor based on factors such as the span length, temperature, and wind conditions. If the sagging is not within the recommended range specified in the sag table, it can lead to the aforementioned issues.The appropriate sag chart to use depends on whether the necessary information is for the initial sag (before installation) or the final sag (after installation). The initial sag chart provides information on how much sag should be applied to the conductor during the installation process, taking into account factors such as the span length, temperature, and wind conditions. The final sag chart provides information on how much sag the conductor will have after it has been installed and settled, considering factors such as the conductor's material properties and the tension applied during installation.
3. The line and sight method of sagging involves visually aligning a sagging point on the conductor with a predetermined sight point on a tower or pole. This method is commonly used for overhead power lines. It requires at least two people, one at each end of the span. The person at the starting point of the span holds a sagging device and adjusts the sag until the predetermined sight point aligns with the sagging point on the conductor. The person at the ending point of the span acts as a guide, ensuring that the sagging point remains aligned with the sight point while the conductor is being sagged. By following this method, the sag of the conductor can be sagging point remains aligned with the sight point while the conductor is being sagged. By feing sagget
2. SAG is the vertical distance from the bottom point of a
conductor to the reference line such as support
structures.
3.
4.
5. 5. Wind loading: Wind exerts pressure on power lines, causing
them to sway or vibrate. This movement affects both sag and
tension, requiring adjustments to maintain stability.
6. Tension
• refers to the force applied to
a line or cable to keep it taut
and maintain its structural
integrity.
7. • Maintaining appropriate tension levels is
crucial for ensuring proper clearance.
• Power transmission lines have higher tensions
than distribution lines due to longer spans and
higher voltage.
• Tensioning plays a role in the determination of
the maximum allowable loading capacity of
power lines.
• Proper tensioning is achieved through the use
of guy wires suspension clamps and insulators
8. Relationship (Sag and Tension)
One parameter depends on the other.
When the sagging of a line is too tight, it can lead to excessive tension on the
conductor, which can result in mechanical stress and potential damage to the
line
On the other hand, if the sagging is too loose, it can cause the conductor to
hang too low, increasing the risk of it coming into contact with obstacles such
as trees or buildings. This can lead to electrical faults, power outages, and
safety hazards.
. Ice or snow accumulation: The accumulation of ice or snow on power lines
increases their weight, leading to increased sag and requiring higher tension
levels.
When tension increases conductor is tighter reducing its vertical displacement.
Conversely, when tension decreases, the cable becomes more taut and sags
more under its own g decreases because higher tension pulls the weight.
9. Determining sag on a line can be done using various
methods.
One common method is to use a sagging device, such
as a laser or optical instrument, to measure the
distance between the conductor and the ground or
other reference points. This can be done by positioning
the device at various points along the line and taking
measurements.
Another method is to use a tension meter to measure
the tension in the conductor at different points along
the line. By comparing the measured sag or tension
with the recommended sag or tension specified in the
sag table, the sag of the existing line can be
determined.
How to determine the correct sag and tension on a power line
10. In summary, sag and tension in line construction are
interconnected.
The tension applied to a power line determines its
sag, while the sag influences the tension required to
maintain stability.
Various factors such as span length, conductor
weight, temperature variations, wind loading, and
ice or snow accumulation affect the relationship
between sag and tension.
