Span length is the distance between each pole. This dimension is directly correlated with the number of poles that will be installed along a corridor. … For example, when the poles are spaced farther apart, they must be taller in order to ensure the wires are a safe distance from the ground.
What is sag and span?
The horizontal distance between consecutive supports of an Overhead line is called span. … The vertical distance between the straight line joining the points of consecutive supports and the lowest point of the conductor is called sag.
What is equivalent span in transmission line?
A ruling span, also known as equivalent span or mean effective span (MES), is an assumed uniform design span which approximately portray the mechanical performance of a section of line between its dead-end supports.
What is mid span in transmission line?
Mid Span Joints are used to connect two lengths of overhead line conductor together between the pylon towers and are classed as overhead tension joints.
How do you find your ruling span?
The industry accepted method to determine the tension to be used for all the spans is to calculate a weighted average of the span lengths. The weighted average is called the “ruling span.” The ruling span is the square root of the sum of each span length cubed divided by the sum of the spans.
Why do electrical cables sag?
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.
Why is SAG necessary?
Why is Sag Mandatory in Transmission Line Conductors? Sag is mandatory in transmission line conductor suspension. The conductors are attached between two supports with the perfect value of sag. This is because it protects the conductor from excessive tension.
What is wind span?
The wind span is that on which the wind is assumed to act transversely on the conductors and is taken as half the sum of the two spans, adjacent to the support.In order to take full advantage of towers located on elevated ground, it is usual to allow a wind span of 10 to 15 percent in excess of the normal span.
What are the types of insulators?
A look at some types of insulators and the conditions under which they are deployed.
- Pin-type insulators. …
- Line post insulators. …
- Suspension insulators. …
- Strain insulators. …
- Shackle insulators. …
- Post insulators. …
- Cap and pin insulators. …
- Stay insulators.
What is a slack span?
Dead-end towers may be used at a substation as a transition to a “slack span” entering the equipment, when the circuit changes to a buried cable, when a transmission line changes direction by more than a few degrees, or at intervals along a straight run to limit the extent of a catastrophic collapse.
What is Corona in power system?
Corona is a phenomenon associated with all transmission lines. Under certain conditions, the localized electric field near energized components and conductors can produce a tiny electric discharge or corona, that causes the surrounding air molecules to ionize, or undergo a slight localized change of electric charge.
Which type of joint is used in overhead lines for high tensile?
Britannia Joint : The Britannia joint is a form of electrical joint used for bare overhead wires where great tensile strength is required.