design considerations for transmission lines
design considerations for transmission lines
(OP)
can any one tell me about electrical design considerations of transmission lines.Is there any thumb rule for calculating sag for transmission lines and for errecting supporting poles? details will be appreciated






RE: design considerations for transmission lines
As you can see there is a lot to take into consideration. Even with more details from your end I don't know how much help I can provide as far as rules of thumb.
RE: design considerations for transmission lines
RE: design considerations for transmission lines
For shorter spans, sag can be approximated by parabola: SAG = (Conductor Weight x (Span Length^2))/(8 * Tension). Sag is actually a catenary curve whose calculation involves hyperbolic trig. Keep in mind that tension can vary dramatically with conductor temperature and ice.
REA (or RUS) has published guides for line design which are probably available on their website, http://www.usda.gov/rus ; The National Electrical Safety Code (NESC, IEEE C2) has loading districts defined, as well as other helpful data. These are for USA; I'm not familiar with requirements elsewhere.
RE: design considerations for transmission lines
Also some utilities publish their design standards, with stringing charts for various sags and ruling spans already determined. They also have anchoring and pole setting standard details. However, these are usually more often found for distribution than transmission.
RE: design considerations for transmission lines
The equation of catenary is:
Y = (T/w)cosh(wX/T) + C
Where
T = Horizontal Component of tension at the supporting point of cable.
w = weight per unit of the cable
Length of the catenary (cable) between two points 'a' & 'b' (Span length = b - a) is :
L = (T/w)[ sinh(wb/T) - sinh(wa/T) ]
RE: design considerations for transmission lines
1. Reference:
C.L. Wadhwa "Electrical Power Systems," John Wiley & Sons, 1991
Chapter 7 "Mechanical Design of Transmission Lines"
2. The sag has already some posting in this Forum. Try Advanced Search for quick results.
3. Sag is defined as a difference between an arbitrary point on the line P(x,y) and the lowest transmission line point H. The maximum sag d is
d=(L**2)/(8 x c)
where
L is the distance between 2 poles
c = To/W
To is the tension at the lowest point, i.e. point H
W is the weight per unit length of the wire
RE: design considerations for transmission lines
Actually I am alos working upon making a software for designing of Aerial Optical Fiber Cables. Yesterday I was browsing net and came across the follwing site which has explaind in brief yet precisely how to determine sag, length of cable, tension etc.
http://www.du.edu/~jcalvert/math/catenary.htm
Hope this helps. Keep us updated.
RE: design considerations for transmission lines