Conductor Tension
Conductor Tension
(OP)
Hi Gents,
Could you advise me please what appropriate %CBL should be applied for existing 3/4/2.50 ACSR conductor with a span of 180m. For new conductors,the recommended %CBL is 20%.
regards,
Danilo
Could you advise me please what appropriate %CBL should be applied for existing 3/4/2.50 ACSR conductor with a span of 180m. For new conductors,the recommended %CBL is 20%.
regards,
Danilo






RE: Conductor Tension
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RE: Conductor Tension
If the sag will be 5.5 m [taken into consideration -5 degree C and an average ice thickness] 20% will be fair. It is my opinion.
RE: Conductor Tension
-5degree C?I presume that it is the initial temperature applied which has an equivalent tension.How did you conclude that 20% is just fair? Please show computation to enlighten me on this.
Many Thanks
RE: Conductor Tension
Siemens Manual "Tables and Formulas for Electrical Engineer"
"Formel- und Tabellenbuch für Starkstrom-Ingenieure"
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use the following relationship:
sag=span^2*gammaZ/8/sigmaZ where:
gammaZ=conductor weight +supplimentary load[ice] divided by rated conductor cross-section [kgf/cm^3].
sigmaZ=the tension of conductor at -5 oC including supplementary load[ice].
Note: At -5 oC the ice thickness would be the maximum.
gammaZ=conductor weight [kgf/cm^3]+0.18*sqrt(d)/q where:
d=conductor diameter [mm] q=conductor cross section [mm^2].
sigmaZ=K%/100*CBL[kgf/cm^2].
From Manufacturer data:
d=7.5 mm ; q= 34.36 mm^2; CBL =72.39 kgf/mm^2 [recalculated].
CBL=72.39*100=7239 kg/cm^2.
Conductor weight =193 kg/km.
conductor weight/q= weight[kg/km]/10^3/q=193/10^3/34.36=0.005617 kgf/cm^3
gammaZ=0.005617+0.18*SQRT(7.5)/34.36=0.019964 kgf/cm^3.
If K%=20% then sag=(180*100)^2*0.019964/(20/100*7239)/8=558.46 cm.=5.58 m.
The wind is not taken into consideration.
In the same Manual it is indicated wind pressure 10.5 kg/m^2.
For wind load see[in the same forum]:
http://www.eng-tips.com/viewthread.cfm?qid=8018
Following the calculation indicated in these posts the conductor tension will be 7 kN [28%].If we intend to be not more than 20% we have to admit a bigger sag [8 m].
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