The tension of attached wires to structures are the major loads they are required to support, under a variety of load cases. As such, any deviation from expected norms for tensions will have a significant effect on calculated single and multi-structure analysis results. Their resulting sags under various load cases are also key in meeting clearance to ground requirements in the respective code and utility standards. So both Sags and Tensions should be evaluated in a comparable manner under a very wide range of scenarios. To meet code and utility standard requirements, each span of wires attached to a structure needs to be assessed under any load case that may have an impact. All wires are assumed to have nonlinear material characteristics. Wire states such as birdcaging, will also come into play for wires composed of more than one material.


Evaluation tests should include:

  1. Values for:
    1. Tension at both support structures
    2. Horizontal tension
    3. Line of sight sag
    4. Vertical sag (sag below lowest attachment support)
    5. Horizontal and vertical loads per meter on the wire.
  2. Weather loads that test wire 
    1. stretching behavior with different possible loads in the vertical and transverse planes. 
      1. 400 pascals wind pressure
      2. 12.5mm radial ice accretion
    2. Line of Sight and Vertical Sags will be collected for sag comparisons
    3. Thermal condition (50C for steel wires and 100C for all others)
  3. Level spans of varied typical lengths, plus additional amounts for extreme tests
    1. 20m
    2. 40m
    3. 60m
    4. 80m
    5. 100m
    6. 120m
    7. 140m
    8. 160m
    9. 180m
    10. 200m
  4. Unlevel spans
    1. varied lengths as above
    2. varied elevation changes up to 60 degree incline
      1. 5 degrees
      2. 10 degrees
      3. 20 degrees
      4. 30 degrees
      5. 40 degrees
      6. 50 degrees
      7. 60 degrees
    3. measure both upper and lower attachment point tensions plus sags described above
  5. Observance of any birdcaging effects for multi-material wires and what temperature they occurred. Increments of 10C temperature increments are recommended.
    1. If birdcaging criteria is modifiable, test at different values than default to ensure change is respected. Otherwise state values used and justification.
  6. Wire types:
    1. All aluminum
      1. 566.5 Dahlia AAC
      2. 336.4 Tulip ASC
      3. 4/0 Oxlip AAC
      4. 1/0 Poppy AAC
    2. Aluminum and Steel
      1. 795 Drake ACSR
      2. 477 Hawk
      3. 4/0 Penguin ACSR
      4. 3/0 Pigeon ACSR
      5. 1/0 Raven ACSR
      6. #2 Sparrow AW 6/1
    3. Multiplex wires
      1. #2 ACSR
      2. 1/0 ACSR
      3. 4/0 Quadruplex
    4. Copper
      1. 750 kcmil 37 strands
      2. 4/0 7 strands
      3. 1/0 7 strands
      4. #6 7 strands
    5. Steel
      1. 3/4 inch Grades 110,160,180,220
      2. 1/2 inch Grades 110,160,180,220
      3. 3/8 inch Grades 110,160,180,220
      4. 1/4 inch Grades 110,160,180,220
      5. 3/16 inch Grades 110,160,180,220
    6. Dielectric cables with a fiberglass core messenger
      1. ADSS cable from AFL AE2889CO31BA5
        1. Wire mass=0.393kg/m
        2. Strength=24225N
        3. Diameter=22.61mm
        4. Cross sectional area=401.16mm2
        5. Thermal exp. 2.9069e-3
        6. Stress polynomials= 0.0, 29.83, 0.0,0.0,0.0
        7. Creep Polynomials=0.0,24.86,0.0,0.0,0.0
  7. Wire states:
    1. Initial
    2. Final after Creep
      1. Average day temperature for creep and installation shall be 10%RTS @ 10C. Additional creep temperatures of 0C and 20C shall be tested. 
    3. Final after Load


To properly evaluate Sag & Tension calculations, some details need to be taken into account. Softwares need to model all wires/messengers in a way that they are typically installed, assuming new material. When wires are installed and sagged in one operation in a line section of several equal or unequal, level or unlevel spans, the structures between the dead-ends of the stringing section support the wire with stringing sheaves or blocks, that permits the conductor to move freely between spans. Once the wire’s tension is set to the desired value, the conductor is secured to its supporting insulator or connection hardware. This fixes the amount of wire used between the structure supports under initial stringing conditions. Software will need to be configured to respect this assumption. Testing existing wire scenarios is out of scope for this document. 


For sag-tension calculation for communication cables, the exact same procedure needs to be followed as for conductors, for the messenger alone. After the messenger unstretched length is fixed, the communication cables get lashed onto the messenger. All loadcases are calculated, and wire stretch scenarios are calculated using this additional cable weight and larger bundle diameter. This is representative of how communication cables are strung in the field.