Changes to design criteria for application of additional load to existing distribution poles

Design Criteria for the application of additional load to existing poles.

Our current CEOM7097 Overhead Design Manual section 3.5.10 design requirements apply full design loads and a strength reduction factor of 0.5 to existing distribution poles. While this often results in only a modest tip load increase, it requires existing pole replacement.

To limit the need for existing pole replacements, the following changes will be made to CEOM7097 section 3.5.10 Timber pole assessment for additional loads:

• For evaluating the suitability of retaining existing poles for additional loads, a Strength Reduction Factor (ǿ) of up to 0.7 can be applied for existing preservative treated poles only. All new poles and existing natural round (untreated) poles shall use a Strength Reduction Factor of 0.5 as per Essential Energy Overhead Construction Manual drawing CEOM7101.03.
• Wind loads and drag coefficients shall correspond to the values shown in clause 3.5.6.8 – Table 3.5.6.8.2 (Regions A1-A7) and Table 3.5.6.8.3 (Region B) as applicable for a 50 Year Design Working Life and 50 Year Wind Return Period.

These changes are effective immediately and will be updated in the next release of the design manual.

Please note:

These changes apply to distribution poles only, not sub-transmission poles.

When determining the ultimate limit strength of existing wood poles all ASPs are required to calculate the residual pole strength using the Wall Thickness, the lower of either the Critical Zone diameter or Above Ground diameter and the Fibre Stress of the wood pole as defined by the pole species in conjunction with AS2878. These inputs are all found in Essential Energy’s GIS or alternatively residual pole strengths are automatically calculated for each pole when using the Power Lines Pro platform and Essential Energy’s Network Automodel.

Two examples of residual pole strength are shown in the table below for existing wood poles.

• Pole 1 is an existing Preservative Treated 17 m, 6 kN Stress grade S2 (85 MPa) timber pole.
• Pole 2 is an existing Natural Round 17 m, 6 kN Stress grade S2 (85 MPa) timber pole. Pole 1 and Pole 2 have different Ground line diameters (GD) and Wall thickness (W).

The available capacity value in the table is compared against the total design load on the structure determined by design assessment.

These new requirements have been updated in Essential Energy’s Network Automodel for Asps who use Power Lines Pro, as shown in the diagram below:

What do you need to do?

1. Review the above additional load on existing poles.
2. Communicate this information to relevant members of your organisation.
3. View this communication via Essential Engagement at engage.essentialenergy.com.au/ASP

Further Information

If you need further information, please email aspinfo@essentialenergy.com.au