PSI - Issue 64

Jayathilake S. et al. / Procedia Structural Integrity 64 (2024) 137–144 Jayathilake S. et al. / Structural Integrity Procedia 00 (2024) 000–000

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7

The performance of the ACSR was compared with the 7/3.75 AAC powerline, which has the same tension at zero wind and atmospheric temperature. Fig. 7 shows the safety factor for the AAC powerline under the same conditions. Here, the damage limit for AAC is 70% of the CBL capacity, and the safety factor was considered as the ratio of conductor tension to 70% of CBL. According to the European standards developed by the International Electrotechnical Commission (IEC), the damage limit of the conductor under normal conditions is designed to be within 30-50% of maximum tensile stress, while the failure limit is within 70-80% of maximum tensile stress. However, other international standards procedures are not covered in this paper.

Fig. 7. AAC conductor Safety factor due to wind at different temperature levels (a) New Conductor (b) Old Conductor.

Fig. 6 and Fig. 7 illustrate the critical wind events necessary for both new and old conductors to reach their damage and failure limits. Both the new and old ACSR and AAC conductors can function below these limits until they encounter the wind velocities outlined in Table 1.

Table 1. Minimum wind velocities to exceed the damage limit and failure limit.

Minimum Velocity to reach Damage limit (ms -1 )

Minimum Velocity to reach Failure limit (ms -1 )

Conductor

ACSR - New ACSR - Old AAC - New AAC - Old

35 30 33 25

- -

42 32

At temperatures around 25°C, the critical tensile force may reach the damage threshold in ACSR, necessitating a higher wind speed for failure as temperature rises. Conversely, AAC can approach failure thresholds at higher temperatures with increased wind velocities. The new conductor requires a higher minimum wind speed to surpass the damage threshold compared to the old conductor. This difference is notably greater in ACSR than in AAC, across both new and old categories. Critical wind velocity for the ACSR’s failure threshold is not within the selected wind velocity (42 ms -1 ) for this specific case according to the BOM data. However, the old AAC can surpass the failure limit of the CBL at a minimum wind velocity of 32 ms -1 . Consequently, it no longer meets standard requirements, as the design value surpasses the velocity limit in AAC conductors. 6. Conclusion Experimental evaluations were conducted to assess the impact of temperature on aluminum and steel strands in the OPDN under steady-state elevated temperature conditions. Two sets of strands, aluminum, and steel were examined. One set was new, while the other had been in service for 55 years. The prediction based on standards was used to estimate the tensile force in the conductors across various wind and temperature scenarios. The safety factor