PSI - Issue 64

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

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

duration and can cause sudden failures and power outages in the OPDN. Therefore, it is crucial to understand the performance of power conductors under elevated temperature conditions and high wind events and continue the

reliability assessment of conductors to have proper asset management. 3. Evaluation of temperature effect via laboratory experiments

In order to investigate the effect of temperature on a conductor, a laboratory experiment was carried out at various elevated temperature levels. The INSTRON UTS 100kN machine was used for the testing as shown in Fig. 1. Due to the limitations of the machinery grips, testing was carried out for individual strands. Here, 3.75 mm steel and aluminium strands were used for the experiment from new and 55-year-old 6/1/3.75 ACSR. Here, 6/1/3.75 represents the conductor comprised with six aluminium strands and one steel strand. The tests were done at room temperature and elevated temperatures by following the standards of AS1391 (2020) and AS2291 (2020) respectively. The test was conducted to measure the tensile properties at 25°C (Room temperature), 50°C, 65°C, 80°C and 100°C. Strands were kept inside the temperature chamber for 30 minutes to heat up to the expected temperature level and it is monitored by the temperature controller in the machine. Finally, loading was applied at a frequency of 1mm/min and 0.5mm/min for steel and aluminium strands respectively. Tensile testing of the strands was performed and the stress-strain relationship for the single-strand at different temperatures was plotted separately for new and 55-year-old aluminium and steel. The conductor breaking load (CBL) and Young’s modulus at different temperatures for each Aluminium and steel strand were evaluated separately. Furthermore, the CBL value for the conductor was calculated using the guidelines given in the AS 3607-1989.

0-7 mm Grips

Manual Extensometer

Fig. 1. Tensile testing setup for the single strand with an extensometer with 50 mm gauge

4. Evaluation of wind effect with temperature variation Axial force on the conductor was evaluated by considering the wind pressure. Here, historical wind data for the calculation was obtained from the Bureau of Meteorology (BOM) to understand the wind load variations in the Point Cook Raaf weather station area. Then, a wind hazard curve was developed as shown in Fig. 2 for the identification of frequencies in a proper way for the easiness of extraction data for the calculations. Wind is the dominant force in this case and the snow and ice loads were ignored as the Alpine areas are not much common in Melbourne. For the calculation of force at the different wind velocities, the MATLAB programming platform is used. According to the data received from BOM, two major wind events occurred in the year 2022 which have 3s gust wind velocities of 40 ms -1 and 42 ms -1 . Therefore, these two major wind events were considered in the load calculation in addition to nominal wind velocities including zero wind speed. Furthermore, the regional wind speed of 39 ms -1 is also considered in this analysis for a 50-year return period in Melbourne (AS/NZS1170.2, 2021). In this study, a medium span (150m length) power line of the same ACSR was considered as it is a common conductor used in Australian OPDN (Naranpanawe, 2018). The pole height was considered as 14 m, and the modulus of elasticity value was taken from Table B1 in the AS3607 (1989). Then, conductor tension was calculated