Experimental Evaluation of S-N Curves for Drake ACSR Conductor

This paper reports on an experimental effort to generate S-N (dynamic stress-fatigue life) curves for a Drake ACSR (aluminum conductor steel reinforced) conductor. In the testing, aeolian vibrations were simulated by mechanical means in a controlled laboratory environment for one set of line conditions. Fatigue data for the first five strand breaks were evaluated, and S-N curves for the first through fifth strand breaks were fit to the data using linear regression analyses. A minimum of four duplicative tests at each stress level tested were conducted to allow an evaluation of the statistical parameters and to provide statistical credibility to the results. A pseudo endurance limit of 21.31 MPa (3.09 ksi) was estimated from the S-N data. The S-N curves generated in this study provide much needed information for transmission line designers on the fatigue characteristics of Drake ACSR conductors. It is recommended that the S-N curves be used in conjunction with a probabilistic approach in designing transmission lines for aeolian fatigue.