The effect of prestressing on the inelastic (creep) behaviour of Australian made bare overhead conductors

The creep behaviour of Australian manufactured bare overhead conductors was examined. The CIGRE proposed relationship for prestressing behaviour was assessed. A comprehensive literature survey yielded alternative experimental models and extensive amounts of creep constants for many conductor constructions. 19, 37 and 61 strand ACSR and AAAC/1120 conductors were tested. 1(X)0 hour creep tests were performed at tensile loads of 20, 30 and 40% of the NBL of the conductor at 20°C. Prestressing overloads of either 10 or 20% NBL were applied for periods of 1,2 or 7 days. It was found that prestressing removed a considerable portion of the total predicted creep of a conductor in a relatively short time, i.e. has the effect on creep, of "overaging" a conductor. Analysis of the tests revealed that prestressing will stabilise creep strains for a period of time after load reduction. The stabilised period is adequately described by the CIGRE equivalent time relationship. a µ t eq = ( ơ1 ) t 1 σ2 Creep constants determined by this work and revealed by the literature survey for Australian conductors, were compared with those published for comparable conductors manufactured overseas. It was shown that there are significant differences between the creep constants of Australian and overseas conductors. Creep constants therefore, for overseas conductors, are not applicable to Australian conductors.