Mechanical behavior of underground laminar pipe type power cable systems. Progress report

An earlier progress report of December 1978 that was devoted to developing a theory describing the mechanical interaction between the conductor and the insulation is updated. Raw test data was included to indicate the progress made with various tests. It is shown for the first time how this theory is to be combined with some rather sophisticated experimental procedures to describe the detailed internal mechanical response to applied load. It is shown, for example, how compressive and torsional forces give rise to changing tape tensions in the insulation making the gross moduli function of the composite properties of the insulation and the conductor. More importantly, as the Pirelli group has pointed out, overly large tape tensions obviate intratape slip and lead directly to cable failure. This implies that the results showing significant increase in tape tensions under TMB can have an important impact in underground laminar pipe type power cable designs.