DURING the past few years a number of papers concerning dielectric losses of impregnated paper insulation has been presented to the Institute and has contributed interesting and valuable information tour knowledge of this subject. As this knowledge increased, it has been apparent to some engineers that many of our transmission cable burn outs were due to the dielectric losses and the resultant heating and not primarily to the dielectric stresses. In the past, engineers in charge of the operation of to be presented at the A.I.E.E. Annual Convention, Niagara Falls, Ontario, June26-30,1922. Transmission cables have repeatedly stated that transmission cables did not burnout from overload, and apparently based this statement on their experience with the carrying capacity of low voltage cables. It now appears that these statements were in error, and that in making these statements, the engineers did not appreciate the extent to which the carrying capacity was limited by the dielectric losses. If the present symposium, of which this paper is apart, will do something toward clarifying our ideas on the relation of dielectric losses, dielectric stresses and temperature of the insulation to cable failures, it will have served a very useful purpose.