Effect of electro-thermal, load cycling and thermal transients stresses on high voltage XLPE and EPR p0wer cable life

All insulation systems life is definite and analysis of insulations life is very important. Power cables designed for 30 years life, but electrical, thermal, load cycling and other stresses caused reduced it. In this paper, a procedure is presented for the life estimation of high-voltage cables subjected to electro-thermal stress due to applied voltage and load cycles. Thermal transients due to load cyclic current are modeled by means of the well-known two-loop thermal network analog. The effect of the relevant cyclically varying electro-thermal stress is accounted for via the cumulative damage law of Miner. The life fractions lost during each step of the load cycle are evaluated by a proper combined electro-thermal life model holding for cable insulation. The procedure is applied to high voltage AC XLPE and EPR insulated cables, subjected to stepwise constant daily load cycles.