Reduced neutral XLPE cable design

The authors describe the theoretical, laboratory, and economic analyses undertaken by B.C. Hydro to determine the optimum metallic concentric neutral design for its single-conductor 750 and 500 kcmil aluminum XLPE (cross-linked polyethylene) 15 kV and 25 kV insulated concentric-neutral-type feeder cables. The results suggest that reducing the cross-section area of this concentric neutral from the currently recognized industry standard of 20% of the central conductor to 7% results in an overall present-worth system cost saving of approximately $3 per conductor meter or approximately 22% of the cable first cost. The neutral configuration ultimately chosen to replace the previous standard 37#14 AWG wires was two 1-in×5 mil tinned copper tapes overlapped by 25%. Line voltage fault tests were run in the high-power laboratory on samples with various neutral configurations to confirm that they would successfully pass the worst-case fault duty of 10 kA for 20 cycles (i.e. .33 s) with no reclosing