Question:

In Alternatives, Issue 12, page 14, you say that line losses are estimated to be 2.5% of total consumption. Would the losses be identical for overhead lines and buried lines?

Answer:

Line losses in an electricity transmission system are higher for underground cables than for overhead lines, at least in very high voltage transmission (400 kV). This is due to the fact that air provides better insulation than synthetic polyethylene cable sheaths, which cause losses due to stray capacitance, which increases with voltage. On the other hand, conventional losses due to the Joule effect, themselves linked to current intensity, are obviously identical in both cases. The 2.5% indicated (2.6%, to be exact) should be evenly split between the very high voltage transmission system and the high and medium voltage transmission system (225 kV and 90 kV).