A power cable includes at least two power conductors, at least one earth conductor, and a tubular outer jacket surrounding the power conductors and earth conductor. Each power conductor may comprise a conductive core and an insulating layer surrounding said conductive core. The power conductors may be twisted and contact each other. The earth conductor may have a diameter smaller than the power conductors and may be positioned in the interstitial area between two adjacent power conductors and the outer jacket. The earth conductor may contact the two power conductors along two respective contact lines and the outer jacket along an extrados portion facing outward with respect to the cable. The outer jacket may have substantially constant thickness. The lateral surfaces of the earth conductor may be free from constraints between the contact lines with the power conductors and the extrados contacted by the outer jacket.