Transmitting power within a wellbore

An isolator sub disposed in a first cavity between casing walls in a wellbore of a subterranean formation, the isolator sub comprising:

• an outer case comprising an electrically conductive material, a first aperture that traverses a top end of the outer case, and a second aperture that traverses a bottom end of the outer case;
• an inner wall disposed within the outer case and forming a second cavity therethrough, wherein the second cavity is bounded by the first aperture and the second aperture, wherein the inner wall is mechanically coupled to a neutral portion of a tubing string adjacent to the top end of the outer case and to a power-transmitting portion of the tubing string adjacent to the bottom end of the outer case;
• and
• an insulating material disposed between the outer case and the inner wall, wherein the insulating material is electrically nonconductive,
• wherein the insulating material surrounds a portion of the power-transmitting portion of the tubing string,
• wherein the power-transmitting portion of the tubing string is electrically coupled to a power source and is disposed between the casing walls in the wellbore,
• wherein the outer case is configured to couple to the neutral portion of the tubing string at the first aperture, and
• wherein the second aperture of the outer case avoids contact with the tubing string.

An isolator sub disposed in a first cavity between casing walls in a wellbore of a subterranean formation, the isolator sub comprising:

• an outer case comprising an electrically conductive material, a first aperture that traverses a bottom end of the outer case, and a second aperture that traverses a top end of the outer case;
• an inner wall disposed within the outer case and forming a second cavity therethrough, wherein the second cavity is bounded by the first aperture and the second aperture, wherein the inner wall is mechanically coupled to a neutral portion of a tubing string adjacent to the bottom end of the outer case and to a power-transmitting portion of the tubing string adjacent to the top end of the outer case;
• and
• an insulating material disposed between the outer case and the inner wall, wherein the insulating material is electrically nonconductive,
• wherein the insulating material surrounds a portion of the power-transmitting portion of the tubing string,
• wherein the power-transmitting portion of the tubing string is electrically coupled to a power source and is disposed between the casing walls in the wellbore,
• wherein the outer case is configured to couple to the neutral portion of the tubing string at the first aperture, and
• wherein the second aperture of the outer case avoids contact with the tubing string.