You can only have two segments attached to a point in a curve, but you can have multiple disconnected segments in the same curve object.
While in edit mode, many of the steps you use in mesh editing work in a similar way.
- ⇧ ShiftA to add a new curve that is part of the existing object
- ⇧ ShiftD to duplicate the current selection
- E to extrude a segment that is connected to the selected point/s
- L to select points linked to the point under the cursor
- ⎈ CtrlL to select points linked to selected points
- F to fill in a segment between two selected points
Each point has a radius property so you can give the shielding a larger bevel than the inner wires. You use ⎇ AltS to adjust the radius of a point, this can also be edited in the properties sidebar.
The disconnected pieces can be positioned close together so that the smaller wires appear to continue on inside the larger wire. Different materials can be assigned to different curve segments the same as assigning materials to selected faces in a mesh.
Then after setting the bevel, you get one object that appears to be multiple wires.