kilogram per kilometer

The kilogram per kilometre is the cable industry's unit because cable is made, priced and shipped by the kilometre. Conductor datasheets list mass in kg/km as a matter of course: a bare high-voltage ACSR conductor runs on the order of 1,000 to 2,000 kg/km, a residential mains cable a few hundred, and the glass in a standard 125 μm optical fibre only about 30 g/km, which is why the weight of a fibre cable is almost entirely jacket and strength member rather than fibre.

Reel logistics is the everyday use: kg/km times route length is the shipping weight, the drum size and the crane requirement. The structural use is sag. An overhead span hangs under its own weight per unit length, and the cable tension solvers on this site take weight per unit of span, so a kg/km figure enters them after a multiplication by g, and in a real line design it also picks up ice and wind loading on the way.

The unit has a secret identity. The tex of the textile trade is defined as a gram per kilometre, so one kg/km is exactly one kilotex, and the measure rating a transmission conductor and the family rating sewing thread are the same unit a thousandfold apart. Numerically it is also just grams per metre, which is how climbing rope and cordage makers print the identical quantity.