Stockholm-Gothenburg railway cable

The cable was laid to carry the telegraph and telephone circuits alongside the electrified railway line between the two terminals. It was decided that satisfactory operation of telegraph and telephone circuits could be expected if the circuits were separated from the railway by at least 200 metres and the railway power circuit provided with an insulated return with transformers designed so that for each transformer station the unbalance current, at the maximum load, multiplied by the length of circuit traversed, should not exceed 300 ampere-kilometres, or 1500 ampere-kilometres under short-circuit conditions. The former value corresponds to an induced voltage of fifteen for a communication circuit 200 metres from the railway. The cable is lead-sheathed and armoured with two layers of iron tape 1 mm. thick, all joints bonded. The loading coils were made of iron dust and designed to stand a current of 1 amp. through one-line winding without the initial inductance being changed more than 2%. Conductor resistance with d.c. at 15deg C. was not to exceed 17.5 ohms per sq. mm. cross-section per km. of wire. The resistance unbalance between two wires of a pair within a loading section must not exceed 1% of the resistance of one conductor. The capacity wire to wire at 800 cycles was not to be greater than 0.039 mf. per km. The methods of installing the cable are dealt with at length, and the test results on the completed cable are appended.