110 CONSTANT- VOLTAGE TRANSMISSION 



the circuit, only that part of the flux must be considered 

 which cuts one cable and not the other. It is necessary 

 to calculate the voltage induced in each small wire of 

 the cable A (Fig. 12) by the flux in the space s produced 

 by each of the wires of cable A. 



The radius of the cable is considered small compared 

 with the distance s, since overhead lines are being con- 

 sidered. Round wires may be considered to be replaced 

 by very small conductors located at the centres of the 

 wires, so far as the inductance of one wire on another is 



FIG. 12. Single-phase Circuit. 



concerned. The correction in inductance due to skin 

 effect may be neglected, as it is very small for ordinary 

 cables at 25 or 60 cycles, being only one-half of the skin 

 effect correction in resistance. 



Although the spiraling of the wires has a marked 

 effect on the resistance of a strand (amounting to i or 

 2 per cent), there is practically no effect on the react- 

 ance, due to spiraling. The spiraling adds a component 

 to the magnetic field produced by each wire, which would 

 be in a plane parallel to the axis of the strand. The top 

 wires cross the strand in the opposite direction to the 

 bottom wires. The part of the above component which 

 would be outside the strand would, therefore, produce 



