The influence of manufacturing tolerances on the magnetic field of compensated three-phase power cables

Due to compensation effects the magnetic field of a twisted three-phase power cable built up by 3 wires of finite length can be reduced by splitting each conductor into N smaller wires. Maximum compensation occurs if the 3N conductors are placed on their exact positions prescribed by the theory. In reality the perfect order is affected by tolerances of the manufacturing process. Compared with the ideal 3N-wire cable this leads to higher field values. By our investigation we found that despite the impairing influence of inaccuracies the split of the 3-wire cable leads to a remarkable field reduction in the range from 30 to 50 dB. Attenuation diagrams show how the field of the 3N-wire cable depends on different splitting steps N and on the jitter domain ΔΦ of the random angle deviation of the wires.