Experimental investigation into harmonic impedance of low-voltage cables

Harmonic characteristics of power cables used in low-voltage distribution systems of commercial buildings are investigated. Analytical discussion of cable resistance and reactance at harmonic frequencies is presented. An experimental procedure for obtaining full matrix impedance of cables at harmonic frequency is introduced. It is found that cable resistance increases with increasing harmonic order. Cable inductance, however, decreases due to the effect of flux cancellation. The analytical formulas presented yield reasonable accuracy for cable resistance for single-core cables, but provide an overestimation for multicore cables. The impact of various parameters on cable resistance and reactance, such as harmonic order, cable installation method, cable current distribution and the presence of magnetic material is also addressed, as well as the mechanisms for impedance variation. Finally, recommendations for using the approximate formulas for cables in low-voltage installations are provided