Determining the Correction Factors of Overhead-Conductors in 6kV Mining System of QuangNinh, VietNam with the Consideration of Power Harmonic Impact

Abstract

Understanding the impact of power harmonic on energy transmission play an important role not only in the operation process but also
in the designing procedure of MV grid. In 6kV mining grids of Vietnamese coal mines, because of rapidly utilizing the power electronic
machines, the power quality violation occurs very frequently. This lead to many disadvantages such as: the increase of power losses, voltage
distortion, over-heating in transformers and conductors. Moreover, the presence of power harmonic bring the bad impact of skin effect and
proximity on conductor including overhead-conductors and cables. The actual operation exhibits that the losses of transmission lines are
approximately over 50% of total network losses. If there are power quality violation, this amount could be higher. Basing on investigating
the fact of power harmonic violations in 6kV grid of both underground and surface mines, the paper will analyze this kind of impact. An
algorithm relying on Matlab programming is used to calculate the energy losses. Results are compared with on-site measurement datas
and lab-measurement to obtain series of correction factors corresponding to individual line’s cross section. The outcomes of research could
be applicable for power utilities to have better analysis in the designing stage of mining MV grids.