ABSTRACT
The ratio of earthing in underground mines’ electrical systems is in the range of 75% to 86% of the total faults. When an earth fault happens, there are always odd power harmonic levels (3, 5, 7, 9, 11 and 13). These harmonics can have a bad influence on the relay system, and consequently the protection system could operate abnormally or have wrong tripping. This article is based on real data measurements and on simulation in MATLAB, to analyze the kinds of harmonics to fill/eliminate in order to improve the sensitivity, as well as to improve the discriminative tripping of the relay system. The analysis also provides recommendations for operators of the 6 kV grid in order to have a better relay protection system performance.
