This article assesses the impact on the Power Quality produced by the interconnection of a microgrid to a transmission system, real-time simulation have been used to carry out the study, applying national and international power quality standards, IEEE 1547 of 2018, IEEE 519 of 2014 and NTC 5001 of 2008. The phenomena of voltage harmonics, current harmonics, flicker and DC injection were evaluated on a microgrid case study. The results show that the interconnection of the microgrid produces a high impact on the current harmonics and the DC injection of the local transmission system, while the flicker phenomena and voltage harmonics have a smaller impact.