Harmonic resonances due to transmission-system cables

This paper gives some examples of harmonic issues that can occur when long ac cables are connected in the transmission grid . The main impact is that reso nances can occur at much lower frequencies than when only overhead lines are present. T wo illustrative case studies are presented : one for a 275 - kV cable, one for a 400 - kV cable in combination with a 132 - kV capacitor bank. A simple rule - of - thumb is given, to decide if a detailed harmonic study is needed. Some guidelines for such a study are given as well.