Effect of harmonics on distance relay in short and medium transmission lines

The continuous increasing in the number and the power ratings of the non-linear loads are the main sources of harmonics that affect the performance of all electrical elements. This harmonics either current or voltage harmonics have a serious effect on the quality of electricity power supply and all network elements like protection elements especially distance relays. In this paper, the effect of harmonics on distance relay is presented through a comparative study between the distance relay performance in the short and the medium models of the cable under different levels of harmonics including many components of current and voltage. This study is presented using Matlab to describe the distance relay, harmonics (current source), transmission line, fault simulation as a single line to ground fault SLG and the impedance type distance characteristic are chosen to be as the protection scheme.