Research on Off-line Fault Location Technology of Active Distribution Network Based on DG Excitation

Aiming at the problem that the short-circuit current injected by a large number of distributed generations (DGs) leads to the failure of the fault location method based on over-current protection, a fault location method using DG as the external excitation of the de-energized line is proposed. Firstly, by analyzing the frequency domain characteristics differences of the inter-phase equivalent impedance between normal and short-circuit fault states, a fault location criterion based on the deviation of the ratio between the real and imaginary parts of the harmonic impedance is established. Secondly, on the basis of accurate measurement of inter-phase harmonic impedance, the sensitivity analysis of the criterion under the influence of fault resistance, load, and three-phase imbalance is conducted to assess its effectiveness. This fault location method does not rely on short-circuit current, so it is not affected by the contribution of DG to the short-circuit current and has a minimal impact on the load.