High impedance arcing fault detector for three-wire power distribution networks

A new approach to a high impedance fault (HIF) detector is presented, suitable for the European scene where the power distribution systems are usually three-phase and three-wire configured. This paper aims to be a contribution to the proposals that, in the last twenty years, have been trying to solve the HIF problem with no definitive solution known yet. The purpose of the study presented is to design an electric arc detector and characterise the danger of the fault looking at fault context conditions. The detector system input signals are the three individual phase currents which comply with 3I₀=I₁+I₂+I₃≠0 at the three-wire configuration. First, a continuous HIF context conditions study is proposed: overcurrent or reclosing in every phase, noticeable load variation monitoring and 3I₀ monitoring. Secondly, a short, medium and long-term statistical analysis is performed both with odd harmonics (third, fifth, seventh and ninth) and even harmonics (second and fourth) of the I₀ current. Thirdly, the estimated arc probability is calculated and combined with context conditions in order to determine a diagnosis. The proposed detector has been tested on 100 unfaulted condition event records (some have leakage current) and 32 staged fault records on different surfaces. The test results presented in the paper are satisfactory both in the sense of dependability and sensitivity.