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The detection of a single line-to-ground fault in compensated distribution networks can be hampered by important capacitive currents. The way to deal with this problem depends on the particular regime where data are acquired. In the transient regime, the relays diagnosis based on the analysis of charging components can deceive with a massive presence of discharging currents. The latter, however, will disclose data for directional function if the sampling frequency is high enough for acquisition in the wave propagation area. The fault detection can also be out of reach of steady-state methods which are based on the detection of active components in faulty currents. The efficiency of these methods vanishes when strong capacitive currents squeeze the phase shift between faulty and sound zero-sequence currents below the actual acquisition limits. In such a situation, however, it is still possible to obtain the faulty feeder indication from the way the residual currents cross the zero level soon after inception.
Date of Publication: Oct. 2007