Symmetrical components to suppress voltage sensors in directional relays for distribution networks: effect of distributed generation

Directional relays without voltage sensors for distribution networks with distributed generation: Use of symmetrical components

“…This algorithm uses the argument of the ratio I 2 /I 1sound (I 1sound is the positive current before the fault) to detect a fault upstream or downstream the detector. Unfortunately the argument of this ratio becomes very uncertain when a distributed generator (DG) is connected to a MV feeder, especially for a compensative grounding [12]. In the paper [12] the argument of the ratio I 2 /I 1sound was precisely studied using analytics formula, and then the limits of this ratio were identified and confirmed by the EMTP simulations.…”

“…Unfortunately the argument of this ratio becomes very uncertain when a distributed generator (DG) is connected to a MV feeder, especially for a compensative grounding [12]. In the paper [12] the argument of the ratio I 2 /I 1sound was precisely studied using analytics formula, and then the limits of this ratio were identified and confirmed by the EMTP simulations. The main drawback comes from the positive current that depends on the power flows on the feeders.…”

“…But the voltage sensors generate an additional cost. To suppress these voltage sensors, an algorithm using the symmetrical components was proposed in a previous paper [12]. This algorithm uses the argument of the ratio I 2 /I 1sound (I 1sound is the positive current before the fault) to detect a fault upstream or downstream the detector.…”