Ground Fault Protection - engineering site - Schneider Electric

In shortThe Multisource diagram with severalearthings is easy to implement.However, at ground fault protection (GFP)level, special relays must be used if theneutral conductor is not broken.Use of four-pole incoming and couplingcircuit-breakers eliminates such problemsand ensures easy and effectivemanagement of ground fault protection(GFP).DB1172944.2. A multisource system with severalearthingsThe neutral points on the LV transformers of S1 and S2 power sources are directlyearthed. This earthing can be common to both or separate. A current in the U1 loadneutral conductor can flow back directly to S1 or flow through the earthings.Diagram 31 - "multisource system with 2 earthings"4.2.1. System studyb by applying the implementation methodology to normal operation.a1 criterion: balanced loads without harmonics in U1 and U2For U1 loads, the current in the neutral is weak or non-existant. Currents in paths Aand B are also weak or non-existant. The supply end GFP devices (GFP1 and GFP2)do not measure any currents. Operation functions correctly. Id, if one looks at U2loads.DB117295a2 criterion with harmonicson U1 loadsCurrent flowing in the neutral isstrong and thus currents inpaths A and B are strong as well.Supply end GFP devices (GFP1and GFP2) measure a currentthat, depending on thresholdlevels, can cause nuisancetripping. Operation does notfunction correctly.Currents following path B flow inthe structures. a2 criterion is notverified.Diagram 32a - "a2 criterion": current flow in structures30