LV generator protection - engineering site - Schneider Electric

Protection and Monitoringof a LV Generator Set3.4.1.2. Generator Set faults as a loadOne of the parallel-connected Generator Sets may no longer operate as agenerator but as a motor (by loss of its excitation for example). This maygenerate overloading of the other Generator Set(s) and thus place the electricalinstallation out of operation.To check that the Generator Set really is supplying the installation with power(operation as a generator), you need to check the proper flow direction of energyon the coupling busbar using a specific “reverse power” check. Should a faultoccur, i.e. the Set operates as a motor, this function will eliminate the faulty Set.E88043E E88015EMV incomerGSHV busbarSetSet.LVFigure 21: Energy transfer direction - GS as a generator.MV incomerHV busbarGSLVFigure 22: Energy transfer direction - GS as a load.3.4.2. Grounding parallel-connected Generator SetsGrounding of connected Generator Sets may lead to circulation of earth faultcurrents (3 rd order and multiple of 3 harmonics) by connection of Neutrals forcommon grounding (grounding system of the TN or TT type). Consequently, toprevent these currents from flowing between the Generator Sets, we recommendthat you install a decoupling resistance in the grounding circuit.26