LV generator protection - engineering site - Schneider Electric

6.2. Control unitscharacteristicsCompact NS400 to 630In shortPossible combinations:b Ib Tb I + Tb I + COMb I + T + COMb ZSIb ZSI + Ib ZSI + Tb ZSI + I + Tb ZSI +I + COMb ZSI + I + T + COMOptions for the STR53UE electronic trip unitEarth-fault protection (T)typeResidualpick-up Ig = In x … 0.2 to 1accuracy ± 15%adjustable, 8 settingstime delayadjustable, 4 settings"constant I 2 t" function max. resettable time 60 140 230 350max. break time y 140 y 230 y 350 y 500Ammeter (I)A digital display continuously indicates the current of the phase with the greatestload. The value of each current (I1, I2, I3, Ineutral) may be successivelydisplayed by pressing a scroll button.LEDs indicate the phase for which the current is displayed.Ammeter display limits:b minimum current u 0.2 x In. Lower currents are not displayedb maximum current y 10 x In.Zone selective interlocking (ZSI)A number of circuit breakers are interconnected one after another by a pilot wire.In the event of a short-time or earth fault:b if a given STR53UE trip unit detects the fault, it informs the upstream circuitbreaker, which applies the set time delayb if the STR53UE trip unit does not detect the fault, the upstream circuit breakertrips after its shortest time delay.In this manner, the fault is cleared rapidly by the nearest circuit breaker.The thermal stresses on the circuits are minimised and time discrimination ismaintained throughout the installation.The STR53UE trip unit can handle only the downstream end of a zone selectiveinterlocking function. Consequently, the ZSI option cannot be implementedbetween two Compact NS circuit breakers.Opto-electronic outputsUsing opto-transistors, these outputs ensure total isolation between the internalcircuits of the trip unit and the circuits wired by the user.Communications option (COM)This option transmits data to Digipact distribution monitoring and control modules.Transmitted data:b settingsb phase and neutral currents (rms values)b highest current of the three phasesb overload-condition alarmb cause of tripping (overload, short-circuit, etc.).56