Eaton Power Xpert Solar 1500 User Manua

TroubleshootingPower Xpert Solar 1500/1670 kW Inverter MN141001EN—October 2014 www.eaton.com 57During normal operation while exporting power (current) tothe grid, should a PV ground fault occur, either CB3 will trip(open) or the fuse clear (based upon actual fault). In eithercase, the inverter will stop, opening contactors K8/K9/K10,CB1, and disconnects DS1-3. This will isolate the inverterstacks from the fault and annunciate the required GroundFault Error Message, DC Ground on the HMI and Modbus.Once fuse F3 and/or CB3 is tripped, the GFDI circuitcontinues to maintain system safety through the 4000 OhmRG1-4 resistors. With either/both CB3-open or F3-cleared,the resulting single-point-ground’s open-circuit will allow asmall electric current (Voc/4000 = X mA | 1000/4000 =250 mA) to trickle through resistors RG1-4 to the PV-negativeconductors grounded bus at the inverter’s re-combiner.Understanding Kirchhoff’s Voltage Law (KVL), each RG1resistor will drop (X mA x 1000 = XV | 250 mA x 1000 =250 V) volts, in essence the entire Voc potential (disregardingPV-system conductor resistance). This will minimize theshock-potential between equipment ground andgrounded-PV conductors. Note: When diagnosing a PVground fault, if voltage measured across RG1-4 is lower thanthe expected string-voltage (Voc), expect a ground-fault alongthe string(s) at the relative voltage corresponding to thenumber of modules (Voc). Furthermore, individual Module Iscis equal to the “string Isc” due to the series-connection ofthe modules per string. Only at the source-combiner, poststring fuses, is the module or string Isc additive (increased).Critical to an effective GFDI is the PV grounding electrodesystem, and its bonding to the inverter GET (i.e., GET bus-1).The PV system must always be built with a PV GroundingElectrode System, bonded to the inverter’s GET. Theminimum bonding conductor size is 3/0 as per UL1741 forthe 1500/1670 kW inverters.DANGER of Electric Shock HazardWhen a Ground-Fault is present.WARNING!When a Ground-Fault is present.NOTICE!IF A GROUND FAULT IS INDICATED,NORMALLY GROUNDED CONDUCTORSMAY BE UNGROUNDED AND ENERGIZED.Ground Fault Troubleshooting ChecksFigure 29 shows the GFDI connections. The circuit iscomprised of 3 components:1. Ground Fault Device (sensor) GFD1 set to 5 A.2. Fuse—opens the ground path during a ground fault.● Fuse has a trip-indicator, evoking the holder’smicroswitch change-state.● Operates even when AC power is removed from theinverter3. Circuit-breaker—shunt tripped by the CS1 or fuse-holdermicroswitch during a fault.● Operates when the inverter is ON (control powermust be present).The fault-interrupter design is a redundancy system, as eitherCB3 or F3 (both are in series connection) can react to open/operate/function during a ground fault event.Step 1: Verify the GFDI tripped CB3 or cleared 5 A F3If tripped or cleared; determine if the fault is a positive ornegative ground fault.Measure the DC voltage across resistors RG1-4, looking for a“negative” value if the DMM ground-lead is placed on GET.● GET Bus-1 to Grounded-PV-Conductor busIf voltage is present, there is a faulted PV positive conductorin the PV-array system. Typical damage is found innon-protected module string-conductors in-route to thesource-combiners, or source-combiner output circuits faultedinside conduit in-route to the PV-Disconnects or inverter.● Once the fault is repaired, install a new 5 A F3 fuse ifdamaged● (check fuse for an open circuit: ∞ Ohms)● Re-set (close) CB3● Re-cycle inverter power● Turn-on the inverterIf voltage is NOT present across resistors RG1-4, suspecta negative PV ground fault. Typical damage is found innon-protected module string-conductors in-route to thesource-combiners, or source-combiner output circuits faultedinside conduit in-route to the PV-Disconnects or inverter …circumventing the fundamental single-point-ground of agrounded PV system.● Once the fault is repaired, install a new 5 A F3 fuse ifdamaged● (check fuse for an open circuit: ∞ Ohms)● Re-set (close) CB3● Re-cycle inverter power● Turn-on the inverter