2.7 Anti-Islanding Detection
The CPS SCA36/50/60KTL-DO/US-480 3-Phase String Inverters include
Unintentional Islanding detection as required by UL 1741/IEEE 1547. The
inverter will continuously make bi-directional perturbations to the frequency
of the output current by injecting a small amount of reactive power to detect
a possible islanding condition. If the grid is stable, these small perturbations
will have negligible effects on the system voltage frequency. However, in an
islanded condition the changes in reactive power will force the frequency of
the system voltage to deviate significantly, which will trigger the inverter to
cease operation and disconnect from the grid.
2.8 DC Ground Fault Protection
The inverters include residual current detection GFCI as part of the DC ground
fault detection method required by UL 1741. If there is a ground fault in the
PV array, the ground fault detection circuitry will detect leakage current,
trigger an alarm, and the inverter will cease operation. See Chapter 5 for
further information regarding GFCI Static and Dynamic trip thresholds and
operation.
2.9 Surge Suppression
Table 2-1 Standard Waveform Peak Values
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