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2.7 Anti-Islanding Detection
The SCA50KTL-DO/US-480 and SCA60KTL-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
Standard Waveform Peak Values
Surge Category Ring Wave Combination Wave
B 6kV/0.5kA 6kV/3kA
"Standard 1.2/50 μs - 8/20 us Combination Wave"
"Standard 0.5 μs - 100 kHz Ring Wave"
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