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Safety Features
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Safety Features
Anti-Island Protection
A condition referred to as "Islanding" occurs when a distributed generation source
(such as the PV225S Grid-tied Photovoltaic Inverter) continues to energize a
portion of the utility grid after the utility experiences an interruption in service.
This type of condition may compromise personnel safety, restoration of service,
and equipment reliability.
The PV225S employs a method for detecting the islanding condition using a
Phase-Shift-Loop (PSL). This method is implemented in the CCU2 to prevent
islanding of the PV225S. The CCU2 continuously makes minor adjustments to
the power factor phase angle above and below unity. In the event of a utility
interruption or outage, these adjustments destabilize the feedback between the
inverter and the remaining load, resulting in an over/under frequency or voltage
condition.
Upon detection of such a condition, the PV225S then performs an immediate
orderly shutdown and opens both the main AC and DC contactors. The fault
condition will remain latched until the utility voltage and frequency have returned
to normal for at least 5 minutes.
This method has been extensively tested and proven to exceed the requirements of
IEEE-929 (Recommended Practices for Utility Interface of Photovoltaic [PV]
Systems) and UL-1741 (Static Inverters and Converters for use in Independent
Power Systems).
PV Ground Fault Detection
The PV225S is equipped with a ground fault detection circuit by means of a
Hall-effect current transducer (CT8). This circuit is active when the PV array is
properly grounded. In the event of a ground fault exceeding 10 amps DC, the
PV225S will execute an immediate orderly shutdown, open both the main AC and
DC contactors, and report a ground fault on the LCD of the UFCU. The PV225S
will remain faulted until the ground fault is remedied and the advisory is cleared at
the operator interface.
For additional information, see Chapter 4, “Troubleshooting”.
DC Over-voltage Detection
In the event of DC voltage greater than 600 Vdc, the PV225S will execute an
orderly shutdown and will report a fault to the operator interface. If DC voltage
remains greater than 600 Vdc, the PV225S may be irreparably damaged.
See Chapter 4, “Troubleshooting” for further information on this fault condition.