The NEC requires all utility interactive inverters to be listed to UL 1741.Please explain the two key requirements of the standard.

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The Answer is The NEC requires all utility-interactive inverters to be listed to UL 1741.PV system designers and installers should be aware of two key requirements of the standard.The first is known as anti- islanding.Utility-interactive inverters are required to automatically turn off when utility power is lost.This prevents an inverter from feeding electricity back into the utility electrical grid, which would be extremely dangerous for utility workers.Remember that the 240 volts produced by an inverter can produce 12,000 volts or more on the primary side of utility transformers if the inverter were allowed to back-feed the utility system.In effect, the utility transformer would be operating
as a step-up transformer.Another important requirement of UL 1741 is for dc ground-fault protection (GFP).Ground faults in PV source circuits (array) do not result in the high fault currents produced by utility electrical services.Photovoltaic modules are a current-limited source.Short- circuit current from a module is slightly higher than normal module output to the inverter, but not enough to open an overcurrent device (fuse or circuit breaker).Ground-fault current will flow through bonded exposed metallic structures and raceways to the inverter and then back to the source (modules).

The NEC Requires All Utility Interactive Inverters to Be Listed