This occurs when the grid has failed and the "neighborhood" that the Trace SW inverter is powering requires the same amount of power that the inverter can supply. This balanced condition is often called "islanding". The islanding detection circuit checks the grid condition on each cycle. The inverter watches the utility grid and waits for it to rise a couple of volts before it begins to invert again. This is done on each cycle when SELL mode is activated. Typically, disconnection is achieved in a few cycles after the utility has failed. If a large electric motor is connected, it may provide enough generator capacity that the inverter thinks the grid is still connected. This can fool this protective system. Two additional protective systems are provided to then handle this condition over/under frequency and over/under voltage detection.
This occurs when the grid power fails or is shut off for service and a grid tied inverter continues providing power to the grid, to power an "island" of local homes that are separated from the rest of the grid. This essentially theoretical situation would occur if the neighborhood's loads were within the inverter's output capacity. UL listed grid-tie inverters will disconnect from the grid in this situation in milliseconds,so as to avoid powering a local section of the grid that was purposefully shut down by utility personnel for service. G,H I,J K,L N,O P,Q U,V W,X Y,Z Page 1 This Page Page 3