Patent ID: 7825542

Claim:
An electrical power supply apparatus, comprising: at least one electrical load connection for connection of an electrical load to the apparatus; a first electrical power supply connection to be connected to a mains power supply; an autonomous electrical power supply; a second electrical power supply connection connected to said autonomous electrical power supply; and a switching apparatus for selectively switching the connection of the at least one electrical load connection between said first electrical power supply connection for mains operation and said second electrical power supply connection for island operation; and an evaluation and control apparatus connected to said at least one electrical load connection and configured to identify the island operation of the electrical power supply apparatus and to switch the at least one electrical load connection on or off, at least during the island operation, in dependence on given preset criteria; said autonomous electrical power supply configured, upon a start and/or upon a termination of island operation, to send a specific signal to said at least one evaluation and control apparatus; said at least one evaluation and control apparatus configured to identify the island operation of the power supply apparatus on a basis of the specific signal sent by said autonomous electrical power supply; and the specific signal sent by said autonomous electrical power supply being a brief discrepancy in a voltage and/or a frequency available at said at least one electrical load connection.