Method for detecting formation of a separate system

A method for controlling a generation unit that feeds an electrical supply network using one or more converters or inverters, comprising:

• determining whether a first-degree separate network fault is present by:
• detecting current control deviation;
• and
• determining whether the detected current control deviation deviates from a predetermined reference range, wherein determining whether the detected current control deviation deviates from the predetermined reference range includes:
• identifying a checking variable or checking function from the current control deviation;
• and
• comparing the checking variable or checking function with at least one reference variable or reference function;
• if the first-degree separate network fault is present, determining whether a second-degree separate network fault is present;
• and
• identifying network isolation in the case of which a separate network is produced, the separate network being separated from the electrical supply network and the generation unit being connected to the separate network.

A generation unit, comprising:

• one or more converters or inverters configured to feed electrical power into an electrical supply network;
• an installation controller configured to detect network isolation or a formation of a separate network;
• a feed controller configured to control feeding the electrical power at least by current control;
• a detection device configured to detect current control deviation;
• and
• a checking device configured to check whether the detected current control deviation deviates from a predetermined reference range by at least:
• identifying a checking variable or checking function from the current control deviation;
• and
• comparing the checking variable or checking function with at least one reference variable or reference function,
• wherein the installation controller is configured to, if the checking device detects the deviation from the predetermined reference range, identify the network isolation in the case of which the separate network is formed, the separate network being separated from the electrical supply network and the generation unit being connected to the separate network.