Patent ID: 8346402

Claim:
An intelligent electronic device for detecting an islanding condition in an electrical power delivery system, comprising: an input for receiving a signal of the electrical power delivery system; a processing unit configured to detect an islanding condition based on the signal, the processing unit being operable to determine from the signal a frequency deviation of electrical power delivery system from nominal frequency and a rate-of-change of frequency of the electrical power delivery system, the frequency deviation and the rate-of-change of frequency defining an operating point of the electrical power delivery system, the processing unit being operable to compare the operating point to a protection characteristic of the intelligent electronic device, wherein the processing unit is operable to issue a command based upon the comparison; and an output in communication with the processing unit to communicate the command from the processing unit; wherein the protection characteristic comprises a trip region that includes a frequency deviation axis and a rate-of-change of frequency axis.