Patent ID: 7877169

Claim:
A method for controlling the interconnection of an auxiliary AC generator with an electrical distribution system in an intelligent electronic device for monitoring electrical parameters of the electrical distribution system, the method comprising: determining a frequency of the auxiliary AC generator by: (a) detecting a rising edge zero-crossing of a reference line voltage of the electrical distribution system in two consecutive waveform cycles; (b) determining a time value associated with the detected rising edge zero-crossings in the two consecutive waveform cycles; and (c) computing a time difference value between the respective time values associated with the detected rising edge zero-crossings in the two consecutive waveform cycles; adjusting the frequency of the auxiliary AC generator until a phase angle difference between the auxiliary AC generator frequency and a frequency of a corresponding phase of the electrical distribution system is determined to be within a defined tolerance; and closing a set of interconnecting contactors to connect the auxiliary AC generator to the electrical distribution system when said phase angle difference is determined to be within the defined tolerance.