Patent ID: 7342758
Filing Date: 2008-03-11
Classification: H02J

Abstract:
1. A method for detecting stand-alone operation of a distributed generating system, said distributed generating system having a generating source connected in shunt with an independent power distribution system via a first branch breaker, said method comprising the steps of: a. reading a voltage signal or a frequency signal on said independent power distribution system; b. performing a wavelet transformation to the signal read in step a to form high and low frequency components of the transformed signal, a time versus high-frequency component window for the high frequency component and a time versus low-frequency component window for the low frequency component for detecting a perturbation in a transient time domain of said read signal; c. determining whether an absolute amplitude value of the high-frequency component is greater than an amplitude threshold value and whether the amplitude threshold value is exceeded for a duration longer than a time threshold value and deciding that a stand-alone operation occurs if both answers are yes; and d. generating an alarm signal and sending said alarm signal to said first branch breaker to drive said first branch breaker to release a parallel connection between said generating source and said power distribution system.