In a widespread blackout, system restoration must begin from pre-selected generating units with the ability to start themselves. Units, which participate in this ancillary service, must have the ability to provide at least three sequential black starts, within two hours, to allow for possible tripping of the transmission or distribution system during the re-instatement. Unwanted tripping of the black-start generators caused by inrush current during energization of the transformers, can misspend these sequential black-starts. This paper suggests a new start-up method to reduce such unwanted tripping. Almost all generators are equipped with under voltage relays, which operate when the voltage reaches under 95 percent of nominal value. It is shown in this paper, if the generator is connected to the transformer with %95 of its nominal voltage, inrush current will be reduced considerably. Simulations done by MATLAB software, confirm the capability and usefulness of the proposed method.

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