 The problems started with a fault in an Arizona Public Service substation near Yuma, Arizona that caused widespread problems in western Arizona and eastern California.In time, SDG&E's system was drawing from the San Onofre Nuclear Generating Station (SONGS) considerably more power than was being produced, pulling it from Los Angeles, and a "safety net" system cut it off from the nuclear plant.Once this happened, SDG&E's system rapidly collapsed due to mismatch of generation and load, unable to drop load faster than generation was lost.