An investigation by the California Independent System Operator revealed that there was not enough coordination between the five power system operators impacted by the Sept. 8 outage, which left several million people in Orange and San Diego and Imperial Counties as well as part of Mexico and Arizona without power."There were 23 major events that occurred within an 11-minute time period within five different power grids," said ISO spokeswoman Stephanie McCorkle.The outage began on Sept. 8th at 3:27 p.m. when a worker in Arizona accidentally shorted the Southwest Powerlink, which feeds power to Imperial and San Diego Counties.To compensate for the loss, Imperial County started pulling power from the north, which shut down a line when it overloaded. Then, automated systems began pulling power from the San Diego area. At the same time, a power plant in Mexicali shut down and forced Baja, Mexico to pull power from the San Diego area as well.Since San Diego was losing power to the east, it started pulling power from Orange County lines. When those lines overloaded, they shut down too."The powerlink from the north, coming through San Onofre and the local generation by itself is enough to supply San Diego but it's not near enough to supply San Diego and Imperial County," said San Diego State University professor Murray Jennex.Jennex said there should have been a barrier in place to prevent Imperial County from tapping into San Diego's power.There was no barrier or if there was, it was not working, so the entire area went black. The entire sequence of events took less than 11 minutes."What is not known at this point is why it occurred," said McCorkle.McCorkle said there are five different power operators that were impacted by the power outage. She admitted the cooperation and communication between the five needs to be improved.The ISO said it could take months before it has any results from its investigation.