Investigators in Florida are still looking into the causes of the Feb. 26 power outage in south Florida. But Florida Power & Light Co., Juno Beach, Fla., the utility where it originated, says its preliminary findings point to “human error.” A field engineer diagnosing a switch at FPL’s Flagami substation in west Miami disabled two levels of relay protection without authorization, says a utility spokesman. When the engineer asked an off-site dispatcher to test the equipment, the test triggered a series of faults, causing a voltage drop on the grid. Protective relays tripped a total of 3,400 MW of powerplant capacity off-line.