Fires within Venezuela’s heavily-fortified El Guri hydroelectric complex could have triggered the massive blackout that plunged the nation into darkness last week, according to an analysis of thermal conditions along hundreds of miles of transmission lines by Venezuelan industry experts and U.S.-based researchers. The analysis uses images from NASA’s Suomi satellite and was made available to The Wall Street Journal Thursday night. The experts and researchers involved in the analysis said it offers the most plausible explanation…