Electrical fag here. What happens when you have a high voltage electrical short is the actual air itself starts to burn, a plasma fire. Totally intense and extreme high temperatures. Also, as this was a substation, you probably had arcing between the conductors and insulators and it took time to break the arcs. Would account for the blue skies.
Let us consider the size of the substation, the voltage/current and how long it takes to don an arc flash suit, grab fiberglass poles, get out to the field, then perform the work….. 4 minutes is rather good….