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According to the website:

A ground fault on the Low Voltage side of this substation creates an arcing fault that behaves like an uncontrollable welding torch from Hell, chewing up everything in its path. Unfortunately, protection hardware fails to open the High Voltage side or is unable to sense the presence of the fault. Excessive current eventually causes the windings on the substation's power transformer to overheat, severely cooking its innards and causing the mineral oil inside to begin boiling. In a vain attempt to prevent the transformer's tank from exploding, pressure release valves or a failing tank gasket vents clouds of superheated oil vapor which then ignite and explode in a ball of flame. Finally, a phase to phase short circuit occurs, perhaps caused by a flashover within the flames or a heat induced fault within the transformer. This causes a high side expulsion fuse to blow with a flash and a resounding BANG, finally killing power to the substation.
However, by this time, the weakened transformer's tank fails, and it dumps hundreds of gallons of flaming mineral oil onto the already devastated substation. Local firefighters can only watch from a distance since, with the substation energized, there's no way to safely fight the fire, and the substation is a total loss. As linemen often say, "Firemen don't mess with their wires, and linemen don't mess with their fires". A very sobering look at the explosive power lurking within that quietly humming substation in your neighborhood...
NOTE: Based on input from a number of linemen, this is believed to be the Ives Dairy Substation located near San Simeon Way and Biscayne Boulevard in Miami, Florida. This incident may have occurred in 2000 or 2001, and the footage may have been taken by local emergency responders. There were apparently a sequence of faults that led to this spectacular failure. Initially, the substation's protective relays became disabled when a small fuse feeding the protective control circuits blew. This would normally trigger an alarm to the dispatcher. However, a defective fuse holder prevented an alarm from being sent, so the power company was unaware that the substation was unprotected. Later on, a low voltage side capacitor bank failed, creating an arcing fault that could no longer be cleared due since protection hardware was inoperable. The ongoing, undetected arcing fault ultimately leads to the total destruction of the substation.