Backing up what David said: it was a 180MVAR 230kV reactor.
They are rather hard to protect as you can't apply diff. protection to them. It is on a LBS sharing a breaker with two switched cap banks. No reports of even a noticeable dip so the breaker must have opened quick.
I'm surprised the reactor was live mid-day. Keeler is the Westmost 500kV sub in the Portland area with power going through other nearby subs first where there are loading reactors on the long lines. The problem at Keeler is usually not enough VARs.
What was the cause of this transformer fire? I had seen that any internal fault,however severe cannot start a fire. It is always a bushing failure,tap changer burst where an arc occurs in presence of oxygen. The most tragic case that come to my mind occurred in my town. In the main street, a pole mounted distribution transformer was leaking. Everyone took it lightly. It was a free breathing transformer with conservator and breather.Once the oil level went below the winding top,insulation broke down in air, paper/oil caught fire and the tank exploded with burning oil splashing down.The same second,an engineer from nearby shipyard was going near the transformer in a two wheeler. The oil and tank fell over him,resulting in his death.
My comments are limited to large transformers and reactors. I have seen some tank explosions from internal fault,but without fire.May be the arc and gases getting cooled by the time it comes out.But this may not be true for cable boxes where the fault starts from the cable terminations.
Many years back came across failures in two 50 MVA 3 phase 420 kV shunt Reactors. It was failure at middle of winding height between phases. Line was at the middle of winding. Heavy gas formation and tank bulging and rupture,but no fire.
Best tutorial on the subject- CIGRE Brochure No.537-2013 Guide for transfoirmer Fire Safety Practices by WG A2.33 (139 pages)
