Thank you for your concern. I had a sync check relay as part of the synchroscope in circuit at the time, but as it only looks a single phase on each of the grid and generator, there is no way for it to check phase rotation. That part is the responsibility of the commissioning engineer (me) and I'd already done that the previous day and run tests, but then someone, unkown to me, had swapped an extension cable with one that had the phases crossed over!Yikes! You're lucky nobody was hurt. The whole thing could have melted and flown apart. There are sync check relays to prevent mistakes, but those relays too can be wired incorrectly.
I am not quite sure how the whole thing could have melted in the 20 ms or so that the breaker took to trip, but the inertia could have done some damage. As I said, luckily it was a small system which has significant resistance and reactance in both machines. It is that which prevented a more serious incident. Incorrect phasing / synchronisation of larger machines has resulted in the generator ripping free of it's mountings and bending it's shaft through 90 degrees. I guess it also flung itself a fair distance too, but thankfully I have never been present!