Enroute LHR - VIE, all three engine generators tripped off*.
When this occurs, all three N3 gauges very briefly decrease below 51% (unless a service bulletin has been completed, to prevent this power interruption), thus sending a signal to the RAT that all engines have flamed out, and therefore the RAT would be needed to supply hydraulic system B with pressure/flow.
Only applicable with those aircraft equipped with -22B engines.
In this instance, the RAT was left extended until RTB, where it was restowed with a new squib.
*Reason for engine generator problems....a fat fingered Flight Engineer.
