https://www.osha.gov/pls/imis/accidentsearch.accident_detail?id=201127594
Could a ballast failure really cause 700 volts?
The thing is, you need such voltage for the lamp ignition, there is no way around that.
Mainly with old US IS magnetic ballast it is not only in failure mode, but also during normal operation when there is lamp missing. It is just the ballast OCV.
There should be a cutout contact/switch at the cold end tube socket (to disconnect the ballast when there is no tube inserted), but when the lamp is inserted, the voltage is there. So if there was some dirt on the tube causing leakage from the hot contact to the tube surface or the tube or sockets are damaged and so the live wiring gets exposed, you may easily get shocked by this.
The modern electronic ballasts deliver the ignition for just in short time (a second or so), either once after power ON or repeating with few second gap, so when touched limit the exposure and give breaks to allow muscles to release the grip, greatly reducing the risk of health consequences. Plus the voltage is of high frequency, which is of less risk for severe shock injury, it becomes more of a burn than electrocution risk.
There indeed the failure of the ignition sequecer may cause the high voltage to be present for longer time than designed so become dangerous. But usually the ballast circuit is stressed by that state quite a lot, so it physically would not survive that state for too long.
So to me it was not the ballast failure, but either the tube or socket failure, together with inadequate work practices (touching the dangerous areas without checking their safety, PPE,...) then led to the deadly accident...
