C-H, here is a fairly recent paper on US practices.
http://www.neiengineering.com/papers/paper1JN.pdf The general consensus seems to be against ungrounded systems, while using high-resistance-grounded systems to limit resonant- and transient-overvoltage incidents. The idea is to alarm on first ø-g fault, so an “orderly shutdown” can proceed—limiting production loss. If an effort isn’t made to repair soon after the first fault, then a second ø-g fault can easily take out two overcurrent devices—and two pieces of equipment.
