The code does not require tripping the ground fault within a specified time frame for a high resistance ground fault. In fact one of the main advantages is that you can continue to operate on a ground fault (similar to ungrounded systems) but that the ground is easier to locate and the...
Another great book for Power System Engineers is "Industrial Power System Grounding Design Handbook"
by J.R. Dunki-Jacobs • F.J. Shields • Conrad St. Pierre
http://www.groundingdesignbook.com/index.html
It is really a very very good book to have.
