I havn't personally ever seen a IT system. They need special measuring devices to keep track of faults. This device is installed between neutral and earth.
What exactly do you want me to describe? How a IT system works or a schema/plan?
Well, according to my knowledge, the neutral of the transfo is Isolated from earth, (that's what the I stands for) . The mass of appliances are connected to earth. The fault of first fase is of no danger but has to be repaired before that a fault of second fase occurs, so that there is no short circuit.
In hospitals they also have a special backup generator.
This system is also used in industrial installations which have grave implications if machines have to be stopped. e.g. The chemical sector...
Here is a link to more info, but it's in French: http://220.127.116.11/fr_pdf_princ.htm?BTKP225