I work in the maintenance team of an industrial site, which is using IT earthing system on most of the electrical installation. My experience is that this IT earthing scheme is difficult to maintain, because whenever there is a fault, it takes us a very long time to locate this fault. We are using clamp-on meters which are difficult to use when you have to clamp on several rigid cables. As there are many circuits to check the fault localization may take us several hours. I find that aspect a major drawback of the IT earthing system.