Ungrounded, unearthed, “floating” or IT (Isolé-terré or Isolated Terra)
are all terms used to describe power systems that have no intentional conductive connection to earth’s or chassis ground. The main advantage of the IT power system is that a single “short” will not disable its ability to continue delivering power. It is essential for the safety of such systems to continuously monitor their isolation state as
even a single fault can generate hazards to personnel in contact with these systems. “Isolation monitors” are the devices required by several international standards to perform this function. This paper reviews the potential hazards in an IT system and the most common methods employed today for detection of isolation faults. It identifies safety related shortcomings inherent to each method and illustrates some of the unique features of Sendyne’s SIM100 designed to overcome them.

Keep Reading