In unearthed networks or IT systems - as described in DIN VDE 0100-410 and IEC 60364-4-41 in section 411 - an initial fault does not lead to the automatic shutdown of the power supply and thus to the failure of the entire system. Instead, IT systems can continue to operate in a controlled manner and faults can be rectified at a suitable later point in time. The basis for this are insulation monitoring systems that monitor the insulation resistance and report when it falls below a certain value. However, as the subsequent localization of the insulation fault can be time-consuming and costly, especially in complex system components and widely distributed power supply systems, insulation fault location devices are available in accordance with the product standard DIN EN 61557-9 (IEC 61557-9), which automatically search for insulation faults during operation and display the faulty outgoing circuit.

The insulation monitoring device 'Isometer iso685D-P' from Bender is suitable for systems with insulation fault location. An integrated locating current generator generates a limited locating current to earth when an insulation fault occurs. This locating current is variably adjustable. The insulation fault locator 'EDS44x' can be used to assign this locating current to a faulty load via measuring current transformers. An automatic bus scan to detect the connected 'EDS44x' and individual text input for the alarm messages make the insulation monitoring device easy for personnel to operate. Thanks to its small housing width and compact design, the 'EDS44x' is particularly suitable for installation in switch cabinets where space is at a premium.

The insulation fault locator is connected via plug-in terminals, which are optionally available as screw or spring terminals. Its measuring technology is based on that of the 'EDS460' and the 'EDS195P', but has been optimized. The device series basically comprises four variants: 'EDS440-S' and 'EDS440-L' for use in main circuits with a response value for the generated test current of 2 to 10 mA as well as 'EDS441-S' and 'EDS441-L' for use in control circuits with a response value for the generated test current of 0.2 to 1 mA.