“Passive” insulation monitoring devices were considered state-of-the-art until well into the 20th century. These devices, however, only were used for “checking the insulation” of unearthed power supply systems which until the seventies were called “protective conductor systems”. For a long time it was common practice to use these devices in the mining sector.

The breakthrough to “active” insulation monitoring came in 1939 with the publication of a patent for “Insulation monitoring and earth fault display devices for three-phase installations” by Dipl.-Ing Walther Bender. Since then, Walther Bender has been seen as the “father of active insulation monitoring”.

The technology of insulation monitoring devices also developed quickly. Until the 1960s, the technology used was almost exclusively superimposed measuring voltage. But it was not only the measurement technology for insulation monitoring devices which has changed, the nature of the IT systems and applications had also been subject to huge changes. Many new applications have been added. The inverter technology brought attention to possible three-phase faults, i.e. insulation faults behind rectifier elements. A device technology was then developed which was also able to detect device faults behind rectifiers. This was followed by pulse overlay technology, which was eventually superseded by the “pulse superimposition technology”. The EMC wiring frequently required necessitates new measurement technologies for insulation monitoring devices with high system leakage capacitances. PV systems also need to be able to cope with leakage capacitances into the µF range.

The development of Bender insulation monitoring device always followed these new requirements, and continues to do so. In the future, too, the company will face new challenges with innovation and know-how and continue to lead the field in terms of insulation monitoring.


Bender UK

Low Mill Business Park
LA12 9EE

For further information or to enquire online visit www.bender-uk.com/contact