Insulation monitoring device

How does an insulation monitoring device work and where do I have to use it? What does the device protect against and what advantages does it offer me? Read here why the correct insulation of an electrical system is an essential prerequisite for its safe operation. Protect yourself and your system with high-quality measuring devices and reliable testing technology from the eibabo® online shop.

The History of Insulation Monitoring Devices

The first insulation monitoring device was invented by Walther Hans Bender in Frankfurt/Oder in 1939 and a patent was applied for. It was a device for three-phase systems in brown coal mining. In 1952 the 'Isometer' was protected as a trademark and has belonged to Bender GmbH & Co. KG ever since.

Source: eibabo®, Dold IL5880.12 insulation monitor Image: Dold IL5880.12 insulation monitor

How does an insulation monitoring device work?

An insulation monitoring device is also referred to as a ground fault monitoring device. Connect this between your active power lines and the earth line. With continuous insulation monitoring, you can discover weak points in the insulation of your electrical systems. These can be caused, among other things, by moisture or by age-related fatigue of the material. You want to detect a problem like this before voltage breakdown occurs. Voltage breakdown will damage the insulator and cause sparks or arcing, which can lead to power failures, fires, property damage, and personal injury.

The device sends a measuring voltage to your system and monitors it. If there is a ground fault, the measuring circuit between the mains line and the ground is closed. A measuring current proportional to the earth fault thus occurs. A voltage drop occurs at the measuring resistor of the device. Conversely, this means that the insulation resistance of the system is reduced. The insulation monitor registers the change and evaluates it. It is not only the resistance itself that is important, but also its course over time. In the case of undamaged insulation, the insulation resistance asymptotically approaches a certain reference value.

term asymptote

A value behaves asymptotically if, over time, it approaches a reference value without ever reaching it.

If the insulation resistance falls below the reference value, this is an indication of the increase in the conductivity of the insulator. From this it can be concluded that the insulator has changed chemically due to external influences or that its material is gradually enriched with decomposition substances. If a critical point is reached, the device sends a message. This allows you to recognize the deterioration of the technical condition of the insulation at an early stage and to take the appropriate steps for repair or maintenance in good time.

Where is the use of an insulation monitoring device required?

The measurement of the insulation resistance is used in local low-voltage networks without an operationally grounded star point (so-called IT power supplies).

For explanation

Basically, low-voltage systems are divided into TN systems, TT systems and IT systems. The main difference lies in the way of grounding. While residual current is used for monitoring in TN systems, insulation monitoring devices are used in IT systems.

Modern insulation monitoring devices have a history memory and record the insulation resistance measurements. The data can be called up later and serve as suitable monitoring evidence during controls.

What are the advantages of insulation monitoring devices?

With insulation monitoring devices, you continuously monitor safety-relevant circuits for residual currents and residual currents. This results in a number of advantages in daily use:

Measurement without switching off ongoing operations
Reducing the risk of failure and increasing the availability of monitored electrical systems
Reduction of electromagnetic interference
Reducing the risk of fire
Saving of time-consuming and expensive maintenance and repairs

You also prevent the safety of people and machines and thus avoid accidents, property damage and personal injury.

Which manufacturers offer high-quality and reliable insulation monitoring devices?

In the eibabo® technology store you only get quality goods from well-known manufacturers. These include ABB, Bender, Dold, Eaton, Pilz, Schneider Electric and Siemens. As a leading specialist center for electrical installations, lighting and smart home, we offer a huge selection as well as: