Ungrounded system: Application examples

Where to use an IT system?

he need for a continuous power supply is constantly increasing – in hospitals, on ships, in manufacturing plants, process plants, data centres, control rooms, airports, railway systems, transport systems, heating systems, cooling systems, etc. In tunnels and below ground, lighting and ventilation must work faultlessly; submarine crews as well as astronauts in space equally depend on a reliable power supply.

IT systems with insulation monitoring represent the ideal technical solution in these cases. For this reason, IT systems are used in particularly critical applications like control circuits, medical locations or mobile power generators. However, by now they can also be found in newer applications, such as electric vehicles, photovoltaic systems or industrial plants with variable-speed drives.

In combination with innovative insulation monitoring technology, the IT system contributes to protecting people and installations against the hazards of electrical current by eliminating critical system and operating conditions or by detecting and signalling them at an early stage. Besides the increased safety, this helps to minimise maintenance and downtime costs. In addition, operators are able to evaluate system data according to their requirements and use it to improve the condition of the installation. Due to the various economic and technical advantages, an unearthed system with high-performance insulation monitoring is almost always profitable in rather complex installations.

For more detailed application possibilities, please visit our Solutions area!

Monitoring of a main circuit

Monitoring of a control circuit

Monitoring a disconnected load

Many loads are only switched on in an “emergency” (e.g. fire pumps, slides, all types of heating, etc.). Whilst they are offline, however, moisture or other factors can cause insulation faults in the associated supply cable or on the load itself. When these loads are switched on, the protective device will respond or fires will start, thereby preventing operation.

The insulation monitoring device, also known as the offline monitor, monitors the insulation resistance during offline periods and signals insulation faults immediately. When the load is switched on, insulation measurement based on the K contactor is deactivated. The fault memory is also able to detect transient insulation faults. If it can be assured that all poles on the load will be taken offline, this monitoring can also be used in TN and/or TT systems.

Response value of the insulation monitoring device: The insulation monitoring device must signal insulation faults ≤ 1 MΩ, this is because motors are frequently rendered non-operational at an insulation resistance of ≤ 500 kΩ.

Monitoring of mobile generators

Electrical safety is often difficult to assure on mobile power generators.

  • In very few cases does the ground/environment permit an earthing system to be installed (stones, rubble, rock, asphalt, etc. would have to be penetrated).
  • Time is of the essence, there is not enough time to measure and check the protective measure.
  • The relevant skilled person is lacking.

However, the ability to respond immediately and appropriately is vital in an emergency situation. It is for this reason that mobile power generators feature the protective measure (Protection by electrical separation with insulation monitoring and disconnection) in accordance with IEC 60364-5-51.


Why the IT System is Often the Best Choice for Power Supply Systems of All Types Technical article 3.0 MB EN2019/07/1111.07.2019
High Availability for Reliable Operation in Waste Water Treatment Facilities Technical article 601.8 KB EN2019/05/1313.05.2019
IT System Ensures Electrical Safety at the Munich Airport Technical article 284.0 KB EN2019/05/1313.05.2019
The Stone Age Meets Modern Network Protection Technology Technical article 338.5 KB EN2019/05/1313.05.2019
The Largest Photovoltaic System in Latin America Technical article 447.8 KB EN2019/05/1313.05.2019

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