Insulation status monitoring of low voltage direct current IT power supply system

We also encounter direct current voltage distribution in industrial applications. When it comes to the distribution of security or communication technology, or the distribution of low voltage for the supply of e.g., PLC automats, we most often encounter a voltage level of 24 V DC. Industrial sources generating this voltage are usually realized as galvanically isolated from the input voltage, and the output voltage is also separated from the ground. As a result, each such source in principle creates an isolated system at its output, which can be monitored by an insulation monitoring device.

HAKEL company has developed HIG**VDC product line for low DC voltage monitoring. Speciality of these insulation monitors is that they monitor separately the insulation resistance in the positive pole of the IT power supply system against the ground and separately in the negative pole against the ground. Devices therefore provide two numerical data on the two insulation resistances. This is especially useful when looking for insulation breakthrough, where the service team can only inspect a specific half of the DC voltage distribution.

We distinguish two basic product lines, namely HIG**VDC and HIG**VDC-L. These two series differ in the measured range of insulation resistance. HIG**VDC series monitors insulation resistance in the range of 5 to 990 kΩ, HIG**VDC-L series monitors insulation resistance in the range of 2 to 550 kΩ. If the measured resistance value is less than the measured range, the status "<5" respectively "<2" kΩ is signalled.

HIG**VDC device are intended to monitor voltage of 12, 24, 48 and 110 V DC, are supplied from the measured system and communication with master system is possible by using RS485 bus or relay outputs. Devices can be connected to the HAKEL MDS-D supervision panel.

Devices meet the temperature class OT3 (according to EN 50155), i.e., surroundings operating temperature from -25 °C to 70 °C. If a higher temperature class is required, HIG99 device, which meets the OT4 temperature class (from -40 °C), can be used.