The insulation monitoring device HIG91/QL produced by HAKEL for the ISOLGUARD series is designed for monitoring the insulation status of single-phase ungrounded IT power supply systems, are designed and operated according to standards IEC 61010-1:2010, EN 50522, IEC 61936-1:2010, IEC 61557-8:2007.

Device enables monitoring of single-phase IT power supplies systems up to the maximum operating voltage 275V AC, eventually 3x275V AC. If the insulation status monitoring of a single-phase IT power supply system with higher operating voltage is required, it is necessary to create an artificial centre using TL500 inductors produced by HAKEL. Such a created centre is connected to the terminal of insulation monitoring device HIG91/QL.

The insulation monitoring device enables to display the numeric value of the measured insulation resistance, than there are buttons for setting module parameters and signalling LED diodes for displaying the status of monitored power supply system and of the device.

HIG91/485/QL can communicate with the master computer via industrial RS485 bus with the protocol based on the PROFIBUS protocol.

Inbuilt signalling relay with switching contact enables alarm signalling for two independently set values of critical insulation resistance. The device has an optional alarm memory function with the option to terminate the alarm using the button on the insulation monitoring device. Local and remote testing of the insulation monitoring device function can be done.

Basic characteristics

  • Insulation monitoring device for AC systems with 0 to 275 V voltage without additional devices, for greater voltages additional inductor is needed
  • Display of the measured insulation resistance Risol in the range 1 kΩ to 90 kΩ
  • Insulating resistance status signalling relay equipped with switching contact
  • Connection to RS485 bus for version 485, insulation strength 2500 Vrms against the internal circuits and network circuits
  • Optional memory of the invoked alarm with possibility to unlock by push-button on the device or remote button
  • Option to set monitored insulation resistance value Rcrit using the display and push-buttons in the range 1 kΩ to 90 kΩ
  • Adjustable hysteresis of the insulation resistance limit value in the range from 0 to 100 % using the display and push-buttons
  • Adjustable delay in signalling relay response tON in the range from 0 to 60 seconds
  • Access to the device parameter setting can be locked, unlocking by a push-button combination
  • Separate supply voltage also allows to monitor IT power supply systems, which are not under voltage
  • 2M (36 mm) module width for assembling on DIN rail 35
Dimension drawing
Dimension drawing
Installation diagram
Installation diagram
Supply voltage range Us 90 ÷ 265 V AC (47 ÷ 440 Hz) or 90 ÷ 370 V DC
Maximum IT power supply system operating voltage (without external inductor) Un 275 V AC
Power consumption P max. 5 VA
Measuring voltage Um 12 V DC
Measuring current Im < 0,6 mA
Internal resistance of the measuring input Zi > 2 MΩ
Displayed value’s range Risol 0.1 kΩ ÷ 90 kΩ
Measurement accuracy 5 kΩ … 10 kΩ 2 kΩ
Measurement accuracy 10 kΩ … 900 kΩ ± 10%
Critical insulation resistence Rcrit adjustable 0.1 kΩ až 90 kΩ
Insulation resistance hysteresis Rhyst adjustable 0 ÷ +100% Rcrit
Delay in response of signalling tON adjustable 0 ÷ 60 sec.
Signalling relay 1/ Signalling potential-free switching contact / Electric strength to the internal circuits and supply circuits 250 V AC / 1A / 3750 Vef / 3750 Vef
General data
Degree of protection according to IEC 60529 IP20
Weight m 160 g
Method of assembly DIN rail 35
Recommended section of the connected conductors S 1 mm2
Operating conditions
Operating temperature ϑ -10°C ÷ +60°C
Relative humidity 28 g H2O /kg suchého vzduchu
Atmospheric pressure 86 ÷ 106 kPa
Operating position any
External magnetic and electric field max. 400A/m
Overvoltage category / testing voltage III, according to IEC 60664-1:2007
Pollution degree 2, according to IEC 60664-1:2007
Operational mode permanent
Article number 70 911QL
2D model (728.74 KB) for registered only
3D model (469.2 KB) for registered only