The insulation monitoring device, type ISOLGUARD HIG99, is designed for monitoring the insulation status of single-phase, multiphase and direct ungrounded IT power supply systems. Device is also able to monitor combined IT power supply systems, type AC/DC according to standard IEC 61557-8. HIG99 is mainly designed for use on rail vehicles and industrial systems containing rectifiers, inverters and frequency converters.

Maximum operating voltage of monitored IT power supply system is 1 000 V DC / 710 V AC. Device is directly connected to the monitored IT power supply system, no additional inductor is needed.

This device is also equipped with a blocking function thanks to which it is possible to disconnect HIG99 from the monitored system.

HIG99 monitors two insulation status’s critical levels, it is equipped with signalling diodes for local status of the device and IT power supply system signalization. Local signalization is complemented by a pair of switching relays for IT power supply fault status signalization. It is possible to realize remote signalization using communication module type HIG99 KM by CAN interface with CAN OPEN protocol.

Using the CAN communication module, numerical information on the status and value of the insulation resistance can be read, the device’s settings can be checked and changed or test cycles can be performed.

Only one insulation monitoring device can be connected to the same ungrounded IT power supply system.

HIG99 module complies with standard:

• IEC 61557-8:2014 – Insulation monitoring devices for IT systems
• IEC 61557-1:2007 – Equipment for testing measuring or monitoring of protective measures
• IEC 61010-1:2010 – Safety requirements for electrical equipment for measurement, control and laboratory use
• EN 50155:2017 – Rolling stock – Electronic equipment
• EN 45545-2:2013 – Railway applications – Fire protection on railway vehicles
• EN 50121-3-2:2016 – Railway applications – Electromagnetic compatibility
• EN 50125-1:2014 – Railway applications – Environmental conditions for equipment
• IEC 61373:2010 – Railway applications – Rolling stock equipment – Shock and vibration tests

HIG99 basic characteristics:

• Insulation monitoring device for AC, DC, AC/DC systems with 9 to 1 000 V DC / 710 V AC voltage, direct or with 10 – 440 Hz frequency.
• Device is designed for use on rail vehicles and industrial systems containing rectifiers, inverters and frequency converters.
• Device is powered from an independent 24 V DC power supply.
• Loss of connection indication with the measured power supply system and the ground.
• Automatic internal test for unfunctional device detection.
• Device evaluates two insulation resistance critical limits.
• Two monitored power supply system’s insulation resistance status signalling relays with switching contact for two insulation resistance critical limits.
• Option to start device test by push-button on the module.
• Option to connect communication module, type HIG99 KM, for device’s connection to master bus-bar system.
• Option to set critical values, hysteresis values and other parameters by KM type module.
• HIG99, in connection with any HIG99 KM module, is 9TE (158 mm) wide and is designed for assembling on 35 mm DIN rail.

Recommended connection of HIG99 and HIG99 KM CAN to the monitored It power supply system

HIG99 and HIG99 KM CAN terminals meaning:

• Terminals X1: Used to device’s connection to monitored power supply system.
• Terminals X2: Used to connect connection module to monitoring module.
• Terminals X3: Two potential free relays with switching contact and COM common pole. Serves to forward information about insulation resistance status.
• Terminals X4: Used to connect the connection module to the monitoring module. Furthermore, it is used to supply a low voltage for HIG device and to provide functional and control grounding.
• Terminals X5, X7: Serves to HIG99 and HIG99 KM CAN connection. Other uses are excluded.
• Terminals X6: Galvanicaly separated inputs for device commanding. Used for device test and device’s disconnection and connection from monitored power supply system. The inputs have a common ground potential – terminal E.COM.
• Terminals X8: CAN bus-bar’s output. NC terminals are not used, V+ and SH terminals are not internally connected, they can be used for bus-bar connection.

Installation instructions:

• NC terminals (Not Connected) are not connected, it is forbidden to connect them.
• FE and KE terminals are necessary to connect by separate conductors to PE bridge.
• It is possible to use Rte switch for CAN bus-bar termination.
• Keep linear CAN bus-bar connection, turns cannot be created.
• Install only one cable type along the CAN bus-bar entire length.

Maintenance and service

It is necessary to follow specified conditions for reliable operation, do not expose the device to rough handling, keep it clean and ensure maximum admissible temperature of environment.

Only qualified personnel are allowed to install and set up the device. Only the producer provides repairs of the device. No personnel are needed to operate the insulation monitoring device. Technology service is during the operation informed by local and remote signalization about the monitored power supply.


Dimension drawing
Dimension drawing
Installation diagram
Installation diagram Počet fotek v galerii: 3
Possible type of the monitored IT power supply system AC, DC, AC/DC
Maximum operating voltage of the monitored ungrounded IT power supply system Un 9 ÷ 1 000 V DC / 9 ÷ 710 V AC (10 ÷ 440 Hz)
Supply voltage range Us 24 V DC
9 ÷ 36 V DC
Power consumption P max. 5 VA
Measuring circuit
Measuring voltage Um 40 V⎓
Measuring current Im < 0,5 mA
Internal impedance of the measuring input Zi > 1 MΩ
Internal direct resistance Ri > 1 MΩ
Permissible system leakage capacitance Ce 10 µF
Measuring range RF 1 kΩ ÷ 10 MΩ
Measuring accuracy ± 15 %
Reaction value’s setting range Ran Ran adjustable 1 kΩ ÷ 500 kΩ
Insulation resistance hysteresis Rhyst adjustable 0 ÷ +100 % Ran
Two signalling switching contacts with optional position NO or NC / Electrical strength to the internal circuits and supply circuits 24 V∼ / 1 A
24 V⎓ / 1 A
3 kV DC
3 kV DC
Remote monitoring Using communication modules type HIG99 KM.
General data
Degree of protection according to IEC 60529 front panel IP40, protection except front panel IP20
Weight m 222 g
Housing material PA - UL 94 V0
Method of assembly On the 35 DIN rail
Recommended section of the connected conductors S Terminal box X1: 2,52
Other: 1 mm2
Back-up fuse 6 A
Operating conditions
Operating temperature ϑ -40 °C ÷ +70 °C (OT4 dle EN 50155)
Storage temperature -40 °C ÷ +70 °C
Height above sea level up to 2000 meters above sea level
Operating position any
Operational mode permanent
Article number 70 970
Installation instructions (1.3 MB)
2D model (705.67 KB) for registered only
3D model (1.79 MB) for registered only