Bender ISOMETER®IRDH275 IRDH275B

Insulation monitoring device for unearthed 

AC, AC/DC and DC systems (IT systems)

Product description

The ISOMETER® of the IRDH275 series is designed to monitor the insulation resistance of unearthed main circuits (IT systems) AC, AC/DC 0…793 V resp. DC 0…650 V. The AMPPlus measurement method meets the particular requirements of modern power supplies which often include rectifiers, converters, thyristor-controlled DC drives and directly connected DC components. In these systems often high leakage capacitances against earth occur due to interference suppression measures. The IRDH275 automatically adapts itself to the existing system conditions.

In combination with a coupling device, the devices can also be used for higher voltages. An external supply voltage allows de-energised systems to be monitored too. For door mounting into distribution panels, refer to type IRDH375(B).

Device features

•  Insulation monitoring for unearthed AC, AC/DC systems 0…793 V, DC 0…650 V •  Nominal voltage extendable via coupling device •  Two separately adjustable response val ues1 kΩ…10 MΩ • AMPPlus measurement method •  Automatic adaptation to the system leakage capacitance •  Info button to display device settings and system leakage capacitance • Self monitoring with automatic alarm • Automatic self test, selectable • Connection for external kΩ indication • Test and reset button •  External test/reset button can be connected •  Two separate alarm relays with two   potential-free changeover contacts • N/O or N/C operation, selectable • Backlit LC display • RS-485 interface

Application

• AC, DC or AC/DC main circuits •  AC/DC main circuits with directly connected DC components, such as rectifiers,   converters, and thyristor-controlled   DC drives • UPS systems, battery systems F • Heaters with phase control •  Installations including switch-mode power supplies •  IT systems including high leakage   capacitances • Coupled IT systems

Function

When the insulation resistance between the system conductors and earth falls below the set response value, the alarm relays switch and the alarm LEDs light up. Two separately adjustable alarm relays allow to distinguish between prewarning and alarm. The measured value is indicated on the LC display or an externally connectable measuring instrument. In this way any changes, for example when circuits are connected to the system, can be recognised easily. The fault message can be stored. The fault memory can be reset by pressing the reset button. By pressing the test button, the function of the device as well as the connections to system and earth can be tested. Pressing the Info button provides additional information, such as the existing system leakage capacitance or device settings. The function of the device and the system and earth connections are continuously monito red. When a fault occurs, the system fault relay switches and the alarm LED “system fault” lights up. The parameterisation of the device can be carried out via the LC display or the function buttons integrated in the front plate.

Device version IRDH275B

Device version IRDH275B includes the following additional functions: 

 • History memory with real-time clock to store all alarm messages with date and time stamp 

 •  Electrically isolated RS-485 interface (BMS protocol) for communication with other Bender devices 

 •  Isometer disconnecting relays for the operation of several ISOMETER®s in coupled   IT systems 

 • Current output 0(4 )…20 mA (electrically isolated)

Use in coupled IT systems

Only one ISOMETER® may be active when several IT systems are coupled. Isometer dis connecting relays and the control inputs F1/F2 integrated in version IRDH275B guarantee that only one ISOMETER® is active at any one time.

Measurement method

The IRDH275(B) uses the patented AMP Plus measurement method. This measurement method allows concise monitoring of modern power supply systems, also in case of extensive, directly connected DC components and high system leakage capacitances.

Standards

The ISOMETER® of the IRDH257 series complies with the requirements of the device standards: DIN EN 61557-8 (VDE 0413-8), EN 61557-8, IEC 61557-8, IEC 61326-2-4, DIN EN 60664-1   (VDE 0110-1), DIN EN 60664-3 (VDE 0110-3), ASTM F1669M-96 (2007), ASTM F1207M-96 (2007)

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