Bender IRDH275B-435 Insulation Monitoring Device

 

 

Product Overview

The BENDER IRDH275B-435 is an ISOMETER® insulation monitoring device (IMD) used in IT electrical systems (ungrounded AC/DC systems).

Its main function is to continuously monitor insulation resistance between live conductors and earth (ground) and detect leakage faults at an early stage.

Key Specifications

• Brand: BENDER
• Model: IRDH275B-435
• Series: IRDH275 / ISOMETER®
• Type: Insulation Monitoring Device (IMD)

Electrical Monitoring Range

• System voltage range:
  • AC: up to 793 V
  • DC: up to 650 V
• Insulation resistance measurement range: approx. 1 kΩ – 10 MΩ
• Operating systems:
  • AC IT systems
  • AC/DC mixed systems (rectifiers, VFDs)
  • DC systems

Power & Output

• External power supply (not powered by monitored system)
• Alarm relay outputs (pre-warning + main alarm)
• Analog output 0/4–20 mA
• RS-485 communication (BMS protocol)
• Event history with real-time clock (B version feature)

Function Principle

The device injects a small measuring signal into the electrical system and continuously evaluates:

• Insulation resistance to ground
• Leakage current paths
• System capacitance influence

When insulation resistance drops below the set threshold:

• Alarm relay activates
• Warning LED turns ON
• Fault signal sent to PLC / safety system

Advantages & Features

• Early detection of ground faults (before tripping or damage)
• Suitable for modern systems with VFDs and rectifiers
• Automatic adaptation to system capacitance
• High sensitivity and stable measurement accuracy
• Communication interface for SCADA / PLC integration
• Built-in self-test and diagnostics
• Event history logging (B version)

Applications

• Industrial power distribution (IT systems)
• Hospitals (critical power supply systems)
• Marine electrical systems
• Mining and heavy industry
• Data centers and UPS systems
• Renewable energy systems (DC monitoring)
• Automation plants with high safety requirements

Precautions

• Only suitable for ungrounded (IT) systems
• Must NOT be used in standard grounded TN/TT systems
• Incorrect wiring can cause false alarms or damage
• Requires correct configuration of response resistance threshold
• High leakage systems (VFD-heavy) may need tuning
• Proper grounding and shielding required for stable measurement
• Installation should follow Bender system guidelines