The Bender ISOMETER® isoRW425-D4W-4 is an insulation monitoring device for ungrounded AC, AC/DC, and DC networks, specifically designed for use in railway applications. It monitors the insulation condition in IT systems with a nominal network voltage up to 3(N)AC, AC/DC 440 V, and is designed for frequencies ranging from 15 to 460 Hz. The device provides continuous monitoring of insulation quality to detect insulation faults early, thereby ensuring the safety and reliability of electrical systems in rail vehicle technology. Power supply is provided via a voltage source in the range of DC 24…240 V or AC 100…240 V, with the supply frequency required to be between 47 and 63 Hz. Connections are made via spring terminals, enabling quick and secure connections.

Applications
This device is primarily intended for railway applications, where the reliability of electrical systems is crucial. It is suitable for ungrounded networks in rail vehicles, where continuous insulation monitoring is required to prevent short circuits, fire hazards, or system failures. The application covers both AC and DC systems, as well as combined AC/DC networks, with a maximum voltage of 440 V. The frequency range of 15 to 460 Hz makes it flexible for various vehicle types and operating conditions.

Functions and Features in Detail
The ISOMETER® isoRW425-D4W-4 monitors insulation resistance (R-mode) and insulation impedance (Z-mode), where the R-mode measures the pure resistance component and the Z-mode takes into account total impedance, including resistance and reactance. This enables more precise diagnosis of insulation faults. Additionally, the device can respond to under- and over-voltage conditions, which is important in unstable network conditions in railway installations. A reset command allows clearing the fault memory, and a stop mode can temporarily interrupt monitoring. The device performs self-tests and displays fault codes to facilitate troubleshooting. The alarm relay K1 and K2 can be configured to trigger different alarm levels or control external systems. Measurement and response times are designed to meet the requirements of railway applications.

Technology Explained Simply
Insulation monitoring is performed by periodically measuring the resistance between conductors and the enclosure or ground. A resistance value that is too low indicates reduced insulation, which could lead to a fault. The device measures either pure resistance (R-mode) or total impedance (Z-mode), with the latter also accounting for capacitive or inductive components. Voltage monitoring detects deviations from nominal voltage, which is relevant in fluctuating network conditions in railway installations. Power supply is provided via an external voltage source in the range of DC 24…240 V or AC 100…240 V, enabling flexible integration into existing systems. Spring terminals ensure secure and quick connections without requiring additional tools.

Compatibility and Accessories
The device is designed for use in IT systems with ungrounded AC, AC/DC, and DC networks up to 440 V. It is specifically designed for railway applications, with the frequency range of 15 to 460 Hz ensuring broad applicability. No specific accessories are included in the delivery scope; the connection terminals are part of the device. Compatibility is limited to the specified network types and voltage ranges. No special accessories are required to operate the device.

Mounting and Installation
Mounting is done using the integrated spring terminals, which allow for quick and secure connections. No additional tools are required to connect the terminals. Installation typically takes place in the control cabinet or control unit of the vehicle, with environmental conditions meeting the requirements of railway applications. Detailed mounting instructions are provided in the manual, which is included with the device.

Operational Advantages
Continuous insulation monitoring enables early detection of faults, increasing safety and minimizing downtime. The ability to measure both resistance and impedance provides a more comprehensive diagnosis. Voltage monitoring protects against damage caused by under- or over-voltage. The flexible power supply voltage and spring terminals simplify integration into existing systems. The device is optimized for railway applications, where reliability and safety are top priorities.

Availability Note
According to sources, the device is no longer being manufactured. However, it will still be available from existing stock, with availability varying depending on the supplier. Technical specifications and functions correspond to the status of the last production phase.

Delivery Contents
The delivery includes the insulation monitoring device ISOMETER® isoRW425-D4W-4 and the operating manual. Batteries, additional cables, or mounting materials are not included.