Cable monitoring for DC cables
Here you can find out more VertriebsanfrageThe WITT WB-CM3 monitors the insulation between the shield or conductor and an earthing point and signals the event via potential-free signaling contacts. Measurement data can also be transferred to third-party systems.
Description
Areas of application
In high-power direct-current cables, micro-defects in the insulation can develop and accelerate the deterioration of both the power and return conductors. VDV Publication 515 therefore stipulates that direct-current cables must be monitored.
The episode:
- Stray currents and damage to buildings
- Electric shocks
- Energy losses
Typical applications and common energy systems:
- Light rail (subway, streetcar, etc.)
- Charging stations for trains, buses and trucks
- Battery buffer systems
- Solar systems
In the context of monitoring shielded power cables, the WB-CM3 fulfils the requirements set out in VDV Publication 515, Issue 4/1993, for monitoring cables with a concentric shield or conductor and an insulating outer sheath.
Function overview
- The WB-CM 3 cable monitoring system for DC cables is designed to detect breaks in the conductor or shield, as well as insulation faults.
- It can withstand high voltages of up to 1,500 V and insulation voltages of up to 2,100 V DC.
- The current status is indicated on site by indicator lights.
- Potential-free changeover contacts enable external signaling.
- Any number of threshold values can be stored for monitoring the cable structure.
- The WB-CM 3 is a fully digital measuring system that can transmit the available measured values to third-party systems via communication protocols.
Additional information
| Standard | VDV-515 |
|---|---|
| DC System voltage (UA) | 1,000 VDC, 1,500 VDC, 600 V DC, 750 V DC, customer requirement |
Functional description
The following description covers the basic functions of the device. These can also vary considerably due to extensions or customer functions.
The voltage between the cable sheath and a ground is taken via a rectifier. As soon as this voltage rises above an adjustable threshold, the alarm relay is triggered. The circuit operates according to the constant current principle, i.e. even if the voltage rises to 1000 V or above, the current requirement does not increase any further. The leakage current flowing to earth is very low at 2 mA; the current load only rises to 6 mA in the event of a fault. The switching status is indicated locally via a signal lamp.
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