Our TracFeed® VLD2 voltage limiting device offers a safe solution to the risk of life-threatening touch voltages between the return circuit and earth. Our voltage limiting device monitors the voltage between the return circuit and earth and reacts immediately with a controlled short circuit of the two potentials if operating and short circuit currents occur. The limit values for permissible touch voltages in accordance with EN 50122-1 and the required switching time in accordance with EN 50122-1/-3 are decisive for this process. In combination with the TracFeed® DCP3 protection and control unit and a fast contactor, TracFeed® VLD2 is an important component of passenger safety on platforms and in depots in DC-powered local and urban transport.
TracFeed® VLD2 works in conjunction with the newly developed TracFeed® DCP3 protection and control unit.
TracFeed® DCP3 monitors the voltage and current and controls the contactor. Depending on the impermissible voltage increase and duration, the switched NC contact is closed. TracFeed® VLD2 is blocked if a parameterisable inrush current value is exceeded. The control unit provides a separate signal that can be used to switch off the corresponding feeder section.
All important settings can be parameterised. Protection against touch voltages in the range of less than DC 120 V (e.g. in a depot) can also be set via convenient menu navigation.
Integration into modern control system concepts is ensured by Ethernet protocols such as ModbusTCP or IEC 608705104.
TracFeed® VLD2 limits the touch voltage as required by EN 50122-1/-3. The standard distinguishes between operation and faults. The terms VLD-O (operation) and VLD-F (failure) have been introduced for this purpose. VLDs are available in different technical designs. Voltage changes are recorded and processed in milliseconds and limited in time in accordance with EN 50122-1.
During normal operation, the operating currents within the track may result in dangerous touch voltages. The VLD makes it possible to utilise the maximum times at permitted voltages in the system. In the event of a short circuit, unwanted stray currents occur that can be minimised by briefly opening the contact.
The safety functions are provided for high voltages that occur in the event of a fault, such as a torn contact line. In addition, the resulting peak voltages trigger a block of the VLD and issue a trip signal; for example, a substation intertrip.
The current is conducted by a main contactor with a normally closed contact. If the control voltage fails, the main contactor switches to idle mode, causing the normally closed contact to trip. This mode of operation ensures personal safety at all times.
TracFeed® VLD2 allows short circuiting of the two potentials between earth and the return circuit, the flow of a higher current and opening under load. This limits the stray current issue. The device is ready for integration into the TracFeed® SCM stray current monitoring system. Recording and pre-processing are implemented.
Rail Power Systems is your systems provider with over 130 years of experience. On request, we can provide you with the complete package – from planning and installation to commissioning and maintenance. Our products and solutions for protecting people and railway operation have proven themselves over decades of use in a wide variety of conditions. Feel free to contact us for more information. We are there for you from the big picture to the smallest component.
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