ACER VOLTAGE
This article first appeared in the Railway-News magazine Issue 3 2021.
Low-Voltage Limiters for Railway Vehicles in DC Systems
P60G and P120G are new types of low-voltage limiters Type 1 VLD-F based on the requirements of EN 50122-1: 2011, which are designed to protect the non-live parts of metallic structures in DC or AC traction power supply systems. They are used to provide effective protection to individuals who may come into contact with these parts during lightning strikes or during a defect of the tractive overhead line. The limiter has a high internal resistance if there is a voltage lower than its specified DC sparkover voltage UVDC and becomes conductive when this level is exceeded. In case of failure due to the live part of the traction power supply system and the conductive part (which are connected) unintentionally coming into contact with the return circuit, the limiter protects against impermissible touch voltage by becoming conductive and causing the power to turn off. According to EN 50122-1: 2011, this type of limiter is mainly recommended for the connection between the protected part and return circuit in the overhead line areas (or pantograph areas) that may be in contact with the conductors or damaged current collector, as well as on the support structures / pylons which can become live due to an insulation failure. When the applied voltage drops again below the specified value of its nominal level, the limiter returns into a non-conductive state again…
