ALVL 60 - Low voltage limiter - 50807

ALVL 60 and ALVL 120 are automatic low-voltage VLD surge arresters, class 2.2 (bidirectional); type VLD-O+F, designed to protect normally non-conductive structural parts in DC or AC traction power supply networks. They are used to effectively protect persons who may come into contact with these parts during a lightning strike or in the event of a traction power line failure. In the event of a fault resulting from a connection between a live part of the traction power supply network and a conductive part accidentally connected to the return line, the arrester protects against inadmissible touch voltage by conducting and disconnecting the power supply. In accordance with ČSN EN 50122-1 ed. 2: 2011, this type of arrester is primarily recommended for the connection between the protected part and the return line of a traction line or in the area of ​​a pantograph (current collector), which may be in contact with a conductor or a damaged current collector. It can also be used on supporting structures of masts, which may be live following an insulation failure. If an overvoltage occurs (ms to h), the thyristors are activated, limiting the touch voltage. When the overvoltage disappears, the thyristors interrupt the current flow and restore the original state. The ALVL consists of MOVs, high-performance thyristors, and electronic components (delay circuit) that activate both high-performance thyristors after approximately 1 ms. Activation is caused by a voltage drop across the varistor. According to the polarity of the varistor, the corresponding thyristor is activated, absorbing the current previously flowing through the activated varistor. The arrester is designed to conduct high temperatures generated inside the device to the aluminum structure. ALVL arresters are maintenance-free, have a high insulation resistance (kΩ), and offer excellent protection. The outer casing is made of silicone rubber, which is characterized by excellent resistance to surface leakage currents and electric arcs. It is hydrophobic and has excellent resistance to weather conditions, pollution, and UV radiation, and is also resistant to rough handling and mechanical damage.