HVL Voltage Limiting Device
Voltage limiting device for use in d.c. traction systems, for personal protection (touch voltages) and protection of equipment (over-voltage protection).
The HVL is a combination of a metal oxide (MO) surge arrester without gaps and a low voltage limiter. The MO-surge arrester is realised by a MO-varistor, the low voltage limiter is realised by two anti-parallel connected thyristors. The MO-varistors and the low-voltage limiter are connected in parallel.
Overvoltages generated by lightning with a time duration of some ten microseconds are limited by the MO-varistor. Overvoltages with a time duration of 0,4 ms and longer will be limited by the thyristors to a voltage below 3 V. The HVL is completely moulded in silicon.
Range of application
- Protective provisions for wholly or partially conductive structures and conductive parts, which are not utilized for carrying the traction current and located in the overhead contact line zone or the pantograph zone (Masts for overhead contact lines, reinforced concrete pylons, metallic fences, drainpipes, running rails of non-electric traction systems over 15 m in length, measured parallel to the overhead contact line zone, or 2 m measured in a directon at right angle to and away from the overhead contact line zone).
- Protection angianst the danger of rail potential during normal operating conditions or under fault conditions.
- Personal protection against indirect contact (touching of conductive parts of electrical equipment which can become live from the voltage of the contact (line under fault conditions)
- Personal protection and protection of equipment for electric power-, telecommunication- and other electrical installations against the danger of the traction power supply system.
- Surge protection of equipment (overvoltage protection).
Advantages of HVL Voltage Limiting Device
- Combined protection of personal and equipment with high energy absorption capability.
- Limitation of touch voltage and accessible voltage according EN 50122-1
- Guaranteed reversibility of low voltage limiter under normal operating conditions for currents up to 300 Amps and 60 seconds for protection against the danger of rail potential difference
- Potential difference is limited to a safe value below 3 V when exceeding the maximum limiting voltage of 120 V.
- Rated short circuit current corresponds to all levels of short circuit currents occurring in d.c. traction power supply systems
- In case of overload the low voltage limiter generates a durable conductive current path
- Stable U-I- characteristics and low residual voltage of the metal oxide varistor
- Explosion and shatter resistant design
- Pollution resistant and UV stable
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