Low voltage limiters
August 1st 2006

ABB's new generation HVL (hybrid voltage limiter) low voltage limiters combine a metal oxide surge arrester without gaps and a thyristor-based low voltage limiter and have been developed to ensure effective protection of personnel and equipment in DC traction systems.

They are said to fulfil all the requirements for voltage limitation, while reducing touch potentials to harmless levels.

As well as touch voltages caused by failure in the supply system, impulse over voltages caused by lightning or switching can occur on the rails. These can travel along the rails to substations and damage electrical equipment so, in addition to personnel protection, over voltage protection has to be provided for the electrical system.

With the HVL, over voltages generated by lightning with a duration of some 10microseconds are limited by the MO-varistor. Those with a duration of 0.4milliseconds and longer are limited by the thyristors to a voltage below 3V.

More articles from ABB Ltd: