ABB'S HVL LOW VOLTAGE LIMITERS PROVIDE BOTH PERSONNEL & EQUIPMENT PROTECTION FOR DC TRACTION SYSTEMS
19 March 2007 - ABB Limited (Group Headquarters)

ABB's new generation hybrid voltage limiter low voltage limiters, that combine an metal oxide surge arrester without gaps and a thyristor-based low voltage limiter, have been developed to ensure effective protection of personnel and equipment in DC traction systems. They fulfil all the requirements for voltage limitation while reducing touch potentials to harmless levels.

In DC traction systems stray currents can flow in the ground from the rails to other metallic structures (such as drainpipes, bridges, fences and so on) where they can cause corrosion and considerable erosion of the metal. To avoid this problem, it is common practice not to have direct earthing of the rails where possible. However, this can lead to unacceptable potential rises and too high touch voltages, both in normal train operation but especially in the case of a failure such as a broken overhead line or derailed pantograph. In such installations, protection for personnel has to be provided by the use of low voltage limiters.

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

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