What do arc faults and air bags have in common?

Ultra fast earthing switch extinguishes arcs before they can cause any damage

We’re all familiar with electric arcs that occur when a current ‘jumps’ an air gap, if only from the bolts of forked lightning that crash to earth during a thunderstorm. Sometimes, these short circuit currents can be useful, like in arc welding, but an unplanned arc (often referred to as an ‘arc-fault’) can have devastating consequences in electrical equipment. It can reduce a large electrical switchgear cabinet, containing several hundreds of kilos of metal, and costing a significant amount of money, to useless scrap in milliseconds.

As you might imagine, helping customers to avoid arc faults is a top priority. That’s why we at ABB have developed an ultra-fast earthing switch (UFES) that uses air-bag technology for instant results.

In switchgear, arc faults can have a variety of causes; a loose connection, defective insulation, even operator error. When they occur the temperature rises instantaneously to around 20,000°C. That’s well above the melting point of steel, copper and insulation materials. The instant heat vaporizes electrical components and the resulting plasma (ionized gas) explodes, releasing huge amounts of energy, similar to a rocket launch.

In addition to damaging equipment and threatening the lives of near-by workers or others, arc faults also interrupt power supplies, disrupting homes and businesses, hospitals and factories. Outages might be short-lived, but their consequences can be disastrous and long lasting. When it comes to arc faults, prevention is better than cure.

The key is to extinguish the arc before it can cause any damage. ABB’s UFES does this by making a near-instantaneous connection to earth, snuffing out the arc within 4 milliseconds.

This super-fast response is triggered by a light and current sensor that detects a developing arc. This sets off tiny, ultra-fast, gas generators, similar to those used in cars to instantly inflate air bags. In UFES, the gas effectively throws the earthing switch and extinguishes the arc, before it can cause any damage.

The great thing about the UFES is that, in addition to being compatible with new switchgear, it can also be fitted into existing installations, whether they were built by ABB or other suppliers.

Have you ever experienced an arc fault in a substation? Tell us about your experiences!


Related power articles:

IEC 61850: could you live without it?

Strengthening the electricity bond between the US and Mexico


*Image credit: marked141 on Flickr


Comment this article(2)

Community guidelines
  • Jyoti Bhatia

    An arc fault is a high power discharge of electricity between two
    or more conductors. This discharge translates into heat, which can
    break down the wire's insulation and possibly trigger an electrical
    fire. These arc faults can range in power from a few amps up to
    thousands of amps high and are highly variable in terms of strength and
    duration. Common causes of arc faults include faulty connections due to
    corrosion and faulty initial installation.
     The development of airbags began with the idea for a system
    that would restrain automobile drivers and passengers in an
    accident, whether or not they were wearing their seat belts. The
    road from that idea to the airbags we have today has been long,
    and it has involved many turnabouts in the vision for what
    airbags would be expected to do. Today, airbags are mandatory in
    new cars and are designed to act as a supplemental safety device
    in addition to a seat belt. Airbags have been commonly available
    since the late 1980's; however, they were first invented (and a
    version was patented) in 1953. The automobile industry started in
    the late 1950's to research airbags and soon discovered that
    there were many more difficulties in the development of an airbag
    than anyone had expected. Crash tests showed that for an airbag
    to be useful as a protective device, the bag must deploy and
    inflate within 40 milliseconds. The system must also be able to
    detect the difference between a severe crash and a minor

  • Jyoti Bhatia

    Ultra fast earthing switch extinguishes arcs before they can cause any damage.