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Why Is It Important For You To Understand Arc Interruption Theory and Application?

rscasny

When current-carrying contacts of a circuit breaker or a relay are caused to separate (e,g. system fault), an arc is formed. As long as this arc is sustained in between the contacts the current through the circuit breaker will not be completely interrupted because the arc is itself a path of conduction. Thus, the circuit breaker or relay must be designed to interrupt (also called "extinct" or "quench") the arc.

There has been a lot of research over the years on arc interruption. High speed photography and simulations have been the two most of common methods of research. Believe it or not, there are also two theories on arc formation/extinction: Energy Balance Theory (Cassie's theory) and Recovery Rate Theory (Slepian's Theory).

Before we launch into a dissertation on the arcing phenomenon, we wanted to gauge your interest in the Arc Interruption, as a piece of professional knowledge. So, here's the discussion question: Why Is It Important For You To Understand Arc Interruption Theory and Application?

  • I am interested in understanding arcing and arc extinguishing although I can't say it is "currently" important to me. I've mostly run into it causing pitting and erosion of contacts, and of course some exciting inadvertent arc-welding with car batteries. In the past I have had to design intrinsically safe systems, where arcs are really bad news.

  • imageAccording to the NFPA 70 (National Electrical Code 202) here in the states "In the 2020 edition of the NEC®, Section 210.12 requires that for dwelling units, all 120-volt, single-phase, 15- and 20-ampere branch circuits supplying outlets or devices installed in dwelling unit kitchens, family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, laundry areas, or similar rooms or areas shall be protected by AFCIs."

    According to the NFPA 70210.8(A)(1) through (A)(11): Bathrooms, Garages and Accessory Buildings, Outdoors, Crawl Spaces, Basements, Kitchens, Sinks, Boathouses, Bathtubs and Shower Stalls, Laundry Areas, Indoor Damp and Wet Locations are required to have GFI breakers

    I personally hate AFCI breakers as they have LOTS of false trips!!!

  • With a circuit with substantial flash energy to wear PPE 1 and above, it gets interesting how to coordinate protection components and fusing to reduce people risk and needed PPE. 

  • 400A ContactorWhy is it important?

    This is a 400 ampere transfer switch.  It's considered a moderately sized switch and is a fairly common size for large homes and small businesses.

    I THINK I understand but... electric things can go BANG!  The more I know the better.  Anything that mitigates arc current has my interest.

    That blue thing in the middle is a one foot long plastic ruler - for scale.