Behaviour of the SF6 - MV circuit-breakers Fluarc for switching motor starting currents

Many years ago, oil circuit-breakers (OCB) and air magnetic circuit-breakers (AMB) were the main breaking techniques for MV applications. OCB, mainly in Europe, i.e. bulk oil CB and minimum oil CB, were the single technology in the catalogue of the majority of world-wide CB manufacturers. However the qualities of AMC were greatly appreciated by users in the industrial distribution field for 6.6 and 11 kV in Asia, Europe and 5 or 15 kV in America. With AMB, from LV to MV applications, users did not worry about voltage surges and, for the most part, were unaware of the existence of such phenomena. Thanks to magnetic blowing, arc cooling depends on the value of the breaking current, leading to a very smooth breaking. Since 1970 or 1975 (depending on the different countries) SF6 and vacuum breaking techniques have appeared on the MV market, first for the primary substations. The success of these new breaking techniques is well known. The advantages are: - a longer life time, in comparison with OCB, - a better behaviour for rapid reclosing, capacitor switching etc... in comparison with OCB and AMB, - a smaller volume in comparison with AMB.