Application of high speed photography for high current vacuum arcs

Abstract

A high speed image detection system for 10/sup 6/ frames per second or 10/sup 7/ streaks per second has been developed for the testing of vacuum circuit breakers, using 10/spl times/16 optical fibres for light transfer to 160 fast photo diodes. The output of these diodes is multiplexed, AD converted in a 4 bit logarithmic flash-converter and stored in a 16 kB RAM. For accurate current zero voltage and current measurements a fast, 10 MHz, 12 bit AD converter with 4 kB memory has been made. Wide band high voltage dividers and current derivation M coils have been developed too. The simultaneous use of these methods opens the possibility for further research on the high current behaviour of arcs under various pressure conditions. The current up to 100 kA is supplied by a 15 kV 100 kJ capacitor bank in series with a group of four 10/0.4 kV transformers. The recovery voltage is supplied by a current injection circuit for 30 kV, 500 Hz. During the first current half wave the transition from diffuse into contracted arc is analysed. After current zero the post arc current and light emission need further investigation at the limits of reignition or restrikes.