Arc Extinction Phenomena in High Voltage Circuit Breakers-Studied With a Cathode Ray Oscillograph

A medium-speed cathode-ray oscillograph with a rotating film has been built for the study of circuit breaker transients. The film is wrapped around a drum and rotated in the vacuum at high speed. Each film shows in a continuous trace a complete story of the formation of arc, subsequent reignitions, and final extinction. More than 15 complete cycles may be recorded without excessive blurring. Each film is self-calibrated. A stutdy of several types of circuit breakers with this instrument shows that the nature of the transients at time of arc extinction varies with the type of breaker on test. Different types of breakers tested on the same circuit have different rates of rise of recovery voltage. The deionizing efficiency of a breaker influences not only the arcing time, but the transient oscillation at current zero. The influence of the deionizing efficiency of the breaker upon the stability of the decreasing arc current near current zero is studied and interesting conclusions made.