An Improved Type of Limiting Gap for Protecting Station Apparatus

The wide range of transients to which station apparatus is subjected is pointed out and the desirability shown for having adequate protection. The different breakdown characteristics of the various insulating members of a station are illustrated and the importance emphasized for considering this in choosing a voltage limiting device. The need is also shown for having protective gap discharges reduced to a minimum in order to limit the number of service interruptions. The characteristics and limitations of several forms of gaps are shown and discussed. A new form of limiting gap is described in which it is possible to change the sparkover characteristic over a considerable range to allow for the differences in time lag and polarity characteristics of station insulation. The advantage of using a limiting gap in multiple with a lightning arrester to provide maximum protection and reduce interruptions to a minimum is discussed.