The expulsion protective gap

THE EXPULSION protective gap consists of a fiber tube of proper bore and dimensions so arranged with an internal gap that lightning discharges are conducted within the tube and the power follow current is stopped through the expulsion action of the tube. Its action during interruption of follow current is similar to that of the expulsion fuse. In practice the expulsion gap is provided with a series gap, the whole assembly being electrically in parallel with the insulation to be protected.