Small scale arc fault testing in air

Full scale arc fault experiments are expensive, time consuming, and demand high power laboratory facilities. This paper presents a literature study performed to evaluate the possibilities of performing representative experiments on small scale by reducing the size of the test object. Previous model experiments have shown that the arc energy must be scaled down by the same factor as the volume in order to produce the same pressure build-up during the tests. The arc energy is given by the arc voltage and current, which both are functions of the arc length. In arc fault experiments one usually assumes a linear voltage drop along the length of the arc and experiments have shown that a voltage gradient of 20–30 V/cm can be assumed for arcs in switchgears filled with air. This value will however depend on volume, pressure, and electrode material. Experiments also indicate that there is a limit for short arcs where the linear voltage drop no longer can be assumed. To reveal possible consequences this may have on small scale experiments, a more systematic experimental study is required.