In gas circuit breakers, the arc voltage is usually in the range of a few hundred volts to KV is depending:
- The length of the arc: The voltage drop across the arc is proportional to the length of the arc. The length of an arc can be much longer than the contact distance (gap length).
- The gas in which the arc occurs: The arc voltage depends on a number of physical parameters of the surrounding medium.
- The contacts on which the arc foot-points reside: The material of the arcing contacts has a minor influence on arc voltage, since it influences only the voltage in the anode and cathode voltage-drop region. The main voltage drop of gaseous arcs is across the arc body, keeping the effect of the contact material marginal.
- The cooling of the arc: The internal power of the arc is the product of the current and the arcvoltage. In the case of higher thermal losses, the arc increases its power by increasing the arc voltage.
- The current through the arc: Arcs in gases have a negative volt-ampere characteristic. This implies that arc voltage increases with decreasing current and vice versa.
In figure shown a arc voltage random excursions and collapses near current zero.