New approach to arc resistance calculation

An important macroscopic arc parameter, describing its complex nature is arc resistance. As known, the fault arc resistance can be calculated by the Warrington formula. The authors investigated the results of Warrington's tests. Warrington derived a relation for the arc voltage by using the measured arc voltage gradient and arc current as input data. By analyzing these measurements and by taking into account the conditions under which they are obtained (inaccurate measurement devices), it is unquestionable that the results are highly empirical and not accurate and general enough. Laboratory testing, provided in the high power test laboratory FGH-Mannheim (Germany), in which long high current arcs are initiated, was the base for the research results presented. In this paper a new approach to arc resistance calculation is given. Two independent approaches delivered the same equation. Both approaches are based on a suitable and a simple arc model assuming the rectangular wave form of the arc voltage, which is in phase with the arc current wave form. The new formula for arc resistance is compared with the Warrington formula. The influences of arc elongation are also investigated.