Attached to this FAQ a pfd file containing two DPL scripts that calculate arc resistance depending on the short-circuit current can be found.

Both scripts are stored in the local library and can be executed by pressing execution button stored on the single line diagram, while single line diagram is in freeze mode.

Both scripts are using the given short-circuit command of the study case to calculate the arc resistance.

- First script "Shc_Arc_Resistance" is calculating according to the following equation:

Rf = Uarc * len / Ishc in Ohm

Uarc = arc voltage in V/m

len = arc length in m

Ishc = calculated short-circuit current (arc current) in A

- Second  script  "arc resistance calculation with warrington equation" is calculating according to the Warrington equation:

Rf = Kwarrington * len /(Ishc^1.4); in Ohm

Kwarrington = warrington constant in V^1.4/m

len = arc length in m

Ishc = calculated short-circuit current (arc current) in A

(M. Warrington: Protection Relays theory and practical Chapman and Hall Bd.1 London 1962)

Both calculations are iterations until the difference between the new calculated short-circuit current and the old smaller than eps ( in kA ).

The calculated arc resistance will be stored in the short-circuit command.