The relationship between current and channel diameter of 30 cm long laboratory sparks

In this study the dependence of channel diameter of 30 cm long sparks on discharge current is analyzed using a photographic technique. The results show the radial channel intensity variation follows a Gaussian distribution. The channel diameter (D), defined as the width of the intensity profile at 10% level, increases with the increasing peak current (Ip) up to 3 kA. The relationship between the two parameters can be represented by the equation, D = 8.36 ln(Ip) + 1.598, where D is in mm and Ip is in kA. The experimental results agree reasonably well with the available theory.

► A spark of 30 cm was created in air. ► The voltage and the current in the air gap were measured. ► By using a photographic technique an image of the spark was recorded. ► The diameter of the spark channel was estimated from the image of the spark. ► A correlation between the current and the channel diameter was found and presented.