Experimental results of the development of a negative discharge in a 16.7 m rod-plane air gap are presented. Similarities with the cloud-to-earth discharge are found and some characteristic parameters are compared. Use of an image converter linked to two still cameras allows quite accurate analysis of the discharge propagation. Information relative to the space leader inception is provided. The current pulse shapes are related to the mechanisms of propagation and the thermal channel diameter of the discharge in the vicinity of the rod, which is measured with the help of schlieren records.

No abstract

Experimental results concerning the propagation of a spark in a 16.7 m rod-plane gap are presented. Positive switching impulses are used. The parameters of the discharge are measured and the trajectory of the leader-leader corona system is studied as a function of time (withstand and breakdown events). Three main types of propagation are found: continuous, oscillatory and restrike. For each type, the propagation mechanisms of the leader-leader corona system are discussed from a physical point of view.

No abstract

In Part one, the formation and development of leader filaments in large air-gap discharges are studied by Schlieren techniques. The time evolution of the thermal diameter of the leader at a given point in space is studied for several gap spacings ranging from 1 to 16.7 m and for different wave forms and voltage levels. In Part two, the authors review the main phases of the positive leader development. Experimental results obtained by Schlieren methods are used to test previous models of leader behaviour. Information is obtained about reduced field values and neutral temperature values in the leader channel.