Tests of the `early streamer emission´ principle for protection against lightning

Experiments are described which are designed to test two devices based on the `early streamer emission´ (ESE) principle, for lightning protection, against the traditional Franklin rod. In all three cases, the device was subjected to a steady negative electric field from a sphere, simulating the field beneath a thundercloud, prior to application of a superimposed negative impulse field, simulating the field due to the downward leader. The first device consisted of a vertical rod to which a subsidiary 1/50 μs positive impulse voltage, variable up to 40 kV peak, could be applied with varying delays from the start of the negative impulse field. Energising of the rod was thus independent of the applied negative field. The second device was a commercial product, energising of which was controlled by its own power supply. Sparkover voltages in the sphere/device gaps and times to breakdown were measured. It is shown that the ESE devices showed a small advantage, in time to breakdown, over the Franklin rod