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The needs for reliable protection of the electric devices in networks against the heavy atmospheric lightening discharges (i.e., 25-100 kA) are rapidly increasing during the last decades. The mentioned protection is usually solved by special air gaps or special gas controlled gaps which are very often combined with another basic elements. There is a strong need to develop gas arresters which would extinguish after tension-current stroke as fast as possible - also under very demanding conditions, ie. at high strokes and at high follow-on currents.
Demonstration of the self-extinguishing capabilities of a protection element requires the samples that hold out the current stroke superimposed on the sinusoid of the chosen follow-on current. Tests consist of a series of strokes, between which some minutes pauses are allowed for element cooling.
Interactions between plasma and material surfaces in a gas arrester last only some ms and in this short time the main happenings are: (i) ignition, (ii) spreading through the space to the cell surfaces and (iii) energy extinguishing.
Our development activities showed that it is possible to construct the gas discharge cell so that the external energy via the physical processes in the plasma will be dissipated within the cell volume rather than on its surface, with a good surface load distribution. This can be achieved mainly through suitable electrode construction, with proper material and gas selection combined with suitable external electric elements.
The present contribution represents the basic activities of overvoltage protection research and development.
Key words: overvoltage protection, gas discharge tube, follow-on current, plasma ignition and selfextinguishing, electrical tests
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