The monograph presents the detailed properties of gas arresters and physical background of their operation. To this end, many studies were made of electric breakdowns in gas arresters with different filling gases, different geometries and different materials. It also presents the manufacturing processes of gas arresters, where the knowledge of vacuum technology and other hightech processes is very important. In addition, the paper also includes examples of occurrence of voltage surges and proper use of surge in practice.
C.02 Editorial board of a national monograph
COBISS.SI-ID: 253193216The technical problem is a constructional solution to a gas discharge tube configured on a metal body and having a function of an external electrode in combination with a protecting element for graphite coatings, which must be shaped in a way to allow optimum reaction of a gas discharge tube in case of an excess voltage increase. The shape of a protecting element must be such to provide protection of an insulating element in case of arc formation in the interior of the gas discharge tube against material vapours, preferably copper, of which the body and the external electrode are made of. Heating induced by arc burn causes a relatively rapid melting and evaporation of copper, which may cause severe thermal damages on the external electrode in the interior of the gas discharge tube. The evaporated material may cause formation of a thin conductive layer on insulating elements, which results in reduced ohmic resistance between the two electrodes. All that can have influence on the change of ignition voltages and consequently on the applicability of a gas discharge tube. In order to improve high-temperature resistance of the interior of the external electrode, a shield of materials must be produced, which have good resistance to high temperatures and are good electric current conductors. Typical materials are molybdenum and tungsten-copper, where the share of tungsten is at least 10 %. The shield must cover at least the most heavily burdened parts of the external electrode, i. e. especially the area around the peak of the internal part of the central electrode, which preferably also consists of high-temperature resistant materials (molybdenum or tungsten-copper). The electrodes are separated by an insulating element preferably of ceramics or a material having similar chemical properties. Graphite paths should be applied on one or both insulating elements, wherein the shape of graphite paths should be such to allow an adequately rapid reaction of the gas discharge tube to increasing overvoltage. This is important especially in case of a rapid increase in voltage, which is normally of an order of magnitude of 109 V/s or more. The speed of reaction of a gas discharge tube defines a dynamic ignition voltage, which is always higher than the ignition voltage in case of a slow increase in voltage (e. g. 100 V/s). Application of graphite paths onto an insulating element can reduce the dynamic ignition voltage thus increasing the protection level of overvoltage protection, as the highest possible voltage on a gas discharge tube with a rapid reaction is lower than in case of a gas discharge tube with a slow reaction. These dynamic ignition voltages in gas discharge tubes for high-current surges must normally lie below 1500 V.
F.33 Slovenian patent
COBISS.SI-ID: 36599557This manuscript is intended to integrate the inter- and multi-disciplinary knowledge and expertise, gained during last several years, in one single document to be of future use for both students and experts interested and/or involved in these issues. Aspects regarding, e.g., electrical circuits, plasma-material-field-gas interactions, mathematical theory, numerical modelling and simulations, e.t.c., up to the level of some relevant basic principles, relevant to both stationary and pulsed discharges, will be embedded in a versatile ''virtual-experimental discharge-device’’ (VEDD). Such a virtual device will be built in the form of a suite of kinetic and fluid numerical codes, similar to those which we are currently developing with our collaborators from Michigen University (PTSG-group) but ''equipped'' with more physics and diagnostics, that has been found appropriate for small-scale high density pulsed plasmas. Present document is a first draft of a monography into which this document has to arise (as already has been agreed with e.g., Prof Osmokrovic and his group from Belgrade) to be still further articulated, written and formated and published before the end of present project. Unpublished material presented here currently consists of a relatively small initial number of particular issues, that has been investigated during the present project.
F.02 Acquisition of new scientific knowledge
COBISS.SI-ID: 12738587