Experimental evaluation of properties of spark safety protective barriers with nonlinear current-voltage characteristic

It has been stated that the application of standard IEC spark gap for technical realisation of failure commutation of "shorting" or "open" type in testing electric circuits with making use of spark safety barriers with nonlinear current-voltage characteristic of foldback type becomes impossible. It results from their mechanical construction which does not ensure the proper operation of such barriers which carry out short-circuiting protected circuit input terminals. In other words, at the rotational speed of 80 rot/min of the spark gap wolfram electrodes and the cadmium electrode which rotates slower in the opposite direction and has two parallel gaps of 2 mm wide in the disk of 30 mm in diameter disallowing the spark safety barrier to return to its primary condition after carrying out supply poles short-circuiting. This problem is especially shown during testing spark safety barriers with making use of the current derivative value or voltage in operational algorithm. Experimental methodology of evaluation of protective properties of spark safety barriers with non linear current-voltage characteristic and their technical realisation has been proposed. The basis of the methodology constitutes oscilloscope measurements with the mechanical system (spark gap) for carrying out failure commutation of "short circuit" or "open" type in the tested electrical system without the application of test gas and air mixture. Mechanical construction of the spark gap has been elaborated. It is suitable to the empiric estimation of the electrical energy value which is emitted at the point of failure commutation at the application of spark safety barriers with nonlinear current- voltage characteristic. A measuring position has been built and verification measurements have been carried out. Presented methodology of experimental estimation of electrical energy value that releases in the channel of electrical discharge and its equipment realisation enables: - to convince a priori of the spark safety of a designed electric system, - to carry out the analysis of the spark safety level of an electric system depending on the value of elements and systems creating the circuit (system), - to test spark safety of electric circuits, - to decrease generally the cost of its elaboration and implementation of electric apparatus assigned for working in explosive conditions zones, - to test the spark safety of electric circuits with increased, in terms of spark safety, current intensity. The experimental methodology of estimation does not require the application of test gas and air mixture so it may be applied by economic units dealing with designing and manufacturing electric apparatus, assigned for working in explosive conditions zones, for the initial before-verification analysis of applied technical solutions.