Hartmut Knobloch

Optimization of high-voltage self-blast interrupters by gas flow and electric field computations

Self-blast interrupters have the advantage of operating with low mechanical energy as they build up the pressure of the arc extinguishing gas flow from the thermal energy of the arc. This creates a higher pressure, but also a higher gas temperature than in interrupters with mechanical compression. Detailed flow field and electric field computations are necessary to achieve under such conditions the energy removal and dielectric recovery in view of an increase in breaking capacity and voltage rating. In particular, the optimization of the electric field/gas density distribution E//spl rho/ is a tool to improve the short-circuit and capacitive current breaking performance.

The Comparison of Arc-Extinguishing Capability of Sulfur Hexafluoride (SF6) with Alternative Gases in High-Voltage Circuit-Breakers

This paper describes the influence of the switchgear geometry, the priming pressure of the SF6 switchgear and the magnitude of the short-circuit current on the dielectric recovery of the arc gap, using the example of a high-voltage circuit-breaker for a 145 kV network. the results of other tests document the influence of the arc-quenching gases nitrogen (N2), carbon dioxide (CO2) and a nitrogen/SF6 mixture on the arc gap recovery in comparison with SF6. the results show that the arc control capability of these gases is very limited compared with SF6. Consequently, it will not be possible totally to replace the SF6 in high-voltage switchgear in the short to medium-term.

Responsible Handling of Sulfur Hexafluoride (SF6) by Manufacturers of High-Voltage Switchgear

The electricity industry has been using sulphur hexafluoride (SF6) for more than 40 years. SF6 is an excellent insulating and arc-quenching medium and allows systems to be more powerful and more compact than any other available medium. As well as handling the highest voltages and make/break ratings, SF6 switchgear is also very compact and has been responsible for many resourcesaving developments, superseding both oil and air for arc-quenching and insulation1. Over the last few years, however, criticism of SF6 gas has become ever stronger due to its potential effect on the world’s climate. Although the contribution of accumulated SF6 to manmade greenhouse gases in the atmosphere is, at 0.2%, relatively minimal, the Kyoto Conference in 1997 nevertheless still included it on the list of the six human-made greenhouse gases for monitoring2.