Sammendrag
The current interrupting capability of a load break
switch (LBS) depends on many design parameters, such as contact
and nozzle geometry, contact movement, and gas flow. For developing
more compact gas blow LBSs for air, it is necessary to find
design recommendations where each parameter is addressed individually.
In this paper, a current interruption test switch is built
for this purpose. The interruption tests are conducted with a directly
powered high-voltage circuit. The result shows theminimum
gas flow required for current interruption for various basic nozzle
geometries and at different contact positions. The study is particular
relevant for the 24 kV/630 A class, and it is shown that 0.3
bar upstream pressure appears to be a threshold value for successful
interruption. Some conclusions are also applicable for other
medium-voltage ratings.An LBS should be designed so that at least
one current zero crossing comes outside the nozzle when the switch
is still blowing with full strength.
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