The function and working principle of outdoor high voltage vacuum circuit breaker

When the vacuum circuit breaker is in the closed position, which is received by the insulation support insulator, once the vacuum circuit breaker is permanently connected to ground fault, tripping the circuit breaker, a ground fault point and is not cleared, then the electrical bus also the insulation is subjected to a vacuum circuit breaker of the fracture gap; when various faults breaking vacuum insulated gap between one pair of fracture to withstand the role of the various sub-touch recovery voltage breakdown does not occur. Therefore, the insulation characteristics of the vacuum gap become the main research topics for improving the voltage at the interrupter of the arc extinguishing chamber and developing the single-break vacuum circuit breaker to the high voltage level.

Representation <br> <br> degree of vacuum less than one atmosphere absolute pressure of the lean gas space, called vacuum space, i.e., the higher the degree of vacuum in the space, the lower gas pressure. There are three ways of expressing the unit of vacuum: bracket (ie 1 mm mercury column height), millibar (103 bar) or Pa (Pascal: Pa). (1 Torr = 131.6Pa, 1 mbar = 100Pa) we usually refer to a degree of vacuum inside the vacuum interrupter chamber to 10-4 Torr means of the gas pressure in the interrupter chamber only "millionth mm Hg "High", which is 1.31x10-2Pa.

"Paisen's theorem" has also been translated as "Paschen's law", which refers to the relationship between the strength of gap voltage withstand and gas pressure. Figure 1 shows that the relationship curve of Pissen's theorem is in a "V" shape, that is, the increase or decrease in the inflation pressure can increase the insulation strength of the interpolar gap. Breakdown mechanism which is still not clear, since the vacuum inside the vacuum interrupter chamber is higher than 10-4 Torr, such a free stroke thin air space, the gas molecules are 103mm, in such a vacuum interrupter chamber volume size, the occurrence of The probability of a collision is almost zero. Therefore, no collision will break free and the vacuum gap will break down. The “V” curve of the Pisen's theorem is empirically derived, provided that in the case of a uniform electric field, the gap breakdown voltage Uj can be expressed as:

Uj=KLa

L------ clearance distance;

a------Interval coefficient (a=1 when the clearance is less than 5mm, a=0.5 when >5mm)

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