Gaozhuang Mine is a water mining well that was trial-produced in 1997. At present, all high-voltage switches and low-voltage explosion-proof switches implement “vacuumization.†The use of a large number of vacuum switches has brought us new issues.
Vacuum switch is a novel power switch device. It seals a pair of contacts in the main circuit and blocks it in a vacuum interrupter isolated from the environment. Vacuum is used as the insulating medium and the arc extinguishing means. When the main circuit is switched on and off, the arc and the hot gas are not exposed, so no explosion of flammable gas occurs. In addition, the vacuum switch also has a small contact distance, fast action, short arcing time, fast arc extinguishing, light burned contact, long service life, and is suitable for frequent operation. During the service life of the vacuum tube, the contact part is not required. Maintenance, inspection and other advantages. However, vacuum switches have problems such as operating over-voltage and leakage of vacuum tubes.
The operating overvoltage is caused by the abrupt change of the circuit state and energy conversion and oscillation of the energy storage element. When the vacuum switch is turned off, overvoltage may be caused due to the cutoff, or overvoltage may occur due to re-ignition and repeated cutoff of the high-frequency current. When the switch closes, the closure of the contact bounce or the breaking and re-ignition of the transient high-frequency current occurs. Overvoltage may also be generated. To this end, to prevent this over-voltage hazards, in particular to mitigate the harm of high-frequency over-voltage on the motor insulation accelerated aging, vacuum switch starter motor must be set over-voltage protection device.
The measure to suppress overvoltage in this mine is to use zinc oxide arrester and RC surge suppressor. Zinc Oxide arresters have the characteristics of semiconductor transistors. Under the normal operating voltage, the resistance is very large and the current is very small. When the voltage is increased to a certain value, the resistance drops sharply and shows the regulation characteristic. Zinc-oxide arresters can limit the magnitude of overvoltages, but they cannot slow down the rise of overvoltage. Therefore, the residual voltage of the high-frequency over-voltage still impacts the insulation of the motor. Frequent high-frequency voltage impact will accelerate the insulation aging of the motor and should be noticed.
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