Overvoltage occurring during the operation of outdoor high-voltage vacuum circuit breakers endangers the insulation of power equipment. Therefore, corresponding measures should be taken according to the type of overvoltage to reduce its generation and magnitude. In addition to addressing manufacturing process issues of the circuit breakers themselves, protective devices can be installed to adjust load parameters, thereby achieving the goal of overvoltage prevention.
1. Capacitor Protection
Connecting capacitors in parallel at the inductive load terminals can effectively reduce load impedance, thereby lowering the amplitude of chopping overvoltage and slowing down the front edge steepness of overvoltage. This not only protects inductive loads from damage caused by chopping overvoltage but also mitigates the harm of multiple restrike overvoltage to motor insulation. When outdoor high-voltage vacuum circuit breakers are connected to transformers or motors via cables, the cables’ large distributed capacitance acts equivalently to parallel capacitors, yielding excellent results.
2. RC (Resistor-Capacitor) Protection
An RC overvoltage suppressor is constructed by connecting a resistor (R) and a capacitor (C) in series as a protective component, which is then connected in parallel at the load incoming terminals. The capacitor can both slow down the rising steepness of overvoltage and reduce the load’s wave impedance, thus lowering chopping overvoltage. The function of the resistor is: when chopping occurs, its presence increases the attenuation coefficient of the high-frequency discharge circuit, reducing the number of restrikes, lowering multiple restrike overvoltage, and even effectively preventing such overvoltage from occurring. Using RC suppressors to protect loads such as motors achieves reliable overvoltage protection.
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