What are the factors that cause capacitor explosion?

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What are the factors that cause capacitor explosion? [Copy link]

　   The possible causes of capacitor explosion are as follows: (1) Breakdown of internal components of the capacitor: mainly caused by poor manufacturing process. (2) Damage to the insulation of the capacitor to the shell. The lead wire on the high-voltage side of the capacitor is made of thin steel sheets. If the manufacturing process is poor, the edge is uneven with burrs or severely bent, and its tip is prone to corona, which will cause oil decomposition, box shell expansion, and oil level drop, resulting in breakdown. In addition, when sealing the cap, if the welding time at the corner is too long, the internal insulation will be burned and oil and gas will be generated, causing the voltage to drop significantly and cause damage. (3) Poor sealing and oil leakage: Due to poor sealing of the assembly sleeve, moisture enters the interior, reducing the insulation resistance; or due to oil leakage, the oil level drops, resulting in discharge in the direction of the pole to the shell or component breakdown. (4) Bulging and internal dissociation: Due to the internal corona, breakdown discharge and severe dissociation, the capacitor, under the action of overvoltage, reduces the initial dissociation voltage of the component to below the working electric field strength, thereby causing physical, chemical and electrical effects, accelerating the aging and decomposition of the insulation, generating gas, forming a vicious cycle, increasing the pressure of the box shell, causing the box wall to bulge and even explode. (5) Closing with charge causes capacitor explosion: It is forbidden to close the capacitor bank with charge on any rated voltage. Each time the capacitor bank is closed again, the capacitor must be discharged for 3 minutes with the switch disconnected before it can be closed again, otherwise the voltage polarity at the moment of closing may be opposite to the polarity of the residual charge on the capacitor and cause an explosion. For this reason, it is generally stipulated that capacitor banks with a capacity of more than 160kvar should be equipped with an automatic tripping device when there is no pressure, and it is stipulated that the switch of the capacitor bank is not allowed to be equipped with an automatic reclosing switch. In addition, explosions may also be caused by reasons such as excessive temperature, poor ventilation, excessive operating voltage, excessive voltage harmonic components or operating overvoltage.