Damage reason and operation specification of power electronic capacitor

There are more and more power electronic capacitors, but poor management and other technical reasons often lead to damage of power capacitors and explosion. The reasons are as follows:

Breakdown of internal components of capacitor: it is mainly caused by poor manufacturing process.

Insulation damage of capacitor to shell: the high voltage side outlet of capacitor is made of thin copper sheet. If the manufacturing process is poor, the edge is uneven with burr or serious bending, which is easy to produce corona. Corona will cause oil decomposition, tank shell expansion, oil level drop and cause breakdown. In addition, if the welding time at the corner is too long, the internal insulation will be burned and oil and gas will be produced, which will greatly reduce the voltage and cause damage to the capacitor.

Poor sealing and oil leakage: due to poor sealing of assembly sleeve, moisture enters into the interior, which reduces the insulation resistance; or oil level drops due to oil leakage, resulting in shell discharge or component breakdown.

Bulge and internal dissociation: due to corona, breakdown discharge and internal dissociation, the capacitor will reduce the initial free voltage of the components to below the working electric field strength under the action of overvoltage, which will cause physical, chemical and electrical effects, accelerate the aging and decomposition of insulation, produce gas, form a vicious cycle, increase the pressure of the box shell, cause the external bulge of the box wall and cause explosion 。

Capacitor explosion caused by closing with charge: it is forbidden to switch on with charge for any capacitor bank with rated voltage

Operating procedures

1、 The exposed conductive part of high-voltage capacitor bank shall be provided with mesh barrier. It is forbidden to open the barrier of operating capacitor bank during external inspection.

2、 Replace the fuse of capacitor when there is no voltage in capacitor. Therefore, discharge the capacitor before proceeding.

3、 The maintenance work of capacitor bank should be carried out when all power is cut off. The work can be carried out only after the power supply is disconnected and the capacitor is discharged and grounded. High voltage capacitor shall be based on work order, and low voltage capacitor can be ordered by oral or telephone. However, written records should be made.