Common Problems of Capacitor

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1. Common failures of capacitors. When one of the following conditions of the capacitor is found, the power supply should be cut off immediately.
(1) The capacitor shell is swollen or leaks oil.
(2) The casing is ruptured, and flashover occurs with sparks.
(3) The sound inside the capacitor is abnormal.
(4) The shell temperature rises above 55 °C, and the temperature indicator sheet falls off.

2. Fault handling of capacitors
(1) When the capacitor explodes and catches fire, immediately disconnect the power supply and extinguish the fire with sand and a dry fire extinguisher.

(2) When the safety of the capacitor is fused, it should be reported to the dispatcher, and the circuit breaker of the capacitor should be pulled open after obtaining consent. Cut off the power supply to discharge it, first carry out external inspection, such as whether there are flashover traces on the outside of the casing, whether the shell is deformed, whether the oil leakage and grounding device have short circuit phenomenon, etc., and shake the insulation resistance value between the poles and the pole to the ground, check whether the capacitor bank wiring is complete and firm, whether there is a phase loss phenomenon, if no fault phenomenon is found, you can replace the insurance and put in. If the safety is still blown after power transmission, the faulty capacitor should be withdrawn and power to the rest should be resumed. If the circuit breaker also tripps at the same time as the insurance blows, it cannot be forcibly sent at this time. It must be put in after the above inspection is completed and the insurance is changed.

(3) The circuit breaker of the capacitor trips, and the shunt insurance is not broken, the capacitor should be discharged for three minutes, and then check the circuit breaker, current transformer, power cable and external of the capacitor. If no abnormalities are found, it may be due to fluctuations in the voltage of the external faulty bus. After inspection, it can be tested for investment; Otherwise, a thorough energization test for protection should be carried out. After the above inspection and test, if the cause cannot be found, it is necessary to follow the system and gradually test the capacitor. Before the reason is ascertained, the test investment shall not be made.

3. Safety precautions when dealing with faulty capacitors. Since the two poles of the capacitor have the characteristics of residual charge, it is necessary to try to drain the charge first, otherwise it is prone to electric shock. When dealing with faulty capacitors, the circuit breaker of the capacitor bank and its upper and lower disconnectors should be pulled apart first, and if the fuse protection is used, the fuse tube should be removed first. At this time, although the capacitor bank has been discharged by the discharge resistor, there will still be a part of the residual charge, so artificial discharge must be performed. When discharging, the grounding end of the grounding wire should be fixed with the grounding grid, and then the capacitor should be discharged multiple times with the grounding rod until there is no spark and discharge sound, and finally the grounding wire should be fixed. At the same time, it should also be noted that if the capacitor has an internal disconnection, a fuse is blown or the lead is in poor contact, there may be residual charges between its two poles, and these residual charges will not be discharged during automatic discharge or artificial discharge. Therefore, before the operation or maintenance personnel contact the faulty capacitor, they should also wear insulating gloves and short-connect the poles of the faulty capacitor with a short circuit to discharge it. In addition, capacitors using the series wire method should be discharged separately.