1. Common faults of capacitors
When any of the following conditions are found in the capacitor, the power should be cut off immediately.
(1) The capacitor casing may expand or leak oil.
(2) The casing ruptures, causing flashover and sparks.
(3) Abnormal sound inside the capacitor.
(4) If the shell temperature rises above 55 ℃, the temperature indicator will detach.
2. Troubleshooting of capacitors
(1) When a capacitor explodes and catches fire, immediately disconnect the power supply and use sand and dry fire extinguishers to extinguish the fire.
(2) When the fuse of the capacitor is blown, it should be reported to the dispatcher and the circuit breaker of the capacitor should be opened after obtaining approval. Cut off the power supply and discharge it. First, conduct an external inspection, such as checking for any flashover marks on the outside of the casing, deformation of the shell, oil leakage, and short circuits in the grounding device. Shake the insulation resistance values between poles and between poles to ground, check if the capacitor bank wiring is complete and firm, and if there is any phase loss. If no fault is found, replace the fuse before putting it into operation. If the fuse still melts after power transmission, the faulty capacitor should be removed and power should be restored to the remaining parts. If the circuit breaker trips at the same time as the fuse is blown, it cannot be forcibly sent at this time. Please wait until the above inspection is completed and the insurance is replaced before putting it into use.
(3) If the circuit breaker of the capacitor trips but the shunt fuse is not disconnected, the capacitor should be discharged for three minutes before checking the current transformer, power cable, and external components of the capacitor. If no abnormalities are found, it may be due to external fault bus voltage fluctuations. After inspection, it can be put into trial use; Otherwise, further comprehensive power on tests should be conducted for protection. If the cause cannot be found through the above inspection and testing, it is necessary to follow the system and gradually test the capacitor. Trial investment is not allowed until the cause is identified.
3. Safety precautions when handling faulty capacitors
Due to the characteristic of residual charge at the two poles of a capacitor, it is necessary to first try to discharge its charge completely, otherwise electric shock accidents may occur. When dealing with faulty capacitors, the first step is to open the circuit breaker and its upper and lower isolation switches of the capacitor bank. If fuse protection is used, the fuse tube should be removed first. At this point, although the capacitor bank has already discharged through the discharge resistor, there will still be some residual charge, so manual discharge is necessary. When discharging, first fix the grounding terminal of the grounding wire to the grounding grid, then discharge the capacitor multiple times with a grounding rod until there is no spark or discharge sound, and finally fix the grounding wire. At the same time, it should be noted that if there is an internal disconnection, blown fuse, or poor lead contact in a capacitor, there may still be residual charges between its two poles, which will not be discharged during automatic or manual discharge. Before operating or maintenance personnel come into contact with faulty capacitors, they should also wear insulated gloves and short-circuit the two poles of the faulty capacitor with a short circuit to discharge it. In addition, capacitors connected in series should also be discharged separately.
