1. Overvoltage
Overvoltage is extremely harmful to power capacitors. The life of a power capacitor is closely related to the duration, amplitude, and frequency of overvoltage. Especially prolonged overvoltage can cause the capacitor to heat up, accelerating insulation aging. Therefore, when the grid voltage exceeds 1.1 times the rated voltage of the capacitor, it should be taken out of service. The power frequency withstand voltage test device is suitable for withstand voltage tests of large hydro/thermal generators, using multiple reactors in parallel, and adjusting the inductance of the adjustable reactor.
2. Overcurrent
When the capacitor current exceeds 1.3 times the rated current or the three-phase unbalanced current exceeds 5%, it should be taken out of service. Because excessive current can cause the capacitor to burn out.
3. Oil Leakage
Power capacitors are fully sealed devices. If the seal is not tight, air, moisture, and impurities may enter the capacitor. When oil leakage occurs, the load should be reduced or the ambient temperature lowered, but long-term operation is not advisable. If severe oil leakage is found, the capacitor should be taken out of service as soon as possible.
4. Bulging Deformation
When a fault occurs inside the capacitor tank during operation, the insulating oil is decomposed by the high temperature of the arc, producing a large amount of gas, which can cause the tank to bulge and deform. In this case, it should be immediately taken out of service and replaced with a spare.
5. Automatic Trip of Capacitor Circuit Breaker
After the circuit breaker trips, do not force reclose. First, check the protection operation and the relevant primary circuit, such as checking whether the capacitor has exploded, bulged, or sprayed oil. Also inspect the capacitor's circuit breaker, current transformer, voltage transformer, power cable, etc., to determine the nature of the fault. If none of the above conditions exist, and the trip was caused by bus voltage fluctuation due to an external fault, a trial closing is allowed after 15 minutes. Do not attempt to reclose before the cause is identified.
6. Capacitor Out-of-Service Handling
If any of the following faults occur, the capacitor bank should be taken out of service, and the duty dispatcher and department head should be notified.
(1) The capacitor explodes;
(2) The capacitor bushing cracks and has flashover discharge;
(3) The capacitor severely sprays oil or catches fire;
(4) The capacitor shell is obviously swollen, with oil flowing out, or the three-phase current imbalance exceeds 5%, or there is abnormal sound inside the capacitor or reactor;
(5) The joint is severely overheated;
(6) The oil temperature of the dense capacitor exceeds 65°C, or the pressure relief valve operates
