Capacitor safe operation
In the operation of the capacitor, the current should not exceed 1.3 times the rated current of the capacitor for a long time, and the voltage should not exceed 1.1 times the rated voltage of the capacitor for a long time. The ambient temperature used by the capacitors must not exceed the limits listed in Table 6-11. The temperature of the capacitor case must not exceed the manufacturer's specification (usually 60 or 65). Capacitors should maintain good contact, there must be no signs of loose or overheating; casing should be clean and there should be no traces of discharge; shell should not be significantly deformed, there should be no traces of oil leakage. The switching devices, protective appliances and discharge devices of the capacitors should be kept intact.
Under normal circumstances, the shunt capacitor should be put in or out based on the level of the power factor on the line and the level of the voltage. When the power factor is lower than 0.9 and the voltage is low, it should be put into the capacitor bank; when the power factor approaches 1 and there is a trend in advance and the voltage is high, the capacitor bank should be withdrawn.
When the operating parameters are abnormal and the operating conditions of the capacitor are exceeded, the capacitor bank should be withdrawn. If the capacitor's three-phase current is significantly unbalanced, it should also be taken out of operation.
When the capacitor connection point is found to be severely overheated or even melted, the porcelain casing is severely flashed and discharged, the casing is severely deformed, and the capacitor or its discharge device emits a severely abnormal sound. When the capacitor bursts, or when a fire or smoke occurs, it should be quitted.
The following points should be noted when performing capacitor operations:
(1) Under normal circumstances, when the whole station is powered off, the switch of the capacitor is first opened, and then the switch of each path is opened; under normal circumstances, when the power is restored at the entire station, the switch of each outlet is closed firstly. Close the capacitor line switch.
(2) After the whole station accident power failure, the capacitor switch should be opened.
(3) After the capacitor breaker is tripped, it shall not force transmission; after the fuse is blown, the fuse may not be replaced and the power transmission may be replaced before the cause is identified.
(4) Whether it is a high-voltage capacitor or a low-voltage capacitor, it is not allowed to gate with residual charge. Otherwise, a large current surge may occur. Before the capacitor is reclosed, it should be discharged for at least 3 minutes.
(5) For the purpose of inspection and repair, after the capacitor is disconnected from the power source and the staff is approaching, regardless of whether or not the capacitor is equipped with a discharge device, it must be manually discharged with a special portable discharge load.
When the total capacity of the high-voltage capacitor bank does not exceed 100kvar, it can be protected and controlled by the down-time fuse; when the total capacity is 100~300kvar, it should be protected and controlled by a load switch; when the total capacity is 300kvar, a vacuum circuit breaker or other Circuit breaker protection and control.
When the total capacity of a low-voltage capacitor bank does not exceed 100 kvar, AC contactors, knife switches, fuses or knife fuses can be used for protection and control. When the total capacity is above 100 kvar, low-voltage circuit breakers should be used for protection and control.
Power capacitor compensation principle and application