Do you know how power capacitors work?

How does power capacitor work? You know what? Let the power capacitor manufacturers tell you!

(1) Safe operation of capacitor

Capacitors shall operate at rated voltage. If it is not possible for the time being, it is allowed to operate within 5% of the rated voltage; when it exceeds 1.1 times of the rated voltage, it is only allowed to operate for a short time. But in case of over-voltage of outgoing line for a long time, we should try to eliminate it.

The capacitor shall operate at the rated current of three-phase balance. If it is not possible for the time being, it is not allowed to work for a long time under more than 1.3 times of the rated current to ensure the service life of the capacitor.

The ambient temperature of the place where the capacitor bank is installed shall not exceed 40 ℃, the average temperature within 24 hours shall not exceed 30 ℃, and the average temperature within one year shall not exceed 20 ℃. The temperature of capacitor shell should not exceed 60 ℃. If the above phenomenon is found, manual cooling shall be adopted and the capacitor bank shall be disconnected from the network if necessary.

(2) Monitoring of capacitor related parameters

1) Temperature monitoring. When there is no manufacturer's regulation, the temperature of the capacitor should be - 40 ℃ ~ 40 ℃, and the temperature indicating wax sheet should be pasted on the capacitor shell. The causes of abnormal temperature rise of capacitor in operation include: too high operating voltage (large dielectric loss); the influence of harmonics (small capacitive reactance and large current); switching inrush current (frequent switching); deterioration of heat dissipation conditions.

2) Voltage monitoring. It shall operate at rated voltage, and it is also allowed to operate at 1.05 times of rated voltage, and it shall not operate for more than 4 hours at 1.1 times of rated voltage.

3) Current monitoring. It shall operate at rated current or 1.3 times of rated current. The difference of three-phase current of capacitor bank shall not exceed ± 5%.

(3) Capacitor on / off

When the power factor is lower than 0.85 and the voltage is low, it should be put into operation; when the power factor is close to 1 and has a leading trend, it should be withdrawn when the voltage is high.

In case of one of the following faults, it should be exited urgently: ① the connection point is seriously overheated or even melted; ② the porcelain bushing flashover discharge; ③ the shell expands and deforms; ④ the sound of the capacitor bank or discharge device is abnormal; ⑤ the capacitor smokes, catches fire or explodes.

Before the power capacitor bank is connected, the megohmmeter shall be used to check the discharge network. When switching on and off the capacitor bank, the following points should be considered:

1) When the voltage on the bus bar (bus) exceeds the allowable value of 1.1 times the rated voltage, it is forbidden to connect the capacitor bank to the power grid.

2) The capacitor bank shall not be re connected within 1 minute after it is disconnected from the grid, except for automatic re connection.

3) When connecting and disconnecting the capacitor bank, the circuit breaker that cannot produce dangerous overvoltage shall be selected, and the rated current of the circuit breaker shall not be less than 1.3 times of the rated current of the capacitor bank.

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