Protection measures for low-voltage power capacitors in the reactive power compensation cabinet

The capacitor bank should be equipped with appropriate protective measures, such as using balanced or differential relay protection or instantaneous overcurrent relay protection. For capacitors with a voltage of 3.15kV and above, a separate fuse should be installed on each capacitor. The rated current of the fuse should be selected based on the characteristics of the fuse wire and the inrush current during connection. Generally, it is advisable to choose 1.5 times the rated current of the capacitor. This is to prevent the explosion of the capacitor tank.

2. In addition to the protection methods mentioned above, in certain cases, the following types of protection can also be adopted:

① If the voltage increase is frequent and prolonged, measures should be taken to ensure that the voltage increase does not exceed 1.1 times the rated voltage.
② Use an appropriate current automatic switch for protection, ensuring that the current increase does not exceed 1.3 times the rated current.
③ If the capacitor is connected to the overhead line, a suitable lightning arrester can be used for atmospheric overvoltage protection.
④ In a high-voltage network, when the short-circuit current exceeds 20A and the short-circuit current protection device or fuse cannot reliably protect against ground short circuit, a single-phase short-circuit protection device should be adopted.

3. Choosing the appropriate protection method for the capacitor bank is crucial for ensuring the safe and reliable operation of the capacitor. However, regardless of the protection method adopted, the following requirements must be met:
① The protection device should have sufficient sensitivity. Whether a single capacitor within the capacitor bank has a fault or some components are damaged, the protection device should be able to act reliably.
② It should be able to selectively trip the faulty capacitor or, after the power supply of the capacitor bank is completely disconnected, facilitate the detection of the damaged capacitors.
③ During the power-on and power-off of the capacitor and when there is a grounding or other faults in the power system, the protection device should not have any incorrect actions.
④ The protection device should be convenient for installation, adjustment, testing, and operation maintenance.
⑤ The power consumption should be low and the operating cost should be low.

4. Automatic reclosing devices are not allowed to be installed for capacitors. Instead, non-voltage release automatic tripping devices should be installed. The main reason for this is that capacitor discharge requires a certain amount of time. When the switch of the capacitor bank trips, if the reclosing is performed immediately after the tripping, the capacitor will not have enough time to discharge. There may still be charges in the capacitor with the opposite polarity to the reclosing voltage. This will cause a large impact current at the moment of closing, thereby resulting in the expansion of the capacitor shell, oil spraying, and even explosion.

The original low-voltage parallel power capacitor from Jinneng Electric is made by rolling metallized polypropylene film. It features a special gold-plating process and a cylindrical aluminum shell structure, ensuring stable performance and quality. In the power system, it can increase effective

power, reduce reactive power loss, perform reactive power compensation, and save power energy. Depending on the situation, it is divided into single-phase capacitors and three-phase capacitors.