The working principle of self-healing parallel capacitors

Self-healing parallel capacitors, as the name suggests, are characterized by their self-healing ability. These capacitors are mainly composed of capacitor units, dielectric materials, and electrodes. They are commonly used in power systems to compensate for reactive power and improve power quality. Compared with traditional parallel capacitors, self-healing capacitors can automatically restore their functions when encountering overload or short-circuit faults, thereby maximizing the guarantee of power grid safety and stability.

I. Working Principle of Self-healing Parallel Capacitors

Self-healing parallel capacitors are a type of capacitor used for reactive power compensation and power factor correction. Their core feature is the "self-healing" capability, meaning that when the dielectric breaks down, they can quickly restore their insulation ability to ensure the capacitor can continue to operate normally.

II. Structural Composition

Self-healing parallel capacitors usually consist of the following components:

1. Dielectric material: Mainly uses metallized polypropylene film (Metallized Polypropylene Film).

2. Electrode: An aluminum or zinc-aluminum alloy layer is deposited on the polypropylene film through a vacuum evaporation process, forming a metallized electrode.

3. Encapsulation shell: Metal or plastic shell. The interior may be filled with dry gas or vegetable oil to enhance heat dissipation performance.

III. Working Principle

1. Capacitors operate in parallel in the AC power grid, providing reactive power to improve the power factor and reduce line losses.

2. Due to the use of metallized electrodes, the capacitor undergoes charging and discharging during normal operation. Through the action of the electric field, it stores and releases electrical energy.

IV. Self-healing Principle

When the dielectric layer of the capacitor undergoes local breakdown (discharge breakdown) due to local overvoltage, impurities, mechanical defects, etc., the special design of the metallization layer enables the capacitor to automatically restore its insulation capability and continue to operate normally. The process is as follows:

1. Local breakdown occurs: The high electric field intensity causes the polypropylene film to undergo local carbonization or breakdown, forming tiny conductive pathways.

2. Self-healing reaction: Due to the instantaneous high temperature (3000°C) generated at the breakdown point, the surrounding metallized layer is vaporized by the electric arc and rapidly spreads to the surrounding medium, forming an insulating area.

3. Restoration of insulation: After the short-circuit path was removed, the capacitance function of this area was lost, but the overall capacitor still maintained a good working condition.

Self-healing parallel capacitors, as an important component of modern power systems, have demonstrated their unique self-healing capabilities and superior performance in enhancing power quality, promoting energy conservation and emission reduction, and ensuring equipment safety. With the continuous advancement of technology, the application scenarios of self-healing parallel capacitors will become increasingly widespread, and they will become indispensable guardians in the power system.