Which type of capacitor, dry-type or oil-type, is more suitable for industrial use?

In the field of industrial reactive power compensation, capacitors are the core components, and their performance and reliability directly affect the effectiveness and safety of the entire compensation system. For a long time, oil-type capacitors (or oil-immersed capacitors) have dominated the market. However, in recent years, dry-type capacitors (or dry technology/inert gas capacitors) have rapidly emerged and have become the preferred choice for many new projects.

Ⅰ. Safety: Dry-type capacitors have significant advantages.

1. Dry capacitor: The interior is filled with inert gas or solid materials, completely eliminating the risks of oil leakage, fire, and explosion. Even if internal gas production occurs due to extreme conditions (such as breakdown), the explosion-proof valve in the shell will quickly release the pressure, ensuring the maximum safety of equipment and personnel. This is of vital importance for industries with extremely high safety requirements, such as oil, chemical, mining, and data centers.

2. Oil-type capacitors: They are filled with insulating oil, which poses potential risks of oil leakage and combustion. Although products using vegetable oil (BI oil) have improved environmental friendliness and ignition point, the risks still exist. Once the casing is damaged or the seal ages, oil leakage will cause the capacitor to fail, pollute the cabinet, and make maintenance and cleaning very troublesome.

II. Environmental Protection and Maintenance: The "Maintenance-Free" Feature of Dry Type

1. Dry capacitor: With a fully sealed structure, it requires no maintenance throughout its lifespan. There is no need to worry about the leakage or deterioration of the filling medium. It conforms to the modern industrial trend of green and environmental protection.

2. Oil-based capacitors: There is a risk of oil leakage, and regular inspections are necessary. The leakage of traditional mineral oil can pollute the soil, while plant oil, although biodegradable, still requires cleaning up after leakage.

III. Electrical Performance and Lifespan: Each has its own advantages, but dry-type is more suitable for modern power grids.

1. Loss and temperature rise: Oil-type capacitors rely on oil circulation for heat dissipation, and their heat dissipation performance is slightly better than that of earlier dry-type products. However, modern advanced dry-type capacitors, through metal casings for heat dissipation and optimized design, have very low loss values and excellent temperature rise control.

2. Overload capacity: Harmonic currents are prevalent in industrial power grids. The metallized film of dry-type capacitors has better self-healing properties, enabling them to better withstand the impact of harmonic currents and experiencing a more gradual capacity decline in the final stage of their lifespan. In contrast, oil-type capacitors may age at a faster rate in severe harmonic environments.

3. Lifespan: Under ideal conditions, both designs can achieve a design lifespan of over 100,000 hours. However, in actual industrial applications, due to the superior harmonic resistance capability and higher safety of dry-type capacitors, their actual operational lifespan is often longer and more reliable.

dry-type capacitors have emerged as the absolute mainstream and preferred solution for reactive power compensation in modern industrial settings, thanks to their outstanding safety, maintenance-free features, and strong adaptability to complex industrial power grids.