The 2.8 kV, 8 mF fully domestically produced dry-type DC capacitors led by the China Electric Power Research Institute (CEPRI) have recently completed batch demonstration application in the Zhangbei Flexible DC Grid Test and Demonstration Project in Hebei. The project adopted domestic prototypes produced by multiple enterprises, covering actual operating scenarios of different phases and bridge arms of converter valves, and verified the engineering adaptability of domestic polypropylene raw materials, insulating films, and complete capacitor units.

The product was jointly developed by CEPRI together with industry chain enterprises including PetroChina Lanzhou Petrochemical, Quanzhou Jiadeli, Tongfeng Electronics, Faratronic, and Ningbo Bicai. Technical research began in 2018 and covered polypropylene resin preparation, film processing, capacitor manufacturing, and performance evaluation.

The raw material preparation adopts the process route of "efficient bulk polymerization + deep washing purification," using a continuous washing production unit with an annual capacity of 40,000 tons to deeply purify polypropylene resin. Downstream enterprises process the domestic resin into electrical-grade polypropylene film, which is then used in the manufacture of dry-type DC capacitors. This demonstration application verified the adaptability of domestic film materials to two mainstream capacitor design schemes.

This series of domestic products and supporting technologies passed technical appraisal in 2025. Previously, CEPRI had built an integrated comprehensive test platform for high-end capacitors, capable of conducting dielectric loss, impulse discharge, thermal stability, durability, and capacitor destructive tests, and had completed testing and performance evaluation of samples from multiple domestic capacitor enterprises.