Research on Application of Self-Healing Metallized Film Capacitors of DC Filter for HVDC System

Based on the standards of DC filter capacitor and self-healing power electronic capacitor, this paper analyzes the differences between the two standards, and points out that self-healing capacitor should be used in DC filter capacitor, and self-healing test, durability test and destructive test should be added. The series-parallel connection and rated parameters of self-healing DC filter capacitor bank can be made the same as that of oil-immersed capacitor. The insulation resistance of dry capacitors is evenly distributed, and the resistance value of the voltage equalizing resistance can be appropriately increased. The larger the capacitance of the DC filter capacitor, the smaller the voltage equalizing resistance required. The internal pressure of the circular element of the self-healing capacitor is large, which will have a certain limiting effect on the plate vibration in the elements. The colloidal solidification helps to limit the vibration response of the cased, and the attenuation of acoustic scattering is better than that of the oil all-film capacitor. The measured results show that the noise level is better than that of the oil capacitor. Traditional capacitor bank fault protection is not suitable for self-healing capacitor protection. The protection suggestions of self-healing metallized film DC filter capacitors are as follows: The first is segment film + increase design margin + bridge imbalance current protection and the second is the use of pressure relief valve + increase design margin + bridge imbalance current protection.